Binding of 125I-labeled Cry1Ca to S. exigua BBMV. (A) Homologous competition. 125I-labeled Cry1C was incubated with BBMV from susceptible (FRA) or resistant (Xen-R) insects in the presence of increasing concentrations of unlabeled Cry1C toxin. (B) Dissection of total binding into their reversible and irreversible components. Contribution of both components to the binding of 125I-labeled Cry1Ca to BBMV from susceptible and resistant insects were compared. T-test (P = 0.7244 for the reversible component) (P = 0.0170 for the irreversible component). BBMV, brush border membrane vesicles.