Protein mobility and GABA-induced conformational changes in GABAA receptor pore-lining M2 segment
Protein mobility and GABA-induced conformational changes in GABAA receptor pore-lining M2 segment
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DOI：
10.1038/87425
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发表时间：
2001-05-01
影响因子：
25
通讯作者：
Akabas, MH
中科院分区：
文献类型：
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作者：
Horenstein, J;Wagner, DA;Akabas, MH
配体门控离子通道激活下的蛋白质运动尚不清楚。在这里，我们使用二硫键捕获来检测半胱氨酸取代GABA(A)受体α(1)和β (1) M2段通道衬里残基在静止和激活受体中的接近性和迁移性。有GABA或没有GABA，在靠近细胞外端的α (1)N275C/ β (1)E270C（20‘）和α (1)S272C/ β (1)H267C（17’）处形成二硫键，表明这一端比其他部分更具移动性和/或柔韧性。靠近M2的中间，在alpha (1)T261C/beta (1)T256C（6’）处，只有在GABA存在的情况下才形成二硫键，并锁定通道打开。通道激活必须涉及两个相邻亚基相互之间的不对称旋转。这将使不同亚基上对齐的工程半胱氨酸靠近，并允许在不阻断传导的情况下形成二硫键。在其他配体门控离子通道中，M2段的不对称旋转可能是一种常见的门控机制。
Protein movements underlying ligand-gated ion channel activation are poorly understood. Here we used disulfide bond trapping to examine the proximity and mobility of cysteines substituted for aligned GABA(A) receptor alpha (1) and beta (1) M2 segment channel-lining residues in resting and activated receptors. With or without GABA, disulfide bonds formed at alpha (1)N275C/beta (1)E270C (20') and alpha (1)S272C/beta (1)H267C (17'), near the extracellular end, suggesting that this end is more mobile and/or flexible than the rest of the segment. Near the middle of M2, at alpha (1)T261C/beta (1)T256C (6'), a disulfide bond formed only in the presence of GABA and locked the channels open. Channel activation must involve an asymmetric rotation of two adjacent subunits toward each other. This would move aligned engineered cysteines on different subunits into proximity and allow disulfide bond formation without blocking conduction. Asymmetric rotation of M2 segments is probably a common gating mechanism in other ligand-gated ion channels.