Bacillus thuringiensis Cry1Aa toxin-binding region of Bombyx mori aminopeptidase N

The Bacillus thuringiensis Cry1Aa toxin-binding region of Bombyx mori amino peptidase N (APN) was analyzed, to better understand the molecular mechanis m of susceptibility to the toxin and the development of resistance in insec ts. APN was digested with lyslendopeptidase and the ability of the resultin g fragments to bind to Cry1Aa and 1Ac toxins was examined. The binding abil ities of the tno toxins to these fragments were different. The Cry1Aa toxin bound to the fragment containing 40-Asp to 313-Lys, suggesting that the Cr y1Aa toxin-binding site is located in the region between 40-Asp and 313-Lys , while Cry1Ac toxin bound exclusively to mature IPN. Nest, recombinant APN of various lengths,vas expressed in Escherichia coli cells and its ability to bind to Cry1Aa toxin was examined, The results localized the Cry1Aa tox in binding to the region between 135-Ile and 198-Pro. (C) 1999 Federation o f European Biochemical Societies.