Bacillus thuringiensis toxin, Cry1C interacts with 128HLHFHLP134 region of aminopeptidase N of agricultural pest, Spodoptera litura

摘要

We modeled Cry1C toxin and its Aminopeptidase-N receptor and in silico docking analysis was performed. Further, we utilized biopanning against Cry1C followed by blocking assays and mutagenesis analysis to identify the binding epitope of SIAPN. We have identified a putative SIAPN binding region, APN-CRY (128HLHFHLP134). A derivative of SIAPN carrying the 128HLHFHLP134 region termed as binding region of APN (BR-APN) was cloned and its involvement in Cry1C binding and toxicity was checked. Cry1C-BR-APN binding was competed by synthetic peptides homologous to Ioop2 and Ioop3 of domain Ⅱ but not by that of loopa. Additionally, alanines substitution of residues H128, H130, H132 and P134 affect the binding efficiency of receptor to Cry1C toxin (upto 4-fold lower affinity).These residues are also implicated in Cry1C toxicity as shown by the reduced ability to affect the mortality of Cry1C on S. litura larvae when toxin was preincubated with a fragment of the receptor.