The potassium channel from Streptomyces lividans is an integral membrane protein with sequence similarity to all known K+ channels, particularly in the pore region. X-ray analysis with data to 3.2 angstroms reveals that four identical subunits create an inverted teepee, or cone, cradling the selectivity filter of the pore in its outer end. The narrow selectivity filter is only 12 angstroms long, whereas the remainder of the pore is wider and lined with hydrophobic amino acids. A large water-filled cavity and helix dipoles are positioned so as to overcome electrostatic destabilization of an ion in the pore at the center of the bilayer. Main chain carbonyl oxygen atoms from the K+ channel signature sequence line the selectivity filter, which is held open by structural constraints to coordinate K+ ions but not smaller Na+ ions. The selectivity filter contains two K+ ions about 7.5 angstroms apart. This configuration promotes ion conduction by exploiting electrostatic repulsive forces to overcome attractive forces between K+ ions and the selectivity filter. The architecture of the pore establishes the physical principles underlying selective K+ conduction.

中文翻译：

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钾通道的结构：钾离子传导和选择性的分子基础。

链霉菌链霉菌的钾通道是一种完整的膜蛋白，与所有已知的K +通道具有序列相似性，尤其是在孔区域。对数据进行3.2埃的X射线分析后发现，四个相同的亚基形成了一个倒置的圆锥形圆锥体或圆锥形，从而在其外端形成了孔的选择性过滤器。狭窄的选择性过滤器只有12埃长，而孔的其余部分更宽且衬有疏水性氨基酸。放置一个充满水的大空腔和螺旋偶极子，以克服双层中心孔中离子的静电不稳定作用。来自K +通道标记序列的主链羰基氧原子排列在选择性过滤器上，选择性过滤器因结构限制而保持打开状态，以协调K +离子而不是较小的Na +离子。选择性滤光片包含两个相距约7.5埃的K +离子。通过利用静电排斥力克服K +离子与选择性过滤器之间的吸引力，此配置可促进离子传导。孔的结构建立了选择性K +传导基础的物理原理。