CA2+ CHANNEL SELECTIVITY AT A SINGLE-LOCUS FOR HIGH-AFFINITY CA2+ INTERACTIONS
CA2+ CHANNEL SELECTIVITY AT A SINGLE-LOCUS FOR HIGH-AFFINITY CA2+ INTERACTIONS
复制标题
DOI：
10.1016/0896-6273(95)90100-0
复制
发表时间：
1995-11-01
期刊：
影响因子：
16.2
通讯作者：
TSIEN, RW
中科院分区：
文献类型：
--
作者：
ELLINOR, PT;YANG, J;TSIEN, RW
Ca 2+通道显示出显着的选择性和渗透性，传统上归因于多个，离散的Ca 2+结合位点内衬孔。Ca 2+通道α 1亚基的四个成孔区段中的每一个都含有一个谷氨酸残基，其有助于高亲和力的Ca 2+相互作用。用谷氨酰胺或丙氨酸替换所有四个P-区谷氨酸盐废除了微摩尔Ca 2+对单价电流的阻断，而没有揭示任何额外的独立的高亲和力Ca 2+结合位点。四个谷氨酸的成对替换排除了它们形成两个独立的高亲和力位点的假设。通过用天冬氨酸、谷氨酰胺或丙氨酸取代谷氨酸来系统性改变侧链长度、电荷和极性，削弱了Ca 2+相互作用，并且从一个重复到另一个重复具有相当大的不对称性。重复I中的P-区谷氨酸对天冬氨酸替代而不是谷氨酰胺替代的敏感性是不寻常的。虽然所有四种谷氨酸盐在支持与单个Ca 2+离子的高亲和力相互作用方面合作，但它们也影响多个二价阳离子之间的相互作用。
Ca2+ channels display remarkable selectivity and permeability, traditionally attributed to multiple, discrete Ca2+ binding sites lining the pore. Each of the four pore-forming segments of Ca2+ channel al subunits contains a glutamate residue that contributes to high-affinity Ca2+ interactions. Replacement of all four P-region glutamates with glutamine or alanine abolished micromolar Ca2+ block of monovalent current without revealing any additional independent high-affinity Ca2+ binding site. Pairwise replacements of the four glutamates excluded the hypothesis that they form two independent high-affinity sites. Systematic alterations of side-chain length, charge, and polarity by glutamate replacement with aspartate, glutamine, or alanine weakened the Ca2+ interaction, with considerable asymmetry from one repeat to another. The P-region glutamate in repeat I was unusual in its sensitivity to aspartate replacement but not glutamine substitution. While all four glutamates cooperate in supporting high-affinity interactions with single Ca2+ ions, they also influence the interaction between multiple divalent cations.