BUNGAROTOXINS

Toxins found in the venom of Bungarus multicinctus. a -bungarotoxin: polypeptide toxin (74 residues). A powerful antagonist of acetylcholine it causes virtually irreversible block of the vertebrate neuromuscular junction by binding (as a monomer) to each of the a -subunits of the postsynaptic nicotinic acetycholine receptors (nAChR) Has been much used in identifying, quantifying and localizing these receptors on muscle cells.Will also bind some neuronal nAChR ; b -bungarotoxin: a two-chain phospholipase A2 neurotoxin that acts at the presynaptic site of motor nerve terminals and blocks transmitter release. Subunit A (120 residues) is structurally homologous to other PLA2s, the B subunit (60 residues) has homology with Kunitz-type serine protease inhibitors and dendrotoxins. Binds to subtype of voltage-sensitive potassium channels. k -bungarotoxin: (bungarotoxin 3.1; Toxin F, neuronal bungarotoxin) is a polypeptide (66 residues) from the venom of Bungarus multicinctus. Has considerable homology with a -bungarotoxin. Functional toxin a homodimer. Potent antagonist for a subset of neuronal nAChR but is much less active against muscle receptors.