Brush border membrane aminopeptidase-N in the midgut of the gypsy moth serves as the receptor for the CryIA(c) delta-endotoxin of Bacillus thuringiensis.

Aminopeptidase-N (AP-N) was purified from gypsy moth (Lymantria dispar, L.) brush border membrane vesicles (BBMV) proteins by mono-Q chromatography and Superdex-75 gel filtration in the presence of the zwitterionic detergent, CHAPS, using FPLC. The purified AP-N, identified by its enzymatic activity, had an apparent size of 100 kDa, and was identified as the unique Bacillus thuringiensis insecticidal toxin, CryIA(c), binding protein. AP-N clearly displayed strong binding to CryIA(c), exhibiting little or no binding to CryIA(a) or CryIA(b), and showing no binding for the coleopteran-specific toxin, CryIIIA. Protein blots of the BBMV proteins probed with biotin-labeled and 125I-labeled insecticidal proteins revealed that CryIAc binds only to 120 kDa protein which is a slightly larger size in comparison to purified AP-N. Antibodies raised against the gypsy moth AP-N demonstrated that the purified AP-N and the 120 kDa CryIA(c) binding protein of total BBMV proteins are antigenically identical.