Hanke W, Breer H
Fachbereich Biologie/Chemie, Universität Osnabrück, Federal Republic of Germany.
J Gen Physiol. 1987 Dec;90(6):855-79. doi: 10.1085/jgp.90.6.855.
An alpha-toxin-binding membrane protein, isolated from the head and thoracic ganglia of the locus (Locusta migratoria), was reconstituted into planar lipid bilayers. Cholinergic agonists such as acetylcholine, carbamylcholine, and suberyldicholine induced fluctuations of single channels, which suggests that the protein represents a functional cholinergic receptor channel. The antagonist d-tubocurarine blocked the activation of the channels, whereas hexamethonium had only a weak effect; similar properties have been described for nicotinic insect receptors in situ. The channel was selectively permeable to monovalent cations but was impermeable to anions. The conductance of the channel (75 pS in 100 mM NaCl) was independent of the type of agonist used to activate the receptor. Kinetic analysis of the channel gating revealed that, at high agonist concentrations (50 microM carbamylcholine), more than one closed state exists and that multiple gating events, bursting as well as fast flickering, appeared. At very high agonist concentrations (500 microM carbamylcholine), desensitization was observed. Channel kinetics were dependent on the transmembrane potential. Comparing the conductance, the kinetics, and the pharmacology of nicotinic acetylcholine receptor from insect ganglia and fish electroplax reconstituted into bilayers revealed obvious similarities but also significant differences.
从飞蝗（Locusta migratoria）的头部和胸神经节中分离出一种α-毒素结合膜蛋白，并将其重组到平面脂质双分子层中。乙酰胆碱、氨甲酰胆碱和辛二酰胆碱等胆碱能激动剂可诱导单通道波动，这表明该蛋白代表一种功能性胆碱能受体通道。拮抗剂筒箭毒碱可阻断通道的激活，而六甲铵的作用较弱；原位烟碱型昆虫受体也具有类似特性。该通道对单价阳离子具有选择性通透性，对阴离子则不通透。通道的电导（在100 mM NaCl中为75 pS）与用于激活受体的激动剂类型无关。通道门控的动力学分析表明，在高激动剂浓度（50 μM氨甲酰胆碱）下，存在不止一种关闭状态，并且出现了多种门控事件，包括爆发和快速闪烁。在非常高的激动剂浓度（500 μM氨甲酰胆碱）下，观察到脱敏现象。通道动力学取决于跨膜电位。比较重组到双分子层中的昆虫神经节和鱼电板的烟碱型乙酰胆碱受体的电导、动力学和药理学，发现它们既有明显的相似之处，也有显著差异。
