Nucleotide sequence of the Salmonella typhimurium mutB gene, the homolog of Escherichia coli mutY

The mutB gene of Salmonella typhimurium is involved in a methylation-independent repair pathway specific for A/G or A/C mismatches and is the homolog of the Escherichia coli mutY gene. The mutB gene of S. typhimurium was cloned and sequenced. The isolated mutB clone reduced the mutation rate of the mutB mutant to wild-type levels and also restored A/G mismatch-specific nicking activity, which is defective in mutB extracts. The amino acid sequence encoded by the mutB gene is 91% homologous to that encoded by the E. coli mutY gene.