Construction, expression, and purification of recombinant RBD-Fc.

Construction, expression, and purification of recombinant RBD-Fc. The code optimized recombinant DNA encoding the fragment containing 194 aa (331-524) of the SARS-CoV-2 S protein RBD region fused with human IgG1 Fc was inserted into the GS expression vector (Beijing JOINN Biologics, China), and the resulting plasmid was named RBD007. The DNA sequence of the assembled RBD and IgG1 Fc region recombinant DNA in the final construct was verified by DNA sequencing. The RBD007 plasmid was transfected into CHO-K1 cells by electroporation using a GenPulser (Bio-Rad, USA), after which stable clones were isolated by the limiting dilution method in the presence of 50 μM of Methionine Sulfoximine (MSX). The recombinant RBD-Fc protein was purified using affinity chromatography and anion exchange chromatography. The purity of recombinant protein was examined by SDS-PAGE and the molecular mass was determined by mass spectroscopy. The expression and purification were performed in GLP laboratory at Beijing JOINN Biologics Co. Ltd, China.