Cadherin-like receptor from the European corn borer

Bacillus thuringiensis Cry1A toxins are lethal to the corn pest European corn borer (Ostrinia nubilalis) larvae. Cry1Aa, Cry1Ab and Cry1Ac bind to a protein of ~205-kDa in the brush border membrane vesicles. In addition, Cry1Ab binds to proteins of ~ 150 and 170-kDa and Cry1Ac binds to proteins of ~120 kDa. A competition ligand blot using unlabeled Cry1Ab to compete with 125I-Cry1Ab shows that binding to the 150, 170 and 205-kDa proteins is compateted away by Cry1Ab. Furthermore, toxin-receptor dissociation constant Kd shows that the binding occurs with high affinity (Kd ~ 1.2 nM). These results suggest that Cry1Aa, Cry1Ab and Cry1Ac share a 205-kDa common membrane binding protein and they bind specifically with high affinity. The Southern blot and polymerase chain reaction analysis show that O. nubilalis contains a homologue to the 210-kDa Manduca Sexta BT-R1 cadherin-like receptor which mediates toxicity for Cry1A toxins. Consequently, these results suggest that the 205-kDa protein band is a cadherin-like receptor homologous to the 210-kDa tobacco horn worm receptor. Therefore, it is more likely that the 205-kDa receptor is mediating toxicity to O. nubilalis but not the 120, 150 or 170-kDa proteins