Abstract:  In order to clarify the physiological function of AcerCSP3, a chemosensory protein (CSP) in Apis cerana cerana, the recombinant protein AcerCSP3 was successfully expressed in a optimized prokaryotic expression system, and the binding properties of the purified AcerCSP3 with 1-NPN was then investigated. Scatchard plot analysis indicated that the dissociation constant between 1-NPN and AcerCSP3 was 8.29 μmol/L and the binding site number was about one. In the competitive binding assays, all the five candidate ligands at the concentration of 200 μmol/L reduced the relative fluorescence intensity of 1-NPN by more than 50%, with β-ionone causing 90% reduction in the relative fluorescence intensity, suggesting that all the tested ligands have strong binding capability with AcerCSP3. 3, 4-Dimethylbenzaldehyde had the strongest binding capability with a dissociation constant as high as 18.77 μmol/L. All the candidate chemical ligands are plant volatile secondary metabolites, indicating that AcerCSP3 may act as a carrier for odor molecules released from flower and nectar and play a role in searching for honey sources.

Key words: Apis cerana cerana, chemosensory protein, prokaryotic expression, purification, chemical ligand, binding properties