Glucose lowers CRP* levels resulting in repression of the lac operon in cells lacking cAMP.

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  • Author(s): Tagami H;Tagami H; Inada T; Kunimura T; Aiba H
  • Source:
    Molecular microbiology [Mol Microbiol] 1995 Jul; Vol. 17 (2), pp. 251-8.
  • Publication Type:
    Journal Article; Research Support, Non-U.S. Gov't
  • Language:
    English
  • Additional Information
    • Source:
      Publisher: Blackwell Scientific Publications Country of Publication: England NLM ID: 8712028 Publication Model: Print Cited Medium: Print ISSN: 0950-382X (Print) Linking ISSN: 0950382X NLM ISO Abbreviation: Mol Microbiol Subsets: MEDLINE
    • Publication Information:
      Original Publication: Oxford, OX ; Boston, MA : Blackwell Scientific Publications, c1987-
    • Subject Terms:
      Cyclic AMP Receptor Protein/*genetics ; Gene Expression Regulation, Bacterial/*drug effects ; Glucose/*pharmacology ; Lac Operon/*genetics; Adenylyl Cyclases/physiology ; Carrier Proteins ; Cyclic AMP/metabolism ; Cyclic AMP Receptor Protein/biosynthesis ; Enzyme Repression ; Escherichia coli/enzymology ; Escherichia coli/genetics ; Gene Amplification ; Genes, Bacterial ; Plasmids/genetics ; Point Mutation ; Promoter Regions, Genetic/genetics ; RNA, Bacterial/biosynthesis ; RNA, Messenger/biosynthesis ; beta-Galactosidase/biosynthesis ; beta-Galactosidase/metabolism
    • Abstract:
      CRP-cAMP-dependent operons of Escherichia coli can be expressed in cells lacking functional adenylate cyclase when they carry a second-site mutation in the crp gene (crp*). It is known that the expression of these operons is repressed by glucose, but the molecular mechanism underlying this cAMP-independent catabolite repression has been a long-standing mystery. Here we address the question of how glucose inhibits the expression of beta-galactosidase in the absence of cAMP. We have isolated several mutations in the crp gene that confer a CRP* phenotype. The expression of beta-galactosidase is reduced by glucose in cells carrying these mutations. Using Western blotting and/or SDS-PAGE analysis, we demonstrate that glucose lowers the cellular concentration of CRP* through a reduction in crp* mRNA levels. The level of CRP* protein correlates with beta-galactosidase activity. When the crp promoter is replaced with the bla promoter, the inhibitory effect of glucose on crp* expression is virtually abolished. These data strongly suggest that the lowered level of CRP* caused by glucose mediates catabolite repression in cya- crp* cells and that the autoregulatory circuit of the crp gene is involved in the down-regulation of CRP* expression by glucose.
    • Accession Number:
      0 (Carrier Proteins)
      0 (Cyclic AMP Receptor Protein)
      0 (RNA, Bacterial)
      0 (RNA, Messenger)
      E0399OZS9N (Cyclic AMP)
      EC 3.2.1.23 (beta-Galactosidase)
      EC 4.6.1.1 (Adenylyl Cyclases)
      IY9XDZ35W2 (Glucose)
    • Publication Date:
      Date Created: 19950701 Date Completed: 19960111 Latest Revision: 20190725
    • Publication Date:
      20221213
    • Accession Number:
      10.1111/j.1365-2958.1995.mmi_17020251.x
    • Accession Number:
      7494474