Expression and functional identification of recombinant SARS-CoV-2 receptor binding domain (RBD) from E. coli system.

The receptor binding domain (RBD) of SARS-CoV-2 is located in the C-terminal of S1 subunit of the spike (S) protein which is responsible for recognizing and binding to the angiotensin-converting enzyme 2 (ACE2) receptor. The DNA encoding the SARS-CoV-2 RBD was inserted into pET-28a (+) to construct expression plasmid pET-28a (+)/RBD. The desired RBD protein was produced in E. coli Rosetta (DE) and purified by a Ni-NTA column. The recombinant RBD was analyzed by SDS-PAGE and Western blot. The flow cytometry analysis indicated that the recombinant RBD is capable of binding to human ACE2 (hACE2) in the ACE2-overexpressed HEK293A-hACE2 cells. Our results demonstrated that recombinant RBD expressed in E. coli Rosetta (DE) strain has bioactivities and can be used as an antigen for diagnosis and as a tool for the development of novel anti-viral drugs against SASR-CoV-2.