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J Bacteriol, February 1998, p. 498-504, Vol. 180, No. 3
Department of Biology, University of
California at San Diego, La Jolla, California 92093-0116
Received 14 July 1997/Accepted 10 November 1997
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 GlcT, which controls PtsG synthesis, and (iii) a
previously uncharacterized carrier of the major facilitator superfamily, which we have designated GlcP. The last protein exhibits greatest sequence similarity to the fucose:H+ symporter of
Escherichia coli 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
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Characterization of Glucose-Specific Catabolite
Repression-Resistant Mutants of Bacillus subtilis:
Identification of a Novel Hexose:H+ Symporter


-glucoside uptake. In a
pts
genetic background no phenotype was observed, suggesting that
expression of the glcP gene required a functional
phosphotransferase system. When overproduced in a
pts
mutant of E. coli, GlcP could be shown to specifically
transport glucose, mannose, 2-deoxyglucose and methyl
-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.
*
Corresponding author. Mailing address: Department of
Biology, 0116, University of California at San Diego, La Jolla, CA
92093-0116. Phone: (619) 534-4084. Fax: (619) 534-7108. E-mail:
msaier{at}ucsd.edu.
Present address: School of Biological Sciences, University of
Sydney, Sydney, NSW 2006, Australia.
Present address: Unité de Physiologie Cellulaire,
Département des Biotechnologies, Institut Pasteur, 75724 Paris
Cedex 15, France.
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