Fig. 3.

Schematic representation of the SARS-CoV-2 spike protein. A. Spike protein consists of the S1 and S2 units. In the S1 subunit, there is an extracellular N-terminal domain and a receptor-binding domain which play a role in the viral entrance into the cell through ACE2 receptor. In the S2 subunit, there is the fusion protein (FP), heptapeptide repeat sequence 1 and 2 (HR1 and HR2), as well as the transmembrane domain and a short C-terminal domain. B. Open or closed three dimensional conformation of S protein implicate in the binding of cell receptor ACE2. Created with BioRender.com.