Amino-acid sequence of the beta 1 isosubunit of taipoxin, an extremely potent presynaptic neurotoxin from the Australian snake taipan (Oxyuranus s. scutellatus).

The amino acid sequence of the beta 1 isosubunit of taipoxin, an extremely potent presynaptic neurotoxin from the Australian snake taipan, has been determined. The beta 1 isosubunit, which is neither toxic nor enzymatically active on its own, consists of a single polypeptide chain of 118 amino acids. The main fragmentation of the reduced and S-carboxymethylated derivative was accomplished by cleavage with Staphylococcus aureus V8 protease. Tryptic peptides were used to align and complete the sequence, which was determined by automated Edman degradation. The taipoxin beta 1 isosubunit is closely homologous to the taipoxin alpha and gamma subunits and to enzymatically active pancreatic and elapid snake venom phospholipases A2.