Selective enzymatic hydrolysis of nerve terminal phospholipids by beta-bungarotoxin: biochemical and morphological studies.

beta-Bungarotoxin, a presynaptic protein neurotoxin isolated from the venom of the snake Bungarus multicinctus, modifies release of neurotransmitter at the neuromuscular junction. The toxin has a potent phospholipase activity toward both natural membranes and phospholipid liposomes. Studies of ionic requirements and selective chemical modification demonstrate that beta-bungarotoxin can only modify synaptic transmission under conditions in which the phospholipase is active. Morphological studies on frog cutaneous pectoris neuromuscular junctions incubated with beta-toxin and horseradish peroxidase-conjugated beta-toxin support the hypothesis that beta-toxin specifically interacts with presynaptic plasma membranes and selectively hydrolyzes nerve terminal phospholipids.