Unshared binding sites for Bacillus thuringiensis Cry3Aa and Cry3Ca proteins in the weevil Cylas puncticollis (Brentidae)

- N-terminal sequence of Cry3C activated by trypsin or chymotrypsin was identified at 159 and 153 positions, respectively.
- Cry3Aa and Cry3Ca proteins bound specifically to C. puncticollis BBMV.
- Cry3Aa and Cry3Ca proteins do not completely compete for the same binding sites.

Bacillus thuringiensis Cry3Aa and Cry3Ca proteins have been reported to be toxic against the African sweetpotato pest Cylas puncticollis. In the present work, the binding sites of these proteins in C. puncticollis brush border vesicles suggest the occurrence of different binding sites, but only one of them is shared. Our results suggest that pest resistance mediated by alteration of the shared Cry-receptor binding site might not render both Cry proteins ineffective.