Conversion of aquaporin 6 from an anion channel to a water-selective channel by a single amino acid substitution
Conversion of aquaporin 6 from an anion channel to a water-selective channel by a single amino acid substitution
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DOI：
10.1073/pnas.0409232102
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发表时间：
2005-02-08
影响因子：
11.1
通讯作者：
Yasui, M
中科院分区：
文献类型：
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作者：
Liu, K;Kozono, D;Yasui, M
水通道蛋白（Aquaporin，AQP）6属于水通道蛋白家族。与其他水通道蛋白不同，AQP 6不是水通道，而是阴离子选择性通道。单通道分析表明，AQP 6在关闭和打开状态之间快速闪烁。AQP 1的原子结构和哺乳动物水通道蛋白的氨基酸序列比对揭示了两个非常保守的甘氨酸残基：跨膜螺旋（TM）2中的Gly-57和TM 5中的Gly-173，它们位于人AQP 1中两个螺旋交叉的接触点。独特的是，所有已知的AQP 6的哺乳动物直系同源物在对应于Gly-57的位置处具有天冬酰胺残基（Asn-60）。在这里，我们表明，一个单一的残基取代（N60 G在大鼠AQP 6）完全消除了阴离子渗透性AQP 6在非洲爪蟾卵母细胞中表达时，但N60 G卵母细胞表现出显着更高的渗透水渗透性基础条件下。替换在这个网站上的AQP 0，AQP 1，和AQP 2阻断突变体在卵母细胞质膜的表达。我们建议，在AQP 6中的TM 2和TM 5之间的接触点处的天冬酰胺残基可以作为在阴离子渗透过程中快速结构振荡所需的摇摆板。
Aquaporin (AQP) 6 belongs to the aquaporin water channel family. Unlike other aquaporins, AQP6 functions not as a water channel but as an anion-selective channel. Single-channel analyses have shown AQP6 to flicker rapidly between closed and open status. The atomic structure of AQP1 and amino acid sequence alignments of the mammalian aquaporins reveal two well conserved glycine residues: Gly-57 in transmembrane helix (TM) 2 and Gly-173 in TM5 reside at the contact point where the two helices cross in human AQP1. Uniquely, all known mammalian orthologs of AQP6 have an asparagine residue (Asn-60) at the position corresponding to Gly-57. Here we show that a single residue substitution (N60G in rat AQP6) totally eliminates the anion permeability of AQP6 when expressed in Xenopus oocytes, but the N60G oocytes exhibit significantly higher osmotic water permeability under basal conditions. Replacement of the glycine at this site in AQP0, AQP1, and AQP2 blocked expression of the mutants at the oocyte plasma membrane. We propose that the asparagine residue at the contact point between TM2 and TM5 in AQP6 may function as a teeter board needed for rapid structural oscillations during anion permeation.