title: Glycerol-3-phosphate-mediated repression of malT in Escherichia coli does not require metabolism, depends on enzyme IIAGlc and is mediated by cAMP levels.
abstract: malT encodes the central activator of the maltose system in Escherichia coli, a gene that is typically under positive control of the cAMP/CAP catabolite repression system. When cells were grown in tryptone broth, the addition of glycerol reduced malT expression two- to threefold. Phosphorylation of glycerol to glycerol-3-phosphate (G3P) was necessary for this repression, but further metabolism to dihydroxyacetone phosphate was not. Mutants lacking adenylate cyclase and harbouring a crp* mutation (synthesizing a cAMP receptor protein that is independent of cAMP) no longer repressed a transcriptional malT-lacZ fusion but still repressed a translational malT-lacZ fusion. Similar results were obtained with a mutant lacking enzyme IIAGlc. For the translational fusion (in a cya crp* genetic background) to be repressed by glycerol, a drop to pH 5 of the growth medium was necessary. Thus, while transcriptional repression by glycerol requires enzyme IIAGlc, cAMP and CAP, pH-mediated translational repression is cAMP independent. Other sugars that are not transported by the phosphotransferase system, most notably D-xylose, showed the same effect as glycerol.
authors.affiliation: Department of Biology, University of Konstanz, D-78457 Konstanz, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Eppler
authors.forename: W
authors.initials: W
authors.lastname: Boos
mesh_terms: D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D015870:Gene Expression / Q000187:drug effects; D005798:Genes, Bacterial; D005990:Glycerol / Q000378:metabolism / Q000494:pharmacology; D005994:Glycerophosphates / Q000494:pharmacology*; D007763:Lac Operon; D009154:Mutation; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D005994:Glycerophosphates; C058976:MalT protein, E coli; D014157:Transcription Factors; C032242:crr protein, E coli; C029620:alpha-glycerophosphoric acid; D000242:Cyclic AMP; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D005990:Glycerol