ALTERATION OF IONIC SELECTIVITY OF A K+ CHANNEL BY MUTATION OF THE H5 REGION
ALTERATION OF IONIC SELECTIVITY OF A K+ CHANNEL BY MUTATION OF THE H5 REGION
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DOI：
10.1038/349700a0
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发表时间：
1991-02-21
期刊：
影响因子：
64.8
通讯作者：
SCHWARZ, TL
中科院分区：
文献类型：
--
作者：
YOOL, AJ;SCHWARZ, TL
钾离子通道的高离子选择性是这种不同类型的膜蛋白的一个统一特征。尽管K+通道在调节和动力学方面有很大的不同，但生理学研究提出了一个共同的结构：一个包含多个离子结合位点的单列孔，在1-5的两端具有更宽的前庭。我们已经使用定点突变和单通道记录来确定影响果蝇克隆的A型K+通道离子选择性的分子区域。H5(第五疏水区6)上的单一氨基酸取代增强了直径大于K+的NH4+和Rb+离子的通过，而不影响通道排除较小阳离子Na+的能力。实质上改变了选择性的突变对通道的选通特性几乎没有影响。我们得出结论，H5区很可能排列在K+通道的孔道上。
THE high ionic selectivity of K+ channels is a unifying feature of this diverse class of membrane proteins. Though K+ channels differ widely in regulation and kinetics, physiological studies have suggested a common structure: a single file pore containing mulitiple ion-binding sites and having broader vestibules at both ends 1-5. We have used site-directed mutagenesis and single-channel recordings to identify a molecular region that influences ionic selectivity in a cloned A-type K+ channel from Drosophila. Single amino-acid substitutions in H5, the fifth hydrophobic region 6, enhanced the passage of NH4+ and Rb+, ions with diameters larger than K+, without compromising the ability of the channel to exclude the smaller cation, Na+. The mutations that substantially altered selectivity had little effect on the gating properties of the channel. We conclude that the H5 region is likely to line the pore of the K+ channel.