Primary structures of cardiotoxin analogues II and IV from the venom of Naja jaja atra.

Cardiotoxin analogues II and IV were isolated from the venom of Naja naja atra by gel filtration on Sephadex G-50 followed by CM-cellulose chromatography. The venom contains at least four cardiotoxin analogues that account for about 54% of the weight of the lyophilized crude venom. These four cardiotoxin analogues, named cardiotoxin analogues I, II, III, and IV, show strong cytotoxicity to Yoshida sarcoma cells but the lethal toxicity is one-order less. These toxins contain 60 amino acid residues in a single peptide chain. Cardiotoxin analogue IV differs from cardiotoxin analogue II only by the presence of arginine in place of a leucine residue at position 1. A comparison of the amino acid sequences of these toxins with that of cobrotoxin, a neurotoxin containing 62 amino acid residues obtained from the same snake venom, shows that about 20 amino acid residues, including 8 half cystine residues, are identical, assuming 3 residues deletion and 2 residues insertion in the cardiotoxin molecule.