The Na+/e− stoichiometry of the Na+‐motive NADH : quinone oxidoreductase in Vibrio alginolyticus

[摘要]

A method is proposed to estimate the stoichiometries of primary Na⁺-pumps in intact bacterial cells. It is based on technique when the H⁺/e⁻ stoichiometry is measured in the presence of protophorous uncoupler and in the absence of penetrating ions other than H⁺. Under these conditions, the H⁺ influx discharges membrane potential generated by the Na⁺ pump so the Na⁺/e⁻ and H⁺/e⁻ ratios become equal. Using this approach it is shown that the Na⁺/e⁻ ratio for the Na⁺-motive NADH : quinone oxidoreductase of Vibrio alginolyticus is equal to 0.71±0.06. The Na⁺/e⁻ stoichiometry appears to be ≈1, provided that the contribution of the non-coupled NADH : quinone oxidoreductase, which is resistant to low HQNO concentrations, is taken into account.

[学科分类] 生物化学/生物物理

[关键词] Na+/e− stoichiometry;Na+-motive NADH : quinone oxidoreductase;Vibrio alginolyticus;and;transmembrane differences in H+ and Na+ electrochemical potentials;respectively;ΔΨ;transmembrane difference in electric potentials;CCCP;m-chlorocarbonylcyanide phenylhydrazone;HQNO;2-heptyl-4-hydrooxyquinoline N-oxide;TPP+;tetraphenyl phosphonium;TTFB;4;5;6;7-tetra-chloro-2-trifluoromethylbenzimidazole