Abstract
In Rhodobacter sphaeroides f. sp. denitrificans, the DmsS/DmsR two-component signal transduction system regulates expression of dmsCBA operon encoding DMSO (dimethylsulfoxide) respiration system. DmsS has no putative membrane-spanning hydrophobic amino acid regions, although other sensor histidine kinase generally contains transmembrane region. To analyze membrane-binding region of DmsS, dmsS-lacZ fusion genes were constructed. Each strain had the LacZ activity, suggesting that each LacZ fusion protein was located in the cytoplasm. The LacZ fusion protein with no hydrophobic region and other proteins with the hydrophobic region were recovered in the cytoplasmic and membrane fractions, respectively, suggesting that the fusion proteins bound to the membrane from the cytoplasmic side. Although DMSO induces the expression of DmsA protein under anaerobic conditions, no change of dmsS promoter activity was observed by DMSO, suggesting that DMSO itself is not a signal for the transcription of dmsS.
