Insect Specific Neurotoxins from Scorpion Venom that Affect Sodium Current Inactivation

AbstractA new toxin, LqhαlT, which causes a unique mode of paralysis in blowfly larvae, was purified from the venom of the scorpion Leiurus quinquestriatus hebraeus, and its structural and pharmacological properties were compared to those of three other groups of neurotoxins found in Buthinae scorpion venoms. Like the excitatory and depressant insect-selective neurotoxins, LqhαlT was highly toxic to insects, but it differed from these toxins in two important characteristics: (a) LqhαlT lacked strict selectivity for insects; was highly toxic to crustaceans and had a measurable but low toxicity to mice. (b) It did not displace an excitatory insect toxin from its binding sites in insect neuronal membrane. However, in its primary structure and its effect on excitable tissues, LqhαlT strongly resembled the well-characterized α scorpion toxins, which affect mammals. The amino acid sequence was identical with α toxin sequences in 55%-75% of positions, a degree of homology comparable to that seen among the α toxi...