Brown I I, Kim Iu V
Biokhimiia. 1982 Jan;47(1):137-44.
The role of Na+/K+ gradients as a stabilizing factor for the energetics of bacterial cell has been evaluated. It was shown that in the presence of a Na+/K+ gradient across the membrane the cells of the unc mutant of E. coli retain their motility for some time under anaerobic conditions. This time coincides with that of dissipation of the K+ gradient by the bacteria during the anaerobiosis. A switch-off of the generator (respiration) entails a collapse of the membrane potential (delta psi). The anaerobiosis-induced efflux of K+ from the cells is uncoupler-stimulated, thus suggesting that the K+ efflux has an electrogenic nature and stabilizes delta psi. The use of valinomycin allowed to establish a correlation between the rate of K+ efflux, the delta psi value and the rate of bacterial motion under anaerobic conditions. After the onset of anaerobiosis the level of delta psi decreases faster as the concentration of extracellular K+ increases. It was shown that the capacity of the K+ gradient as te delta psi buffer depends on the pH of the medium and that artificial Na+ gradient can energize the E. coli cells by Na+/K+ exchange.
已评估了Na⁺/K⁺梯度作为细菌细胞能量学稳定因素的作用。结果表明，在膜两侧存在Na⁺/K⁺梯度的情况下，大肠杆菌unc突变体的细胞在厌氧条件下能在一段时间内保持其运动性。这段时间与细菌在厌氧期间K⁺梯度的耗散时间一致。发生器（呼吸作用）的关闭会导致膜电位（Δψ）的崩溃。厌氧诱导的K⁺从细胞中流出是解偶联剂刺激的，因此表明K⁺流出具有电生性并稳定了Δψ。使用缬氨霉素可以确定厌氧条件下K⁺流出速率、Δψ值与细菌运动速率之间的相关性。厌氧开始后，随着细胞外K⁺浓度的增加，Δψ水平下降得更快。结果表明，K⁺梯度作为Δψ缓冲剂的能力取决于培养基的pH值，并且人工Na⁺梯度可以通过Na⁺/K⁺交换为大肠杆菌细胞提供能量。
