6U7T | pdb_00006u7t

Oxidative DNA damage is caused by reactive oxygen species that are generated during aerobic respiration and immune response. The oxidative lesions in DNA caused are repaired by the base excision repair pathway. Hydroxyl radicals rapidly react with guanine C8 producing a steady state level of mutagenic 8-oxoguanines in cells. It also creates 8-oxo-GTP that, like 8-oxoguanines in DNA template, is often mispaired with adenine by replicative polymerases, creating A-T to C-G and G-C to T-A transversion mutations.

DNA glycosylase MutY recognises the mutational intermediate 8-oxoguanine-adenine mispair and excises adenine from the mispair. This creates an abasic site that is then processed by the multi-enzyme base excision repair pathway. The sequence of MutY is conserved from bacteria to humans suggesting its fundamental importance in DNA repair. Mutations of MutY increases transversion frequencies and hence cancer susceptibility in human. MutY belongs to the base excision repair glycosylases superfamily which includes both pure DNA glycosylases and DNA glycosylase/lyases. The most conserved structural element in this family is the Helix-hairpin-Helix (HhH) motif. A revised MutY reaction mechanism was published in 2016, which involves a covalent intermediate and two oxocarbenium ion-like transition states. There is sufficient structural, mutagenesis and biochemical date to support the proposed mechanism described.