Amino-Acid Sequence of the α-Subunit of Taipoxin, an Extremely Potent Presynaptic Neurotoxin from the Australian Snake Taipan (Oxyurunus s. scutellatus)



The amino acid sequence of the α-subunit of taipoxin, an extremely potent presynaptic neurotoxin from the Australian snake taipan has been determined. The very basic protein, by itself a moderately neurotoxic phospholipase, consists of a single polypeptide chain of 119 amino acids. The main fragmentation of the reduced and S-carboxymethylated derivative was accomplished by cleavage with Staphylocoeus aureus V8 pro- tease and trypsin. Chymotryptic peptides and cyanogen bromide fragments were used to align and complete the sequence, which was determined by automated Edman degradation. The taipoxin γ-subunit is closely homologous to the other taipoxin subunits and to other elapid snake venom phospholipases A2.