Isolation and characterization of a novel type of neurotoxic peptide from the venom of the South African scorpion Parabuthus transvaalicus (Buthidae)

The venom of the South African scorpion Parabuthus transvaalicus was charac terized using a combination of mass spectrometry and R-P-HPLC separation an d bioassays. The crude venom was initially separated into 10 fractions. A n ovel, moderately toxic but very high abundance peptide (birtoxin) of 58 ami no-acid residues was isolated, identified and characterized. Each purificat ion step was followed by bioassays and mass spectroscopy. First a C-4 RP-HP LC column was used, then a Cis RP Microbore column purification resulted in >95% purity in the case of birtoxin from a starting material of 230 mug of crude venom. About 12-14% of the D-214 absorbance of the total venom as ob served after the first chromatography step was composed of birtoxin. This p eptide was lethal to mice at low microgram quantities and it induced seriou s symptoms including tremors, which lasted up to 24 h post injection, at su bmicrogram amounts. At least seven other fractions that showed different ac tivities including one fraction with specificity against blowfly larvae wer e identified. Identification of potent components is an important step in d esigning and obtaining effective antivenom. Antibodies raised against the c ritical toxic components have the potential to block the toxic effects and reduce the pain associated with the scorpion envenomation. The discovery of birtoxin, a bioactive long chain neurotoxin peptide with only three disulf ide bridges, offers new insight into understanding the role of conserved di sulfide bridges with respect to scorpion toxin structure and function.