Alternative gene for biotin sulfoxide reduction inEscherichia coli K-12

A gene at 42 min on theEscherichia coli chromosome, identified as the locus of pseudoreversion of knockout mutations in the biotin sulfoxide reductase gene,bisC, has 64% base sequence identity withbisC. 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 inbisC mutants. Sequence comparison of the new gene (bisZ) withbisC indicates that certaints mutants ofbisC arise by gene conversion between the two loci.