[Analytical investigations of the delta-endotoxin of Bacillus thuriginiensis (author's transl)].

Biochemical properties of the crystalline delta-endotoxin of Bacillus thuringiensis, such as stability and solubility in different solvents, were investigated. The dissolved compounds were characterized by gel-electrophoresis and gel-filtration. Covalent and non-covalent bonds are responsible for the crystallisation of the protein molecules. The solubilisation of crystals with non-enzymatic solvents led to high molecular weight products (MW greater than or equal to 800,000) and to components with a molecular weight less than or equal to 10,000. Only the high molecular weight compounds showed toxic activity. The enzymatic degradation of the protein crystals yielded components with molecular weights of greater than or equal to 800,000, 250,000, 100,000, and less than or equal to 10,000. Again, the fraction less than or equal to 10,000 showed no toxic activity. Digestion of the crystals with proteases isolated from the gut juice of Pieris brassicae resulted in a highly toxic fraction with a molecular weight of 100,000. This component, which is resistant to further degradation, appears to be the toxic unit of the protein crystal.