Amino acid sequence of a presynaptic neurotoxin, agkistrodotoxin, from the venom of Agkistrodon halys Pallas.

The amino acid sequence of a presynaptic neurotoxin, agkistrodotoxin (ATX) isolated from the venom of Agkistrodon halys Pallas, was determined by automated Edman degradation and the carboxypeptidase digestion of the S-carboxymethylated ATX and by sequence analyses of peptides produced with cyanogen bromide cleavage and with trypsin or staphylococcal V8 protease digestion of the S-carboxymethylated ATX. ATX consists of 122 amino acid residues, including the histidine residue and 14 half-cystine residues. The amino acid sequence of ATX is very similar to those of toxic phospholipases and the phospholipase subunits of presynaptic neurotoxins from snake venoms. The residues responsible for the toxic activity of the presynaptic neurotoxins are discussed.