title: Generation of Na+ electrochemical potential by the Na+-motive NADH oxidase and Na+/H+ antiport system of a moderately halophilic Vibrio costicola.
abstract: Cells of Vibrio costicola at pH 8.5 generate both membrane potential (inside negative) and delta pH (inside acidic) in the presence of a proton conductor, carbonyl cyanide m-chlorophenylhydrazone (CCCP). The generation of CCCP-resistant membrane potential was inhibited by 2-heptyl-4-hydroxyquinoline-N-oxide that is known to inhibit the Na+-motive NADH oxidase of Vibrio alginolyticus. NADH oxidase, but not lactate oxidase, of inverted membrane vesicles prepared from V. costicola required Na+ for a maximum activity and was inhibited by 2-heptyl-4-hydroxyquinoline-N-oxide. By the oxidation of NADH, inverted membrane vesicles generated concentration gradients of Na+ across the membrane, whose magnitude was always larger than that of delta pH by about 50 mV. In contrast, magnitudes of delta pH and Na+ concentration gradients generated by the oxidation of lactate were similar. Na+ translocation in the presence of lactate was inhibited by CCCP but little affected by valinomycin. On the other hand, Na+ translocation in the presence of NADH was resistant to CCCP and stimulated by valinomycin. Amiloride, an inhibitor for a eucaryotic Na+/H+ antiport system, inhibited the lactate-dependent Na+ translocation but had little effect on the NADH-dependent Na+ translocation. These results indicate that a primary event of lactate oxidation is the translocation of H+, which then causes the generation of Na+ concentration gradients via the secondary Na+/H+ antiport system. We conclude that the NADH oxidase of V. costicola translocates Na+ as an immediate result of respiration, leading to the generation of Na+ electrochemical potential.
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D004563:Electrochemistry; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008564:Membrane Potentials; D009097:Multienzyme Complexes / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010101:Oxygen Consumption; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D013757:Tetraethylammonium Compounds / Q000378:metabolism; D014634:Valinomycin / Q000494:pharmacology; D014733:Vibrio / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D007773:Lactates; D009097:Multienzyme Complexes; D017923:Sodium-Hydrogen Exchangers; D013757:Tetraethylammonium Compounds; D014634:Valinomycin; D019344:Lactic Acid; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000584:Amiloride; D012964:Sodium; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases