We describe molecular-level functional changes in the α4β2 nicotinic acetylcholine receptor by a leucine residue insertion in the M2 transmembrane domain of the α4 subunit associated with sleep-related hyperkinetic epilepsy. Measurements of agonist-elicited single-channel currents reveal the primary effect is to stabilize the open channel state, while the secondary effect is to promote reopening of the channel. These dual effects prolong the durations of bursts of channel openings equally for the two major stoichiometric forms of the receptor, (α4)(β2) and (α4)(β2), indicating the functional impact is independent of mutant copy number per receptor. Altering the location of the residue insertion within M2 shows that functionally pivotal structures are confined to a half turn of the M2 α-helix. Residue substitutions within M2 and surrounding α-helices reveal that both intrasubunit and intersubunit interactions mediate the increase in burst duration. These interactions impacting burst duration depend linearly on the size and hydrophobicity of the substituting residue. Together, the results reveal a novel structural region of the α4β2 nicotinic acetylcholine receptor in which interhelical interactions tune the stability of the open channel state.

中文翻译：

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神经元烟碱受体中的致病残基插入改变亚基内和亚基间的相互作用，从而调节通道门控


我们通过在与睡眠相关的多动性癫痫相关的 α4 亚基的 M2 跨膜结构域中插入亮氨酸残基来描述 α4β2 烟碱乙酰胆碱受体的分子水平功能变化。激动剂引起的单通道电流的测量表明，主要作用是稳定开放通道状态，而次要作用是促进通道重新开放。对于受体的两种主要化学计量形式（α4）（β2）和（α4）（β2），这些双重效应同等地延长了通道开放爆发的持续时间，表明功能影响与每个受体的突变拷贝数无关。改变 M2 内残基插入的位置表明功能关键结构仅限于 M2 α 螺旋的半圈。 M2 和周围 α 螺旋内的残基取代表明，亚基内和亚基间相互作用均介导爆发持续时间的增加。这些影响突发持续时间的相互作用与取代残基的大小和疏水性线性相关。总之，这些结果揭示了 α4β2 烟碱乙酰胆碱受体的一个新结构区域，其中螺旋间相互作用调节开放通道状态的稳定性。