Studies on nicotinic acetylcholine receptors in mammalian brain. Interaction of solubilized protein with cholinergic ligands

Binding of alpha-bungarotoxin, labeled with 125I, has been studied in detergent extracts and affinity purified acetylcholine receptor from rat cerebral cortex. Binding to detergent extracts is saturable and appears to be due to one class of binding sites present at a level of 0.27 pmol/mg of protein. The association constant is 2 X 10(7) liters mol-1 . Competition with cholinergic ligands indicates that toxin binding to both detergent solubilized and affinity purified receptor retains its nicotinic nature. Values for the ligand concentrations required to produce 50% inhibition of extent and rate of toxin binding are presented.