Fig. 1.
(a) Life cycle of SARS-CoV-2. (1) The replication of SAR-CoV-2 begins with the binding of its spike protein (S) with receptor angiotensin-converting enzyme 2 (ACE2) on the cell surface molecules of the host. (2) The viral S protein undergoes conformational changes leading to a fusion between the viral envelope with the plasma or endosomal membranes, entering the cell's cytoplasm, and releasing RNA. (3) The positive-strand viral RNA serves as mRNA for translation of ORF 1a and 1b, encoding units of the RNA-dependent RNA polymerase. (4) RNA polymerase transcribes full-length complementary negative-sense RNA. Viral proteins (S, M, E, and N) get translated (5) The proteins are further processed in the Endoplasmic Reticulum and Golgi Apparatus. (6) Packaging of viral proteins and positive-strand RNA. (7) Assembling complete virion surrounded by the plasma membrane. (8) Apoptosis of cells with the release of the virion. (b) Role of Main protease Mpro in SARS-CoV-2.