Characterization of glucose-specific catabolite repression-resistant mutants of Bacillus subtilis: identification of a novel hexose:H+ symporter

Ian T. Paulsen, Sylvie Chauvaux, Peter Choi, Milton H. Saier

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Insertional mutagenesis was conducted on Bacillus subtilis cells to screen for mutants resistant to catabolite repression. Three classes of mutants that were resistant to glucose-promoted but not mannitol-promoted catabolite repression were identified. Cloning and sequencing of the mutated genes revealed that the mutations occurred in the structural genes for (i) enzyme II of the phosphoenolpyruvate-glucose phosphotransferase (PtsG), (ii) antiterminator GIcT, which controls PtsG synthesis, and (iii) a previously uncharacterized carrier of the major facilitator superfamily, which we have designated GIcP. The last protein exhibits greatest sequence similarity to the fucose:H+ symporter of Escherichia coil and the glucose/galactose:H+ symporter of Brucella abortus. In a wild-type B. subtilis genetic background, the glcP::Tn10 mutation (i) partially but specifically relieved glucose- and sucrose-promoted catabolite repression, (ii) reduced the growth rate in minimal glucose medium, and (iii) reduced rates of [14C]glucose and [14C]methyl α-glucoside uptake. In a Δpts genetic background no phenotype was observed, suggesting that expression of the glcP gene required a functional phosphotransferase system. When overproduced in a Δpts mutant of E. coli, GlcP could be shown to specifically transport glucose, mannose, 2- deoxyglucose and methyl α-glucoside with low micromolar affinities. Accumulation of the nonmetabolizable glucose analogs was demonstrated, and inhibitor studies suggested a dependency on the proton motive force. We conclude that B. subtilis possesses at least two distinct routes of glucose entry, both of which contribute to the phenomenon of catabolite repression.

Original languageEnglish
Pages (from-to)498-504
Number of pages7
JournalJournal of Bacteriology
Volume180
Issue number3
Publication statusPublished - Feb 1998
Externally publishedYes

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