Study on Interaction and Binding Properties of Terpenes repellent active compounds with Odorant Binding Protein 9B in Tribolium castaneum

To screen the odorant binding proteins (OBPs) of Tribolium castaneum related to repellent activity and explore the repellent mechanism of terpenoids by studying the interaction between ligands and Tc OBPs. Behavior tests indicated that (1R)-(+)- α -Pinene and β -Caryophyllene had repellent activity against T. castaneum . Through homology modeling and molecular docking, we screened Tc OBP-9B, which is highly expressed in antennae and has strong interactions with (1R)-(+)- α -Pinene, β -Caryophylne, as target protein for recombinantly expressed. Fluorescence spectra and UV absorption spectra showed that Tc OBP-9B had strong bind to (1R)-(+)- α -Pinene and β -Caryophyllene with concentration-dependent in static quenching. Thermodynamic date revealed that they formed stable complexes through van der Waals force, electrostatic and hydrophobic interactions. By fluorescence competitive binding assay, molecular docking and circular dichroism spectra, the binding sites of Tc OBP-9B was confirmed as the α -helix, where the ligands were competitively bound to 1-NPN. These results suggested that Tc OBP-9B was a significant target protein associated with repellent activity, providing new approach for screening repellents against T. castaneum .