The main features of Bacillus thuringiensis δ-endotoxin molecular structure

The crystal-forming proteins (δ-endotoxins) produced by various serotypes of Bacillus thuringiensis and toxic for Lepidoptera reveal the same pattern of molecular organisation. These proteins (Mr of ca. 145,000–130,000) contain an N-terminal domain (Mr of 85,000–65,000) resistant to proteolysis whereas their C-terminal moieties (Mr of 65,000) undergo an extensive degradation by trypsin that leads to stepwise cleavage off the fragments with Mr of 15,000–35,000.