X-ray structure of a DNA decamer containing 7,8-dihydro-8-oxoguanine

Abstract

We have determined the x-ray structure of a DNA fragment containing 7,8- dihydro-8-oxoguanine (G(O)). The structure of the duplex form of d(CCAG(O)CGCTGG) has been determined to 1.6-Å resolution. The results demonstrate that Go forms Watson-Crick base pairs with the opposite C and that Go is in the anti conformation. Structural perturbations induced by C · G(O)(anti) base pairs are subtle. The structure allows us to identify probable elements by which the DNA repair protein MutM recognizes its substrates. Hydrogen bond donors/acceptors within the major groove are the most likely element. In that groove, the pattern of hydrogen-bond donors/acceptors of C · G(O)(anti) is unique. Additional structural analysis indicates that conversion of G to G(O) would not significantly influence the glycosidic torsion preference of the nucleoside. There is no steric interaction of the 8-oxygen of G(O) with the phospho-deoxyribose backbone.