Interaction of batrachotoxinin-A benzoate with voltage-sensitive sodium channels: the effects of pH.
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.
D000818:Animals; D001496:Batrachotoxins / Q000378:metabolism* / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D051379:Mice; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*
D001496:Batrachotoxins; D015222:Sodium Channels; C031775:batrachotoxinin A 20-alpha-benzoate