Mikhailov Michael V, Campbell Jeff D, de Wet Heidi, Shimomura Kenju, Zadek Brittany, Collins Richard F, Sansom Mark S P, Ford Robert C, Ashcroft Frances M
Laboratory of Physiology, University of Oxford, Oxford, UK.
EMBO J. 2005 Dec 7;24(23):4166-75. doi: 10.1038/sj.emboj.7600877. Epub 2005 Nov 24.
ATP-sensitive potassium (K(ATP)) channels conduct potassium ions across cell membranes and thereby couple cellular energy metabolism to membrane electrical activity. Here, we report the heterologous expression and purification of a functionally active K(ATP) channel complex composed of pore-forming Kir6.2 and regulatory SUR1 subunits, and determination of its structure at 18 A resolution by single-particle electron microscopy. The purified channel shows ATP-ase activity similar to that of ATP-binding cassette proteins related to SUR1, and supports Rb(+) fluxes when reconstituted into liposomes. It has a compact structure, with four SUR1 subunits embracing a central Kir6.2 tetramer in both transmembrane and cytosolic domains. A cleft between adjacent SUR1s provides a route by which ATP may access its binding site on Kir6.2. The nucleotide-binding domains of adjacent SUR1 appear to interact, and form a large docking platform for cytosolic proteins. The structure, in combination with molecular modelling, suggests how SUR1 interacts with Kir6.2.
ATP敏感性钾（K(ATP)）通道介导钾离子跨细胞膜转运，从而将细胞能量代谢与膜电活动联系起来。在此，我们报告了一种由成孔亚基Kir6.2和调节亚基SUR1组成的具有功能活性的K(ATP)通道复合物的异源表达和纯化，并通过单颗粒电子显微镜在18埃分辨率下测定了其结构。纯化后的通道显示出与SUR1相关的ATP结合盒蛋白相似的ATP酶活性，并且在重构到脂质体中时支持铷离子通量。它具有紧凑的结构，在跨膜和胞质结构域中，四个SUR1亚基围绕着一个中央Kir6.2四聚体。相邻SUR1之间的裂隙提供了一条途径，通过该途径ATP可以进入其在Kir6.2上的结合位点。相邻SUR1的核苷酸结合结构域似乎相互作用，并形成了一个用于胞质蛋白的大型对接平台。该结构与分子建模相结合，揭示了SUR1与Kir6.2的相互作用方式。
