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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Topological analysis of a plant vacuolar Na+/H+ antiporter reveals a luminal C terminus that regulates antiporter cation selectivity.
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Topological analysis of a plant vacuolar Na+/H+ antiporter reveals a luminal C terminus that regulates antiporter cation selectivity.

机译：植物液泡Na + / H +反向转运蛋白的拓扑分析显示，腔C末端可调节反向转运阳离子的选择性。

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摘要

We conducted an analysis of the topology of AtNHX1, an Arabidopsis thaliana vacuolar Na+/H+ antiporter. Several hydrophilic regions of the antiporter were tagged with a hemagglutinin epitope, and protease protection assays were conducted to determine the membrane topology of the antiporter by using yeast as a heterologous expression system. The overall structure of AtNHX1 is distinct from the human Na+/H+ antiporter NHE1 or any known Na+/H+ antiporter. It is comprised of nine transmembrane domains and a hydrophilic C-terminal domain. Three hydrophobic regions do not appear to span the tonoplast membrane, yet appear to be membrane associated. Our results also indicate that, whereas the N terminus of AtNHX1 is facing the cytosol, almost the entire C-terminal hydrophilic region resides in the vacuolar lumen. Deletion of the hydrophilic C terminus resulted in a dramatic increase in the relative rate of Na+/H+ transport. The ratio of Na+/K+ transport was twice that of the unmodified AtNHX1. This altered ratio resulted from a relatively small decrease in K+/H+ transport with a large increase in Na+/H+ transport. The vacuolar localization of the C terminus of the AtNHX1, taken together with the regulation of the antiporter selectivity by its C terminus, demonstrates the existence of luminal vacuolar regulatory mechanisms of the antiporter activity.
机译：我们对拟南芥液泡Na + / H +反向转运蛋白AtNHX1的拓扑结构进行了分析。用血凝素表位标记反转运蛋白的几个亲水区域，并通过使用酵母作为异源表达系统进行蛋白酶保护测定以确定反转运蛋白的膜拓扑。 AtNHX1的整体结构不同于人的Na + / H +反向转运蛋白NHE1或任何已知的Na + / H +反向转运蛋白。它由九个跨膜结构域和一个亲水性C端结构域组成。三个疏水区似乎不跨越液泡膜，但似乎与膜相关。我们的结果还表明，尽管AtNHX1的N端面向细胞质，但几乎整个C端亲水区都位于液泡腔中。亲水性C末端的删除导致Na + / H +相对转运速率的急剧增加。 Na + / K +传输的比率是未修饰的AtNHX1的两倍。这种变化的比率是由于K + / H +传输量相对较小的下降以及Na + / H +传输量的较大增加所致。 AtNHX1的C末端的液泡定位，连同其C末端对反向转运蛋白选择性的调节，证明了存在反向转运蛋白活性的腔液泡调节机制。

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