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首页> 外文期刊>Biochimica et biophysica acta. Biomembranes >Characterization of the ion transport activity of the budding yeast Na+/H+ antiporter, Nha1p, using isolated secretory vesicles
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Characterization of the ion transport activity of the budding yeast Na+/H+ antiporter, Nha1p, using isolated secretory vesicles

机译：使用分离的分泌小泡表征出芽酵母Na + / H +反转运蛋白Nha1p的离子转运活性

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摘要

The Saccharomyces cerevisiae Nha1p, a plasma membrane protein belonging to the monovalent cation/proton antiporter family, plays a key role in the salt tolerance and pH regulation of cells. We examined the molecular function of Nha1p by using secretory vesicles isolated from a temperature sensitive secretory mutant, sec4-2, in vitro. The isolated secretory vesicles contained newly synthesized Nha1p en route to the plasma membrane and showed antiporter activity exchanging H+ for monovalent alkali metal cations. An amino acid substitution in Nha1p (D266N, Asp-266 to Asn) almost completely abolished the Na+/H+ but not K+/H+ antiport activity, confirming the validity of this assay system as well as the functional importance of Asp-266, especially for selectivity of substrate cations. Nha1p catalyzes transport of Na+ and K+ with similar affinity (12.7 mM and 12.4 mM), and with lower affinity for Rb+ and Li+. Nha1p activity is associated with a net charge movement across the membrane, transporting more protons per single sodium ion (i.e., electrogenic). This feature is similar to the bacterial Na+/H+ antiporters, whereas other known eukaryotic Na+/H+ antiporters are electroneutral. The ion selectivity and the stoichiometry suggest a unique physiological role of Nha1p which is distinct from that of other known Na+/H+ antiporters. (c) 2005 Elsevier B.V. All rights reserved.
机译：酿酒酵母Nha1p是一种属于单价阳离子/质子反转运蛋白家族的质膜蛋白，在细胞的耐盐性和pH调节中起关键作用。我们通过使用从温度敏感分泌突变体sec4-2分离的分泌小泡体外研究了Nha1p的分子功能。分离的分泌囊泡在到达质膜的途中含有新合成的Nha1p，并表现出交换转运蛋白H +交换一价碱金属阳离子的抗转运蛋白活性。 Nha1p中的氨基酸取代（D266N，Asp-266转为Asn）几乎完全消除了Na + / H +，但没有消除K + / H +的反转运活性，证实了该测定系统的有效性以及Asp-266的功能重要性，特别是对于底物阳离子的选择性。 Nha1p催化Na +和K +的转运，具有相似的亲和力（12.7 mM和12.4 mM），并且对Rb +和Li +的亲和力较低。 Nha1p的活性与整个膜上的净电荷运动有关，每一个钠离子（即电离子）传输更多的质子。此特征类似于细菌Na + / H +反向转运蛋白，而其他已知的真核Na + / H +反向转运蛋白是电子中性的。离子选择性和化学计量表明Nha1p具有独特的生理作用，这与其他已知的Na + / H +反转运蛋白不同。 （c）2005 Elsevier B.V.保留所有权利。

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