middle (M) domain of coronavirus Nonstructural protein 15 (Nsp15) and the N-terminal domain (NTD) of arterivirus Nsp11 and related proteins
Nidovirus endoribonucleases (NendoUs) are uridylate-specific endoribonucleases, which release a cleavage product containing a 2',3'-cyclic phosphate at the 3' terminal end. NendoUs include Nsp15 from coronaviruses and Nsp11 from arteriviruses, both of which may participate in the viral replication process and in the evasion of the host immune system. Coronavirus Nsp15 NendoUs have an N-terminal domain, a middle (M) domain, and a C-terminal catalytic (NendoU) domain. Arterivirus Nsp11 has an N-terminal domain (NTD) and a C-terminal catalytic (NendoU) domain. The NTD of Nsp11 superimposes onto the M-domain of coronavirus Nsp15. Coronavirus Nsp15 from Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV), human Coronavirus 229E (HCoV229E), and Murine Hepatitis Virus (MHV) form a functional hexamer. Oligomerization of Porcine DeltaCoronavirus (PDCoV) Nsp15 differs from that of other coronavirus members; it has been shown to exist as a dimer and a monomer in solution. Nsp11 from the arterivirus PRRSV functions as a dimer.
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