Primary structure of scorpion anti‐insect toxins isolated from the venom of Leiurus quinquestriatus quinquestriatus

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Abstract
The amino acid sequences of insect‐selective scorpion toxins, purified from the venom of Leiurus quinquestriatus quinquestriatus, have been determined by automatic phenyl isothiocyanate degradation of the S‐carboxymethylated proteins and derived proteolytic peptides. The excitatory toxin Lqq IT1 and Lqq IT1' (70 residues) show the shift of one half‐cystine from an external position, which is characteristic of anti‐mammal toxins, to an internal sequence position. Lqq IT2, (61 residues) displays the half‐cystine residue in position 12, common to the sequence of all known antimammal toxins; it induces flaccid paralysis on insects but is non‐toxic for the mouse. Lqq IT2, structurally defines a new type of anti‐insect toxins from scorpion venoms. CD spectra and immunological data are in agreement with this finding.