Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons.
Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons.
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DOI：
10.1085/jgp.58.4.413
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发表时间：
1971-10
期刊：
影响因子：
--
通讯作者：
Armstrong CM
中科院分区：
文献类型：
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作者：
Armstrong CM
将与TEA+(四乙基氨离子)有关的一些化合物注入鱿鱼轴突，测定它们对钾电导的影响。在大多数这些离子中，季氮被三个乙基和第四个非常疏水的基团包围。几种离子导致gK失活，这是一种在鱿鱼轴突中不常见的离子门控；即在去极化后，gK增加，然后自发减少到其峰值的一小部分，即使去极化保持不变。对这种门控机制的观察表明：(A)QA(季铵)离子只进入具有开放激活门(正常通透性门)的K+通道。(B)QA闭塞通道的激活门不容易关闭。(C)超极化有助于清除通道中的QA离子。(D)提高外部K+浓度也有助于清除通道中的QA离子。观察结果(C)和(D)强烈地表明K+离子通过孔的方式穿过膜，它们不能用通常类型的载体模型来解释。数据表明，K+孔有两个截然不同的部分：宽大的内口可以接受水合的K+离子或类TEA+离子，而较窄的部分可以接受脱水或部分脱水的K+离子，但不能接受TEA+。
A number of compounds related to TEA+ (tetraethylammoniumion) were injected into squid axons and their effects on g K (the potassium conductance) were determined. In most of these ions a quaternary nitrogen is surrounded by three ethyl groups and a fourth group that is very hydrophobic. Several of the ions cause inactivation of g K, a type of ionic gating that is not normally seen in squid axon; i.e., after depolarization g K increases and then spontaneously decreases to a small fraction of its peak value even though the depolarization is maintained. Observations on the mechanism of this gating show that (a) QA (quaternary ammonium) ions only enter K+ channels that have open activation gates (the normal permeability gates). (b) The activation gates of QA-occluded channels do not close readily. (c) Hyperpolarization helps to clear QA ions from the channels. (d) Raising the external K+ concentration also helps to clear QA ions from the channels. Observations (c) and (d) strongly suggest that K+ ions traverse the membrane by way of pores, and they cannot be explained by the usual type of carrier model. The data suggest that a K+ pore has two distinct parts: a wide inner mouth that can accept a hydrated K+ ion or a TEA+-like ion, and a narrower portion that can accept a dehydrated or partially dehydrated K+ ion, but not TEA+.