UvrAUvrBKomplex

UvrAUvrBKomplex, commonly referred to as the UvrA2B2 complex, is a bacterial protein assembly that initiates nucleotide excision repair (NER) of bulky DNA lesions. It is formed by the DNA damage sensor UvrA and the DNA helicase-like protein UvrB. In many bacteria, UvrA functions as a dimer (UvrA2) and together with two UvrB molecules (UvrB2) creates the functional UvrA2B2 complex that searches DNA for distortions caused by UV-induced lesions, chemical adducts, and other damage.

The complex plays a central role in damage recognition. UvrA contains ATP-binding sites and, in concert with UvrB, binds to damaged DNA and stabilizes the lesion for verification. ATP hydrolysis by UvrA and the loading of UvrB at the lesion facilitate damage verification and recruitment of downstream factors. After the lesion is verified, UvrA dissociates, permitting UvrC to bind to the UvrB-DNA complex. UvrC then makes incisions on the damaged strand: typically a 5’ incision about eight nucleotides upstream of the lesion and a 3’ incision about four nucleotides downstream, excising the damaged segment.

Following excision, the UvrD helicase removes the oligonucleotide containing the lesion. The resulting gap is filled by DNA polymerase I, and DNA ligase seals the repair patch, restoring DNA integrity. The UvrA2B2 complex is a key component of the bacterial response to genotoxic stress and is conserved across many bacterial species, though the exact stoichiometry and regulation can vary.

Mutations that impair UvrA or UvrB function lead to increased sensitivity to UV light and higher mutational potential, underscoring the complex’s essential role in maintaining genome stability.