期刊
JOURNAL OF GENERAL PHYSIOLOGY
卷 138, 期 4, 页码 421-436出版社
ROCKEFELLER UNIV PRESS
DOI: 10.1085/jgp.201110684
关键词
-
类别
资金
- Howard Hughes Medical Institute Funding Source: Medline
- NIGMS NIH HHS [R01 GM094468-02, R01 GM094468, R01 GM096053-01A1, R01 GM096053, T32 GM007596] Funding Source: Medline
Ba2+, a doubly charged analogue of K+, specifically blocks K+ channels by virtue of electrostatic stabilization in the permeation pathway. Ba2+ block is used here as a tool to determine the equilibrium binding affinity for various monovalent cations at specific sites in the selectivity filter of a noninactivating mutant of KcsA. At high concentrations of external K+, the block-time distribution is double exponential, marking at least two Ba2+ sites in the selectivity filter, in accord with a Ba2+-containing crystal structure of KcsA. By analyzing block as a function of extracellular K+, we determined the equilibrium dissociation constant of K+ and of other monovalent cations at an extracellular site, presumably S1, to arrive at a selectivity sequence for binding at this site: Rb+ (3 mu M) > Cs+ (23 mu M) > K+ (29 mu M) > NH4+ (440 mu M) >> Na+ and Li+ (> 1 M). This represents an unusually high selectivity for K+ over Na+, with vertical bar Delta Delta G(0)vertical bar of at least 7 kcal mol(-1). These results fit well with other kinetic measurements of selectivity as well as with the many crystal structures of KcsA in various ionic conditions.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据