Blocking binding of Bacillus thuringiensis Cry1Aa to Bombyx mori cadherin receptor results in only a minor reduction of toxicity

Taek H You² , Mi K Lee³ , Jeremy L Jenkins⁴ , Oscar Alzate⁵ and Donald H Dean¹

¹Departments of Biochemistry, Molecular Genetics and Entomology, The Ohio State University, Columbus, OH 43210, USA

²Department of Biological Sciences, Campbell University, Buise Creek, NC, USA

³Syngenta, Inc., Research Triangle Park, NC, USA

⁴Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA

⁵Neuroproteomics Facility, Duke University, Durham, NC, USA

author email corresponding author email

BMC Biochemistry 2008, 9:3doi:10.1186/1471-2091-9-3


Published:	24 January 2008

Abstract

Background

Bacillus thuringiensis Cry1Aa insecticidal protein is the most active known B. thuringiensis toxin against the forest insect pest Lymantria dispar (gypsy moth), unfortunately it is also highly toxic against the non-target insect Bombyx mori (silk worm).

Results

Surface exposed hydrophobic residues over domains II and III were targeted for site-directed mutagenesis. Substitution of a phenylalanine residue (F328) by alanine reduced binding to the Bombyx mori cadherin by 23-fold, reduced biological activity against B. mori by 4-fold, while retaining activity against Lymantria dispar.

Conclusion

The results identify a novel receptor-binding epitope and demonstrate that virtual elimination of binding to cadherin BR-175 does not completely remove toxicity in the case of B. mori.