Ligand Blot Identification of a Manduca sexta Midgut Binding Protein Specific to Three Bacillus thuringiensis CryIA-Type ICPs

The CryIA(a), CryIA(b) and CryIA(c) Bacillus thuringiensis insecticidal crystal proteins (ICPs) were used in ligand-blot experiments to detect specific binding proteins in brush-border membrane vesicles (BBMV) of Manduca sexta. We identified a protein which binds these three CryIA-type ICPs. The apparent molecular mass of the protein, estimated on SDS-PAGE, was 210 kDa as was the CryIA(b) binding protein previously described by Vadlamudi and col. We have also demonstrated, in ligand blot experiments, that CryIA(a) and ClyIA(c) compete with CryIA(b) for binding this 210 kDa protein. Properties of the binding molecule can be correlated with knowledge previously aquired through radiolabelled binding experiments.