M ! Watchtower Services

nsps and Accessory Proteins

Besides the impo1iant structural proteins, the SARS-CoV-2 geno1ne contains 15 nsps, nsp1 to nsp10 and nsp12 to nsp16, and 8 accessory proteins (3a, 3b, p6, 7a, 7b, 8b, 9b, and ORF14) (16). All these proteins play a specific role in viral replication
(27). Unlike the accessory proteins of SARS-CoV, SARS-CoV-2 does not contain 8a protein and has a longer 8b and shorter 3b protein (16). The nsp7, nsp13, envelope, 1natrix, and p6 and 8b accessory proteins have not been detected with any a1nino acid substih1tions compared to the sequences of other coronaviruses (16).
The virus structure of SARS-CoV-2 is depicted in
Fig. 2.

---====-- Spike glycoprotein (S)
(required for the entry of the infectious virion particle)
::,;:,.---Membrane protein (M)
(most abundant viral protein)
Major structural proteins

-- Envelope glycoprotein (E) (smallest among the major structural proteins)

Nucleocapsid protein (N)

....... + single-stranded positive sense RNA genome

Lipid bilayer

FIG 2 SARS-CoV-2 virus structure.

ribavirin, penciclovir, nitazoxanide, nafan1ostat, and chloroquine, tested in con1parison to re1ndesivir and favipiravir (broad-spectrum antiviral drugs) revealed remdesivir and chloroquine to be highly effective against SARS-CoV-2 infection in vitro (194). Ribavirin, penciclovir, and favipiravir 1night not possess noteworthy in vivo antiviral actions for SARS-CoV-2, since higher concentrations of these nucleoside analogs are needed in vitro to lessen the viral infection. Both re1ndesivir and chloroquine are being used in humans to treat other diseases, and such safer drugs can be explored for assessing their effectiveness in COVTD-19 patients.
Several therapeutic agents, such as lopinavir/ritonavir, chloroquine, and hydroxychloroquine, have been proposed for the clinical manage1nent of COVID-19 (299). A 1nolecular docking study, conducted in the RNA­ dependent RNA poly1nerase (RdRp) of SARS-CoV-2 using different commercially available antipoly1nerase drugs, identified that drugs such as ribavirin, retndesivir, galidesivir, tenofovi r, and sofosbuvir bind RdRp tightly, indicating their vast potential to be used against COVID-19 (305). A broad-spectrun1 antiviral drug that was developed in the United States, tilorone dihydrochloride (tilorone),