生物膜电压门控离子通道的结构和功能性构象

生物膜离子通道具有多种重要的生理功能.近年,已分离、纯化了电压门控的Na~+、Ca~(2+)和K~+通道的蛋白质组分.Na~+和Ca~(2+)通道分别由一个构成离子孔洞的主要亚单位和数目不同的其他亚单位组成,K~+通道是单一的多肽.对Na~+、Ca~(2+)通道主要亚单位和K~+通道的氨基酸序列的测定表明,它们之间有许多相似性.已分别给出了三种通道跨膜排列的二级结构图象.考虑了Na~+通道的功能特性,包括电压敏感性、通道开放动力学、门控电流、神经毒素的作用等,已提出几种Na~+通道功能性构象模型.

THE STPUCTURE AND FUNCTIONAL CONFORMATION OF VOLTAGE-GATED ION CHANNELS IN BIOMEMBRANES

Ion channels in biomembranes have a variaty of the biological functions. In the past several years, the protein components of the voltage-gated Na+, Ca2+, and K+channels have been isolated and purified. Na+ and Ca2+ channels consist of a principal transmembrane subunit with a variadle numder of associated sudunits in different cell types. Amino acid sequences of the principal sudunit in Na+ and Ca2+ channel and the protein of K+ channel have been ditermined, and thier second structures of transmembrane topology have been given. According to the functionnal properties including the voltage sensitivity, opening kinetics, gated currents, and action of neurotoxins, several people have proposed the models of Na+ channel relating the functional three dimensional conformation. Coordinated application of biochemical, biophysical, and molecular genetic methods should lead to a clear understanding of the molecular mechanism of electrical excitadility.