The dmsR gene encoding a dimethyl sulfoxide-responsive regulator for expression of dmsCBA (dimethyl sulfoxide respiration genes) in Rhodobacter sphaeroides f. sp. denitrificans.

Upstream of the dmsCBA genes encoding dimethyl sulfoxide (DMSO) reductase in the phototrophic bacterium Rhodobacter sphaeroides f. sp. denitrificans, there was found one gene (referred to dmsR) which encoded a protein composed of 232 amino acid residues and was divergently transcribed from the dmsCBA genes. The deduced amino acid sequence was homologous to the OmpR subfamily of response regulators in two-component systems for transcriptional regulation. The encoded protein DmsR was shown to bind to a DNA fragment containing the four direct repeats of a decameric nucleotide motif located between the dmsR and dmsCBA genes. The DNA-binding activity of DmsR was observed when the organism was grown anaerobically in the presence of DMSO. A dmsR-defected mutant strain showed no synthesis of DMSO reductase. These results indicate that the dmsR gene product acts as a positive regulator for expression of the dmsCBA genes in response to DMSO under anaerobic growth conditions.