Small-angle X-ray scattering reveals architecture and A₂B₂ stoichiometry of the UvrA-UvrB DNA damage sensor.

The UvrA-UvrB (AB) protein complex operates in the bacterial nucleotide excision repair pathway as the main sensor of DNA damage. Crystallographic analysis of the AB complex revealed a linear UvrB-UvrA-UvrA-UvrB arrangement of subunits with an internal two-fold axis that became incorporated into the crystal. Here, we have used small-angle X-ray scattering (SAXS) to show close correspondence between the crystal structure and the entity in solution. This result confirms the number and disposition of subunits in the crystallographic model and rules out other possible arrangements suggested by packing in the crystal. The current SAXS analysis failed to detect significant changes to the structure as a function of nucleotide.