Biochemical homology between crystal and spore protein of Bacillus thuringiensis

The crystalline inclusion of Bacillus thuringiensis, dissolved in 8 m urea containing 10% 2-mercaptoethanol and dialyzed to pH 8.3 to 8.5, was compared with a fraction obtained by the same extraction procedure from spores broken by dry rupture. The two fractions behaved similarly on chromatography with Sephadex G-100 and diethylaminoethyl cellulose. The preparations behaved identically on acrylamide gel electrophoresis at pH 12 and pH 9.5. Further, peptide maps of the two fractions obtained after digestion with trypsin were almost superimposable. Amino acid analyses of the crystal and spore fraction were closely similar; discrepancies are attributed to contamination of the spore extract with small amounts of other proteins. It is concluded that a significant portion of the spore protein is identical with the crystal protein.