UvrABC endonuclease is a multienzyme complex in

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

involved in

DNA repair DNA repair is a collection of processes by which a cell (biology), cell identifies and corrects damage to the DNA molecules that encode its genome. A weakened capacity for DNA repair is a risk factor for the development of cancer. DNA is cons ...

by nucleotide excision repair, and it is, therefore, sometimes called an excinuclease. This UvrABC repair process, sometimes called the short-patch process, involves the removal of twelve nucleotides where a DNA damage has occurred followed by a DNA polymerase, replacing these aberrant nucleotides with the correct nucleotides and completing the

. The subunits for this enzyme are encoded in the ''uvrA'', ''uvrB'', and ''uvrC'' genes. This enzyme complex is able to repair many different types of damage, including cyclobutyl dimer formation.

Mechanism

# Two UvrA proteins form a

homodimer In biochemistry, a protein dimer is a macromolecular complex or protein multimer, multimer formed by two protein monomers, or single proteins, which are usually Non-covalent interaction, non-covalently bound. Many macromolecules, such as proteins ...

(UvrA₂) and they both have ATPase/GTPase activity. # Two UvrB proteins form a homodimer (UvrB₂). # The UvrA homodimer binds with a UvrB homodimer (UvrA₂B₂) and forms a complex that is able to detect DNA damage. 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 In molecular biology, the term double helix refers to the structure formed by double-stranded molecules of nucleic acids such as DNA. The double helical structure of a nucleic acid complex arises as a consequence of its secondary structure, a ...

. # Upon binding of the UvrA₂B₂ complex to a putative damaged site, the DNA wraps around UvrB # The UvrA dimer leaves and a UvrC protein comes in and binds to the UvrB and, hence, forms a new UvrBC complex. # UvrC is responsible for cleaving the nucleotides either side of the DNA damage. It cleaves a

phosphodiester bond In chemistry, a phosphodiester bond occurs when exactly two of the hydroxyl groups () in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. The "bond" involves this linkage . Discussion of phosphodiesters is d ...

four nucleotides downstream of the DNA damage, and cleaves a

eight nucleotides upstream of the DNA damage and creates a twelve nucleotide excised segment. # DNA helicase II (sometimes called UvrD) then comes in and removes the excised segment by removing the base pairing. The UvrB still remains in place even though UvrC has disassociated at this stage, as UvrB may be involved to prevent the reannealing of the excised DNA. #

DNA polymerase I DNA polymerase I (or Pol I) is an enzyme that participates in the process of prokaryotic DNA replication. Discovered by Arthur Kornberg in 1956, it was the first known DNA polymerase (and the first known of any kind of polymerase). It was init ...

comes in and fills in the correct nucleotides sequence, kicking off UvrB in the process, and the last phosphodiester bond is completed by DNA ligase. Although most of the studies on the UvrABC endonuclease were carried out with the gram negative bacterium ''

Escherichia coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Escherichia'' that is commonly fo ...

'', similar studies have also been reported for the archaeal bacterium ''

Halobacterium ''Halobacterium'' (common abbreviation ''Hbt.'') is a genus in the family Halobacteriaceae. The genus ''Halobacterium'' ("salt" or "ocean bacterium") consists of several species of Archaea with an aerobic metabolism which requires an environm ...

'' sp. NRC-1.Crowley DJ, Boubriak I, Berquist BR, Clark M, Richard E, Sullivan L, DasSarma S, McCready S. The uvrA, uvrB and uvrC genes are required for repair of ultraviolet light induced DNA photoproducts in Halobacterium sp. NRC-1. Saline Syst. 2006 Sep 13;2:11. doi: 10.1186/1746-1448-2-11. PMID 16970815; PMCID: PMC1590041. Investigation of DNA repair in this archaeal ''

halobacterium ''Halobacterium'' (common abbreviation ''Hbt.'') is a genus in the family Halobacteriaceae. The genus ''Halobacterium'' ("salt" or "ocean bacterium") consists of several species of Archaea with an aerobic metabolism which requires an environm ...

'' is important for understanding the diversity and evolution of DNA repair systems generally. In ''Halobacterium'' sp. NRC-1, homologs of the ''E. coli'' bacterial nucleotide excision repair genes ''uvrA'', ''uvrB'' and ''uvrC'' are required tor the removal of UV damages (in the absence of photoreactivating light).

References

External links

* EC 3.1.21 {{Genetics-stub

Mechanism

See also

References

External links