| Autor: |
Van Veen HW; Department of Microbiology, Agricultural University Wageningen, The Netherlands., Abee T, Kleefsman AW, Melgers B, Kortstee GJ, Konings WN, Zehnder AJ |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of bacteriology [J Bacteriol] 1994 May; Vol. 176 (9), pp. 2670-6. |
| DOI: |
10.1128/jb.176.9.2670-2676.1994 |
| Abstrakt: |
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. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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