Figure 2.

(A) 3D graphical presentation of the structure of SARS-CoV-2 and human host cell receptors. (B) SARS-CoV-2 genome encodes for 16 nonstructural proteins (nsp), four structural proteins S, M, E, and N, and accessory proteins. A cartoon figure of the SARS-CoV-2 S protein that contains the two subunits: S1 and S2, where S1 composed of: SP (signal peptide); NTD (N-terminal domain), and CTD (C-terminal domain), while S2 composed of FP (fusion peptide), HR1 (heptad repeat 1), HR2 (heptad repeat 2), TM (transmembrane), and CP (cytoplasmic). There are two cleavage sites at S protein denoted as yellow arrows (S1/S2) and (S2′).