Insect toxic component from the venom of a chactoid scorpion, Scorpio maurus palmatus (Scorpionidae)

Several insect toxic components were isolated from the venom of the chactoid scorpion, Scorpio maurus palmatus (Scorpionidae), by column chromatography, with the following findings. 1) The toxicity of the crude venom to insects is due to three separate groups of substances, the so-called cytotoxins, phospholipases, and neurotoxins, which play a dominant role. 2) The neurotoxic fraction contains two factors: the fast reversibly paralytic and the slow lethal. 3) The slow lethal factor is composed of two toxins (IT1 and IT2), the purity of which was assessed by column chromatography, disc electrophoresis, isoelectrofocusing, analytical ultracentrifugation, and amino acid analyses. 4) IT1 and IT2 are two polypeptides possessing unique amino acid compositions with molecular weights of 3232 and 3963, pHi 8.8 and 9.2, and supposed to contain two and three disulfide bridges, respectively. 5) A clear cooperative interaction was demonstrated between the fast paralytic and lethal fractions as well as between the two insect toxins, resulting in an evident recovery of the original toxicity to insects of the crude venom. 6) When assayed on an isolated insect axonal preparation under current and voltage clamp conditions, the combination of IT1 and IT2 caused a reversible blockage of both the sodium and potassium currents. This may explain the specific symptomatology and the mechanism of the paralysis induced by these toxins to an insect. The above data were compared with information concerning buthoid scorpion venom insect toxins.