Neurotoxins from the venom of the multibanded krait Bungarus multicinctus. α-Bungarotoxin (74 aa) binds to the α subunits of the postsynaptic nicotinic acetycholine receptors (nAChR) causing irreversible blockage of the neuromuscular junction and is used experimentally to identify, quantify, and localize these receptors. β-Bungarotoxin is a heterodimeric phospholipase A2 neurotoxin that acts at the presynaptic site of motor nerve terminals and blocks transmitter release. The A subunit (EC 188.8.131.52, 147 aa) is structurally homologous to other PLA2s, the B subunit (85 aa) has homology with serine peptidase inhibitors (but no inhibitory activity) and dendrotoxins. κ-Bungarotoxin is a homodimeric toxin (bungarotoxin 3.1, Toxin F, neuronal bungarotoxin, 87 aa) similar to α-bungarotoxin but binds more strongly to neuronal receptors than to muscle receptors.
Subjects: Medicine and Health — Chemistry.