Block of muscle nicotinic receptors by choline suggests that the activation and desensitization gates act as distinct molecular entities.
Block of muscle nicotinic receptors by choline suggests that the activation and desensitization gates act as distinct molecular entities.
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胆碱肌肉烟碱受体的块表明，激活和脱敏的门是不同的分子实体。
DOI：
10.1085/jgp.200509437
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发表时间：
2006-06
期刊：
影响因子：
--
通讯作者：
Grosman C
中科院分区：
文献类型：
--
作者：
Purohit Y;Grosman C
肌肉乙酰胆碱烟碱受体（AChRs）的离子通道阻滞是一种广泛报道的现象。然而，离子流中断或阻断剂与通道门的相互作用的机制仍然不完全表征。在本文中，我们研究了快通道阻断胆碱，季铵阳离子，也是一种内源性弱激动剂的这种受体，和一个有价值的工具，在结构-功能研究。作为胆碱浓度和电压的函数的单通道电流幅度的分析揭示，细胞外胆碱以毫摩尔表观亲和力结合至开放通道孔（在155 mM单价和3.5 mM二价无机阳离子的存在下，KB为12 mM），并且它比乙酰胆碱更快地渗透通道。这一点，连同其相对较小的尺寸（沿着其最长轴为5.5微米），表明孔阻塞胆碱结合位点是选择性过滤器本身，目前的堵塞只是反映了胆碱在该位点的长期逗留。单通道的动力学分析痕迹表明，增加占用的孔阻断网站胆碱（从单通道电流振幅的减少判断）是伴随着延长（表观）开放间隔的持续时间。对许多可能机制的考虑坚定地表明，这种延长是由于胆碱干扰激活门的操作的局部效应（被阻断的受体的关闭比未被阻断的受体的关闭慢1/13），而脱敏门的关闭不受影响。因此，我们认为这两个门作为不同的分子实体。此外，这里获得的关于胆碱如何扭曲观察到的开放时间持续时间的详细理解可以用于补偿激活测定期间的这种伪影。如果我们要了解胆碱是如何与乙酰胆碱受体结合并控制乙酰胆碱受体的，这种校正是必要的。
Ion channel block in muscle acetylcholine nicotinic receptors (AChRs) is an extensively reported phenomenon. Yet, the mechanisms underlying the interruption of ion flow or the interaction of the blocker with the channel's gates remain incompletely characterized. In this paper, we studied fast channel block by choline, a quaternary-ammonium cation that is also an endogenous weak agonist of this receptor, and a valuable tool in structure–function studies. Analysis of the single-channel current amplitude as a function of both choline concentration and voltage revealed that extracellular choline binds to the open-channel pore with millimolar apparent affinity (KB ≅ 12 mM in the presence of ∼155 mM monovalent and 3.5 mM divalent, inorganic cations), and that it permeates the channel faster than acetylcholine. This, together with its relatively small size (∼5.5 Å along its longest axis), suggests that the pore-blocking choline binding site is the selectivity filter itself, and that current blockages simply reflect the longer-lived sojourns of choline at this site. Kinetic analysis of single-channel traces indicated that increasing occupancy of the pore-blocking site by choline (as judged from the reduction of the single-channel current amplitude) is accompanied by the lengthening of (apparent) open interval durations. Consideration of a number of possible mechanisms firmly suggests that this prolongation results from the local effect of choline interfering with the operation of the activation gate (closure of blocked receptors is slower than that of unblocked receptors by a factor of ∼13), whereas closure of the desensitization gate remains unaffected. Thus, we suggest that these two gates act as distinct molecular entities. Also, the detailed understanding gained here on how choline distorts the observed open-time durations can be used to compensate for this artifact during activation assays. This correction is necessary if we are to understand how choline binds to and gates the AChR.
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影响因子：
64.8
作者：
IMOTO, K;BUSCH, C;NUMA, S
通讯作者：
NUMA, S
DOI：
10.1085/jgp.58.4.413
发表时间：
1971-10
期刊：
The Journal of general physiology
影响因子：
--
作者：
Armstrong CM
通讯作者：
Armstrong CM
DOI：
10.1073/pnas.251402498
发表时间：
2001-11-20
影响因子：
11.1
作者：
Grosman, C;Auerbach, A
通讯作者：
Auerbach, A
影响因子：
5.5
作者：
COLQUHOUN, D;DREYER, F;SHERIDAN, RE
通讯作者：
SHERIDAN, RE
影响因子：
5.5
作者：
Akk, G;Steinbach, JH
通讯作者：
Steinbach, JH