VOLTAGE DEPENDENT SODIUM CHANNEL--PLANAR LIPID BILAYER

这项研究的长期目标是了解 离子运动的分子特征 跨膜通道 这一目标将通过 对电压依赖性钠通道的研究， 结合到确定组成的平面脂质双层中。 离子 渗透、药理学修饰和电压激活 （门控），将审查，特别强调的作用， 固定电荷在细胞外和细胞内的表面， 蛋白质和宿主双层在调节通道功能中的作用。 将研究离子进入通道的机制， 确定通道入口附近是否有负电荷 具有引导离子进入的生理功能。 离子 由蛙毒素修饰的通道的渗透性和阻断， 藜芦定、拟除虫菊酯类杀虫剂和群体特异性杀虫剂 修改将进行比较，试图澄清为什么 具有降低的单通道电导的通道具有 降低离子选择性。 将使用组特异性修饰和蛋白水解切割 修改通道入口，并检查 胍盐毒素结合位点和细胞外通道 入口 毒素诱导的通道关闭的动力学将是 检查以确定胍毒素诱导的 通道关闭作为两步事件发生，其中通道 封闭的：在毒素作用后通过构象变化而封闭的 约束力 单通道的稳态电压激活将是 检查以定义门控行为受以下因素影响的程度 脂质表面电荷，并进一步定义不对称性， 细胞外和细胞内的表观表面电荷密度 通道的表面。 将研究影响门控的缓慢“模式变化”。 的 目的是表征一些固定构象 发生在一个完整的膜蛋白的波动，以及 以确定是否可以完全考虑模式变化 通过激活的中点电位的离散移位， 曲线.

The long-term goal of the proposed research is to understand molecular characteristics of ion movement through transmembrane channels. This goal will be pursued through studies on voltage-dependent sodium channels that are incorporated into planar lipid bilayers of defined composition. Ion permeation, pharmacological modification, and voltage activation (gating), will be examined, with special emphasis on the role of fixed charges at the extra- and intracellular surface of the protein and host bilayer in modulating channel function. The mechanism of ion entry into the channels will be studied to determine whether negative charges close to the channel entrance have a physiological function as guides for ion entry. Ion permeability and block of channels modified by batrachotoxin, veratradine, pyrethroid insecticides, and group-specific modification will be compared in an attempt to clarify why channels that have a decreased single-channel conductance have a decreased ion selectivity. Group-specific modification and proteolytic cleavage will be used to modify the channel entrance and examine the relation between the guanidinium toxin binding site and the extracellular channel entrance. The kinetics of toxin-induced channel closures will be examined to determine whether the guanidinium toxin-induced channel closures occur as a two-step event, where the channel is closed thorough a conformational change subsequent to toxin binding. The stationary voltage-activation of single channels will be examined to define to what extent gating behavior is affected by lipid surface charges, and to further define the asymmetry in the apparent surface charge density at the extra- and intracellular surfaces of the channel. The slow "mode changes" that affect gating will be studied. The aim is to characterize some of the stationary conformational fluctuations that occur in an integral membrane protein, as well as to determine whether the mode changes can be fully accounted for by discrete shifts in the midpoint potential of the activation curves.