%0 Journal Article
%T Binding specificity of Bacillus thuringiensis Cry1Aa for purified, native Bombyx mori aminopeptidase N and cadherin-like receptors
%A Jeremy L Jenkins
%A Donald H Dean
%J BMC Biochemistry
%D 2001
%I BioMed Central
%R 10.1186/1471-2091-2-12
%X The Bombyx mori (silkworm) aminopeptidase N (APN) and cadherin-like receptors for Bacillus thuringiensis insecticidal Cry1Aa toxin were purified and their real-time binding affinities for Cry toxins were examined by surface plasmon resonance. Cry1Ab and Cry1Ac toxins did not bind to the immobilized native receptors, correlating with their low toxicities. Cry1Aa displayed moderate affinity for B. mori APN (75 nM), and unusually tight binding to the cadherin-like receptor (2.6 nM), which results from slow dissociation rates. The binding of a hybrid toxin (Aa/Aa/Ac) was identical to Cry1Aa.These results indicate domain II of Cry1Aa is essential for binding to native B. mori receptors and for toxicity. Moreover, the high-affinity binding of Cry1Aa to native cadherin-like receptor emphasizes the importance of this receptor class for Bt toxin research.Bacillus thuringiensis (Bt) has been sold commericially and used as a biopesticide worldwide for over half a century. However, growing public concern surrounding Bt use has sparked worldwide debate over current policies [1]. For example, in India, fear over a potential Bombyx mori (silkworm) epizootic, or microbial pathogen outbreak, inspired a governmental ban on the use of Bt, despite the nation's continuing use of traditional chemical pesticides [2].While pest control with Cry toxins that possess low B. mori activity (i.e. Cry1Ac) is a viable solution in affected countries, it is worthwhile to investigate the specific molecular mechanisms that make Cry1Aa highly active. Early work took advantage of the fact that Cry1Aa, but not Cry1Ac, is toxic to B. mori. For example, Ge et al.[3] exchanged hypervariable regions between genes encoding the two toxins and localized the toxicity specifying region of Cry1Aa to residues 332¨C450 in domain II. A follow-up study demonstrated the toxicity specifying residues were involved in binding B. mori brush border membrane vesicles [4]. More specifically, alanine substitution or deletion of
%U http://www.biomedcentral.com/1471-2091/2/12