Indentification of RecBCD Auxiliary ATP binding

The RecBCD helicase initiates double-stranded break repair in bacteria by processively unwinding DNA with a rate approaching ~1,600 bp·second, but the mechanism enabling such a fast rate is unknown. By using crosslinking followed by mass spectrometry, we revealed evidence for the existence of auxiliary binding sites in the RecC subunit. This was validated by equilibrium and time-resolved binding experiments, ensemble, and single-molecule unwinding assays. The essentiality and functionality of these sites are further demonstrated by their impact on the survival of E.coli after exposure to damage-inducing radiation.