title: Regulation of citB expression in Bacillus subtilis: integration of multiple metabolic signals in the citrate pool and by the general nitrogen regulatory system.
abstract: The tricarboxylic acid (TCA) cycle is one of the major routes of carbon catabolism in Bacillus subtilis. The syntheses of the enzymes performing the initial reactions of the cycle, citrate synthase, and aconitase, are synergistically repressed by rapidly metabolizable carbon sources and glutamine. This regulation involves the general transcription factor CcpA and the specific repressor CcpC. In this study, we analyzed the expression and intracellular localization of CcpC. The synthesis of citrate, the effector of CcpC, requires acetyl-CoA. This metabolite is located at a branching point in metabolism. It can be converted to acetate in overflow metabolism or to citrate. Manipulations of the fate of acetyl-CoA revealed that efficient citrate synthesis is required for the expression of the citB gene encoding aconitase and that control of the two pathways utilizing acetyl-CoA converges in the control of citrate synthesis for the induction of the TCA cycle. The citrate pool seems also to be controlled by arginine catabolism. The presence of arginine results in a severe CcpC-dependent repression of citB. In addition to regulators involved in sensing the carbon status of the cell, the pleiotropic nitrogen-related transcription factor, TnrA, activates citB transcription in the absence of glutamine.
authors.affiliation: Abteilung für Allgemeine Mikrobiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstr. 8, 37077, Göttingen, Germany.
authors.forename: Hans-Matti
authors.initials: HM
authors.lastname: Blencke
authors.forename: Irene
authors.initials: I
authors.lastname: Reif
authors.forename: Fabian M
authors.initials: FM
authors.lastname: Commichau
authors.forename: Christian
authors.initials: C
authors.lastname: Detsch
authors.forename: Ingrid
authors.initials: I
authors.lastname: Wacker
authors.forename: Holger
authors.initials: H
authors.lastname: Ludwig
authors.forename: Jörg
authors.initials: J
authors.lastname: Stülke
mesh_terms: D000154:Aconitate Hydratase / Q000235:genetics / Q000378:metabolism; D001120:Arginine / Q000494:pharmacology; D001412:Bacillus subtilis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D002951:Citrates / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial / Q000235:genetics; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D009584:Nitrogen / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002951:Citrates; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; C069286:catabolite control proteins, bacteria; D001120:Arginine; D000154:Aconitate Hydratase; D009584:Nitrogen