Brown G B, Daly J W
Neurosciences Program, University of Alabama, Birmingham 35294.
Cell Mol Neurobiol. 1981 Dec;1(4):361-71. doi: 10.1007/BF00716271.
The binding of labeled batrachotoxinin-A benzoate (BTX-B) to voltage-sensitive sodium channels in broken membrane preparations of mouse cerebral cortex has been measured as a function of the pH. Specific binding is negligible at pH less than 6.0, maximum at pH 8.5, and decreases again at pH 9.0. A major component of nonspecific binding, however, increases linearly in the pH range 7.0-9.0. The pKa of batrachotoxinin-A, an analogue of BTX-B, was found by titrimetric methods to be greater than or equal to 8.2. Analysis of the data shows that at least part of the pH dependence of BTX-B binding is due to the titration of a sodium channel residue(s) associated in some way with the BTX-B recognition site. The possible involvement of a histidine residue is suggested.
已测定标记的苯甲酸蛙毒素 - A（BTX - B）与小鼠大脑皮层破碎膜制剂中电压敏感性钠通道的结合情况，并将其作为pH的函数。在pH小于6.0时，特异性结合可忽略不计，在pH 8.5时达到最大值，而在pH 9.0时又会下降。然而，非特异性结合的一个主要成分在pH范围7.0 - 9.0内呈线性增加。通过滴定法发现，BTX - B的类似物蛙毒素 - A的pKa大于或等于8.2。数据分析表明，BTX - B结合对pH的依赖性至少部分是由于与BTX - B识别位点以某种方式相关联的钠通道残基的滴定所致。有人提出可能涉及组氨酸残基。
