Solubilization of an α-bungarotoxin-binding component from rat brain

Abstract

Binding of [125I]-.alpha.-bungarotoxin to rat brain was investigated. Picomole quantities of specific toxin binding sites per gram of fresh tissue were found in particulate preparations and detergent extracts of whole brain. The toxin-binding macromolecules were solubilized in low concentrations of Triton X-100. Specific binding occurred to a single class of sites with a dissociation constant of 5.6 .times. 10-11 M. The association rate constant in 10 mM sodium phosphate, pH 7.4, was 6.8 .times. 105 M-1 s-1; the half-life of the complex was found to be 5.1 h, corresponding to a dissociation rate constant of 3.8 .times. 10-5 s-1. The binding macromolecules resembled peripheral nicotinic acetylcholine receptors in toxin binding kinetics, solubility, isoelectric point and hydrodynamic properties.