Alternative gene for biotin sulfoxide reduction in Escherichia coli K-12.

A gene at 42 min on the Escherichia coli chromosome, identified as the locus of pseudoreversion of knockout mutations in the biotin sulfoxide reductase gene, bisC, has 64% base sequence identity with bisC. This makes it a member of a multigene family of molybdopterin enzymes that includes genes for anaerobic reduction of trimethylamine oxide (torA) and dimethylsulfoxide (dmsA). Disruption of this gene eliminates the background activity of biotin sulfoxide reduction observed in bisC mutants. Sequence comparison of the new gene (bisZ) with bisC indicates that certain ts mutants of bisC arise by gene conversion between the two loci.