X-RAY STRUCTURE OF A DNA DECAMER CONTAINING 7,8-DIHYDRO-8-OXOGUANINE

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-Angstrom resolution. The results demonstrate that G(O) forms Watson-Crick base pairs with the opposite C and that G(O) 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.