Avetisyan A V, Dibrov P A, Semeykina A L, Skulachev V P, Sokolov M V
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, U.S.S.R.
Biochim Biophys Acta. 1991 Dec 3;1098(1):95-104.
Mechanisms of Na+ transport into the inside-out subcellular vesicles of alkalo- and halotolerant Bacillus FTU and of Escherichia coli grown at different pH have been studied. Both microorganisms growing at pH 7.5 are shown to possess a system of the respiration-dependent Na+ transport which (i) is inhibited by protonophorous uncoupler, by delta pH-discharging agent diethylammonium (DEA) acetate, by micromolar cyanide arresting the H(+)-motive respiratory chain, and by amiloride, and (ii) is resistant to the Na+/H+ antiporter monensin and to Ag+, inhibitor of the Na(+)-motive respiratory chain. Growth at pH 8.6 strongly changes the activator and inhibitor pattern. Now (1) protonophore stimulates the Na+ transport, (2) DEA acetate is without effect in the absence of protonophore and is stimulating in its presence, (3) amiloride and low cyanide are ineffective, (4) monensin and Ag+ completely arrest the Na+ accumulation in the vesicles. Independent of pH of the growth medium, (a) valinomycin is stimulatory for the Na+ transport, (b) Na+ ionophore ETH 157 is inhibitory and, (c) Na+ transport can be supported by NADH----fumarate as well as by ascorbate (TMPD)----O2 electron transfers. Growth at alkaline pH results in the appearance of ascorbate (TMPD) oxidation resistant to low and sensitive to high cyanide concentrations. These relationships are in agreement with the concept (Skulachev, V.P. (1984) Trends Biochem. Sci. 9, 483-485) that adaptation to alkaline conditions in bacteria growing in the high [Na+] media causes substitution of Na+ for H+ as a coupling ion. The obtained data indicate that under alkaline conditions, Na+ can be pumped from the cell by the Na(+)-motive respiratory chain with neither H(+)-motive respiration nor the Na+/H+ antiporter involved. In the Na(+)-motive respiratory chain of Bac. FTU or E. coli, two Na+ pumps are localized, one in its initial and the other in its terminal spans.
对耐碱和耐盐的芽孢杆菌FTU以及在不同pH值下生长的大肠杆菌的内翻式亚细胞囊泡中Na⁺转运机制进行了研究。结果表明，在pH 7.5条件下生长的两种微生物都具有依赖呼吸作用的Na⁺转运系统，该系统：（i）受到质子载体解偶联剂、能消除ΔpH的试剂乙酸二乙铵（DEA）、能阻断H⁺驱动呼吸链的微摩尔级氰化物以及氨氯吡咪的抑制；（ii）对Na⁺/H⁺反向转运体莫能菌素和Na⁺驱动呼吸链抑制剂Ag⁺具有抗性。在pH 8.6条件下生长会强烈改变激活剂和抑制剂模式。此时：（1）质子载体刺激Na⁺转运；（2）在没有质子载体时，乙酸DEA无作用，而在有质子载体时具有刺激作用；（3）氨氯吡咪和低浓度氰化物无效；（4）莫能菌素和Ag⁺完全阻止囊泡中Na⁺的积累。与生长培养基的pH值无关的是：（a）缬氨霉素对Na⁺转运具有刺激作用；（b）Na⁺离子载体ETH 157具有抑制作用；（c）NADH→延胡索酸以及抗坏血酸（TMPD）→O₂的电子传递都能支持Na⁺转运。在碱性pH条件下生长会导致出现对低浓度氰化物有抗性、对高浓度氰化物敏感的抗坏血酸（TMPD）氧化现象。这些关系与以下概念相符（Skulachev, V.P. (1984) Trends Biochem. Sci. 9, 483 - 485）：在高[Na⁺]培养基中生长，并适应碱性条件的细菌会导致Na⁺取代H⁺作为偶联离子。所获得的数据表明，在碱性条件下，Na⁺可以通过Na⁺驱动的呼吸链从细胞中泵出，而不涉及H⁺驱动的呼吸作用或Na⁺/H⁺反向转运体。在芽孢杆菌FTU或大肠杆菌的Na⁺驱动呼吸链中，定位有两个Na⁺泵，一个位于其起始跨度，另一个位于其末端跨度。
