BINDING OF BACILLUS-THURINGIENSIS CRY1AC TOXIN TO AMINOPEPTIDASE IN SUSCEPTIBLE AND RESISTANT DIAMONDBACK MOTHS (PLUTELLA-XYLOSTELLA)

Bacillus thuringiensis Cry1Ac toxin bound to a 120-kDa protein isolate d from the brush border membranes of both susceptible and resistant la rvae of Plutella xylostella, the diamondback moth. The 120-kDa protein was purified by Cry1Ac toxin affinity chromatography. Like Cry1Ac-bin ding aminopeptidase N (EC 3.4.11.2) from other insects, this protein w as eluted from the affinity column with 200 mM N-acetylgalactosamine. The purified protein had aminopeptidase activity and bound Cry1Ac toxi n on ligand blots, Purified aminopeptidase was recognized by antibodie s to the cross-reacting determinant found on phosphatidylinositol-spec ific phospholipase C-solubilized proteins, The results show that the p resence of Cry1Ac-binding aminopeptidase in the brush border membrane is not sufficient to confer susceptibility to Cry1Ac, Furthermore, the results do not support the hypothesis that resistance to Cry1Ac was c aused by lack of a Cry1Ac-binding aminopeptidase.