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Structure of a Na+/H+ antiporter and insights into mechanism of action and regulation by pH

机译：Na + / H +反转运蛋白的结构以及对作用机理和pH调节的见解

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The control by Na+/ H+ antiporters of sodium/proton concentration and cell volume is crucial for the viability of all cells. Adaptation to high salinity and/or extreme pH in plants and bacteria or in human heart muscles requires the action of Na+/H+ antiporters. Their activity is tightly controlled by pH. Here we present the crystal structure of pH-downregulated NhaA, the main antiporter of Escherichia coli and many enterobacteria. A negatively charged ion funnel opens to the cytoplasm and ends in the middle of the membrane at the putative ion-binding site. There, a unique assembly of two pairs of short helices connected by crossed, extended chains creates a balanced electrostatic environment. We propose that the binding of charged substrates causes an electric imbalance, inducing movements, that permit a rapid alternating-access mechanism. This ion-exchange machinery is regulated by a conformational change elicited by a pH signal perceived at the entry to the cytoplasmic funnel.
机译：Na + / H +反向转运蛋白对钠/质子浓度和细胞体积的控制对于所有细胞的生存至关重要。要适应植物和细菌或人心脏肌肉中的高盐度和/或极端pH，需要Na + / H +反转运蛋白的作用。它们的活性受pH值严格控制。在这里，我们介绍pH值下调的NhaA，大肠杆菌和许多肠杆菌的主要反转运蛋白的晶体结构。带负电荷的离子漏斗通向细胞质，并在假定的离子结合位点的膜中间终止。在那里，通过交叉的延伸链连接的两对短螺旋的独特组装产生了平衡的静电环境。我们提出带电基板的结合会引起电不平衡，从而引起运动，从而允许快速交替访问机制。这种离子交换机制受在细胞质漏斗入口处感知到的pH信号引起的构象变化的调节。

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