Specificity of Bacillus thuringiensis delta-endotoxins. Importance of specific receptors on the brush border membrane of the mid-gut of target insects.

摘要: To study the molecular basis of differences in insecticidal spectrum Bacillus thuringienesis delta-endotoxins, we have performed binding studies with three delta-endotoxins on membrane preparations from larval insect mid-gut. Conditions for a standard assay were established through detailed 125I-labeled Bt2 toxin, recombinant B. thuringiensis delta-endotoxin, to brush border vesicles Manduca sexta. The toxins tested (Bt2, Bt3 and Bt73 toxins) are about equally toxic M. sexta but differ their toxicity against Heliothis virescens. Equilibrium revealed saturable, high-affinity sites H. While affinity was not significantly different virescens vesicles, marked site concentration measured which reflected vivo toxicity. Competition experiments heterogeneity sites. For virescens, three-site model proposed. In sexta, one population is shared by all toxins, while another only recognized toxin. Several other non-toxic or much less than did marginally displace toxin this insect. No saturable observed tissues several non-susceptible organisms. Together, these data provide new evidence that specific receptor gut epithelial cells an important determinant respect crystal proteins.