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J. Bacteriol., 05 1995, 2863-2869, Vol 177, No. 10
B Tolner, T Ubbink-Kok, B Poolman and WN Konings
Transport of acidic amino acids in Bacillus subtilis is an electrogenic
process in which L-glutamate or L-aspartate is symported with at least two
protons. This is shown by studies of transport in membrane vesicles in
which a proton motive force is generated by oxidation of ascorbate-
phenazine methosulfate or by artificial ion gradients. An inwards- directed
sodium gradient had no (stimulatory) effect on proton motive force-driven
L-glutamate uptake. The transporter is specific for L- glutamate and
L-aspartate. L-Glutamate transport is inhibited by beta- hydroxyaspartate
and cysteic acid but not by alpha-methyl-glutamate. The gene encoding the
L-glutamate transport protein of B. subtilis (gltPBsu) was cloned by
complementation of Escherichia coli JC5412 for growth on glutamate as the
sole source of carbon, energy, and nitrogen, and its nucleotide sequence
was determined. Putative promoter, terminator, and ribosome binding site
sequences were found in the flanking regions. UUG is most likely the start
codon. gltPBsu encodes a polypeptide of 414 amino acid residues and is
homologous to several proteins that transport glutamate and/or structurally
related compounds such as aspartate, fumarate, malate, and succinate. Both
sodium- and proton-coupled transporters belong to this family of
dicarboxylate transporters. Hydropathy profiling and multiple alignment of
the family of carboxylate transporters suggest that each of the proteins
spans the cytoplasmic membrane 12 times with both the amino and carboxy
termini on the inside.
Copyright © 1995, American Society for Microbiology
Characterization of the proton/glutamate symport protein of Bacillus subtilis and its functional expression in Escherichia coli
Department of Microbiology, University of Groningen, Haren, The Netherlands.
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