Immunochemistry of scorpion alpha-toxins: study with synthetic peptides of the antigenicity of four regions of toxin II of Androctonus australis Hector.

Sequences 19-29 and 28-39 of toxin II of the North African scorpion Androctonus australis Hector have been synthesized. These two peptides correspond to the highest peaks in the hydrophilicity profile of toxin II and were thus believed to account for a significant proportion of toxin antigenicity. Affinity chromatography of solid-phase-bonded peptides allowed us to purify two sub-populations from the total IgGs raised against the native toxin. They both still bound to 125I-toxin II and showed a restricted heterogeneity in their specificity. Solid-phase immunoassays confirmed the antigenicity of these synthetic peptides and also that of two other previously described synthetic replicates of the antigenic regions of toxin II: sequences (5-14) S-S (60-64) and 50-59. The location of the four antigenic regions relative to the postulated location of the receptor-binding site of the toxin is discussed.