Tai K K, Goldstein S A
Department of Pediatrics, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
Nature. 1998 Feb 5;391(6667):605-8. doi: 10.1038/35416.
Ion channels form transmembrane water-filled pores that allow ions to cross membranes in a rapid and selective fashion. The amino acid residues that line these pores have been sought to reveal the mechanisms of ion conduction and selectivity. The pore (P) loop is a stretch of residues that influences single-channel-current amplitude, selectivity among ions and open-channel blockade and is conserved in potassium-channel subunits previously recognized to contribute to pore formation. To date, potassium-channel pores have been shown to form by symmetrical alignment of four P loops around a central conduction pathway. Here we show that the selectivity-determining pore region of the voltage-gated potassium channel of human heart through which the I(Ks) current passes includes the transmembrane segment of the non-P-loop protein minK. Two adjacent residues in this segment of minK are exposed in the pore on either side of a short barrier that restricts the movement of sodium, cadmium and zinc ions across the membrane. Thus, potassium-selective pores are not restricted to P loops or a strict P-loop geometry.
离子通道形成跨膜的充满水的孔道，使离子能够以快速且选择性的方式穿过膜。人们一直在寻找构成这些孔道的氨基酸残基，以揭示离子传导和选择性的机制。孔道（P）环是一段影响单通道电流幅度、离子间选择性以及开放通道阻断的残基序列，并且在先前被认为有助于孔道形成的钾通道亚基中是保守的。迄今为止，已表明钾通道孔道是由围绕中央传导途径对称排列的四个P环形成的。在这里，我们表明人类心脏电压门控钾通道的I(Ks)电流所通过的选择性决定孔道区域包括非P环蛋白minK的跨膜片段。minK这一片段中的两个相邻残基暴露在一个短屏障两侧的孔道中，该屏障限制了钠、镉和锌离子跨膜移动。因此，钾选择性孔道并不局限于P环或严格的P环几何结构。
