The main features of Bacillus thuringiensis δ-endotoxin molecular structure

Research paper by G. G. Chestukhina, L. I. Kostina, A. L. Mikhailova, S. A. Tyurin, F. S. Klepikova, V. M. Stepanov

Indexed on: 01 Aug '82Published on: 01 Aug '82Published in: Archives of Microbiology


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.The N-terminal domain from serotype V δ-endotoxin is active when introduced into the hemocoel of Galleria mellonella larvae. Hence, it correponds to the “true toxin” normally formed by larva proteases action on the crystalforming protein (protoxin). Some differences were found in the properties of the N-terminal domains isolated from the crystal-forming proteins of III, V and IX serotypes, e.g., in their solubility, digestion by subtilisin, molecular weights and the distribution of methionine residues along the polypeptide chains.