The location of a closed channel gate in the GABAA receptor channel.
The location of a closed channel gate in the GABAA receptor channel.
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DOI：
10.1085/jgp.200609639
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发表时间：
2007-02
期刊：
影响因子：
--
通讯作者：
Akabas MH
中科院分区：
文献类型：
--
作者：
Bali M;Akabas MH
在神经递质门控离子通道的Cys-loop受体家族中，包括GABAA、甘氨酸、乙酰胆碱和5-HT3受体在内的成员的关闭通道门的位置存在相当大的争议。半胱氨酸可及性研究得出结论，该门位于乙酰胆碱和GABAA受体通道的细胞质末端附近，但在5-HT3A受体通道的中间。嵌合的5-HT3-ACh受体中的锌离子可及性研究表明，该门位于通道的细胞质末端附近。在用低温电子显微镜确定的乙酰胆碱受体闭合状态的4？分辨结构中，推测为门的最窄区域在9‘-14’通道的中段，但通道细胞质末端的M1-M2环残基没有在该结构中分解。我们使用受体开放通道阻滞剂印防己毒素进行阻滞剂捕获实验，以确定是否存在比印防己毒素结合部位更多的细胞外位置的门，该位置位于通道细胞质末端附近的α1Val257(2‘)附近。我们发现，去除GABA后，印防己毒素可以被困在通道中。通过使用工程半胱氨酸的状态相关可及性作为通道结构状态的报告者，我们推断，在GABA被洗涤后，随着印防己毒素被困在通道中，通道似乎处于关闭状态。我们推测，在印防己毒素结合部位和通道的胞外端之间存在一个门，与通道中间关闭的通道门一致。鉴于与乙酰胆碱和5-HT3受体的同源性，这些通道中可能也有类似的门。这并不排除在细胞质更多的位置上存在额外的门。
Considerable controversy surrounds the location of the closed channel gate in members of the Cys-loop receptor family of neurotransmitter-gated ion channels that includes the GABAA, glycine, acetylcholine, and 5-HT3 receptors. Cysteine-accessibility studies concluded that the gate is near the cytoplasmic end of the channel in acetylcholine and GABAA receptors but in the middle of the 5-HT3A receptor channel. Zn2+ accessibility studies in a chimeric 5-HT3-ACh receptor suggested the gate is near the channel's cytoplasmic end. In the 4-Å resolution structure of the acetylcholine receptor closed state determined by cryoelectron microscopy, the narrowest region, inferred to be the gate, is in the channel's midsection from 9' to 14' but the M1–M2 loop residues at the channel's cytoplasmic end were not resolved in that structure. We used blocker trapping experiments with picrotoxin, a GABAA receptor open channel blocker, to determine whether a gate exists at a position more extracellular than the picrotoxin binding site, which is in the vicinity of α1Val257 (2') near the channel's cytoplasmic end. We show that picrotoxin can be trapped in the channel after removal of GABA. By using the state-dependent accessibility of engineered cysteines as reporters for the channel's structural state we infer that after GABA washout, with picrotoxin trapped in the channel, the channel appears to be in the closed state. We infer that a gate exists between the picrotoxin binding site and the channel's extracellular end, consistent with a closed channel gate in the middle of the channel. Given the homology with acetylcholine and 5-HT3 receptors there is probably a similar gate in those channels as well. This does not preclude the existence of an additional gate at a more cytoplasmic location.
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影响因子：
64.8
作者：
IMOTO, K;BUSCH, C;NUMA, S
通讯作者：
NUMA, S
影响因子：
3.8
作者：
Holmgren, M;Smith, PL;Yellen, G
通讯作者：
Yellen, G
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
影响因子：
2.9
作者：
Baenziger, JE;Chew, JP
通讯作者：
Chew, JP
影响因子：
7.3
作者：
FUJIMOTO, M;MUNAKATA, M;AKAIKE, N
通讯作者：
AKAIKE, N