Fig. 1.

Illustration of the SARS-CoV-2 viral genome, proteins and corresponding assays.

The genome of SARS-CoV-2 is a positive single-stranded RNA with more than 30,000 bp nucleotides. The capsid outside the genome is formed by the nucleocapsid protein (N) and is further wrapped by an envelope composed of three structural proteins: membrane protein (M), spike protein (S), and envelope protein (E). The entry of coronavirus into host cells is mediated by the S protein, which is a homotrimer protruding from the viral envelope that recognizes the receptor angiotensin-converting enzyme 2 (ACE2) via the S1 receptor-binding domain (RBD) and uses the S2 domain for fusion with the host cell membrane to enter host cells. In addition to these four structural proteins, SARS-CoV-2 contains sixteen nonstructural proteins (NSPs). Four NSPs responsible for viral replication or transcription are shown in this illustration. NSP3 separates the translated protein. NSP5 is responsible for cleaving the viral polyprotein into functional units during replication. NSP12 contains the RNA-dependent RNA polymerase (RdRp). NSP13 participates in viral replication or transcription via the zinc-binding domain. ACE2 angiotensin-converting enzyme 2, E envelope protein, M transmembrane protein, N nucleocapsid protein, NSP nonstructural protein, ORF open reading frame, RdRp RNA-dependent RNA polymerase, S spike protein.