The association of tetrodotoxin-sensitive, sodium-selective ionophore of brain membranes with liposomes.

The tetrodotoxin-sensitive, sodsium-selective ionophore of nerve membranes has been associated with liposomes by adding the solubilized brain microsomal fraction to a cholate/phospholipid dispersion and subsequently removing the detergent from suspension by using gel chromatography. A stimulation of the efflux of sodium from the vesicles was observed in the presence of veratrine. Tetrodotoxin itself did not effect the sodium permeability, but inhibited the veratrine-induced increment. The activation was absent in the liposomes prepared without soluble membrane proteins. The effects demonstrated for tetrodotoxin and veratrine were specific for the Na+ movement. It was possible to precipitate the tetrodotoxin-sensitive ionophore by use of (NH4)2SO4.