Abstract
The venom of an Australian elapid snake, the common death adder (Acanthophis antarcticus), was chromatographed on a CM-cellulose CM52 column. One of the neurotoxic components, Acanthophis antarcticus b (toxin Aa b) was isolated in about 9.4% (A280) yield. The complete amino acid sequence of toxin Aa b was elucidated. Toxin Aa b is composed of 73 amino acid residues, with ten half-cystine residues, and has a formula weight of 8135. Toxin Aa b has no histidine or methionine residue in its sequence. The amino acid sequence of toxin Aa b is homologous with those of other neurotoxins with known sequences, although it is novel in having a valine residue at its N-terminus and an arginine residue at position-23, where a lysine residue is found in almost all the so-far-known neurotoxins. Irrespective of the latter replacement, the toxin Aa b is fully active, with an LD50 value (in mice) of 0.13 microgram/g body weight on intramuscular injection.