Shifts in cytosolic pH have been recognized as key signaling events and mounting evidence supports the interdependence between H + and Ca 2+ signaling in eukaryotic cells. Among the cellular pH-stats, K + /H + exchange at various membranes is paramount in plant cells. Vacuolar K + /H + exchangers of the NHX (Na + ,K + /H + exchanger) family control luminal pH and, together with K + and H + transporters at the plasma membrane, have been suggested to also regulate cytoplasmic pH. We show the regulation of vacuolar K + /H + exchange by cytoplasmic pH and the calmodulin-like protein CML18 in Arabidopsis. The crystal structure and physicochemical properties of CML18 indicate that this protein senses pH shifts. Interaction of CML18 with tonoplast exchangers NHX1 and NHX2 was favored at acidic pH, a physiological condition elicited by K + starvation in Arabidopsis roots, whereas excess K + produced cytoplasmic alkalinization and CML18 dissociation. These results imply that the pH-responsive NHX-CML18 module is an essential component of the cellular K + - and pH-stats.

中文翻译：

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液泡 K + / H + 交换剂和钙调蛋白样 CML18 构成调节拟南芥中 K + 状态的 pH 传感模块


胞质 pH 值的变化被认为是关键的信号转导事件，越来越多的证据支持真核细胞中 H + 和 Ca 2+ 信号转导之间的相互依赖性。在细胞 pH 统计中，各种膜的 K + /H + 交换在植物细胞中至关重要。NHX（Na + ，K + /H + 交换蛋白）家族的液泡 K + /H + 交换蛋白控制管腔 pH 值，并且与质膜上的 K + 和 H + 转运蛋白一起，被认为也可以调节细胞质 pH 值。我们展示了拟南芥中细胞质 pH 值和钙调蛋白样蛋白 CML18 对液泡 K + / H + 交换的调节。CML18 的晶体结构和理化性质表明，这种蛋白质会感应 pH 值变化。CML18 与钙质体交换剂 NHX1 和 NHX2 的相互作用在酸性 pH 值下有利，这是由拟南芥根中 K + 饥饿引起的生理条件，而过量的 K + 产生细胞质碱化和 CML18 解离。这些结果表明，pH 响应型 NHX-CML18 模块是蜂窝 K + - 和 pH 统计的重要组成部分。