Characterization of a Thermostable 8-Oxoguanine DNA Glycosylase Specific for GO/N Mismatches from the Thermoacidophilic Archaeon .

The oxidation of guanine (G) to 7,8-dihydro-8-oxoguanine (GO) forms one of the major DNA lesions generated by reactive oxygen species (ROS). The GO can be corrected by GO DNA glycosylases (Ogg), enzymes involved in base excision repair (BER). Unrepaired GO induces mismatched base pairing with adenine (A); as a result, the mismatch causes a point mutation, from G paired with cytosine (C) to thymine (T) paired with adenine (A), during DNA replication. Here, we report the characterization of a putative Ogg from the thermoacidophilic archaeon . The 204-amino acid sequence of the putative Ogg (TVG_RS00315) shares significant sequence homology with the DNA glycosylases of (MjaOgg) and (SsoOgg). The six histidine-tagged recombinant TVG_RS00315 protein gene was expressed in and purified. The Ogg protein is thermostable, with optimal activity near a pH of 7.5 and a temperature of 60°C. The enzyme displays DNA glycosylase, and apurinic/apyrimidinic (AP) lyase activities on GO/N (where N is A, T, G, or C) mismatch; yet it cannot eliminate U from U/G or T from T/G, as mismatch glycosylase (MIG) can. These results indicate that TvoOgg-encoding is a member of the Ogg2 family of .