Abstact

MutM is a bacterial 8-oxoguanine glycosylase responsible for initiating base-excision repair of oxidized guanine residues in DNA. Here we report five different crystal structures of MutM-DNA complexes that represent different steps of the repair reaction cascade catalyzed by the protein and also differ in the identity of the base opposite the lesion (the 'estranged' base). These structures reveal that the MutM active site performs the multiple steps of base-excision and 3' and 5' nicking with minimal rearrangement of the DNA backbone.