title: Direct and indirect roles of CcpA in regulation of Bacillus subtilis Krebs cycle genes.
abstract: Carbon catabolite repression of the Bacillus subtilis citrate synthase (citZ) and aconitase (citB) genes, previously known to be regulated by CcpC, was shown to depend on CcpA as well. Transcription of the citZ gene was partially derepressed in ccpA and ccpC single mutants and fully derepressed in a ccpA ccpC double mutant. DNase I footprinting studies showed that CcpA binds to a catabolite-responsive element (cre) site located at positions +80 to +97 with respect to the transcription start site, whereas CcpC binds at positions -14 to +6 and +16 to +36. Mutations in the citZ cre site greatly altered CcpA binding and repression. A ccpA null mutation also caused partial derepression of citB. Disruption of citrate synthase activity, however, suppressed the effect of the ccpA mutation, suggesting that increased citrate accumulation in a ccpA mutant partially inactivates CcpC and causes partial derepression of citB. Therefore, CcpA controls expression of Krebs cycle genes directly by regulating transcription of citZ and in-directly by regulating availability of citrate, the inducer for CcpC.
authors.affiliation: Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: Hyun-Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Agnes
authors.initials: A
authors.lastname: Roux
authors.forename: Abraham L
authors.initials: AL
authors.lastname: Sonenshein
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins; D002950:Citrate (si)-Synthase / Q000235:genetics / Q000378:metabolism; D019343:Citric Acid / Q000378:metabolism; D002952:Citric Acid Cycle; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; C069286:catabolite control proteins, bacteria; D019343:Citric Acid; D002950:Citrate (si)-Synthase