Proposed lesion recognition mechanism and biochemical studies. (a) The cross-section view of UvrB-dsDNA-ADP·Pi complex in surface representation. Proposed trajectories of undamaged and damaged “bulky” bases are shown in green and red arrows, respectively. Green and blue dashed lines delineate the boundaries of the lesion-selectivity filter and β-hairpin. (b) The cross-section view of the UvrB lesion-selectivity filter.