Primary structure of gamma-bungarotoxin, a new postsynaptic neurotoxin from venom of Bungarus multicinctus

The primary structure of gamma-bungarotoxin, a new toxin from Bungarus mult icinctus venom, was determined using mass spectrometry and Edman degradatio n. The toxin has a mass of 7524.7 D and consists of 68 residues having the following sequence: MQCKTCSFYT CPNSETCPDG KNICVKRSWT AVRGDGPKRE IRRECAATCP PSKLGLTVFC CTTDNCNH. gamma-bungarotoxin is structurally similar to both kap pa-bungarotoxin and elapid long postsynaptic neurotoxins. Its C-terminal ni ne residues are identical to those of the kappa-toxins. Its disulfide bond locations appear identical to those of several elapid toxins of unknown pha rmacology and its hydrophobicity profile is also strikingly similar. Howeve r, with an LD50 of 0.15 mu g/g i.v. in mice, gamma-bungarotoxin is 30-150-f old more toxic than other members of this latter class. Its toxicity is com parable to those of alpha-nicotinic acetylcholine receptor antagonists. (C) 1999 Elsevier Science Ltd. All rights reserved.