accessory protein 9b of severe acute respiratory syndrome-associated coronavirus and similar proteins
This model represents the accessory protein 9b (ORF9b) from Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) and some related betacoronaviruses such as bat coronavirus. 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. ORF9b is a product of an alternative open reading frame within the N gene from SARS coronavirus. It is a lipid-binding protein that has been shown to associate with intracellular vesicles in mammalian cells, consistent with a role in the assembly of the virion. ORF9b localizes to mitochondria and causes mitochondrial elongation by triggering ubiquitination and proteasomal degradation of dynamin-like protein 1, a host protein involved in mitochondrial fission. It also targets the mitochondrial-associated adaptor molecule MAVS signalosome to trigger the degradation of MAVS, TRAF3, and TRAF, which severely limits host cell interferon responses. There are slight differences in the genome organization of SARS-CoV-2 in different studies; not all SARS-CoV-2 isolates are reported as having ORF9b.
Jiyao W et al.(2023). "The conserved domain database in 2023.",