Properties and physiological roles of Na^+-motive respiratory chain in marine bacteria.

海洋细菌溶藻弧菌拥有一个Na~+泵，通过呼吸作用直接产生Na~+的电化学势。对Na~+泵缺陷突变体NAPL和NAP2的检测表明，Na~+是在NADH氧化酶的NADH：Q氧化还原酶片段上挤出的。在野生型中，存在两种类型的NADH：苯醌氧化还原酶(NQR)；一种依赖于Na+依赖的NQR。Na^+和另一种则不是。NAP1和NAP2均缺乏钠离子依赖的NQR活性。对野生型依赖Na~+的NQR进行了纯化，发现其由3个亚基组成：α-gt；-lt；α-gt；，-lt；β-gt；和-lt；-γ&gt；此外，结果表明，nap2在-lt；β&gt；亚基中存在点突变，而Nap1则缺失所有亚基。利用纯化的亚基和NQR复合体，详细研究了依赖Na~+的NQR的电子传递机制。亚基&lt；β&gt；催化泛醌还原为泛半喹酮。亚基和γ亚基是e…更有利于将泛醌还原为泛喹酚。在脂质体中重组的NQR复合体产生一种依赖于Na+的膜电位，Bessues V，akgubiktucysm gakiogukuc V，cistucoka aksi回收BA+动力NADH氧化酶。这需要钠离子才能发挥最大的活性。为了研究Na~+-动力NADH氧化酶在嗜盐细菌中的分布，对纳路氏菌的Na~+-需求进行了研究。在检测的10株细菌中，有9株属于Alteromonas、Alcaliges或Vibrio，保留了依赖Na+的NADH氧化酶。此外，所有NADH氧化酶的Na+依赖部位都存在于NADH：苯醌氧化还原酶上，并被溶藻弧菌和弧菌中Na+泵的特异性抑制剂2-庚基-4-羟基喹啉-N-氧化物(HQNO)所抑制。包括溶藻弧菌在内的所有菌株的依赖于Na+的NADH氧化酶都能氧化脱氨基-NADH，而NAP1和NAP2中的NADH氧化酶对脱氨基-NADH几乎没有活性。这些结果表明，依赖于钠离子(钠离子动力)的NADH氧化酶是海洋细菌产生能量的一般机制，并具有一些共同的性质。较少

The Marine bacterium Vibrio alginolyticus possesses a Na^+ pump that generates an lectrochemical potential of Na^+ as a direct result of respiration. Examinations of Na^+ pump-defective mutants, Napl and Nap2, revealed that Na^+ is extruded at the NADH:quinone oxidoreductase segment of NADH oxidase. In the wild type, two kinds of NADH:quinone oxidoreductases (NQR) are present; one is dependent on Na^+-dependent NQR. The Na^+ and another is not. Both Nap1 and Nap2 lack the activity of Na^+-dependent NQR. The Na^+-dependent NQR of the wild type was purified to near homogeneity and found to be composed of three subunits, <Alpha>, <beta> and <gamma>. Moreover, it was shown that Nap2 has a point mutation in <beta> subunit whereas Napl lacks all the subunits. Mechanism of electron transfer by the Na^+-dependent NQR were examined in detail using purified subunits and NQR complex. The subunit <beta> catalysed the reduction of ubiquinone to ubisemiquinone. The subunit <alpha> and <gamma> were e … More ssential for the reduction of ubiquinone to ubiquinol. NQR complex reconstituted in liposomes generated a membrane potential, which was dependent on Na^+.Besudes V, akgubikttucysm gakiogukuc V, cistucoka aksi retaubs the BA^+-motive NADH oxidase. which requires Na^+ for maximum activity. In order to investigate the distribution of Na^+-motive NADH oxidase in halophiles, Na^+-requiremet of NADH oxidase was exanubed ub narube bacterua. Out of 10 strains examined, 9 strains belonging to Alteromonas, Alcaligenes or Vibrio retained Na^+-dependent NADH oxidases. Moreover,Na^+-dependent site of all NADH oxidases existed at the NADH:quinone oxidoreductase and was inhibited by 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO), a specific inhibitor of the Na^+ pump in V. alginolyticus and V. costicola. Na^+-dependent NADH oxidases in all the strajns including V. alginolyticus were able to oxidize deamino-NADH whereas NADH oxidase in Nap1 and Nap2 showed little activity to deamino-NADH. These results indicated that the Na^+-dependent (Na^+-motive) NADH oxidase is a general mechanism to generate energy in marine bacteria and shares some commmon properties. Less