Article Abstract:
Bacillus thuringiensis produces crystalline inclusions comprised of a mixture of delta-endotoxins during sporulation. Following ingestion by insect larvae, these inclusion proteins are solubilized, and the protoxins are converted to toxins. Research findings showed a greater extent of oligomerization of the Cry1Ac toxin with vesicles from the Heliothis virescens midgut than with those from the Manduca sexta midgut, which correlated with observed differences in toxicity. Tight binding of virtually the entire toxin molecule to the membrane is an important step in toxicity.
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Article Abstract:
Mutations in the third-domain of the Bacillus thuringiensis CryIAa delta-endotoxin protein changes its potency of enhancing the permeability of Bombyx mori midgut brush border membrane vesicles (BBMV). The first, second, and last arginine residues of the conserved third-domain sequence, R-521 YRVRIR-527, are substituted with other amino acids to form the mutant toxins. Three of the mutant toxins have an activity comparable to that of the wild-type toxin. The third-domain probably controls the pore- and channel-forming processes in BBMV.
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Article Abstract:
A study was conducted on the function of the third domain of Bacillus thuringiensis insecticidal toxin CryIAa in membrane permeabilization under a receptor-free environment. Mutants were developed by replacing arginine with glutamine, lysine, histidine and glutamic acid. Results demonstrate the functional role of domain II and indicates that domain I interacts with the residues of the positive arginine face of block 4.
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