title: Sodium-dependent transport of L-leucine in membrane vesicles prepared from Pseudomonas aeruginosa.
abstract: Membrane vesicles were prepared by osmotic lysis of spheroplasts of Pseudomonas aeruginosa strain P14, and the active transport of amino acids was studied. D-Glucose, gluconate, and L-malate supported active transport of various L-amino acids. The respiration-dependent leucine transport was markedly stimulated by Na+. Moreover, without any respiratory substrate, leucine was also transported transiently by the addition of Na+ alone. This transient uptake of leucine was not inhibited either by carbonyl cyanide p-trifluoromethyoxyphenylhydrazone or by valinomycin, but was completely abolished by gramicidin D. Increase in the concentration of Na+ of the medium resulted in a decrease of the Km for L-leucine transport, whereas the Vmax was not significnatly affected. Active transport of leucine was inhibited competitively by isoleucine or by valine, whose transport was also stimulated by Na+. On the other hand, Na+ was not required for the uptake of other L-amino acids tested, but rather was inhibitory for some of them. These results show (i) that a common transport system for branched-chain amino acids exists in membrane vesicles, (ii) that the system requires Na+ for its activity, and (iii) that an Na+ gradient can drive the system.
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism*; D006096:Gramicidin / Q000494:pharmacology; D007700:Kinetics; D007930:Leucine / Q000378:metabolism*; D010101:Oxygen Consumption; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D006096:Gramicidin; D014634:Valinomycin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D012964:Sodium; D007930:Leucine