An argonaute protein from Pyrococcus furiosus. Pyrococcus furiosus is an extremophilic species of Archaea. It is notable for having an optimum growth temperature of 100°C (a temperature which would

Left: A full-length argonaute protein from the archaea species Pyrococcus furiosus. Pyrococcus furiosus is an extremophilic species of Archaea. It is notable for having an optimum growth temperature of 100°C (a temperature which would Right: The PIWI domain of an argonaute protein in complex with double-stranded RNA. The piwi (sometimes also PIWI; originally P-element induced wimpy testis in Drosophila) class of Genes was originally identified as encoding Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units The base-stacking interaction between the 5' base on the guide strand and a conserved tyrosine residue (light blue) is highlighted; the stabilizing divalent cation (magnesium) is shown as a gray sphere. Tyrosine (abbreviated as Tyr or Y) or 4-hydroxyphenylalanine, is one of the 20 Amino acids that are used by cells to synthesize Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24

Argonaute proteins are the catalytic components of the RNA-induced silencing complex (RISC), the protein complex responsible for the gene silencing phenomenon known as RNA interference (RNAi). Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst RNA-induced silencing complex, or RISC, is a multi-protein SiRNA complex which cleaves (incoming viral DsRNA and binds short Antisense RNA strands A protein complex is a group of two or more Proteins Protein complexes are a form of Quaternary structure. Gene silencing is a general term describing Epigenetic processes of Gene regulation. RNA interference ( RNAi) is a mechanism that inhibits Gene expression at the stage of translation or by hindering the transcription of specific Argonaute proteins bind small interfering RNA (siRNA) fragments and have endonuclease activity directed against messenger RNA (mRNA) strands that are complementary to their bound siRNA fragment. Small interfering RNA ( siRNA) sometimes known as short interfering RNA or silencing RNA, is a class of 20-25 Nucleotide -long double-stranded Endonucleases are Enzymes that cleave the Phosphodiester bond within a Polynucleotide chain in contrast to Exonucleases which cleave Phosphodiester Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called The proteins are also partially responsible for selection of the guide strand and destruction of the passenger strand of the siRNA substrate. ^[1]

The structural basis for binding of RNA to the argonaute protein has been examined by X-ray crystallography of the binding domain of an RNA-bound argonaute protein. 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 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 The phosphorylated 5' end of the RNA strand enters a conserved basic surface pocket and makes contacts through a divalent cation such as magnesium and by aromatic stacking between the 5' nucleotide in the siRNA and a conserved tyrosine residue. Phosphorylation is the addition of a Phosphate (PO4 group to a Protein molecule or a small molecule Conservation refers to a high degree of similarity in orthologous DNA sequences protein sequences, or Protein structures amongst various In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and In Biochemistry, a binding site is a region on a Protein, DNA, or RNA to which specific other Molecules and Ions &mdash In chemistry divalent Anions are atoms or radicals with 2 additional Electrons when compared to their elemental state (that is with 2 more electrons than Protons An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Stacking in Supramolecular chemistry refers to a stacked arrangement of Aromatic Molecules which interact through aromatic interactions Tyrosine (abbreviated as Tyr or Y) or 4-hydroxyphenylalanine, is one of the 20 Amino acids that are used by cells to synthesize This site is thought to form a nucleation site for the binding of the siRNA to its mRNA target. ^[2]

In eukaryotes, argonaute proteins have been identified in high concentrations in regions of the cell's cytoplasm known as cytoplasmic bodies, to which mRNA decay is also localized. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. ^[3] The argonaute protein family is shared among not only eukaryotes, but also archaea and certain bacteria such as Aquifex aeolicus. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Aquifex aeolicus is a rod-shaped Bacterium with a length of 2 to 6 micrometers and a diameter of around half a micrometer Based on comparative genomics studies, the argonaute family is thought to have evolved from components of the translation initiation system. Comparative genomics is the study of the relationship of Genome structure and function across different biological Species or strains. eVolution is the third Album by eLDee, it was due to be released in 2008 Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression) ^[4]

Argonaute proteins are named after the argonaute (AGO) phenotype of Arabidopsis mutants, which itself was named after its resemblance to argonauts. Arabidopsis ( A-ra-bi-dóp-sis, rockcress) is a genus in the family Brassicaceae. The argonauts ( Genus Argonauta, the only extant genus in the Argonautidae family are a group of Pelagic Octopuses ^[5]

References

1. ^ Rand TA, Petersen S, Du F, Wang X. (2005). Argonaute2 cleaves the anti-guide strand of siRNA during RISC activation. Cell 123(4):621-9.
2. ^ Ma J, Yuan Y, Meister G, Pei Y, Tuschl T, Patel D (2005). "Structural basis for 5'-end-specific recognition of guide RNA by the A. fulgidus Piwi protein". Nature 434 (7033): 666–70. doi:10.1038/nature03514. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15800629.  
3. ^ Sen GL, Blau HM. (2005). Argonaute 2/RISC resides in sites of mammalian mRNA decay known as cytoplasmic bodies. Nat Cell Biol 7(6):633-6.
4. ^ Anantharaman V, Koonin E, Aravind L (2002). "Comparative genomics and evolution of proteins involved in RNA metabolism". Nucleic Acids Res 30 (7): 1427–64. doi:10.1093/nar/30.7.1427. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 11917006.  
5. ^ Bohmert et al. (1998). AGO1 defines a novel locus of Arabidopsis controlling leaf development. The EMBO Journal 17, 170–180, PubMed