Abstract: 【Aim】To study the olfactory recognition function of odorant-binding protein (OBP) CchiOBP3 in Callosobruchus chinensis by analyzing the binding characteristics of CchiOBP3 with volatile ligands of Vigna radiata, so as to provide a theoretical basis for elucidating the olfactory recognition mechanism of host localization in C. chinensis. 【Methods】The homology modeling of CchiOBP3 was performed by SWISS-MODLE software, the model was evaluated by SAVES 6.0 software, and the molecular docking simulation of ChiOBP3 with 26 volatile ligands of V. radiata was performed by Autodock 4.2.6 software. The recombinant CchiOBP3 was obtained by prokaryotic expression and affinity column chromatography, and its binding characteristics with four volatile ligands of V. radiata with high binding energy were determined by fluorescence competitive binding assay. The responses of female adults of C. chinensis to four volatile ligands were detected by electroantennogram (EAG) assay.【Results】CchiOBP3 formed hydrogen bonds with 17 out of 26 ligands, and the hydrogen bonding position was mainly in the phenylalanine at position 112. Four ligands, trans-caryophyllene, 4-carvomenthenol, cyclohexylbenzene, and 2-methylnaphthalene, with high binding energy to CchiOBP3 were screened out. CchiOBP3 had strong binding ability with 4-carvomenthenol (Ki=7.16 μmol/L), cyclohexylbenzene (Ki=7.45 μmol/L) and 2-methylnaphthalene (Ki=13.97 μmol/L) among the four ligands with high binding energy. In addition, the EAG reaction of female adults of C. chinensis was induced by four volatile ligands and the EAG reaction induced by 4-carvomenthenol was the strongest. 【Conclusion】CchiOBP3 can bind to three types of V. radiata volatile ligands, and it is speculated that CchiOBP3 plays an important role in the localization of hosts by C. chinensis.

Key words: Callosobruchus chinensis, CchiOBP3, molecular docking, prokaryotic expression, fluorescence competitive binding, EAG