Nidoviral uridylate-specific endoribonuclease (NendoU) domain of coronavirus Nonstructural protein 15 (Nsp15), arterivirus Nsp11, torovirus endoribonuclease, 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. This family also includes torovirus NendoUs. Except for turkey coronavirus (TCoV) Nsp15, Mn2+ is generally essential for the catalytic activity of coronavirus Nsp15. Mn2+ is dispensable, and to some extent inhibits the activity of arterivirus (Porcine Reproductive and Respiratory Syndrome virus) PRRSV Nsp11. Coronavirus Nsp15 from Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV), human Coronavirus 229E (HCoV229E), and murine hepatitis virus (MHV) form a functional hexamer while Porcine DeltaCoronavirus (PDCoV) Nsp15 has been shown to exist as a dimer and monomer in solution. Nsp11 from the arterivirus PRRSV is a dimer. NendoUs are distantly related to Xenopus laevis Mn(2+)-dependent uridylate-specific endoribonuclease (XendoU) which is involved in the processing of intron-encoded box C/D U16 small, nucleolar RNA.
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