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

Abstract

The primary structure of γ-bungarotoxin, a new toxin from Bungarus multicinctus venom, was determined using mass spectrometry and Edman degradation. 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. γ-bungarotoxin is structurally similar to both κ-bungarotoxin and elapid long postsynaptic neurotoxins. Its C-terminal nine residues are identical to those of the κ-toxins. Its disulfide bond locations appear identical to those of several elapid toxins of unknown pharmacology and its hydrophobicity profile is also strikingly similar. However, with an LD 50 of 0.15 μg/g i.v. in mice, γ-bungarotoxin is 30–150-fold more toxic than other members of this latter class. Its toxicity is comparable to those of α-nicotinic acetylcholine receptor antagonists.