Nakamura T, Tokuda H, Unemoto T
Biochem Biophys Res Commun. 1986 May 14;136(3):1030-5. doi: 10.1016/0006-291x(86)90436-5.
The K+/H+ antiporter of a marine bacterium, Vibrio alginolyticus, is strongly dependent upon the cytoplasmic pH and functions only at an internal pH above 7.7. In alkaline buffer with an outwardly directed chemical gradient of K+ (delta pK), the internal pH was maintained at about 7.7. Addition of N-ethylmaleimide (NEM) released cellular K+ and acidified the cytosol below pH 7.7. The NEM effect was reversed by the addition of 2-mercaptoethanol: K+ efflux ceased, and the internal pH returned to about 7.7. In acidic buffer, the internal pH was also regulated at about 7.6 even in the absence of delta pK. Following addition of NEM, the internal pH decreased below 7.6, dissipating delta pH. These results suggest that NEM desensitizes the pH-dependence of the K+/H+ antiporter, allowing the antiporter to function at an internal pH below 7.7.
海洋细菌溶藻弧菌的K⁺/H⁺反向转运蛋白强烈依赖于细胞质pH值，且仅在内部pH高于7.7时发挥作用。在具有外向K⁺化学梯度（ΔpK）的碱性缓冲液中，内部pH维持在约7.7。添加N-乙基马来酰亚胺（NEM）会释放细胞内的K⁺并使细胞质酸化至pH 7.7以下。添加2-巯基乙醇可逆转NEM的作用：K⁺外流停止，内部pH恢复至约7.7。在酸性缓冲液中，即使没有ΔpK，内部pH也会调节至约7.6。添加NEM后，内部pH降至7.6以下，消除了ΔpH。这些结果表明，NEM使K⁺/H⁺反向转运蛋白对pH的依赖性脱敏，使反向转运蛋白能够在内部pH低于7.7时发挥作用。
