Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this A peptide bond is a Chemical bond formed between two Molecules when the Carboxyl group of one molecule reacts with the Carboxyl group or CO2H is a Functional group present in Amino acids and Carboxylic acids Its structure is composed of one carbon atom attached Amines are Organic compounds and Functional groups that contain a basic Nitrogen Atom with a Lone pair. In Chemistry, residue refers to the material remaining after a distillation or an evaporation or to a portion of a larger molecule such as a Methyl group. The sequence of amino acids in a protein is defined by a gene and encoded in the genetic code. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Although this genetic code specifies 20 "standard" amino acids plus selenocysteine and - in certain archaea - pyrrolysine, the residues in a protein are sometimes chemically altered in post-translational modification: either before the protein can function in the cell, or as part of control mechanisms. Selenocysteine is an Amino acid that is present in several Enzymes (for example Glutathione peroxidases tetraiodothyronine 5' deiodinases Pyrrolysine is a naturally occurring genetically coded Amino acid used by some Methanogenic Archaea in Enzymes that are part of their Methane Posttranslational modification (PTM is the chemical modification of a Protein after its translation. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Proteins can also work together to achieve a particular function, and they often associate to form stable complexes. A protein complex is a group of two or more Proteins Protein complexes are a form of Quaternary structure. [1]
Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in every process within cells. The term macromolecule by definition implies "large Molecule " Polysaccharides are relatively complex Carbohydrates They are Polymers made up of many Monosaccharides joined together by Glycosidic bonds A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Many proteins are enzymes that catalyze biochemical reactions and are vital to metabolism. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, which form a system of scaffolding that maintains cell shape. Actin is a globular roughly 42-kDa Protein found in all eukaryotic cells (except for Nematode sperm where it may be present at concentrations of Myosins are a large family of Motor proteins found in Eukaryotic tissues. cytoskeleton (also CSK is a cellular " Scaffolding " or " Skeleton " contained within the Cytoplasm. Scaffolding is a temporary framework used to support people and material in the construction or repair of buildings and other large structures Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. Cell signaling is part of a Complex system of Communication that governs basic cellular activities and coordinates cell actions Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily Cellular adhesion is the binding of a cell to another cell or to a Surface or matrix. The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication Proteins are also necessary in animals' diets, since animals cannot synthesize all the amino acids they need and must obtain essential amino acids from food. An essential amino acid or indispensable amino acid is an Amino acid that cannot be synthesized de novo by the organism (usually referring to Through the process of digestion, animals break down ingested protein into free amino acids that are then used in metabolism. Digestion is the breaking down of chemicals in the body into a form that can be absorbed
The word protein comes from the Greek word πρώτα ("prota"), meaning "of primary importance. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly " Proteins were first described and named by the Swedish chemist Jöns Jakob Berzelius in 1838. Friherre Jöns Jacob Berzelius (20 August 1779 &ndash 7 August 1848 was a Swedish chemist However, the central role of proteins in living organisms was not fully appreciated until 1926, when James B. Sumner showed that the enzyme urease was a protein. James Batcheller Sumner ( November 19, 1887 &ndash August 12, 1955) was an American Chemist. Urease ( is an Enzyme that catalyzes the Hydrolysis of Urea into Carbon dioxide and Ammonia. [2] The first protein to be sequenced was insulin, by Frederick Sanger, who won the Nobel Prize for this achievement in 1958. Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance Frederick Sanger, OM, CH, CBE, FRS (born 13 August 1918) is an English biochemist and twice The first protein structures to be solved included hemoglobin and myoglobin, by Max Perutz and Sir John Cowdery Kendrew, respectively, in 1958. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Myoglobin is a single-chain globular Protein of 153 Amino acids containing a Heme ( Iron -containing Porphyrin) Prosthetic Max Ferdinand Perutz, OM ( May 19 1914, Vienna, Austria – February 6 2002, Cambridge, Sir John Cowdery Kendrew ( 24 March 1917 &ndash 23 August 1997) was an English Biochemist and crystallographer [3][4] The three-dimensional structures of both proteins were first determined by x-ray diffraction analysis; Perutz and Kendrew shared the 1962 Nobel Prize in Chemistry for these discoveries. The Nobel Prize in Chemistry (Nobelpriset i kemi is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of Chemistry.
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Biochemistry
Proteins are linear polymers built from 20 different L-α-amino acids. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this All amino acids possess common structural features, including an α carbon to which an amino group, a carboxyl group, and a variable side chain are bonded. The alpha carbon in Organic chemistry refers to the first carbon that attaches to a Functional group (the carbon is attached at the first or alpha position Amines are Organic compounds and Functional groups that contain a basic Nitrogen Atom with a Lone pair. Carboxyl group or CO2H is a Functional group present in Amino acids and Carboxylic acids Its structure is composed of one carbon atom attached A side chain in Organic chemistry and Biochemistry is a part of a Molecule that is attached to a core structure A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic Only proline differs from this basic structure as it contains an unusual ring to the N-end amine group, which forces the CO–NH amide moiety into a fixed conformation. [5] The side chains of the standard amino acids, detailed in the list of standard amino acids, have different chemical properties that produce three-dimensional protein structure and are therefore critical to protein function. The amino acids in a polypeptide chain are linked by peptide bonds formed in a dehydration reaction. A peptide bond is a Chemical bond formed between two Molecules when the Carboxyl group of one molecule reacts with the In Chemistry, a dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule Once linked in the protein chain, an individual amino acid is called a residue, and the linked series of carbon, nitrogen, and oxygen atoms are known as the main chain or protein backbone. The peptide bond has two resonance forms that contribute some double-bond character and inhibit rotation around its axis, so that the alpha carbons are roughly coplanar. Resonance in Chemistry is a theory used to represent and model certain types of non-classical Molecular structures Resonance is a key component In Geometry, a set of points in space is coplanar if the points all lie in the same geometric plane. The other two dihedral angles in the peptide bond determine the local shape assumed by the protein backbone. In Aerospace engineering, the Dihedral is the Angle between the two wings see Dihedral.
Due to the chemical structure of the individual amino acids, the protein chain has directionality. The end of the protein with a free carboxyl group is known as the C-terminus or carboxy terminus, whereas the end with a free amino group is known as the N-terminus or amino terminus. The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal end, or The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or
The words protein, polypeptide, and peptide are a little ambiguous and can overlap in meaning. Peptides (from the Greek πεπτίδια, "small digestibles" are short Polymers formed from the linking in a defined order of α- Amino Peptides (from the Greek πεπτίδια, "small digestibles" are short Polymers formed from the linking in a defined order of α- Amino Protein is generally used to refer to the complete biological molecule in a stable conformation, whereas peptide is generally reserved for a short amino acid oligomers often lacking a stable three-dimensional structure. In Biochemistry and Chemistry, the tertiary structure of a Protein or any other Macromolecule is its three-dimensional structure as defined However, the boundary between the two is not well defined and usually lies near 20–30 residues. [6] Polypeptide can refer to any single linear chain of amino acids, usually regardless of length, but often implies an absence of a defined conformation. In Biochemistry and Chemistry, the tertiary structure of a Protein or any other Macromolecule is its three-dimensional structure as defined
Synthesis
Proteins are assembled from amino acids using information encoded in genes. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Each protein has its own unique amino acid sequence that is specified by the nucleotide sequence of the gene encoding this protein. Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group The genetic code is a set of three-nucleotide sets called codons and each three-nucleotide combination stands for an amino acid, for example AUG stands for methionine. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Methionine ( abbreviated as Met or M) is an α- Amino acid with the Chemical formula HO2CCH(NH2CH2CH2SCH3 Because DNA contains four nucleotides, the total number of possible codons is 64; hence, there is some redundancy in the genetic code, with some amino acids specified by more than one codon. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Genes encoded in DNA are first transcribed into pre-messenger RNA (mRNA) by proteins such as RNA polymerase. Transcription is the synthesis of RNA under the direction of DNA Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product RNA polymerase ( RNAP or RNApol) is an Enzyme that produces RNA. Most organisms then process the pre-mRNA (also known as a primary transcript) using various forms of post-transcriptional modification to form the mature mRNA, which is then used as a template for protein synthesis by the ribosome. Post-transcriptional modification is a process in Cell biology by which in Eukaryotic cells, primary transcript RNA is converted into mature Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that In prokaryotes the mRNA may either be used as soon as it is produced, or be bound by a ribosome after having moved away from the nucleoid. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other In Prokaryotes, the nucleoid (meaning nucleus-like) is an irregularly-shaped region within the cell of Prokaryotes where the Genetic material In contrast, eukaryotes make mRNA in the cell nucleus and then translocate it across the nuclear membrane into the cytoplasm, where protein synthesis then takes place. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed The nuclear envelope (NE(also known as the perinuclear envelope, nuclear membrane, nucleolemma or karyotheca) is a double lipid bilayer that The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. Protein biosynthesis (synthesis is the process in which cells build Proteins The term is sometimes used to refer only to protein translation but more The rate of protein synthesis is higher in prokaryotes than eukaryotes and can reach up to 20 amino acids per second. [7]
The process of synthesizing a protein from an mRNA template is known as translation. Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression) The mRNA is loaded onto the ribosome and is read three nucleotides at a time by matching each codon to its base pairing anticodon located on a transfer RNA molecule, which carries the amino acid corresponding to the codon it recognizes. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called Transfer RNA (abbreviated tRNA) is a small RNA (usually about 74-95 nucleotides that transfers a specific Amino acid to a growing polypeptide chain at Transfer RNA (abbreviated tRNA) is a small RNA (usually about 74-95 nucleotides that transfers a specific Amino acid to a growing polypeptide chain at The enzyme aminoacyl tRNA synthetase "charges" the tRNA molecules with the correct amino acids. An aminoacyl tRNA synthetase ( aaRS) is an Enzyme that catalyzes the Esterification of a specific Amino acid or its precursor to one of all its compatible The growing polypeptide is often termed the nascent chain. Proteins are always biosynthesized from N-terminus to C-terminus. The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal end, or
The size of a synthesized protein can be measured by the number of amino acids it contains and by its total molecular mass, which is normally reported in units of daltons (synonymous with atomic mass units), or the derivative unit kilodalton (kDa). The molecular mass (abbreviated m of a substance, more commonly referred to as molecular weight and abbreviated as MW, is the Mass of one The unified atomic mass unit ( u) or Dalton ( Da) or sometimes universal mass unit, is an unit of Mass used to express Yeast proteins are on average 466 amino acids long and 53 kDa in mass. Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described [6] The largest known proteins are the titins, a component of the muscle sarcomere, with a molecular mass of almost 3,000 kDa and a total length of almost 27,000 amino acids. Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the "A-band" redirects here For other uses of the term see A band. [8]
Chemical synthesis
Short proteins can also be synthesized chemically by a family of methods known as peptide synthesis, which rely on organic synthesis techniques such as chemical ligation to produce peptides in high yield. In Organic chemistry, peptide synthesis is the production of Peptides which are Organic compounds in which multiple Amino acids are linked via Organic synthesis is a special branch of Chemical synthesis and is concerned with the construction of Organic compounds via Organic reactions Organic Chemical ligation is a set of techniques used for creating long Peptide or Protein chains [9] Chemical synthesis allows for the introduction of non-natural amino acids into polypeptide chains, such as attachment of fluorescent probes to amino acid side chains. Fluorescence is a Luminescence that is mostly found as an [10] These methods are useful in laboratory biochemistry and cell biology, though generally not for commercial applications. Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as See also List of basic cell biology topics. Cell biology (also called cellular biology or formerly cytology, from the Chemical synthesis is inefficient for polypeptides longer than about 300 amino acids, and the synthesized proteins may not readily assume their native tertiary structure. In Biochemistry and Chemistry, the tertiary structure of a Protein or any other Macromolecule is its three-dimensional structure as defined Most chemical synthesis methods proceed from C-terminus to N-terminus, opposite the biological reaction.
Structure of proteins
Most proteins fold into unique 3-dimensional structures. Protein folding is the physical process by which a Polypeptide folds into its characteristic and functional three-dimensional structure. The shape into which a protein naturally folds is known as its native state. In Biochemistry, the native state of a Protein is its operative or functional form Although many proteins can fold unassisted, simply through the chemical properties of their amino acids, others require the aid of molecular chaperones to fold into their native states. This article is about the protein For other uses see Chaperone, a disambiguation page Biochemists often refer to four distinct aspects of a protein's structure:
- Primary structure: the amino acid sequence
- Secondary structure: regularly repeating local structures stabilized by hydrogen bonds. In Biochemistry, the primary structure of a biological molecule is the exact specification of its atomic composition and the chemical bonds connecting those atoms (including Peptide sequence or amino acid sequence is the order in which Amino acid residues connected by Peptide bonds lie in the chain in Peptides In Biochemistry and Structural biology, secondary structure is the general three-dimensional form of local segments of Biopolymers such as A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen The most common examples are the alpha helix and beta sheet. A common motif in the Secondary structure of Proteins the alpha helix (α-helix is a right-handed coiled conformation resembling a spring, in which The β sheet (also β-pleated sheet) is the second form of regular Secondary structure in Proteins consisting of beta strands connected laterally [11] Because secondary structures are local, many regions of different secondary structure can be present in the same protein molecule.
- Tertiary structure: the overall shape of a single protein molecule; the spatial relationship of the secondary structures to one another. In Biochemistry and Chemistry, the tertiary structure of a Protein or any other Macromolecule is its three-dimensional structure as defined Tertiary structure is generally stabilized by nonlocal interactions, most commonly the formation of a hydrophobic core, but also through salt bridges, hydrogen bonds, disulfide bonds, and even post-translational modifications. The hydrophobic effect is the property that non-polar molecules tend to form intermolecular aggregates in an aqueous medium and analogous intramolecular interactions In Protein chemistry the term salt bridge or salt bond denotes a relatively weak Ionic bond between positively and negatively charged In Chemistry, a disulfide bond is a single Covalent bond derived from the coupling of Thiol groups Posttranslational modification (PTM is the chemical modification of a Protein after its translation. The term "tertiary structure" is often used as synonymous with the term fold.
- Quaternary structure: the shape or structure that results from the interaction of more than one protein molecule, usually called protein subunits in this context, which function as part of the larger assembly or protein complex. In Biochemistry, quaternary structure is the arrangement of multiple folded Protein molecules in a multi-subunit complex Protein-protein interactions refer to the association of Protein molecules and the study of these associations from the perspective of Biochemistry, Signal transduction In Structural biology, a protein subunit or subunit protein is a single Protein Molecule that assembles (or " coassembles " A protein complex is a group of two or more Proteins Protein complexes are a form of Quaternary structure.
Proteins are not entirely rigid molecules. In addition to these levels of structure, proteins may shift between several related structures while they perform their biological function. In the context of these functional rearrangements, these tertiary or quaternary structures are usually referred to as "conformations," and transitions between them are called conformational changes. In Chemistry, conformational isomerism is a form of Stereoisomerism in which Molecules with the same Structural formula (same connectivity Such changes are often induced by the binding of a substrate molecule to an enzyme's active site, or the physical region of the protein that participates in chemical catalysis. The active site of an Enzyme contains the catalytic and Binding sites. In solution all proteins also undergo variation in structure through thermal vibration and the collision with other molecules, see the animation on the right.
Proteins can be informally divided into three main classes, which correlate with typical tertiary structures: globular proteins, fibrous proteins, and membrane proteins. Globular proteins, or spheroproteins are one of the two main Protein classes comprising "globe" -like proteins that are more or less soluble in Fibrous proteins, also called scleroproteins, are one of the two main classes of protein Quaternary structure (the other being Globular proteins. Also see Transmembrane protein. A membrane protein is a Protein molecule that is attached to or associated with the membrane Almost all globular proteins are soluble and many are enzymes. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Fibrous proteins are often structural; membrane proteins often serve as receptors or provide channels for polar or charged molecules to pass through the cell membrane. In Biochemistry, a receptor is a Protein molecule embedded in either the Plasma membrane or Cytoplasm of a cell to which a mobile signaling
A special case of intramolecular hydrogen bonds within proteins, poorly shielded from water attack and hence promoting their own dehydration, are called dehydrons. Dehydration ( hypohydration) is the removal of Water ( hydro in ancient Greek) from an object A dehydron is an intramolecular Hydrogen bond incompletely shielded from water attack, with a propensity to promote its own Dehydration.
Structure determination
Discovering the tertiary structure of a protein, or the quaternary structure of its complexes, can provide important clues about how the protein performs its function. Common experimental methods of structure determination include X-ray crystallography and NMR spectroscopy, both of which can produce information at atomic resolution. X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters Protein nuclear magnetic resonance spectroscopy (usually abbreviated protein NMR) is a field of Structural biology in which NMR spectroscopy is used History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Cryoelectron microscopy is used to produce lower-resolution structural information about very large protein complexes, including assembled viruses;[11] a variant known as electron crystallography can also produce high-resolution information in some cases, especially for two-dimensional crystals of membrane proteins. Electron cryomicroscopy ( cryo-EM or sometimes cryo-electron microscopy) is a form of Electron microscopy (EM where the sample is studied at Cryogenic A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Electron crystallography is a method to determine the arrangement of atoms in solids using an Electron microscope. [12] Solved structures are usually deposited in the Protein Data Bank (PDB), a freely available resource from which structural data about thousands of proteins can be obtained in the form of Cartesian coordinates for each atom in the protein. The Protein Data Bank ( PDB) is a repository for 3-D structural data of Proteins and Nucleic acids These data typically obtained by X-ray crystallography In Mathematics, the Cartesian coordinate system (also called rectangular coordinate system) is used to determine each point uniquely in a plane
Many more gene sequences are known than protein structures. Further, the set of solved structures is biased toward proteins that can be easily subjected to the conditions required in X-ray crystallography, one of the major structure determination methods. X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters In particular, globular proteins are comparatively easy to crystallize in preparation for X-ray crystallography. Crystallization is the (natural or artificial process of formation of solid Crystals precipitating from a homogeneous --> identical Solution Membrane proteins, by contrast, are difficult to crystallize and are underrepresented in the PDB. [13] Structural genomics initiatives have attempted to remedy these deficiencies by systematically solving representative structures of major fold classes. Structural genomics consists in the determination of the three dimensional structure of all Proteins of a given organism by experimental methods such as X-ray crystallography Protein structure prediction methods attempt to provide a means of generating a plausible structure for proteins whose structures have not been experimentally determined. Protein structure prediction is one of the most important goals pursued by Bioinformatics and Theoretical chemistry.
Cellular functions
Proteins are the chief actors within the cell, said to be carrying out the duties specified by the information encoded in genes. [6] With the exception of certain types of RNA, most other biological molecules are relatively inert elements upon which proteins act. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Proteins make up half the dry weight of an Escherichia coli cell, whereas other macromolecules such as DNA and RNA make up only 3% and 20%, respectively. [14] The set of proteins expressed in a particular cell or cell type is known as its proteome. The proteome is the entire complement of Proteins expressed by a genome cell tissue or organism
The chief characteristic of proteins that allows their diverse set of functions is their ability to bind other molecules specifically and tightly. The region of the protein responsible for binding another molecule is known as the binding site and is often a depression or "pocket" on the molecular surface. In Biochemistry, a binding site is a region on a Protein, DNA, or RNA to which specific other Molecules and Ions &mdash This binding ability is mediated by the tertiary structure of the protein, which defines the binding site pocket, and by the chemical properties of the surrounding amino acids' side chains. Protein binding can be extraordinarily tight and specific; for example, the ribonuclease inhibitor protein binds to human angiogenin with a sub-femtomolar dissociation constant (<10-15 M) but does not bind at all to its amphibian homolog onconase (>1 M). Ribonuclease inhibitor (RI is a large (~450 residues ~49 kDa acidic (pI ~4 Angiogenin (Ang is a small Polypeptide that Ranpirnase is a Ribonuclease Enzyme found in Northern Leopard Frog ( Rana pipiens) Oocytes It is being studied in the treatment of Extremely minor chemical changes such as the addition of a single methyl group to a binding partner can sometimes suffice to nearly eliminate binding; for example, the aminoacyl tRNA synthetase specific to the amino acid valine discriminates against the very similar side chain of the amino acid isoleucine. An aminoacyl tRNA synthetase ( aaRS) is an Enzyme that catalyzes the Esterification of a specific Amino acid or its precursor to one of all its compatible Valine (abbreviated as Val or V) is an α- Amino acid with the Chemical formula HO2CCH(NH2CH(CH32 Isoleucine (abbreviated as Ile or I) is an α- Amino acid with the Chemical formula HO2CCH(NH2CH(CH3CH2CH3
Proteins can bind to other proteins as well as to small-molecule substrates. When proteins bind specifically to other copies of the same molecule, they can oligomerize to form fibrils; this process occurs often in structural proteins that consist of globular monomers that self-associate to form rigid fibers. In Chemistry, an oligomer consists of a limited number of Monomer units (ολιγος or oligos is Greek for "a few" in contrast to a Protein-protein interactions also regulate enzymatic activity, control progression through the cell cycle, and allow the assembly of large protein complexes that carry out many closely related reactions with a common biological function. Protein-protein interactions refer to the association of Protein molecules and the study of these associations from the perspective of Biochemistry, Signal transduction The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication A protein complex is a group of two or more Proteins Protein complexes are a form of Quaternary structure. Proteins can also bind to, or even be integrated into, cell membranes. The ability of binding partners to induce conformational changes in proteins allows the construction of enormously complex signaling networks. Cell signaling is part of a Complex system of Communication that governs basic cellular activities and coordinates cell actions
Enzymes
The best-known role of proteins in the cell is their duty as enzymes, which catalyze chemical reactions. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Enzymes are usually highly specific catalysts that accelerate only one or a few chemical reactions. Enzymes carry out most of the reactions involved in metabolism and catabolism, as well as DNA replication, DNA repair, and RNA synthesis. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. For the related metabolic process see Anabolism. Catabolism is the set of Metabolic pathways which break down molecules into DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. Transcription is the synthesis of RNA under the direction of DNA Some enzymes act on other proteins to add or remove chemical groups in a process known as post-translational modification. Posttranslational modification (PTM is the chemical modification of a Protein after its translation. About 4,000 reactions are known to be catalyzed by enzymes. [15] The rate acceleration conferred by enzymatic catalysis is often enormous - as much as 1017-fold increase in rate over the uncatalyzed reaction in the case of orotate decarboxylase (78 million years without the enzyme, 18 milliseconds with the enzyme). Orotidine 5'-phosphate decarboxylase is an Enzyme involved in Pyrimidine metabolism [16]
The molecules bound and acted upon by enzymes are known as substrates. Although enzymes can consist of hundreds of amino acids, it is usually only a small fraction of the residues that come in contact with the substrate, and an even smaller fraction - 3-4 residues on average - that are directly involved in catalysis. [17] The region of the enzyme that binds the substrate and contains the catalytic residues is known as the active site. The active site of an Enzyme contains the catalytic and Binding sites.
Cell signaling and ligand transport
Many proteins are involved in the process of cell signaling and signal transduction. Cell signaling is part of a Complex system of Communication that governs basic cellular activities and coordinates cell actions In Biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another Some proteins, such as insulin, are extracellular proteins that transmit a signal from the cell in which they were synthesized to other cells in distant tissues. Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance Tissue is a cellular organizational level intermediate between cells and a complete organism Others are membrane proteins that act as receptors whose main function is to bind a signaling molecule and induce a biochemical response in the cell. Also see Transmembrane protein. A membrane protein is a Protein molecule that is attached to or associated with the membrane In Biochemistry, a receptor is a Protein molecule embedded in either the Plasma membrane or Cytoplasm of a cell to which a mobile signaling Many receptors have a binding site exposed on the cell surface and an effector domain within the cell, which may have enzymatic activity or may undergo a conformational change detected by other proteins within the cell. A macromolecule is usually flexible and dynamic It can change its shape in response to changes in its environment or other factors each possible shape is called a conformation and a transition
Antibodies are protein components of adaptive immune system whose main function is to bind antigens, or foreign substances in the body, and target them for destruction. Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily Immune system|Passive immunity|Innate immune system The adaptive immune system is composed of highly specialized systemic cells and processes that eliminate or prevent Pathogenic An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response Antibodies can be secreted into the extracellular environment or anchored in the membranes of specialized B cells known as plasma cells. Secretion is the process of segregating elaborating and releasing chemicals from a cell, or a secreted Chemical substance or amount of substance B cells are Lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by Plasma cells (also called plasma B cells or plasmocytes) are cells of the Immune system that secrete large amounts of antibodies. Whereas enzymes are limited in their binding affinity for their substrates by the necessity of conducting their reaction, antibodies have no such constraints. An antibody's binding affinity to its target is extraordinarily high.
Many ligand transport proteins bind particular small biomolecules and transport them to other locations in the body of a multicellular organism. These proteins must have a high binding affinity when their ligand is present in high concentrations, but must also release the ligand when it is present at low concentrations in the target tissues. In Chemistry, a ligand is either an Atom, Ion, or Molecule (see also Functional group) that bonds to a central metal generally The canonical example of a ligand-binding protein is hemoglobin, which transports oxygen from the lungs to other organs and tissues in all vertebrates and has close homologs in every biological kingdom. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes In Evolutionary biology, homology has come to mean any similarity between characters that is due to their shared ancestry. In biological Taxonomy, a kingdom or regnum is a Taxonomic rank in either (historically the highest rank or (in the new three-domain system
Transmembrane proteins can also serve as ligand transport proteins that alter the permeability of the cell membrane to small molecules and ions. A transmembrane protein is a Protein that spans the entire Biological membrane. A semipermeable membrane, also termed a selectively-permeable membrane, a partially-permeable membrane or a differentially-permeable membrane, is a membrane The membrane alone has a hydrophobic core through which polar or charged molecules cannot diffuse. In Chemistry, hydrophobicity (from the combining form of water in Attic Greek hydro- and for fear phobos) refers to the physical property of "Polar molecule" and "Non-polar" redirect here Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement Membrane proteins contain internal channels that allow such molecules to enter and exit the cell. Many ion channel proteins are specialized to select for only a particular ion; for example, potassium and sodium channels often discriminate for only one of the two ions. Ion channels are pore-forming Proteins that help establish and control the small Voltage Gradient across the Plasma membrane of all living Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22
Structural proteins
Structural proteins confer stiffness and rigidity to otherwise-fluid biological components. Most structural proteins are fibrous proteins; for example, actin and tubulin are globular and soluble as monomers, but polymerize to form long, stiff fibers that comprise the cytoskeleton, which allows the cell to maintain its shape and size. Fibrous proteins, also called scleroproteins, are one of the two main classes of protein Quaternary structure (the other being Globular proteins. Actin is a globular roughly 42-kDa Protein found in all eukaryotic cells (except for Nematode sperm where it may be present at concentrations of A Tubulin is one of several members of a small family of globular Proteins The most common members of the tubulin family are α-tubulin and β-tubulin the proteins that A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds cytoskeleton (also CSK is a cellular " Scaffolding " or " Skeleton " contained within the Cytoplasm. Collagen and elastin are critical components of connective tissue such as cartilage, and keratin is found in hard or filamentous structures such as hair, nails, feathers, hooves, and some animal shells. Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein Elastin is a Protein in Connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, Muscle, and Nervous tissue) Cartilage is a type of dense Connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix Keratins are a family of fibrous structural proteins; tough and insoluble they form the hard but nonmineralized structures found in Reptiles Birds Hair is a keratinised protein filament that grows through the epidermis from follicles deep within the Dermis. A nail is a horn -like structure at the end of an animal's Finger or Toe. Feathers are one of the epidermal growths that form the distinctive outer covering or Plumage, on Birds They are considered the most complex integumentary structures HoofRearHoovesjpg|thumb|200px|right|Rear hooves of a horse]] A hoof is the tip of a Toe of an Ungulate Mammal, strengthened by a thick horny (
Other proteins that serve structural functions are motor proteins such as myosin, kinesin, and dynein, which are capable of generating mechanical forces. Motor proteins are a class of Molecular motors that are able to move along the surface of a suitable substrate Myosins are a large family of Motor proteins found in Eukaryotic tissues. Kinesins are a class of Motor proteins found in Eukaryotic cells Dynein is a Motor protein (also called molecular motor or motor molecule in cells which converts the chemical Energy contained in ATP into the These proteins are crucial for cellular motility of single celled organisms and the sperm of many sexually reproducing multicellular organisms. Motility is a biological term which refers to the ability to move spontaneously and actively consuming energy in the process A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known They also generate the forces exerted by contracting muscles. Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the
Methods of study
As some of the most commonly studied biological molecules, the activities and structures of proteins are examined both in vitro and in vivo. Protein methods are the techniques used to study Proteins List of Protein Methods There are genetic methods for studying proteins methods for detecting proteins In vitro ( Latin: within the glass refers to the technique of performing a given experiment in a controlled environment outside of a living Organism In vivo ( Latin: within the living means that which takes place inside an organism. In vitro studies of purified proteins in controlled environments are useful for learning how a protein carries out its function: for example, enzyme kinetics studies explore the chemical mechanism of an enzyme's catalytic activity and its relative affinity for various possible substrate molecules. Enzyme kinetics is the study of the Chemical reactions that are catalysed by Enzymes, with a focus on their Reaction rates The study of Chemistry, a reaction mechanism is the step by step Sequence of Elementary reactions by which overall Chemical change occurs. By contrast, in vivo experiments on proteins' activities within cells or even within whole organisms can provide complementary information about where a protein functions and how it is regulated.
Protein purification
In order to perform in vitro analysis, a protein must be purified away from other cellular components. Protein purification is a series of processes intended to isolate a single type of Protein from a complex mixture In vitro ( Latin: within the glass refers to the technique of performing a given experiment in a controlled environment outside of a living Organism This process usually begins with cell lysis, in which a cell's membrane is disrupted and its internal contents released into a solution known as a crude lysate. Cytolysis, or osmotic lysis, occurs when a cell bursts due to an osmotic imbalance that has caused excess water to move into the cell A crude lysate is the solution produced when cells are destroyed by disrupting their Cell membranes often with detergent or other chaotropic agent in a process known The resulting mixture can be purified using ultracentrifugation, which fractionates the various cellular components into fractions containing soluble proteins; membrane lipids and proteins; cellular organelles, and nucleic acids. Differential centrifugation is a common procedure in Microbiology and cytology used to separate certain Organelles from whole cells for further Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information Precipitation by a method known as salting out can concentrate the proteins from this lysate. Precipitation is the formation of a Solid in a Solution during a Chemical reaction. Salting out is a method of separating Proteins based on the principle that proteins are less Soluble at high Salt concentrations Various types of chromatography are then used to isolate the protein or proteins of interest based on properties such as molecular weight, net charge and binding affinity. Chromatography (from Greek χρώμα chroma, color and γραφειν"graphein" to write is the collective term for a family of Laboratory The level of purification can be monitored using various types of gel electrophoresis if the desired protein's molecular weight and isoelectric point are known, by spectroscopy if the protein has distinguishable spectroscopic features, or by enzyme assays if the protein has enzymatic activity. The isoelectric point (pI is the PH at which a particular Molecule or surface carries no net electrical charge. Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ Enzyme assays are Laboratory methods for measuring enzymatic activity Additionally, proteins can be isolated according their charge[18] using electrofocusing. Isoelectric focusing (IEF, also known as electrofocusing, is a technique for separating different Molecules by their Electric charge differences
For natural proteins, a series of purification steps may be necessary to obtain protein sufficiently pure for laboratory applications. To simplify this process, genetic engineering is often used to add chemical features to proteins that make them easier to purify without affecting their structure or activity. Genetic engineering, Recombinant DNA technology, genetic modification/manipulation (GM and gene splicing are terms that apply to the direct Here, a "tag" consisting of a specific amino acid sequence, often a series of histidine residues (a "His-tag"), is attached to one terminus of the protein. Histidine (abbreviated as His or H) is one of the 20 standard Amino acids present in Proteins In the Nutritional sense in A polyhistidine-tag is an Amino acid motif in Proteins that consists of at least six Histidine ( His) residues often at the N- or C-terminus As a result, when the lysate is passed over a chromatography column containing nickel, the histidine residues ligate the nickel and attach to the column while the untagged components of the lysate pass unimpeded. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28
Cellular localization
The study of proteins in vivo is often concerned with the synthesis and localization of the protein within the cell. Although many intracellular proteins are synthesized in the cytoplasm and membrane-bound or secreted proteins in the endoplasmic reticulum, the specifics of how proteins are targeted to specific organelles or cellular structures is often unclear. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle This article deals with protein targeting in Eukaryotes except where noted A useful technique for assessing cellular localization uses genetic engineering to express in a cell a fusion protein or chimera consisting of the natural protein of interest linked to a "reporter" such as green fluorescent protein (GFP). Fusion proteins, also known as chimeric proteins, are proteins created through the joining of two or more Genes which originally coded for separate proteins Fusion proteins, also known as chimeric proteins, are proteins created through the joining of two or more Genes which originally coded for separate proteins In Molecular biology, a reporter gene (often simply reporter) is a Gene that researchers attach to another gene of interest in Cell culture The green fluorescent protein ( GFP) is composed of 238 Amino acids (26 The fused protein's position within the cell can be cleanly and efficiently visualized using microscopy, as shown in the figure opposite. Microscopy is the technical field of using microscopes to view samples or objects In these cases, additional fluorescent chimeric proteins are generally required to prove the inferred localization.
Other methods for elucidating the cellular location of proteins requires the use of known compartmental markers for regions such as the ER, the Golgi, lysosomes/vacuoles, mitochondria, chloroplasts, plasma membrane, etc. With the use of fluorescently-tagged versions of these markers or of antibodies to known markers, it becomes much simpler to identify the localization of a protein of interest. For example, indirect immunofluorescence will allow for fluorescence colocalization and demonstration of location. Fluorescent dyes are used to label cellular compartments for a similar purpose.
Other possibilities exist, as well. For example, immunohistochemistry usually utilizes an antibody to one or more proteins of interest that are conjugated to enzymes yielding either luminescent or chromogenic signals that can be compared between samples, allowing for localization information. Immunohistochemistry or IHC refers to the process of localizing proteins in cells of a tissue section exploiting the principle of antibodies binding specifically
Another applicable technique is cofractionation in sucrose (or other material) gradients using isopycnic centrifugation. Isopycnic centrifugation or equilibrium centrifugation is a process used to isolate nucleic acids such as DNA. While this technique does not prove colocalization of a compartment of known density and the protein of interest, it does increase the likelihood, and is more amenable to large-scale studies.
Finally, the gold-standard method of cellular localization is immunoelectron microscopy. This technique also uses an antibody to the protein of interest, along with classical electron microscopy techniques. The sample is prepared for normal electron microscopic examination, and then treated with an antibody to the protein of interest that is conjugated to an extremely electro-dense material, usually gold. This allows for the localization of both ultrastructural details as well as the protein of interest.
Through another genetic engineering application known as site-directed mutagenesis, researchers can alter the protein sequence and hence its structure, cellular localization, and susceptibility to regulation, which can be followed in vivo by GFP tagging or in vitro by enzyme kinetics and binding studies. Site-directed Mutagenesis is a Molecular biology technique in which a Mutation is created at a defined site in a DNA molecule usually a circular Enzyme kinetics is the study of the Chemical reactions that are catalysed by Enzymes, with a focus on their Reaction rates The study of
Proteomics and bioinformatics
The total complement of proteins present at a time in a cell or cell type is known as its proteome, and the study of such large-scale data sets defines the field of proteomics, named by analogy to the related field of genomics. Proteomics is the large-scale study of Proteins particularly their structures and functions. Bioinformatics is the application of information technology to the field of molecular biology The proteome is the entire complement of Proteins expressed by a genome cell tissue or organism Proteomics is the large-scale study of Proteins particularly their structures and functions. Genomics is the study of an organism's entire Genome. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale Genetic Key experimental techniques in proteomics include 2D electrophoresis, which allows the separation of a large number of proteins, mass spectrometry, which allows rapid high-throughput identification of proteins and sequencing of peptides (most often after in-gel digestion), protein microarrays, which allow the detection of the relative levels of a large number of proteins present in a cell, and two-hybrid screening, which allows the systematic exploration of protein-protein interactions. Two-dimensional gel electrophoresis, abbreviated as 2-DE or 2-D electrophoresis, is a form of Gel electrophoresis commonly used to analyze proteins Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the Mass-to-charge ratio of charged particles The in-gel digestion is part of the sample preparation for the mass spectrometric identification of Proteins in course of proteomic analysis. A protein microarray, sometimes referred to as a protein binding microarray, is a piece of glass on which different molecules of Protein have been affixed at separate Two-hybrid screening (also known as yeast two hybrid system or Y2H) is a Molecular biology technique used to discover Protein-protein interactions Protein-protein interactions refer to the association of Protein molecules and the study of these associations from the perspective of Biochemistry, Signal transduction The total complement of biologically possible such interactions is known as the interactome. Interactome is defined as the whole set of molecular interactions in cells A systematic attempt to determine the structures of proteins representing every possible fold is known as structural genomics. Structural genomics consists in the determination of the three dimensional structure of all Proteins of a given organism by experimental methods such as X-ray crystallography
The large amount of genomic and proteomic data available for a variety of organisms, including the human genome, allows researchers to efficiently identify homologous proteins in distantly related organisms by sequence alignment. The human genome is the Genome of Homo sapiens, which is stored on 23 chromosome pairs In Evolutionary biology, homology has come to mean any similarity between characters that is due to their shared ancestry. In Bioinformatics, a sequence alignment is a way of arranging the Primary sequences of DNA, RNA, or Protein to identify regions of Sequence profiling tools can perform more specific sequence manipulations such as restriction enzyme maps, open reading frame analyses for nucleotide sequences, and secondary structure prediction. A sequence profiling tool in Bioinformatics is a type of Software that presents information related to a genetic sequence gene name or keyword input A restriction enzyme (or restriction Endonuclease) is an Enzyme that cuts double-stranded DNA at specific recognition Nucleotide An open reading frame ( ORF) is a portion of an organism's Genome which contains a sequence of bases that could potentially encode a Protein Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group In Biochemistry and Structural biology, secondary structure is the general three-dimensional form of local segments of Biopolymers such as From this data phylogenetic trees can be constructed and evolutionary hypotheses developed using special software like ClustalW regarding the ancestry of modern organisms and the genes they express. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other eVolution is the third Album by eLDee, it was due to be released in 2008 Clustal is a widely used Multiple sequence alignment Computer program. The field of bioinformatics seeks to assemble, annotate, and analyze genomic and proteomic data, applying computational techniques to biological problems such as gene finding and cladistics. Bioinformatics is the application of information technology to the field of molecular biology Computer science (or computing science) is the study and the Science of the theoretical foundations of Information and Computation and their Gene finding typically refers to the area of Computational biology that is concerned with algorithmically identifying stretches of sequence usually genomic DNA Cladistics is the hierarchical classification of Species based on evolutionary ancestry
Structure prediction and simulation
Complementary to the field of structural genomics, protein structure prediction seeks to develop efficient ways to provide plausible models for proteins whose structures have not yet been determined experimentally. Protein structure prediction is one of the most important goals pursued by Bioinformatics and Theoretical chemistry. The most successful type of structure prediction, known as homology modeling, relies on the existence of a "template" structure with sequence similarity to the protein being modeled; structural genomics' goal is to provide sufficient representation in solved structures to model most of those that remain. In Protein structure prediction, homology modeling, also known as comparative modeling, is a class of methods for constructing an atomic-resolution model of a Although producing accurate models remains a challenge when only distantly related template structures are available, it has been suggested that sequence alignment is the bottleneck in this process, as quite accurate models can be produced if a "perfect" sequence alignment is known. [19] Many structure prediction methods have served to inform the emerging field of protein engineering, in which novel protein folds have already been designed. Protein engineering is the application of Science, Mathematics, and Economics to the process of developing useful or valuable Proteins It is [20] A more complex computational problem is the prediction of intermolecular interactions, such as in molecular docking and protein-protein interaction prediction. In the field of Molecular modeling, docking is a method which predicts the preferred orientation of one molecule to a second when bound to each other to form Protein-protein interaction prediction is a field combining Bioinformatics and Structural biology in an attempt to identify and catalog interactions between pairs
The processes of protein folding and binding can be simulated using techniques derived from molecular dynamics, which increasingly take advantage of distributed computing as in the Folding@Home project. Molecular dynamics ( MD) is a form of Computer simulation in which atoms and molecules are allowed to interact for a period of time by approximations of Distributed computing deals with Hardware and Software Systems containing more than one processing element or Storage element concurrent Folding@home (sometimes abbreviated as FAH or F@h) is a Distributed computing (DC project designed to perform computationally intensive simulations The folding of small alpha-helical protein domains such as the villin headpiece[21] and the HIV accessory protein[22] have been successfully simulated in silico, and hybrid methods that combine standard molecular dynamics with quantum mechanics calculations have allowed exploration of the electronic states of rhodopsins. Villin is a 925 kDa tissue-specific Actin-binding protein associated with the actin core bundle of the Brush border. Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Rhodopsin, also known as visual purple, is a Pigment of the Retina that is responsible for both the formation of the Photoreceptor cells and the [23]
Nutrition
- Further information: Protein in nutrition
Most microorganisms and plants can biosynthesize all 20 standard amino acids, while animals, (including humans) must obtain some of the amino acids from the diet. Proteins are broken down in the Stomach during Digestion by Enzymes known as Proteases into smaller Polypeptides to provide A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this This article is primarily about the human diet For a discussion of animal diets see List of feeding behaviours. [14] Key enzymes in the biosynthetic pathways that synthesize certain amino acids - such as aspartokinase, which catalyzes the first step in the synthesis of lysine, methionine, and threonine from aspartate - are not present in animals. Aspartokinase (or Aspartate kinase is an Enzyme that catalyzes the Phosphorylation of the Amino acid Aspartate. Lysine (abbreviated as Lys or K) is an α- Amino acid with the Chemical formula HO2CCH(NH2(CH24NH2 Methionine ( abbreviated as Met or M) is an α- Amino acid with the Chemical formula HO2CCH(NH2CH2CH2SCH3 Threonine (abbreviated as Thr or T) is an α- Amino acid with the Chemical formula HO2CCH(NH2CH(OHCH3 Aspartic acid (abbreviated as Asp or D; Asx or B represent either aspartic acid or Asparagine) is an α- Amino acid The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids. An essential amino acid or indispensable amino acid is an Amino acid that cannot be synthesized de novo by the organism (usually referring to If amino acids are present in the environment, microorganisms can conserve energy by taking up the amino acids from their surroundings and downregulating their biosynthetic pathways.
In animals, amino acids are obtained through the consumption of foods containing protein. Ingested proteins are broken down through digestion, which typically involves denaturation of the protein through exposure to acid and hydrolysis by enzymes called proteases. Digestion is the breaking down of chemicals in the body into a form that can be absorbed Denaturation is a process in which Proteins or Nucleic acids lose their structure (tertiary structure by application of some external stress or compound for In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Hydrolysis is a Chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions which may go on to participate in further reactions A protease is any Enzyme that conducts Proteolysis, that is begins protein Catabolism by Hydrolysis of the Peptide bonds that link Some ingested amino acids are used for protein biosynthesis, while others are converted to glucose through gluconeogenesis, or fed into the citric acid cycle. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Gluconeogenesis (abreviated GNG) is a Metabolic pathway that results in the generation of Glucose from non- Carbohydrate carbon substrates such The citric acid cycle, also known as the tricarboxylic acid cycle ( TCA cycle) or the Krebs cycle, (or rarely the Szent-Györgyi–Krebs cycle This use of protein as a fuel is particularly important under starvation conditions as it allows the body's own proteins to be used to support life, particularly those found in muscle. Starvation (also called inanition) is a severe reduction in Vitamin, Nutrient, and Energy intake and is the most extreme form of Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the [24] Amino acids are also an important dietary source of nitrogen. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14
History
- Further information: History of molecular biology
Proteins were recognized as a distinct class of biological molecules in the eighteenth century by Antoine Fourcroy and others, distinguished by the molecules' ability to coagulate or flocculate under treatments with heat or acid. The history of molecular biology begins in the 1930s with the convergence of various previously distinct biological disciplines Biochemistry, Genetics, Microbiology Antoine François comte de Fourcroy ( June 15, 1755 &ndash December 16, 1809) was a French Chemist and a contemporary Coagulation is a complex process by which Blood forms Clots It is an important part of Hemostasis (the cessation of blood loss from a damaged vessel whereby Flocculation is a process where a Solute comes out of Solution in the form of floc or flakes Noted examples at the time included albumin from egg whites, blood, serum albumin, fibrin, and wheat gluten. Albumen redirects here For other uses see Albumen (disambiguation. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products Serum albumin, often referred to simply as albumin, is the most abundant Plasma protein in humans and other Mammals Albumin is essential for maintaining Fibrin (also called Factor Ia) is a Protein involved in the clotting of blood Gluten is a composite of the proteins Gliadin and Glutenin. These exist conjoined with Starch, in the Endosperms of some Dutch chemist Gerhardus Johannes Mulder carried out elemental analysis of common proteins and found that nearly all proteins had the same empirical formula. Gerardus Johannes Mulder ( Dec 27 1802, Utrecht - Apr 18 1880, Bennekom) was a Dutch Organic chemist Elemental analysis is a process where a sample of some material (e Use in chemistry In Chemistry, the empirical formula of a Chemical compound is a simple expression of the relative number of each type of Atom The term "protein" to describe these molecules was proposed in 1838 by Mulder's associate Jöns Jakob Berzelius. Friherre Jöns Jacob Berzelius (20 August 1779 &ndash 7 August 1848 was a Swedish chemist Mulder went on to identify the products of protein degradation such as the amino acid leucine for which he found a (nearly correct) molecular weight of 131 Da. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Leucine (abbreviated as Leu or L) is an α- Amino acid with the Chemical formula HO2CCH(NH2CH2CH(CH32 The unified atomic mass unit ( u) or Dalton ( Da) or sometimes universal mass unit, is an unit of Mass used to express
The difficulty in purifying proteins in large quantities made them very difficult for early protein biochemists to study. Hence, early studies focused on proteins that could be purified in large quantities, e. g. , those of blood, egg white, various toxins, and digestive/metabolic enzymes obtained from slaughterhouses. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products Albumen redirects here For other uses see Albumen (disambiguation. A toxin ( Greek:, toxikon, lit (poison for use on arrows is a Poisonous substance produced by living cells or organisms that is active at very low A slaughterhouse, also called an abattoir (from the French verb abattre, "to strike down" or freezing works ( New Zealand In the late 1950s, the Armour Hot Dog Co. purified 1 kg (= one million milligrams) of pure bovine pancreatic ribonuclease A and made it freely available to scientists around the world. Armour and Company was an American Slaughterhouse and meatpacking company founded in Chicago Illinois, in 1867 by the Armour brothers led by Ribonuclease A (RNase A is an Endonuclease that cleaves single-stranded RNA.
Linus Pauling is credited with the successful prediction of regular protein secondary structures based on hydrogen bonding, an idea first put forth by William Astbury in 1933. Linus Carl Pauling (February 28 1901 – August 19 1994 was an American Scientist, Peace activist, Author and educator. In Biochemistry and Structural biology, secondary structure is the general three-dimensional form of local segments of Biopolymers such as A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen William Thomas Astbury FRS (Bill Astbury 25 February, 1898 &mdash 4 June, 1961) was an English Physicist and Later work by Walter Kauzmann on denaturation, based partly on previous studies by Kaj Linderstrøm-Lang, contributed an understanding of protein folding and structure mediated by hydrophobic interactions. Walter Kauzmann is an American Chemist and professor emeritus of Princeton University. Denaturation is a process in which Proteins or Nucleic acids lose their structure (tertiary structure by application of some external stress or compound for Kaj Ulrik Linderstrøm-Lang ( November 29, 1896 - May 25, 1959) was a Danish protein scientist who was the director of the Carlsberg Laboratory Protein folding is the physical process by which a Polypeptide folds into its characteristic and functional three-dimensional structure. The hydrophobic effect is the property that non-polar molecules tend to form intermolecular aggregates in an aqueous medium and analogous intramolecular interactions In 1949 Fred Sanger correctly determined the amino acid sequence of insulin, thus conclusively demonstrating that proteins consisted of linear polymers of amino acids rather than branched chains, colloids, or cyclols. Frederick Sanger, OM, CH, CBE, FRS (born 13 August 1918) is an English biochemist and twice Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance A colloid is a type of mechanical Mixture where one substance is dispersed evenly throughout another The cyclol hypothesis is the first structural model of a folded, globular Protein. The first atomic-resolution structures of proteins were solved by X-ray crystallography in the 1960s and by NMR in the 1980s. X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters Protein nuclear magnetic resonance spectroscopy (usually abbreviated protein NMR) is a field of Structural biology in which NMR spectroscopy is used As of 2006, the Protein Data Bank has nearly 40,000 atomic-resolution structures of proteins. The Protein Data Bank ( PDB) is a repository for 3-D structural data of Proteins and Nucleic acids These data typically obtained by X-ray crystallography In more recent times, cryo-electron microscopy of large macromolecular assemblies and computational protein structure prediction of small protein domains are two methods approaching atomic resolution. Electron cryomicroscopy ( cryo-EM or sometimes cryo-electron microscopy) is a form of Electron microscopy (EM where the sample is studied at Cryogenic Protein structure prediction is one of the most important goals pursued by Bioinformatics and Theoretical chemistry. A protein domain is a part of protein sequence and structure that can evolve, function and exist independently of the rest of the protein chain
See also
References
- ^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this An essential amino acid or indispensable amino acid is an Amino acid that cannot be synthesized de novo by the organism (usually referring to Protein design is the design of new Protein molecules from scratch or the deliberate design of a new molecule by making calculated variations on a known structure The isoelectric point (pI is the PH at which a particular Molecule or surface carries no net electrical charge. An intein is a segment of a Protein that is able to excise itself and rejoin the remaining portions (the exteins with a Peptide bond. Since human recombinants have replaced the animal version in human therapeutics the prefix of "rh" for "human recombinant" appears less and less in the literature Human A list of Proteins (and Protein complexes. This list aims to organize information on the protein universe A prion (ˈpriːɒn is thought to be an infectious agent that according to current scientific consensus is comprised entirely of a propagated, mis-folded Edible protein per unit area of land is a measure of agricultural Productivity. Expression cloning is a technique in DNA cloning that uses Expression vectors to generate a library of clones with each clone expressing one protein Proteopathy (Proteo- protein -pathy disease proteopathies pl. Short list of molecular mechanics programs Min - Optimization MD - Molecular Dynamics MC - Monte Carlo QM - Quantum mechanics Proteopedia is a collaborative Wiki 3D encyclopedia of Proteins and other Molecules Proteopedia contains a page for every entry in the Protein Data Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1.
- ^ Sumner, JB (1926). "The Isolation and Crystallization of the Enzyme Urease. Preliminary Paper". J Biol Chem 69: 435-41.
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External links
- Proteins (the journal), also called "Proteins: Structure, Function, and Bioinformatics" and previously "Proteins: Structure, Function, and Genetics" (1986–1995).
Databases and projects
- Bioinformatic Harvester A Meta search engine (29 databases) for gene and protein information.
- The Protein Databank (see also PDB Molecule of the Month, presenting short accounts on selected proteins from the PDB)
- Proteopedia - Life in 3D: rotatable, zoomable 3D model with wiki annotations for every known protein molecular structure.
- UniProt the Universal Protein Resource
- Human Protein Atlas
- iHOP - Information Hyperlinked over Proteins
- MIT's Laboratory for Protein Molecular Self-Assembly
- NCBI Entrez Protein database
- NCBI Protein Structure database
- Human Protein Reference Database
- Human Proteinpedia
- Folding@Home (Stanford University)
Tutorials and educational websites
- Proteins: Biogenesis to Degradation - The Virtual Library of Biochemistry and Cell Biology
- Amino acid metabolism
- Data Book of Molecules - Home Page for Learning Environmental Chemistry
Dictionary
protein
-noun
- (nutrition) One of three major classes of food or source of food energy (4 kcal/gram) abundant in animal-derived foods (ie: meat) and some vegetables, such as legumes. see carbohydrate and fat for the other two major classes
- (biochemistry) A large, complex molecule composed of one or more long chains of amino acids, in which each chain is held together by peptide bonds.
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