Structural basis for Ca2+ selectivity of a voltage-gated calcium channel.
Structural basis for Ca2+ selectivity of a voltage-gated calcium channel.
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作者：
电压门控钙(Cav)通道催化钙离子快速、高选择性地内流到细胞内，尽管胞外Na+浓度高70倍。CAV通道如何解决这一基本的生物物理问题仍不清楚。在这里，我们报告了在同源四聚体细菌NAV通道NAAB中构建的钙选择性过滤器的生理和结晶学分析。我们的结果揭示了水合的Ca~(2+)与两个高亲和力的Ca~(2+)结合部位的相互作用，然后是第三个低亲和力的部位，它将在Ca~(2+)向内移动时协调它。在选择性过滤器入口，位置1由四个羧基侧链组成，它们在决定钙离子选择性方面起着关键作用。Cd~(2+)和Mn~(2+)是以四个羧基和四个主链羰基为靶位的单占位化合物。低亲和力部位3仅由四个主链羰基形成，它们介导出口进入中央空腔。这种孔结构提出了一种传导途径，涉及两个主态之间的转变，其中一个或两个水合钙离子结合在选择性过滤器中，并支持通过逐步结合过程的离子渗透的“敲除”机制。我们的CaVAb模型的多离子选择性过滤器为理解脊椎动物Cav通道的离子选择性和电导机制建立了一个结构框架。
Voltage-gated calcium (CaV) channels catalyze rapid, highly selective influx of Ca2+ into cells despite 70-fold higher extracellular concentration of Na+. How CaV channels solve this fundamental biophysical problem remains unclear. Here we report physiological and crystallographic analyses of a calcium selectivity filter constructed in the homotetrameric bacterial NaV channel NaVAb. Our results reveal interactions of hydrated Ca2+ with two high-affinity Ca2+-binding sites followed by a third lower-affinity site that would coordinate Ca2+ as it moves inward. At the selectivity filter entry, Site 1 is formed by four carboxyl side-chains, which play a critical role in determining Ca2+ selectivity. Four carboxyls plus four backbone carbonyls form Site 2, which is targeted by the blocking cations, Cd2+ and Mn2+, with single occupancy. The lower-affinity Site 3 is formed by four backbone carbonyls alone, which mediate exit into the central cavity. This pore architecture suggests a conduction pathway involving transitions between two main states with one or two hydrated Ca2+ ions bound in the selectivity filter and supports a “knock-off” mechanism of ion permeation through a stepwise-binding process. The multi-ion selectivity filter of our CaVAb model establishes a structural framework for understanding mechanisms of ion selectivity and conductance by vertebrate CaV channels.
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DOI：
10.1085/jgp.201311012
发表时间：
2013-09
期刊：
The Journal of general physiology
影响因子：
--
作者：
Gamal El-Din TM;Martinez GQ;Payandeh J;Scheuer T;Catterall WA
通讯作者：
Catterall WA
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
16.2
作者：
ELLINOR, PT;YANG, J;TSIEN, RW
通讯作者：
TSIEN, RW
影响因子：
5.5
作者：
ALMERS, W;MCCLESKEY, EW;PALADE, PT
通讯作者：
PALADE, PT
DOI：
10.1107/s0907444909052925
发表时间：
2010-02
期刊：
Acta crystallographica. Section D, Biological crystallography
影响因子：
--
作者：
Adams PD;Afonine PV;Bunkóczi G;Chen VB;Davis IW;Echols N;Headd JJ;Hung LW;Kapral GJ;Grosse-Kunstleve RW;McCoy AJ;Moriarty NW;Oeffner R;Read RJ;Richardson DC;Richardson JS;Terwilliger TC;Zwart PH
通讯作者：
Zwart PH