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Energetics of alanine, lysine, and proline transport in cytoplasmic membranes of the polyphosphate-accumulating Acinetobacter johnsonii strain 210A

Authors :
B. Melgers
HW van Veen
T. Abee
A.W.F. Kleefsman
W.N Konings
Alexander J. B. Zehnder
G.J.J. Kortstee
Source :
Journal of Bacteriology 176 (1994), Journal of Bacteriology, 176, 2670-2676, Journal of Bacteriology, 176(9), 2670-2676. AMER SOC MICROBIOLOGY
Publication Year :
1994
Publisher :
AMER SOC MICROBIOLOGY, 1994.

Abstract

Amino acid transport in right-side-out membrane vesicles of Acinetobacter johnsonii 210A was studied. L-Alanine, L-lysine, and L-proline were actively transported when a proton motive force of -76 mV was generated by the oxidation of glucose via the membrane-bound glucose dehydrogenase. Kinetic analysis of amino acid uptake at concentrations of up to 80 microM revealed the presence of a single transport system for each of these amino acids with a Kt of less than 4 microM. The mode of energy coupling to solute uptake was analyzed by imposition of artificial ion diffusion gradients. The uptake of alanine and lysine was driven by a membrane potential and a transmembrane pH gradient. In contrast, the uptake of proline was driven by a membrane potential and a transmembrane chemical gradient of sodium ions. The mechanistic stoichiometry for the solute and the coupling ion was close to unity for all three amino acids. The Na+ dependence of the proline carrier was studied in greater detail. Membrane potential-driven uptake of proline was stimulated by Na+, with a half-maximal Na+ concentration of 26 microM. At Na+ concentrations above 250 microM, proline uptake was strongly inhibited. Generation of a sodium motive force and maintenance of a low internal Na+ concentration are most likely mediated by a sodium/proton antiporter, the presence of which was suggested by the Na(+)-dependent alkalinization of the intravesicular pH in inside-out membrane vesicles. The results show that both H+ and Na+ can function as coupling ions in amino acid transport in Acinetobacter spp.

Details

Language :
English
ISSN :
00219193
Volume :
176
Issue :
9
Database :
OpenAIRE
Journal :
Journal of Bacteriology
Accession number :
edsair.doi.dedup.....3f084f0042fdd0beccb6287449d76073