The C-terminal domain of MutY glycosylase determines the 7,8-dihydro-8-oxo-guanine specificity and is crucial for mutation avoidance

Escherichia coli MutY is an adenine DNA glycosylase active on DNA substrate s containing A/G, A/8-oxoG, or A/C mismatches and also has a weak guanine g lycosylase activity on G/8-oxoG-containing DNA. The N-terminal domain of Mu tY, residues 1-226, has been shown to retain catalytic activity. Substrate binding, glycosylase, and Schiff base intermediate formation activities of the truncated and intact MutY were compared. MutY has high binding affinity with 8-oxoG when mispaired with A, G, T, C, or inosine, The truncated prot ein has more than 18-fold Lower affinities for binding various 8-oxoG-conta ining mismatches when compared with intact MutY. MutY catalytic activity to ward A/8-oxoG-containing DNA is much faster than that on A/G-containing DNA whereas deletion of the C-terminal domain reduces its catalytic preference for A/8-oxoG-DNA over A/G-DNA. MutY exerts more inhibition on the catalyti c activity of MutM (Fpg) protein than does truncated MutY, The tight bindin g of MutY with GO mispaired with T, G, and apurinic/apyrimidinic sites may be involved in the regulation of MutM activity. An E. colt mutY strain that produces an N-terminal 249-residue truncated MutY confers a mutator phenot ype, These findings strongly suggest that the C-terminal domain of MutY det ermines the 8-oxoG specificity and is crucial for mutation avoidance by oxi dative damage.