The papain-like proteinase (PL-PRO) is responsible for the cleavages located at the N-terminus of replicase polyprotein. In addition, PL-PRO possesses a deubiquitinating/deISGylating activity and processes both 'Lys-48'- and 'Lys-63'-linked polyubiquitin chains from cellular substrates. Antagonizes innate immune induction of type I interferon by blocking the phosphorylation, dimerization and subsequent nuclear translocation of host IRF-3 (By similarity). Responsible for the majority of cleavages as it cleaves the C-terminus of replicase polyprotein at 11 sites. Recognizes substrates containing the core sequence [ILMVF]-Q-|-[SGACN]. Inhibited by the substrate-analog Cbz-Val-Asn-Ser-Thr-Leu-Gln-CMK. Also contains an ADP-ribose-1''-phosphate (ADRP)-binding function (By similarity). Nsp7-nsp8 hexadecamer may possibly confer processivity to the polymerase, maybe by binding to dsRNA or by producing primers utilized by the latter. Nsp9 is a ssRNA-binding protein. Binds to the 40S ribosomal subunit and inhibits host translation. The nsp1-40S ribosome complex further induces an endonucleolytic cleavage near the 5'UTR of host mRNAs, targeting them for degradation. By suppressing host gene expression, nsp1 facilitates efficient viral gene expression in infected cells and evasion from host immune response. TSAVLQ-|-SGFRK-NH2 and SGVTFQ-|-GKFKK the two peptides corresponding to the two self-cleavage sites of the SARS 3C-like proteinase are the two most reactive peptide substrates. The enzyme exhibits a strong preference for substrates containing Gln at P1 position and Leu at P2 position. Thiol-dependent hydrolysis of ester, thioester, amide, peptide and isopeptide bonds formed by the C-terminal Gly of ubiquitin (a 76-residue protein attached to proteins as an intracellular targeting signal). 3CL-PRO exists as monomer and homodimer. Eight copies of nsp7 and eight copies of nsp8 assemble to form a heterohexadecamer. Nsp9 is a dimer. Nsp10 forms a dodecamer (By similarity). nsp7, nsp8, nsp9 and nsp10 are localized in cytoplasmic foci, largely perinuclear. Late in infection, they merge into confluent complexes (By similarity). nsp7, nsp8, nsp9 and nsp10 are localized in cytoplasmic foci, largely perinuclear. Late in infection, they merge into confluent complexes (By similarity). nsp7, nsp8, nsp9 and nsp10 are localized in cytoplasmic foci, largely perinuclear. Late in infection, they merge into confluent complexes (By similarity). nsp7, nsp8, nsp9 and nsp10 are localized in cytoplasmic foci, largely perinuclear. Late in infection, they merge into confluent complexes (By similarity). The hydrophobic domains (HD) could mediate the membrane association of the replication complex and thereby alter the architecture of the host cell membrane. Specific enzymatic cleavages in vivo by its own proteases yield mature proteins. 3CL-PRO and PL-PRO proteinases are autocatalytically processed (By similarity). Produced by conventional translation. Belongs to the coronaviruses polyprotein 1ab family.