A RECOMBINANT INSECT-SPECIFIC ALPHA-TOXIN OF BUTHUS-OCCITANUS TUNETANUS SCORPION CONFERS PROTECTION AGAINST HOMOLOGOUS MAMMAL TOXINS

We have constructed a cDNA library from venom glands of the scorpion B uthus occitanus tunetanus and cloned a DNA sequence that encodes an al pha-toxin. This clone was efficiently expressed in Escherichia coli as a fusion protein with two Ig-binding (Z) domains of protein A from St aphylococcus aureus. After CNBr treatment of the fusion protein and HP LC purification, we obtained approximately 1 mg recombinant alpha-toxi n/l bacterial culture. The toxin, called Bot XIV, displays no toxicity towards mammals but is active towards insects as shown by its paralyt ic activity against Blatella germanica cockroach and by electrophysiol ogical studies on Periplaneta americana cockroaches. The Bot XIV prote in fused to two Z domains is highly immunogenic in mice and induces pr oduction of antisera that specifically recognize and neutralize highly toxic components that had been injected into mice. This fusion protei n could be very useful for development of potent protective antisera a gainst scorpion venoms.