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deltacoronavirus accessory protein NS7 and NS7a This family includes the accessory protein NS7 found in deltacoronaviruses from the Buldecovirus subgenus, such as porcine coronavirus HKU15, and several avian coronaviruses found in sparrow, pigeon, quail and falcon, among others. 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. Porcine deltacoronavirus (PDCoV) encodes three accessory proteins, NS6, NS7 and NS7a. NS7a is a 100 amino-acid polypeptide identical to the C-terminus of NS7; it remains unclear whether their functions are redundant. PDCoV HKU15, an emerging swine enteric coronavirus that causes diarrhea in neonatal piglets, has also been found in the respiratory tract of pigs and may be able to cause respiratory infections, thus possibly spreading through the respiratory route. NS7-specific mAbs that recognized cells transfected with an NS7 expression construct or infected with PDCoV also recognized NS7a, which is encoded by a separate subgenome mRNA with a non-canonical transcription regulatory sequence. The NS7 protein is extensively distributed in the mitochondria and may be involved in various cellular processes such as cytoskeleton networks and cell communication, metabolism, and protein biosynthesis. NS7-expressing and PDCoV-infected cells also show a substantial down-regulation of alpha-actinin-4. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",