8-Oxoguanine is an oxidized form of guanine. In DNA, 8-oxo-guanine can mispair with adenine, potentially forming a mutation. 8-Oxoguanine can be removed from DNA by the protein products of the E. coli mutM and mutY genes. The MutM protein removes 8-oxoguanine (and other oxidized bases), while the MutY protein removes adenine that is mispaired to 8-oxoguanine (Figure 25.14).