Crystal structure of UvrB, a DNA helicase adapted for nucleotide excision repair

Nucleotide excision repair (NER) is a highly conserved DNA repair mechanism . NER systems recognize the damaged DNA strand, cleave it on both sides of the lesion, remove and newly synthesize the fragment. UvrB is a central com ponent of the bacterial NER system participating in damage recognition, str and excision and repair synthesis, We have solved the crystal structure of UvrB in the apo and the ATP-bound forms. UvrB contains two domains related in structure to helicases, and two additional domains unique to repair prot eins. The structure contains all elements of an intact helicase, and is evi dence that UvrB utilizes ATP hydrolysis to move along the DNA to probe for damage. The location of conserved residues and structural comparisons allow us to predict the path of the DNA and suggest that the tight preincision c omplex of UvrB and the damaged DNA is formed by insertion of a flexible bet a-hairpin between the two DNA strands.