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Betacoronavirus NS8 protein This family of proteins includes the accessory proteins encoded by the ORF8 in coronaviruses, also known as accessory protein 8, or non-structural protein 8 (NS8). This is distinct from NSP8, which is encoded on the replicase polyprotein. Proteins in this family are typically between 39 to 121 amino acids in length. This protein has two conserved sequence motifs: EDPCP and INCQ. It may modulate viral pathogenicity or replication in favour of human adaptation. ORF8 was suggested as one of the relevant genes in the study of human adaptation of the virus. This entry includes the NS8a and NS8b proteins from human SARS coronavirus (SARS-CoV). Recently, the the structure of SARS-CoV-2 ORF has been determined and revealed a core of approximately 60 residues similar to SARS-CoV ORF7a, the Ig-like fold, with the addition of two dimerization interfaces unique to SARS-CoV-2 ORF8. It forms a covalent disulfide-linker dimer through an N-terminal sequence specific to SARS-CoV-2 and a separate non-covalent interface is formed by another SARS-CoV-2 specific sequence. The presence of these interfaces shows that SARS-CoV-2 ORF8 can form unique large-scale assemblies not possible for SARS-CoV, potentially mediating unique immune suppression and evasion activities. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",