Peptide mapping of different Bacillus thuringiensis toxin gene products by CNBr cleavage in SDS-PAGE gels

A cyanogen bromide fragmentation reaction of 3 hr in sodium dodecyl sulfate gel slices was used for the degradation of the toxins coded by the three cryIA genes from Bacillus thuringiensis kurstaki. Peptide patterns diagnostic for each toxin gene product were observed. Treatment longer than 3 hr led to the weakening and disappearance of protein bands. In 9 out of 16 wild B. thuringiensis strains tested, it was determined that only one of the cryIA genes was being expressed; in 6 strains, one to two genes were identified, with the presence of an additional gene possible and masked because of the overlap of peptide bands; in one strain none of the genes was expressed.