Amino acid sequence of .kappa.-flavitoxin: establishment of a new family of snake venom neurotoxins

The complete amino acid sequence of kappa-flavitoxin, a neurotoxin isolated from the venom of Bungarus flaviceps, has been determined by automated Edman analysis of the intact protein and of peptides derived from digests with trypsin and chymotrypsin. kappa-Flavitoxin consists of a single 66-residue polypeptide chain which is completely devoid of methionine. The amino acid sequence of kappa-flavitoxin demonstrates that although the toxin is related to the alpha-neurotoxin family, it displays a much higher degree of homology with kappa-bungarotoxin. The conserved structural features of the kappa-neurotoxins and their pharmacological profiles, which are distinct from those of all known alpha-neurotoxins, provide evidence for a new, structurally and functionally unique family of snake venom neurotoxins.