Heterologous expression of a gene that codes for Pg8, a scorpion toxin of Parabuthus granulatus, capable of generating protecting antibodies in mice

A novel peptide named Pg8 was purified from the venom of the South African scorpion Parabuthus granulatus and its primary structure was determined. It contains 63 amino acid residues tightly folded by 4 disulfide bridges. The gene coding for this peptide was cloned from a cDNA library. By recursive PCR strategy a hybrid gene was constructed having a factor X recognition site for proteolysis and a modified sequence for preferential codon usage of E. coli. A pQE30 molecular vector already contained a His-tag was used for expression. This construction was expressed in BL21 and Origami strains. The fusion protein from inclusion bodies was separated by HPLC (yield approximately 5 mg/L) and properly folded in vitro. Lethality tests showed that the recombinant peptide was toxic and was used to immunize mice. A volume of 0.25 ml of the anti-serum produced was capable of protecting up to 3 LD50 doses of pure toxin Pg8 but also, and more importantly, the entire soluble venom.