In silico analysis and molecular docking of Cry3Aa toxin with coleopteran specific midgut receptor of ADAM10/APN receptors

Bacillus thuringiensis (Bt) is widely recognized as a safe and effective bioinsecticide, with Cry toxins targeting pests of various insect orders. The present study focuses on the modeling and validation of the Cry3Aa protein (deduced amino acid sequence of cry3Aa gene cloned from native Bt isolate, T121) and its interaction with midgut receptor proteins (ADAM10 and APN).

The three-dimensional structures of Cry3Aa protein and the midgut receptors ADAM10 and APN were predicted using the SWISS model server. Functional domain analysis of Cry3Aa revealed three distinct domains: N-terminal (Domain I), Central (Domain II) and C-terminal (Domain III), providing insights into their structural organization. The predicted models of Cry3Aa, ADAM10 and APN were validated using the Ramachandran plot which demonstrated structural integrity.

Primary structure analysis of Cry3Aa revealed a 652 amino acid protein with a theoretical isoelectric point of 5.59, a molecular weight of 74 kDa and stable characteristics. Protein-protein docking analysis using ClusPro 2.0 showed that Cry3Aa exhibited higher level of interaction with the ADAM10 receptor than with the APN receptor. The Cry3Aa-ADAM10 docked complex demonstrated 23 hydrogen bonds, reasoning for its stability and binding affinity. These findings revealed that the Cry3Aa protein has a strong affinity against coleopteran specific midgut receptors and hence Cry3Aa has a potential to be an effective coleopteran specific insecticidal protein.