Cloning and Expression of the MutM Gene from Obligate Anaerobic Bacterium Desulfovibrio vulgaris (Miyazaki F)*

Abstract

The gene encoding a MutM from Desulfovibrio vulgaris (Miyazaki F) was cloned and expressed in Escherichia coli. A 5.9-kb DNA fragment, isolated from D. vulgaris (Miyazaki F) by XhoI and PvuII, contained a MutM gene and other open reading frames. The nucleotide sequence of the MutM gene indicated that the protein was composed of 336 amino acids. The amino-acid sequence deduced from the MutM gene was highly homologous with the MutM of other bacteria; however an additional insert consisted of 64 amino acids. An expression system for the MutM gene under the control of the T7 promoter was constructed in E. coli. From the kinetic analysis results, the purified His-tagged MutM showed 8-oxoguanine-DNA glycosylase activity comparable with that of MutM from E. coli. In this study, the amounts of mRNA and protein for MutM were scant in the D. vulgaris (Miyazaki F). MutM activity may be induced by oxidative stress. However, its induction may not be frequently generated because sulfate-reducing bacteria generally grow in anaerobic conditions. MutM might play a role in the protection against the mutagenicity of oxygen when oxygen stress exceeded the capacity of the defense systems against oxygen toxicity.