Amino Acid Sequence of Neurotoxin III of the Scorpion Androctonus australis Hector

Abstract

The amino acid sequence of neurotoxin III, purified from the venom of the North African scorpion Androctonus australis Hector, has been determined by Edman degradation using a liquid‐phase sequence. Carboxypeptidase A hydrolyses confirmed not only the sequence of the five last residues but also the presence of a free α‐carboxylic group at the C‐terminus. Edman degradation was conducted on one hand with the Quadrol [N,N,N′,N′‐tetrakis(2‐hydroxypropyl)ethylene diamine] program and S‐alkylated proteins before or after coupling with sulfophenylisothiocyanate (the first 34 residues were thus identified), on the other hand on tryptic and chymotryptic peptides with a dimethylbenzylamine program (residues 1–23 and 31–34 were confirmed, the positions of residues 35–64 were established). Neurotoxin III was found to belong to the same group of scorpion toxins active on mammals as neurotoxin I purified from the same venom (50 homologous positions exist in the two proteins). Copyright © 1979, Wiley Blackwell. All rights reserved