6mwm

Structural highlights

Function

[R1AB_BCHK4] The replicase polyprotein of coronaviruses is a multifunctional protein: it contains the activities necessary for the transcription of negative stranded RNA, leader RNA, subgenomic mRNAs and progeny virion RNA as well as proteinases responsible for the cleavage of the polyprotein into functional products.[UniProtKB:P0C6X7] Host translation inhibitor nsp1: Inhibits host translation by interacting with the 40S ribosomal subunit. The nsp1-40S ribosome complex further induces an endonucleolytic cleavage near the 5'UTR of host mRNAs, targeting them for degradation. Viral mRNAs are not susceptible to nsp1-mediated endonucleolytic RNA cleavage thanks to the presence of a 5'-end leader sequence and are therefore protected from degradation. By suppressing host gene expression, nsp1 facilitates efficient viral gene expression in infected cells and evasion from host immune response.[UniProtKB:P0C6X7] Non-structural protein 2: May play a role in the modulation of host cell survival signaling pathway by interacting with host PHB and PHB2. Indeed, these two proteins play a role in maintaining the functional integrity of the mitochondria and protecting cells from various stresses.[UniProtKB:P0C6X7] Papain-like proteinase: Responsible for the cleavages located at the N-terminus of the 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. Participates together with nsp4 in the assembly of virally-induced cytoplasmic double-membrane vesicles necessary for viral replication. Antagonizes innate immune induction of type I interferon by blocking the phosphorylation, dimerization and subsequent nuclear translocation of host IRF3. Prevents also host NF-kappa-B signaling.[UniProtKB:P0C6X7] Non-structural protein 4: Participates in the assembly of virally-induced cytoplasmic double-membrane vesicles necessary for viral replication.[UniProtKB:P0C6X7] Proteinase 3CL-PRO: Cleaves the C-terminus of replicase polyprotein at 11 sites. Recognizes substrates containing the core sequence [ILMVF]-Q-|-[SGACN]. Also able to bind an ADP-ribose-1-phosphate (ADRP).[UniProtKB:P0C6X7][PROSITE-ProRule:PRU00772] Non-structural protein 6: Plays a role in the initial induction of autophagosomes from host reticulum endoplasmic. Later, limits the expansion of these phagosomes that are no longer able to deliver viral components to lysosomes.[UniProtKB:P0C6X7] Non-structural protein 7: Forms an hexadecamer with nsp8 (8 subunits of each) that may participate in viral replication by acting as a primase. Alternatively, may synthesize substantially longer products than oligonucleotide primers.[UniProtKB:P0C6X7] Non-structural protein 8: Forms an hexadecamer with nsp7 (8 subunits of each) that may participate in viral replication by acting as a primase. Alternatively, may synthesize substantially longer products than oligonucleotide primers.[UniProtKB:P0C6X7] Non-structural protein 9: May participate in viral replication by acting as a ssRNA-binding protein.[UniProtKB:P0C6X7] Non-structural protein 10: Plays a pivotal role in viral transcription by stimulating both nsp14 3'-5' exoribonuclease and nsp16 2'-O-methyltransferase activities. Therefore plays an essential role in viral mRNAs cap methylation.[UniProtKB:P0C6X7] RNA-directed RNA polymerase: Responsible for replication and transcription of the viral RNA genome.[UniProtKB:P0C6X7] Helicase: Multi-functional protein with a zinc-binding domain in N-terminus displaying RNA and DNA duplex-unwinding activities with 5' to 3' polarity. Activity of helicase is dependent on magnesium.[UniProtKB:P0C6X7] Guanine-N7 methyltransferase: Enzyme possessing two different activities: an exoribonuclease activity acting on both ssRNA and dsRNA in a 3' to 5' direction and a N7-guanine methyltransferase activity.[UniProtKB:P0C6X7] Uridylate-specific endoribonuclease: Mn(2+)-dependent, uridylate-specific enzyme, which leaves 2'-3'-cyclic phosphates 5' to the cleaved bond.[UniProtKB:P0C6X7] 2'-O-methyltransferase: Methyltransferase that mediates mRNA cap 2'-O-ribose methylation to the 5'-cap structure of viral mRNAs. N7-methyl guanosine cap is a prerequisite for binding of nsp16. Therefore plays an essential role in viral mRNAs cap methylation which is essential to evade immune system.[UniProtKB:P0C6X7]

References

1. ↑ Staup AJ, De Silva IU, Catt JT, Tan X, Hammond RG, Johnson MA. Structure of the SARS-Unique Domain C From the Bat Coronavirus HKU4. Nat Prod Commun. 2019 May 27;14(5):1934578X19849202. doi:, 10.1177/1934578X19849202. eCollection 2019 May. PMID:32395093 doi:http://dx.doi.org/10.1177/1934578X19849202