Pascual J M, Shieh C C, Kirsch G E, Brown A M
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA.
Biophys J. 1995 Aug;69(2):428-34. doi: 10.1016/S0006-3495(95)79915-5.
We have mapped residues in the carboxyl half of the P region of a voltage-gated K+ channel that influence external tetraethylammonium (TEA) block. Fifteen amino acids were substituted with cysteine and expressed in oocytes from monomeric or heterodimeric cRNAs. From a total of six mutant channels with altered TEA sensitivity, three were susceptible to modification by extracellularly applied charged methanethiosulfonates (MTSX). Another residue did not affect TEA block but was protected from MTSX by TEA. MTSX modification of position Y380C, thought to form the TEA binding site, affected TEA affinity only moderately, and this effect could be reversed by additional charge transfer from an oppositely charged MTSX analog. The results show that TEA block is modulated from multiple sites, including residues located deep in the pore and that several side chains besides that of Y380 are exposed at the TEA receptor.
我们已经绘制出电压门控钾离子通道P区羧基端中影响外部四乙铵（TEA）阻断作用的残基图谱。将15个氨基酸替换为半胱氨酸，并在来自单体或异二聚体cRNA的卵母细胞中表达。在总共六个TEA敏感性改变的突变通道中，有三个易受细胞外施加的带电甲硫基磺酸盐（MTSX）修饰。另一个残基不影响TEA阻断，但可被TEA保护免受MTSX作用。据认为形成TEA结合位点的Y380C位点的MTSX修饰仅适度影响TEA亲和力，并且这种效应可通过来自带相反电荷的MTSX类似物的额外电荷转移来逆转。结果表明，TEA阻断作用从多个位点受到调节，包括位于孔道深处的残基，并且除Y380之外的几个侧链在TEA受体处暴露。
