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首页> 外文期刊>Neurochemistry International: The International Journal for the Rapid Publication of Critical Reviews, Preliminary and Original Research Communications in Neurochemistry >Key histidine residues in the nicotinic acetylcholine receptor.
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Key histidine residues in the nicotinic acetylcholine receptor.

机译：烟碱乙酰胆碱受体中的关键组氨酸残基。

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摘要

Reactivity of histidine residues of the Discopyge tschudii nicotinic acetylcholine receptor was studied by reaction with DEP and the influence of their modification on functional properties of the receptor was evaluated. Determination of two kinetically distinguishable classes was achieved. The fast-reacting class is composed of 7 histidine residues with an apparent velocity constant k1 = 0.0248 +/- 0.0031 min-1. The second includes--at least--21 histidine residues with a velocity constant k2 = 0.0016 +/- 0.0009 min-1. The circular dichroism spectra of the native receptor and the most DEP-derivative indicate no significant modifications in the alpha-helix content, and fourth derivative spectroscopy analyses show that the environment around the aromatic amino acids remains unchanged. DEP treatment of the receptor results in a time- and reagent concentration-dependent loss of its alpha-bungarotoxin binding ability; these results agree with those obtained with the membrane-bound receptor. The decrease in the neurotoxin binding capacity was correlated with the DEP-reaction extent of the slow groups. Incorporation of 1.93 +/- 0.23 mol of DEP accounted for the maximal binding capacity drop, thus indicating the involvement of two histidine residues per alpha-bungarotoxin binding site. Neither amino groups nor tyrosine residues were modified during the reaction with DEP, indicating that the derivatization of histidine residues is responsible for the observed effect. Faster-reacting residues appear to be involved in agonist-induced ion flux through the nAChR channel. These results strongly support the connection between histidine residues and the receptor functional activity and lead us to infer that the changes observed in alpha-bungarotoxin binding and ionic channel capacity are the consequence of independent events induced by reaction with DEP.
机译：通过与DEP反应研究了Disschge tschudii烟碱型乙酰胆碱受体的组氨酸残基的反应性，并评估了其修饰对受体功能特性的影响。确定了两个动力学上可区分的类别。快速反应类别由7个组氨酸残基组成，其表观速度常数k1 = 0.0248 +/- 0.0031 min-1。第二个包括-至少-21个组氨酸残基，其速度常数k2 = 0.0016 +/- 0.0009 min-1。天然受体和大多数DEP衍生物的圆二色性光谱表明，α-螺旋含量没有明显变化，四阶导数光谱分析表明，芳香族氨基酸周围的环境保持不变。受体的DEP处理导致其α-真菌毒素结合能力的时间和试剂浓度依赖性丧失。这些结果与通过膜结合受体获得的结果一致。神经毒素结合能力的下降与慢速组的DEP反应程度有关。掺入1.93 +/- 0.23 mol的DEP导致最大的结合能力下降，因此表明每个α-真菌毒素结合位点涉及两个组氨酸残基。在与DEP反应期间，氨基基团和酪氨酸残基均未修饰，表明组氨酸残基的衍生化是观察到的作用的原因。反应更快的残基似乎与激动剂诱导的通过nAChR通道的离子通量有关。这些结果有力地支持了组氨酸残基与受体功能活性之间的联系，并导致我们推断，α-真菌毒素结合和离子通道容量的变化是与DEP反应诱导的独立事件的结果。

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