title: Involvement of OpcR, a GbsR-type transcriptional regulator, in negative regulation of two evolutionarily closely related choline uptake genes in Bacillus subtilis.
abstract: The osmoprotectant glycine betaine can be generated intracellularly from conversion of the exogenous precursor choline by enzymes encoded by the gbsAB operon in Bacillus subtilis. Uptake of choline from outside B. subtilis cells is mediated through two evolutionarily closely related ATP-binding cassette transporters, OpuB and OpuC. Expression of the opuB operon and of the opuC operon is known to be osmoinducible. Here, we show that choline exerts a suppressive effect on opuC expression during normal growth and under osmotic stress. In the absence of the choline-responsive repressor GbsR, opuB expression is also suppressed by choline. We also report that a gene (formerly yvbF, now designated opcR) located immediately upstream of the opuC operon negatively regulates transcription of the opuC operon and, in the absence of GbsR, also that of the opuB operon. An inverted repeat (TTGTAAA-N8-TTTACAA) that overlaps with the -35 hexamer of the promoters of both operons has been identified as the OpcR operator. OpcR belongs to the GbsR-type transcriptional regulators. Its orthologues with unknown function are present in some other Bacillus species. Moreover, deletion analyses revealed that a region located further upstream of the promoters of the opuB operon and the opuC operon is critical for expression of both operons during normal growth and under osmotic stress. Osmotic induction of these two operons appears not to be OpcR mediated. OpcR is not a choline-responsive repressor. The possible biological role of OpcR is discussed.
authors: Institute of Biochemistry and Molecular Biology, School of Life Science, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors: Chun-Hao
authors: CH
authors: Lee
authors: Institute of Biochemistry and Molecular Biology, School of Life Science, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors: Tien-Yu
authors: TY
authors: Wu
authors: Institute of Biochemistry and Molecular Biology, School of Life Science, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors: Gwo-Chyuan
authors: GC
authors: Shaw
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D001412:Bacillus subtilis / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D001426:Bacterial Proteins / Q000096:biosynthesis*; D002794:Choline / Q000378:metabolism*; D004252:DNA Mutational Analysis; D015964:Gene Expression Regulation, Bacterial; D009875:Operator Regions, Genetic; D009997:Osmotic Pressure; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; C119749:OpuB protein, Bacillus subtilis; C119750:OpuC protein, bacteria; D012097:Repressor Proteins; D002794:Choline