GATING OF SHAKER K+ CHANNELS .2. THE COMPONENTS OF GATING CURRENTS AND A MODEL OF CHANNEL ACTIVATION
GATING OF SHAKER K+ CHANNELS .2. THE COMPONENTS OF GATING CURRENTS AND A MODEL OF CHANNEL ACTIVATION
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DOI：
10.1016/s0006-3495(94)80882-3
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发表时间：
1994-04-01
影响因子：
3.4
通讯作者：
STEFANI, E
中科院分区：
文献类型：
--
作者：
BEZANILLA, F;PEROZO, E;STEFANI, E
研究了非洲爪蟾卵母细胞中表达的Shaker K+通道门控电流的稳态和动力学特性，并用切开卵母细胞电压痉挛法记录了门控电流。电荷-电位（Q-V）曲线揭示了至少两种电荷分量，第一种电荷在超极化区（V-1/2 = -63 mV）运动，第二种电荷具有较大的视价，在去极化区（V-1/2 = -44 mV）运动。门控电流的动力学分析还揭示了两个指数衰减分量，它们的电压依赖关系与稳态中描述的电荷分量相对应。第一个成分被发现与产生离子和门控电流的科尔-摩尔位移的预脉冲效应有关，并且似乎完全发生在通道的封闭构象中。第二个组成部分似乎与发生在封闭状态之间的事件有关，而封闭状态恰好在向开放状态的转换之前，但不包括在向开放状态的转换之前。ON和OFF门控电流在第二分量变得重要的电位处表现出明显的上升相，该区域对应于通道打开的电位范围。结果不能用简单的并行模型来解释，但数据可以拟合到一个序列模型，该模型可能与假定的四个亚基以合作方式的首次重排有关，然后是协调一致的电荷运动，导致开放通道。第一个系列的电荷运动是由几个封闭状态之间的跃迁产生的，每一步携带不到两个电子电荷，而携带大约3.5个电子电荷的步骤可以解释第二个组成部分。这一步之后是过渡到携带少于0.5个电子电荷的开态。该模型能够再现门控电流的所有动力学和稳态特性，并预测离子电流的许多特性。
Steady-state and kinetic properties of gating currents of the Shaker K+ channels were studied in channels expressed in Xenopus oocytes and recorded with the cut-open oocyte voltage cramp. The charge versus potential (Q-V) curve reveals at least two components of charge, the first moving in the hyperpolarized region (V-1/2 = -63 mV) and the second, with a larger apparent valence, moving in the more depolarized region (V-1/2 = -44 mV). The kinetic analysis of gating currents revealed also two exponential decaying components that corresponded in their voltage dependence with the charge components described in the steady-state. The first component was found to correlate with the effects of prepulses that produce the Cole-Moore shift of the ionic and gating currents and seems to be occurring completely within closed conformations of the channel. The second component seems to be related to the events occurring between the closed states just preceding, but not including, the transition to the open state. The ON and OFF gating currents exhibit a pronounced rising phase at potentials at which the second component becomes important, and this region corresponds to the potential range where the channel opens. The results could not be explained with simple parallel models, but the data can be fitted to a sequential model that could be related to a first rearrangement of the putative four subunits in cooperative fashion, followed by a concerted charge movement that leads to the open channel. The first series of charge movements are produced by transitions between several closed states carrying less than two electronic charges per step, while a step carrying about 3.5 electronic charges can explain the second component. This step is followed by the transition to the open state carrying less than 0.5 electronic charges. This model is able to reproduce all the kinetic and steady-state properties of the gating currents and predicts many of the properties of the ionic currents.