Efficient recovery of a functional extracellular domain of bovine IgG2 Fc receptor (boFcγ2R) from inclusion bodies by a rapid dilution refolding system

The extracellular domain of the boFcγ2R gene was constructed and cloned into the Escherichia coli expression vector pET-28a. The recombinant protein was expressed at high level in E. coli BL21(DE3) and existed mainly as inclusion bodies. The inclusion bodies were solubilized in 6 M guanidine hydrochloride and refolded by rapid dilution. After renaturation, the purity of the recovered recombinant protein was up to 95%. ELISA assay showed that the renatured recombinant protein could inhibit bovine IgG2 binding to expressed boFcγ2R on the COS-7 cell surface with an IC50 value of 0.68 μM. The overall yield of the active rsbo2R was up to 20 mg/l of culture. Crystals of the rsbo2R were grown at 293 K by the hanging-drop vapour diffusion method showed weak diffraction.