Oligomerization of Parasporin-2, a �ew Crystal Protein from �on-Insecticidal Bacillus thuringiensis�� in Lipid Rafts

Parasporin-2, a new crystal protein from non-insecticidal Bacillus thuringiensis, exhibits strong cytocidal activity against various mammalian cells with divergent target specificity. The toxin binds to the surface of target cells and increases permeability of plasma membrane. Subcellular fractionation and immunoblot analysis of the toxin-treated cells revealed that the toxin bound to lipid rafts and formed SDSresistant oligomer. The binding and the oligomerization of the toxin were inhibited by the treatment of the cells with phosphatidylinositolspecific phospholipase C. Thus, the interaction of parasporin-2 with glycosylphosphatidylinositol-anchored proteins was required for the formation of oligomeric toxin that could permeabilize the plasma membrane.