Functional domains of Bacillus thuringiensis insecticidal crystal proteins. Refinement of Heliothis virescens and Trichoplusia ni specificity domains on CryIA(c).

摘要: Insecticidal crystal proteins (delta-endotoxins), CryIA(a) and CryIA(c), from Bacillus thuringiensis are 82% homologous. Despite this homology, CryIA(c) was determined to have 10-fold more insecticidal activity toward Heliothis virescens Trichoplusia ni than CryIA(a). Reciprocal recombinations between these two genes were performed by the homolog-scanning technique. The resultant mutants had different segments of their primary sequences exchanged. Bioassays with toxin revealed that amino acids 335-450 on associated against T. ni, whereas 335-615 same required exchange full H. specificity. One chimeric protein toxin, involving residues 450-612 demonstrated 30 times native parental indicating region plays an important role in structural integrity mutant assessed treatment bovine trypsin. All actively toxic formed a 65-kDA trypsin-resistant active core, similar structure not altered significantly. Contrarily, certain inactive susceptible complete protease hydrolysis, lack toxicity may been due alterations.