Snake venom toxins. The amino acid sequences of two toxins (CM-2a and CM-3) from Naja haje annulifera (Egyptian cobra) venom.

Two toxins, CM-2a and CM-3, were purified from the venom of Naja haje annulifera by gel filtration on Sephadex G-50 and by ion-exchange chromatography on CM-cellulose. Whereas toxin CM-2a contains 61 amino acid residues, toxin CM-3 comprises 60 residues. Both toxins are cross-linked by four intra-chain disulphide bridges. The complete amino acid sequences of the toxins have been elucidated. The properties of the toxins were compared with those of a cytotoxin, a short neurotoxin, a long neurotoxin and an angusticeps type. The sequences of toxin CM-2a and CM-3 and some of the invariant residues do not show a high degree of similarity with those of the other toxins. The toxicities of toxins CM-2a and CM-3 are much lower than those encountered for the cytotoxin or the neurotoxins and their immunochemical properties are distinct from both the cytotoxin and the neurotoxins. They probably represent a new class of toxins.