Disulfide Bonds of Toxin II of the Scorpion Androctonus australis Hector

The positions of the disulfide bridges in toxin II of Androctonus australis Hector were investigated using proteolytic enzymes. The resulting peptides were separated by column and paper chromatography and high‐voltage electrophoresis. Determination of the amino acid compositions of the cystine‐containing peptides or their oxidized derivatives and, when necessary, dansyl Edman degradation allowed to locate the disulfide bonds in the toxin. The four disulfide bridges were found to link the half‐cystine residues number 12 and 63, 16 and 36, 22 and 46, 26 and 48. These positions are probably the same in all scorpion neurotoxins.