UvrABC endonuclease is a multienzyme complex in E.coli bacteria involved in DNA repair mechanism by nucleotide excision repair and it is therefore sometimes called an excinuclease. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. Nucleotide excision repair is a DNA repair mechanism DNA constantly requires repair due to damage that can occur to bases from a vast variety of sources including Excision endonuclease also known as "excinuclease" is the Nuclease (enzyme which performs the excision (cut for Nucleotide exchange in DNA repair This UvrABC repair process, sometimes called the short patch process, involves the removal of 12 nucleotides where a genetic mutation has occurred followed by a DNA polymerase replacing these aberrant nucleotides with the correct nucleotides and completing the DNA repair. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. This enzyme complex is able to repair many different types of damage, including cyclobutyl dimer formation. Pyrimidine dimers (cyclobutane dimer are pairs of Thymine and Cytosine bases in DNA that arise via Photochemical reactions Ultraviolet light
Mechanism:
- Two UvrA proteins form a dimer and they both have ATPase/GTPase activity.
- The UvrA dimer binds with UvrB and forms a trimer which is able to detect DNA damage. A dimer is a Chemical or Biological entity consisting of two subunits called Monomers which are held together by either Intramolecular forces DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. The UvrA dimer functions as the unit responsible for the detection of DNA damage, probably through a mechanism of detecting distortions in the DNA double helix. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known
- The UvrB part of the trimer attaches to the double helix at the damaged site.
- The UvrA dimer leaves and an UvrC protein comes in and binds to the UvrB monomer and hence froms a new UvrBC dimer. A monomer (from Greek mono "one" and meros "part" is a small Molecule that may become chemically bonded to other
- This dimer is responsible for cleaving the nucleotides either side of the DNA damage. UvrB cleaves a phosphodiester bond 5 nucleotides downstream of the DNA damage, and the UvrC cleaves a phosphodiester bond 8 nucleotides upstream of the DNA damage and created 12 nucleotide excised segment. A phosphodiester bond is a group of strong covalent bonds between the phosphorus atom in a Phosphate group and two other Molecules over two A phosphodiester bond is a group of strong covalent bonds between the phosphorus atom in a Phosphate group and two other Molecules over two
- DNA helicase II (sometimes called UvrD) then comes in and removes the excised segment by removing the base pairing. Helicases are a class of Enzymes vital to all living Organisms They are motor proteins that move directionally along a Nucleic acid phosphodiester backbone The UvrB still remain in place even though UvrC has disassociated at this stage, as UvrB may be involved in the preventing of the reannealing of the excised DNA. Reannealing is the process by which two single strands of DNA combine to form Double-stranded DNA.
- DNA polymerase I comes in and fills in the correct nucleotides sequence and the last phosphodiester bond is completed by DNA ligase. DNA Polymerase I (or Pol I) is an Enzyme that participates in the process of DNA replication in Prokaryotes It is composed of 928 amino acids
See also
External links
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. Endonucleases are Enzymes that cleave the Phosphodiester bond within a Polynucleotide chain in contrast to Exonucleases which cleave Phosphodiester Nucleotide excision repair is a DNA repair mechanism DNA constantly requires repair due to damage that can occur to bases from a vast variety of sources including Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and booksDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic