Snake venom toxins the primary structure of protein S 4C 11: A neurotoxin homologue from the venom of forest cobra ( Naja melanoleuca)

Abstract

Six minor protein constituents (S 4C 10-S 4C 15) have been isolated from the venom of Naja melanoleuca. The complete amino acid sequence of S 4C 11 has been established and indicates that it is a homologue of the neurotoxins which are found in elapid venoms. The other proteins appear from the amino acid compositions to be homologues of the cyto- or cardiotoxins found in cobra venoms. Protein S 4C 11 has a low toxicity, failing to kill mice at an intravenous dose of 20 μg/g body weight. The sequence of the first 25 residues out of the total of 65, was determined using the automatic sequenator. The remainder of the sequence was derived with the aid of tryptic and chymotryptic peptides. The sequence showed the unusual feature of having 65 amino acid residues including 10 half-cystine residues.