The putative Na+/H+ antiporter of Vibrio cholerae, Vc-NhaP2, mediates the specific K+/H+ exchange in vivo.
The putative Na+/H+ antiporter of Vibrio cholerae, Vc-NhaP2, mediates the specific K+/H+ exchange in vivo.
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DOI：
10.1021/bi902173y
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发表时间：
2010-03-23
期刊：
影响因子：
2.9
通讯作者：
Hase, Claudia C.
中科院分区：
文献类型：
--
作者：
Resch, Craig T.;Winogrodzki, Judith L.;Patterson, Curtis T.;Lind, Erin J.;Quinn, Matthew J.;Dibrov, Pavel;Hase, Claudia C.
细菌K+/H+逆向转运蛋白的存在防止了钾在细胞质中的过度积累，这是彼得·米切尔在近50年前预测的。K+/H+逆向转运对细菌生理的重要性已被广泛认识，但其分子机制尚不清楚。在这里，我们证明了一个可能的Na+/H+逆向转运蛋白VC-NhaP2，可以保护生长在pH 6.0的霍乱弧菌细胞免受高浓度的外部K+的伤害。霍乱弧菌对Na+的抗性与Vc-NhaP2无关。在缺乏逆向转运蛋白的大肠杆菌中，VC-NhaP2催化K+(Rb+)/H+的电中和交换，其最适pH为~7.75，K+的表观Km为1.62 mM。在无K+时，表现为Na+/H+逆向迁移，但强度较弱。有趣的是，虽然VC-NhaP2不能将Li+交换为质子，但功能Vc-NhaP2的消除导致生长在pH 6.0的霍乱弧菌细胞对Li+的抗性显著增加，这表明VC-NhaP2可能介导了Li+/K+反向运输。VC-NhaP2独特的阳离子专一性及其在同一基因组中另外两个类似物的存在使该转运蛋白成为详细分析碱性阳离子交换器底物专一性结构决定因素的一个有吸引力的模型。
The existence of bacterial K+/H+ antiporters preventing the over-accumulation of potassium in the cytoplasm was predicted by Peter Mitchell almost fifty years ago. The importance of K+/H+ antiport for bacterial physiology is widely recognized but its molecular mechanisms remain underinvestigated. Here, we demonstrate that a putative Na+/H+ antiporter, Vc-NhaP2, protects cells of Vibrio cholerae growing at pH 6.0 from high concentrations of external K+. Resistance of V. cholerae to Na+ was found to be independent of Vc-NhaP2. When assayed in inside-out membrane vesicles derived from antiporter-deficient Escherichia coli, Vc-NhaP2 catalyzed the electroneutral K+(Rb+)/H+ exchange with pH optimum at ~7.75 with an apparent Km for K+ of 1.62 mM. In the absence of K+ it exhibited Na+/H+ antiport, albeit rather weakly. Interestingly, while Vc-NhaP2 cannot exchange Li+ for protons, elimination of functional Vc-NhaP2 resulted in a significantly higher Li+ resistance of V. cholerae cells growing at pH 6.0, suggesting the possibility of Vc-NhaP2-mediated Li+/K+ antiport. The peculiar cation specificity of Vc-NhaP2 and the presence of its two additional paralogues in the same genome make this transporter an attractive model for detailed analysis of structural determinants of the substrate specificity in alkali cation exchangers.
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