Stable cation coordination at a single outer pore residue defines permeation properties in Kir channels

被引:26
作者
Wischmeyer, E [1 ]
Döring, F [1 ]
Karschin, A [1 ]
机构
[1] Max Planck Inst Biophys Chem, Dept Mol Neurobiol Signal Transduct, D-37070 Gottingen, Germany
关键词
inwardly rectifying K channel; Kir7.1; Kir2.1; ion selectivity; anomalous mole fraction; multi-ion pore;
D O I
10.1016/S0014-5793(99)01769-X
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
In epithelial Kir7.1 channels a non-conserved methionine in the outer pore region adjacent to the G-Y-G selectivity filter (position +2) was found to determine unique properties for permeant and blocking ions characteristic of a K+ channel in a single-occupancy state. The monovalent cation permeability sequence of Kir7,1 channels expressed in Xenopus oocytes was T1(+) > K+ > Rb+ > NH4+ > Cs+ > Na+ > Li+, but the macroscopic conductance for Rb+ was similar to 8-fold larger than for the smaller K+ ions, and decreased similar to 40-fold with the conserved arginine at the +2 position (Kir7.1M125R). Moreover, in Kir7.1 Rb+ restored the typical permeation properties of other multi-ion channels indicating that a stable coordination of permeant ions at the +2 position defines the initial step in the conduction pathway of Kir channels. (C) 2000 Federation of European Biochemical Societies.
引用
收藏
页码:115 / 120
页数:6
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