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

Toxins C10S2C2 and C13S1C1 from Dendroaspis angusticeps venom were purified by gel filtration and ion-exchange chromatography. Whereas toxin C10S2C2 comprises 60 amino acids, toxin C13S1C1 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 C10S2C2 and C13S1C1 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.