ELISA analysis of binding of Cry1Ab toxins to recombinant APN1, ALP, and CAD receptors. Enhanced toxicity of Cry1Ab domain III mutants correlated with enhanced binding to S. frugiperda CAD, ALP, and APN proteins. A total of 2.5 μg of each protein was fixed to ELISA plates, the plates were incubated with different concentrations of Cry1Ab or Cry1Ab domain III mutants, and bound toxins were revealed with anti-Cry1Ab antibody and anti-rabbit IgG secondary antibody conjugated with horseradish peroxidase. Results are means of three repetitions.