The complete primary structures of two reduced and S-carboxymethylated Angusticeps-type toxins from Dendroaspis angusticeps (green mamba) venom

Abstract

Toxins C 10S 2C 2 and C 13S 1C 1 from Dendroaspis angusticeps venom were purified by gel filtration and ion-exchange chromatography. Whereas toxin C 10S 2C 2 comprises 60 amino acids, toxin C 13S 1C 1 contains only 58 but they each include eight half-cystine residues. The complete primary structures of the toxins have been elucidated. The sequences and the invariant amino acids of toxins C 10S 2C 2 and C 13S 1C 1 from D. angusticeps venom resemble those of the angusticeps-type toxins. In the two toxins the ten structurally invariant amino acids of the neurotoxins and cytotoxins are conserved, but the toxins contain none of the three functionally-invariant amino acids of the neurotoxins. Further, the eight cystine residues of the angusticeps-type toxins are in similar locations to those in short neurotoxins of known structure so they are presumed to link similarly. The only structural characteristic of the angusticeps-type toxins which binds them together as a group, is the serine residue in position 5. The toxicities of the angusticeps-type toxins differ among themselves but appear to be of considerably lower toxicity relative to that of the neurotoxin group.