Synthesis and Characterization of Cry2Ab–AVM Bioconjugate: Enhanced Affinity to Binding Proteins and Insecticidal Activity

Bacillus thuringiensisinsecticidal proteins (Bt toxins) have been widely used in crops for agricultural pest management and to reduce the use of chemical insecticides. Here, we have engineered Bt toxin Cry2Ab30 and bioconjugated it with 4”-O-succinyl avermectin (AVM) to synthesize Cry2Ab–AVM bioconjugate. It was found that Cry2Ab–AVM showed higher insecticidal activity againstPlutella xylostella, up to 154.4 times compared to Cry2Ab30. The binding results showed that Cry2Ab–AVM binds to the cadherin-like binding protein fragments, the 10th and 11th cadherin repeat domains in theP. xylostellacadherin (PxCR10–11), with a much higher affinity (dissociation equilibrium constantKD= 3.44 nM) than Cry2Ab30 (KD= 28.7 nM). Molecular docking suggested that the macrolide lactone group of Cry2Ab–AVM ligand docking into the PxCR10–11is a potential mechanism to enhance the binding affinity of Cry2Ab–AVM to PxCR10–11. These findings offer scope for the engineering of Bt toxins by bioconjugation for improved pest management.Keywords:Cry2Ab–AVM bioconjugate;binding affinity;molecular dockingKey Contribution:The study develops an engineered Cry2Ab by bioconjugation with 4”-O-succinyl avermectin to enhance insecticidal potency againstP. xylostella.This engineering also improves its affinity to the cadherin-like binding fragments. Homology modeling and docking study are also carried out to investigate the binding model.