Specific Binding of Radiolabeled Cry1Fa Insecticidal Protein from Bacillus thuringiensis to Midgut Sites in Lepidopteran Species

Cry1Fa insecticidal protein was successfully radiolabeled with (125)I-Na. Specific binding to brush border membrane vesicles was shown for the lepidopteran species Ostrinia nubilalis, Spodoptera frugiperda, Spodoptera exigua, Helicoverpa armigera, Heliothis virescens, and Plutella xylostella. Homologous competition assays were performed to obtain equilibrium binding parameters (K(d) [dissociation constant] and R(t) [concentration of binding sites]) for these six insect species.