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N-terminal domain of coronavirus Nonstructural protein 15 (Nsp15) and related proteins Coronavirus (CoV) Nsp15 is a nidovirus endoribonuclease (NendoU). NendoUs are uridylate-specific endoribonucleases, which release a cleavage product containing a 2',3'-cyclic phosphate at the 3' terminal end. NendoUs include CoV Nsp15 and arterivirus Nsp11, both of which may participate in the viral replication process and in the evasion of the host immune system. This NTD structure (approximately 60 residues) present in CoV Nsp15, is missing in Nsp11. CoV Nsp15 has an N-terminal domain, a middle (M) domain, and a C-terminal catalytic (NendoU) domain. Nsp15 from Severe Acute Respiratory Syndrome (SARS)-CoV, human CoV 229E (HCoV229E), and Murine Hepatitis Virus (MHV) form a functional hexamer. Oligomerization of Porcine DeltaCoronavirus (PDCoV) Nsp15 differs from the Nsp15 of these alpha- and beta-coronavirus; it has been shown to exist as dimers and monomers in solution, and to function as a dimer. Nsp15 from Turkey CoV (TCoV), a gammaCoV, has been reported to be a homohexamer. |
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