通过溴化乙锭荧光观察到的配体诱导的膜结合乙酰胆碱受体变化。3. 与组氨酰毒蕈碱毒素的停流研究。

Ligand-induced changes in membrane-bound acetylcholine receptor observed by ethidium fluorescence. 3. Stopped-flow studies with histrionicotoxin.

作者信息

Schimerlik M I, Quast U, Raftery M A

出版信息

Biochemistry. 1979 May 15;18(10):1902-6. doi: 10.1021/bi00577a008.

Abstract

Rapid kinetic studies of histrionicotoxin interactions with membrane-bound acetylcholine-receptor showed a conformational change in the receptor-histironicotoxin complex as reflected by a decrease in fluorescence intensity of the extrinsic probe ethidium. The simplest kinetic mechanism consistent with the observed data is one in which a rapid preequiliibrium exists between receptor and toxin (K = 3.33 micrometers), followed by a slow conformational change (k1 congruent to 2 X 10(-2) s-1 and k-1 congruent to 1.5 X 10(-3) s-1). The overall equilibrium constant (Kov) determined from a fit of the amplitude dependence on toxin concentration had a value of 0.25 micrometer. The data preclude kinetic mechanisms where histrionicotoxin acts as an effector, shifting equilibria between preexisting, discrete, and slowly interconverting receptor forms.

摘要

对组织胺毒素与膜结合型乙酰胆碱受体相互作用的快速动力学研究表明，受体 - 组织胺毒素复合物发生了构象变化，这可通过外在探针溴化乙锭荧光强度的降低反映出来。与观测数据相符的最简单动力学机制是，受体与毒素之间存在快速预平衡（K = 3.33微摩尔），随后是缓慢的构象变化（k1约为2×10⁻² s⁻¹ ，k⁻¹约为1.5×10⁻³ s⁻¹）。根据毒素浓度对振幅依赖性的拟合确定的总体平衡常数（Kov）值为0.25微摩尔。这些数据排除了组织胺毒素作为效应物起作用、在预先存在的、离散的且缓慢相互转化的受体形式之间改变平衡的动力学机制。