SARS-CoV-2 Recombinant Proteins

SARS-CoV is a positive-stranded RNA virus belonging to the family Coronaviridae. The SARS-COV-2 genome encodes at least sixteen non-structural proteins and four structural proteins. Structural proteins include Spike Protein (S), Envelope Protein (E), Membrane Protein (M), and Nucleocapsid Protein (N), each of which play primary roles in the structure of the virus particle as well as in other aspects of the viral replication cycle. Non-structural proteins (NSPs) include 3C-like Proteinase (3CLpro), papain-like protease (PLpro), Helicase and RNA-dependent RNA polymerase (RDRP), etc.

SARS-CoV-2 infection starts with virion attachment to the target cells mainly via interactions of the S proteins with host-cell receptor ACE2. After the entry, viral RNA gets released into the host cell and viral polyproteins are translated using the host cell ribosome. During translation, polyproteins (PP) PP1a and PP1ab are formed which are finally cleaved by the viral proteases, PLpro and 3CLPRO to create functional NSPs.

SARS-CoV-2 life cycle

After translation of structural proteins and NSPs, the Replicase–Transcriptase Complex (RTC) is formed by the assembly of RNA-dependent RNA polymerase (RdRp) (NSP12), helicase (NSP13) and other subunits like NSP7 and NSP8. Further, the complex transcribes a viral genome template of negative-sense genes. After transcription, the subgenomic proteins get translated to form structural and accessory proteins such as M, S, and E proteins and encased into the endoplasmic reticulum and then transported to the Endoplasmic Reticulum–Golgi Intermediate Compartment (ERGIC). Next, the previously replicated viral genome can directly join the N protein to form the nucleocapsid that gets insulated into the ERGIC. Finally, nucleocapsids along with several other structural proteins form the virion particles in a vesiculated form, which is exported out of the cell through exocytosis to release virions