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- Title
Glycerol-3-phosphate-mediated repression of malT inEscherichia coli does not require metabolism, depends on enzyme IIA[sup Glc] and is mediated by cAMP levels.
- Authors
Eppler, Tanja; Boos, Winfried
- 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.
- Subjects
ESCHERICHIA coli; MALTOSE; LAC operon; MICROBIAL mutation
- Publication
Molecular Microbiology, 1999, Vol 33, Issue 6, p1221
- ISSN
0950-382X
- Publication type
Article
- DOI
10.1046/j.1365-2958.1999.01570.x