SARS-CoV-2 and SARS-CoV Spike-RBD Structure and Receptor Binding Comparison and Potential Implications on Neutralizing Antibody and Vaccine Development

Chunyun Sun; Long Chen; Ji Yang; Chunxia Luo; Yanjing Zhang; Jing Li; Jiahui Yang; Jie Zhang; Liangzhi Xie

The RBD containing S1 protein, resulted from cleavage of the spike protein on the virus membrane is responsible for the binding of the virus to human receptor on cell membrane, which is important for viral infectivity 31 . Binding curves of recombinant S1 proteins of SARS-CoV-2 and SARS-CoV to human ACE2 were measured by ELISA. Results confirmed that both viruses have similar S1-ACE2 protein-protein binding curves and EC 50 (Figure 2A) . Binding curves of S1 protein to ACE2 expressing 293T cells was further assessed using FACS. Again, similar binding curves and EC 50 values were obtained for the two viruses ( Figure 2B ). The above experimental results are consistent with our structure modeling analysis, which indicates that SARS-CoV-2 virus likely infects human cells through similar mechanisms as SARS-CoV virus by binding to human ACE2 with comparable affinities, and hence may possess similar transmissibility.