UvrABC endonuclease is a multienzyme complex inbacteria involved inDNA repair bynucleotide excision repair, and it is, therefore, sometimes called anexcinuclease. This UvrABC repair process, sometimes called the short-patch process, involves the removal of twelve nucleotides where a genetic mutation has occurred followed by a DNA polymerase, replacing these aberrant nucleotides with the correct nucleotides and completing theDNA repair. The subunits for this enzyme are encoded in theuvrA,uvrB, anduvrC genes. This enzyme complex is able to repair many different types of damage, includingcyclobutyl dimer formation.[1]
Two UvrA proteins form ahomodimer (UvrA2) and they both have ATPase/GTPase activity.
Two UvrB proteins form a homodimer (UvrB2).
The UvrA homodimer binds with a UvrB homodimer (UvrA2B2)[2] and forms a complex that is able to detectDNA damage. The UvrA dimer functions as the unit responsible for the detection of DNA damage, probably through a mechanism of detecting distortions in theDNA double helix.
Upon binding of the UvrA2B2 complex to a putative damaged site, the DNA wraps around UvrB[3]
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 forcleaving the nucleotides either side of the DNA damage.[4] It cleaves aphosphodiester bond four nucleotides downstream of the DNA damage, and cleaves aphosphodiester bond 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 thereannealing of the excised DNA.
DNA polymerase I 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.
^Grossman L, Yeung AT (1990). "The UvrABC endonuclease system of Escherichia coli--a view from Baltimore".Mutation Research.236 (2–3):213–221.doi:10.1016/0921-8777(90)90006-q.PMID2144612.
