1. Energetics of alanine, lysine, and proline transport in cytoplasmic membranes of the polyphosphate-accumulating Acinetobacter johnsonii strain 210A
- Author
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B. Melgers, HW van Veen, T. Abee, A.W.F. Kleefsman, W.N Konings, Alexander J. B. Zehnder, and G.J.J. Kortstee
- Subjects
Proline ,PH ,Antiporter ,Sodium ,Glucose Dehydrogenases ,BACTERIAL-CELLS ,chemistry.chemical_element ,Biology ,Microbiology ,Membrane Potentials ,VESICLES ,DEHYDROGENASE ,Polyphosphates ,Microbiologie ,Glucose dehydrogenase ,Proline transport ,Food Chemistry and Microbiology ,Life Science ,Electrochemical gradient ,LACTOCOCCUS-LACTIS ,Molecular Biology ,VLAG ,Alanine ,chemistry.chemical_classification ,Membranes ,Acinetobacter ,Lysine ,SALMONELLA-TYPHIMURIUM ,Biological Transport ,Glucose 1-Dehydrogenase ,Membrane transport ,STREPTOCOCCUS-CREMORIS ,Amino acid ,Kinetics ,Glucose ,RECONSTITUTION ,Levensmiddelenchemie en -microbiologie ,chemistry ,Biochemistry ,ESCHERICHIA-COLI ,Biophysics ,AMINO-ACID-TRANSPORT ,Protons ,Carrier Proteins ,Energy Metabolism ,Research Article - 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.
- Published
- 1994