FIG 2.

Enhanced toxicity of Cry1Ab domain III mutants correlating with enhanced binding to S. frugiperda BBMV. (A) Binding of Cry1Ab toxins to BBMV from S. frugiperda Sf-IBT or to BBMV from M. sexta. Ten micrograms of BBMV protein was incubated with increasing concentrations (in nanomolar) of biotin-labeled Cry1Ab or domain III-activated toxins, and BBMV were recovered by centrifugation. Unbound toxin was washed out, and the toxin bound to the BBMV was separated by SDS-PAGE (10% acrylamide), electrotransferred to a PVDF membrane, and finally detected by using streptavidin-horseradish peroxidase. (B) Homologous binding competition. Biotin-labeled Cry1Ab or domain III mutants (5 nM) were incubated with BBMV in the presence of a 50-fold or 200-fold excess of the corresponding unlabeled toxin. Results shown are representative of at least three replicates.