The role of loop 5 in acetylcholine receptor channel gating.
The role of loop 5 in acetylcholine receptor channel gating.
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DOI：
10.1085/jgp.200308885
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发表时间：
2003-11
期刊：
影响因子：
--
通讯作者：
Auerbach A
中科院分区：
文献类型：
--
作者：
Chakrapani S;Bailey TD;Auerbach A
烟碱型乙酰胆碱受体通道（AChR）门控是一种有组织的分子运动序列，其将两个递质结合位点处的配体亲和力的变化与孔的离子电导的变化相耦合。环5（L5）是一个9个残基的片段（小鼠α-亚基92-100），连接胞外结构域的β4和β5链，并且（在α-亚基中）含有结合片段A。基于乙酰胆碱结合蛋白的结构，我们推测，在AChRs的L5项目从递质结合位点向膜沿着一个亚基接口。我们使用单通道动力学来量化αD97和其他L5残基突变对激动剂结合（开放和闭合AChR）、通道门控（对于未配体和完全配体AChR）和脱敏的影响。大多数αD97突变增加门控（高达168倍），但对配体结合或脱敏几乎没有影响。速率-平衡自由能关系分析表明，αD97在门控反应早期移动，与递质结合位点的移动同步（Φ = 0.93，这意味着在过渡态具有开放样特征）。两个α亚基中的αD97突变对门控具有不相等的能量后果，但它们的贡献是独立的。我们的结论是，αD97扰动的关键，潜在的功能后果是增加unliganded门控平衡常数。L5在AChR门控反应中作为一个重要的早期环节出现，在没有激动剂的情况下，它可以增加蛋白质闭合构象的相对稳定性。
Nicotinic acetylcholine receptor channel (AChR) gating is an organized sequence of molecular motions that couples a change in the affinity for ligands at the two transmitter binding sites with a change in the ionic conductance of the pore. Loop 5 (L5) is a nine-residue segment (mouse α-subunit 92–100) that links the β4 and β5 strands of the extracellular domain and that (in the α-subunit) contains binding segment A. Based on the structure of the acetylcholine binding protein, we speculate that in AChRs L5 projects from the transmitter binding site toward the membrane along a subunit interface. We used single-channel kinetics to quantify the effects of mutations to αD97 and other L5 residues with respect to agonist binding (to both open and closed AChRs), channel gating (for both unliganded and fully-liganded AChRs), and desensitization. Most αD97 mutations increase gating (up to 168-fold) but have little or no effect on ligand binding or desensitization. Rate-equilibrium free energy relationship analysis indicates that αD97 moves early in the gating reaction, in synchrony with the movement of the transmitter binding site (Φ = 0.93, which implies an open-like character at the transition state). αD97 mutations in the two α-subunits have unequal energetic consequences for gating, but their contributions are independent. We conclude that the key, underlying functional consequence of αD97 perturbations is to increase the unliganded gating equilibrium constant. L5 emerges as an important and early link in the AChR gating reaction which, in the absence of agonist, serves to increase the relative stability of the closed conformation of the protein.
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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
DOI：
10.1073/pnas.86.7.2199
发表时间：
1989-04-01
影响因子：
11.1
作者：
JACKSON, MB
通讯作者：
JACKSON, MB
影响因子：
2
作者：
KARLIN, A
通讯作者：
KARLIN, A
影响因子：
25
作者：
Horenstein, J;Wagner, DA;Akabas, MH
通讯作者：
Akabas, MH
影响因子：
64.8
作者：
Kash, TL;Jenkins, A;Harrison, NL
通讯作者：
Harrison, NL