Trapping of organic blockers by closing of voltage-dependent K+ channels - Evidence for a trap door mechanism of activation gating
Trapping of organic blockers by closing of voltage-dependent K+ channels - Evidence for a trap door mechanism of activation gating
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DOI：
10.1085/jgp.109.5.527
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发表时间：
1997-05-01
影响因子：
3.8
通讯作者：
Yellen, G
中科院分区：
文献类型：
--
作者：
Holmgren, M;Smith, PL;Yellen, G
有机小分子，如季铵化合物，长期以来一直被用于探测电压依赖性K+通道的渗透和门控。对于大多数K+通道，细胞内应用的季铵（OA）化合物，如四乙基铵（TEA）和癸基三乙基铵（C-10），主要表现为开放通道阻断剂：它们只能在通道开放时进入通道，并且它们必须在通道关闭前解离。在某些情况下，可以在QA阻断剂仍然结合的情况下迫使通道关闭，结果是阻断剂被“捕获”。Armstrong（J. Gen. Physiol. 58：413-437）发现，在非常负的电压下，鱿鱼轴突K+通道表现出从QA阻断恢复的缓慢阶段，与这种捕获一致。在我们对克隆的Shaker通道的研究中，我们发现野生型通道既不能捕获TEA也不能捕获C-10，但是在S6中具有点突变的通道可以非常有效地捕获任一化合物。捕获发生在通道门控的能量变化非常小的情况下，这表明在这些通道中，门可以起到活门或铰链盖的作用，其阻塞从细胞内溶液到阻断剂位点和到窄离子选择性孔的通路。
Small organic molecules, like quaternary ammonium compounds, have long been used to probe both the permeation and gating of voltage-dependent K+ channels. For most K+ channels, intracellularly applied quaternary ammonium (OA) compounds such as tetraethylammonium (TEA) and decyltriethylammonium (C-10) behave primarily as open channel blockers: they can enter the channel only when it is open, and they must dissociate before the channel can close. In some cases, it is possible to force the channel to close with a QA blocker still bound, with the result that the blocker is ''trapped.'' Armstrong (J. Gen. Physiol. 58:413-437) found that at very negative voltages, squid axon K+ channels exhibited a slow phase: of recovery from QA blockade consistent with such trapping. In our studies on the cloned Shaker channel, we find that wild-type channels can trap neither TEA nor C-10, but channels with a point mutation in S6 can trap either compound very efficiently. The trapping occurs with very little change in the energetics of channel gating, suggesting that in these channels the gate may function as a trap door or hinged lid that occludes access from the intracellular solution to the blocker site and to the narrow ion-selective pore.