Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 Å resolution
Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 Å resolution
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DOI：
10.1038/35102009
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发表时间：
2001-11-01
期刊：
影响因子：
64.8
通讯作者：
MacKinnon, R
中科院分区：
文献类型：
--
作者：
Zhou, YF;Morais-Cabral, JH;MacKinnon, R
离子转运蛋白必须去除离子的水合外壳，以根据离子的大小和电荷选择性地协调离子。为了发现K+通道如何解决离子传导的这一基本问题，我们用单克隆Fab抗体片段在2.0埃分辨率下解决了复合物中KcsA K+通道的结构。在这里，我们展示了K+通道如何在细胞外入口通道置换离子周围的水分子，以及它如何在细胞内入口通道附近的空腔中将K+离子保持在水分子的方形反棱镜中。选择性过滤器内的羰基氧原子在每个K+结合位点周围形成一个非常相似的方形反棱镜，仿佛在模仿水合作用的水。选择性过滤器在低K+溶液中改变了离子配位结构。这种结构变化对选择性滤波器在细胞环境中的运行至关重要，在细胞环境中，选择性滤波器附近的K+离子浓度随着通道门控的响应而变化。
Ion transport proteins must remove an ion's hydration shell to coordinate the ion selectively on the basis of its size and charge. To discover how the K+ channel solves this fundamental aspect of ion conduction, we solved the structure of the KcsA K+ channel in complex with a monoclonal Fab antibody fragment at 2.0 Angstrom resolution. Here we show how the K+ channel displaces water molecules around an ion at its extracellular entryway, and how it holds a K+ ion in a square antiprism of water molecules in a cavity near its intracellular entryway. Carbonyl oxygen atoms within the selectivity filter form a very similar square antiprism around each K+ binding site, as if to mimic the waters of hydration. The selectivity filter changes its ion coordination structure in low K+ solutions. This structural change is crucial to the operation of the selectivity filter in the cellular context, where the K+ ion concentration near the selectivity filter varies in response to channel gating.