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accessory protein ORF3b of severe acute respiratory syndrome-associated coronavirus This model represents the accessory protein ORF3b of Severe acute respiratory syndrome-associated coronavirus (SARS-CoV). There are five essential genes in CoVs that result in the following gene products: Spike (S) protein, Membrane (M) glycoprotein, Nucleocapsid (N), Envelope (E) protein, and replicase/protease polyproteins (ORF1ab); all are required to produce a structurally complete viral particle. In addition, CoV genomes also contain ORFs coding for accessory proteins that are specific for certain CoV lineages or for a particular CoV. In general, CoV accessory proteins are considered to be dispensable for viral replication; however, several accessory proteins have been shown to exhibit functions in virus-host interactions during CoV infection. SARS-CoV mRNA 3 encodes the distinct proteins ORF3a and ORF3b proteins, which are translated in different reading frames. SARS-CoV accessory protein ORF3b antagonizes interferon (IFN) function by modulating the activity of IFN regulatory factor 3 (IRF3). The IFN system functions as the first line of defense against viral infection in mammalian cells. Viral infection triggers a series of cellular events that lead to the production of IFN and several downstream antiviral genes, helping to establish an antiviral state. Viruses encode IFN antagonists to counteract the antiviral effects of IFN. SARS-CoV ORF3b, ORF6, and N proteins function as IFN antagonists. ORF3b inhibits both IFN synthesis and signaling. It localizes to the nucleus in transfected cells. |
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Jiyao W et al.(2023). "The conserved domain database in 2023.",