Crystal structure of the UvrB dimer: insights into the nature and functioning of the UvrAB damage engagement and UvrB–DNA complexes

UvrB has a central role in the highly conserved UvrABC pathway functioning not only as a damage recognition element but also as an essential component of the lesion tracking machinery. While it has been recently confirmed that the tracking assembly comprises a UvrA(2)B(2) heterotetramer, the configurations of the damage engagement and UvrB–DNA handover complexes remain obscure. Here, we present the first crystal structure of a UvrB dimer whose biological significance has been verified using both chemical cross-linking and electron paramagnetic resonance spectroscopy. We demonstrate that this dimeric species stably associates with UvrA and forms a UvrA(2)B(2)–DNA complex. Our studies also illustrate how signals are transduced between the ATP and DNA binding sites to generate the helicase activity pivotal to handover and formation of the UvrB(2)–DNA complex, providing key insights into the configurations of these important repair intermediates.