Fig. 3.

Scheme of SARS-CoV-2 penetration into recipient cells. ACE 2 is the host cell receptor responsible for mediating infection by SARS-CoV-2, the novel coronavirus responsible for coronavirus disease 2019 (COVID-19). Trimeric spike protein on the virion binds to ACE2 (angiotensin converting enzyme 2), a cell-surface protein. Furin-like serine proteases (TMPRSS2, PACE, PCSK3) are responsible for the cleavage of the S-glycoprotein in the polybasic motif and the subsequent on allowing the fusion protein (FP1 and FP2) to bind to the membrane. It helps the virion enter the cells. SARS-CoV-2 has spike protein trimers spontaneously transitioning from the closed to the open conformation