Referenced in: none

Automatically associated channels: Kv7.1

Title: The sodium channel from rat brain. Reconstitution of voltage-dependent scorpion toxin binding in vesicles of defined lipid composition.

Authors: D J Feller, J A Talvenheimo, W A Catterall

Journal, date & volume: J. Biol. Chem., 1985 Sep 25 , 260, 11542-7

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/2413014

Abstract
Purified sodium channels incorporated into phosphatidylcholine (PC) vesicles mediate neurotoxin-activated 22Na+ influx but do not bind the alpha-scorpion toxin from Leiurus quinquestriatus (LqTx) with high affinity. Addition of phosphatidylethanolamine (PE) or phosphatidylserine to the reconstitution mixture restores high affinity LqTx binding with KD = 1.9 nM for PC/PE vesicles at -90 mV and 36 degrees C in sucrose-substituted medium. Other lipids tested were markedly less effective. The binding of LqTx in vesicles of PC/PE (65:35) is sensitive to both the membrane potential formed by sodium gradients across the reconstituted vesicle membrane and the cation concentration in the extravesicular medium. Binding of LqTx is reduced 3- to 4-fold upon depolarization to 0 mV from -50 to -60 mV in experiments in which [Na+]out/[Na+]in is varied by changing [Na+]in or [Na+]out at constant extravesicular ionic strength. It is concluded that the purified sodium channel contains the receptor site for LqTx in functional form and that restoration of high affinity, voltage-dependent binding of LqTx by the purified sodium channel requires an appropriate ratio of PC to PE and/or phosphatidylserine in the vesicle membrane.