Coronaviruses (CoVs) are enveloped single-stranded positive-sense RNA viruses (Fig. 2A), which widely infected vertebrates including humans and animals, to cause respiratory and enteric diseases [[5], [6], [7]]. Spike glycoprotein (S protein) plays a major role in the pathogenesis of coronavirus, inducing host immune responses, and is considered a primary target for vaccine preparation [1,8]. Current information indicates that SARS-CoV-2 is more contagious than SARS-CoV including person­to­person spread, which poses a serious threat to human health [3,9].
Fig. 2 The structure of CoV virion and S protein, (A) Depiction of the CoV virion; (B) Depiction of S protein. A single S protein is depicted as a rectangle, and relevant structural features are highlighted as follows: N-terminal receptor binding domain (N-RBD) in dark blue; C-RBD in brown; cleavage sites (CS) 1 and 2, fusion peptide (FP) in red, heptad repeat (HR) regions 1 and 2 in green; transmembrane span (TM) depicted as membrane bilayer; cytoplasmic tail (CT) in light blue.; (C) Structure of the MHV N-RBD in complex with its CEACAM receptor.; (D) Structure of the SARS C-RBD in complex with its ACE2 receptor.; (E) Structure of the post-fusion HR1-HR2 bundle [7].