Abstract
In Rhodobacter sphaeroides f. sp. denitrificans IL106, 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 proteins usually contain the transmembrane region. Analisis of the membrane-binding region of DmsS by LacZ fusion showed it did not stick out to the periplasm.
In this study, the essential region of DmsS for sensing on the membrane was studied by deletion methods. Four plasmids containing DNA fragments with the deleted region were constructed. Each plasmid was conjugated into a DmsS-deficient strain and the expression of dmsCBA operon was determined by detecting DMSO reductase (DmsA). All of the strains did not recovered the expression of DMSO reductase, suggesting that membrane-binding region was essential for sensing the signal.
