title: Glucose repression of the Escherichia coli sdhCDAB operon, revisited: regulation by the CRP*cAMP complex.
abstract: Expression of the Escherichia coli sdhCDAB operon encoding the succinate dehydrogenase complex is regulated in response to growth conditions, such as anaerobiosis and carbon sources. An anaerobic repression of sdhCDAB is known to be mediated by the ArcB/A two-component system and the global Fnr anaerobic regulator. While the cAMP receptor protein (CRP) and Cra (formerly FruR) are known as key mediators of catabolite repression, they have been excluded from the glucose repression of the sdhCDAB operon. Although the glucose repression of sdhCDAB was reported to involve a mechanism dependent on the ptsG expression, the molecular mechanism underlying the glucose repression has never been clarified. In this study, we re-examined the mechanism of the sdhCDAB repression by glucose and found that CRP directly regulates expression of the sdhCDAB operon and that the glucose repression of this operon occurs in a cAMP-dependent manner. The levels of phosphorylated enzyme IIA(Glc) and intracellular cAMP on various carbon sources were proportional to the expression levels of sdhC-lacZ. Disruption of crp or cya completely abolished the glucose repression of sdhC-lacZ expression. Together with data showing correlation between the intracellular cAMP concentrations and the sdhC-lacZ expression levels in several mutants and wild type, in vitro transcription assays suggest that the decrease in the CRP.cAMP level in the presence of glucose is the major determinant of the glucose repression of the sdhCDAB operon.
authors.affiliation: Laboratory of Macromolecular Interactions, Department of Biological Sciences and Institute of Microbiology, College of Natural Sciences, Seoul National University, Seoul 151-742, Korea.
authors.forename: Tae-Wook
authors.initials: TW
authors.lastname: Nam
authors.forename: Young-Ha
authors.initials: YH
authors.lastname: Park
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Jeong
authors.forename: Sangryeol
authors.initials: S
authors.lastname: Ryu
authors.forename: Yeong-Jae
authors.initials: YJ
authors.lastname: Seok
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D000242:Cyclic AMP / Q000378:metabolism*; D002373:Cyclic AMP Receptor Protein; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009876:Operon; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013385:Succinate Dehydrogenase / Q000096:biosynthesis / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D029968:Escherichia coli Proteins; D011956:Receptors, Cell Surface; C486355:SdhC protein, bacteria; D014157:Transcription Factors; C481662:crp protein, E coli; C032242:crr protein, E coli; D000242:Cyclic AMP; D013385:Succinate Dehydrogenase; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D005947:Glucose