|  |   Structural highlights   Function [R1A_CVHSA] 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.[1] [2] [3]   The main proteinase 3CL-PRO is 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 (By similarity). Also contains an ADP-ribose-1-phosphate (ADRP)-binding function.[4] [5] [6]   Nsp7-nsp8 hexadecamer may possibly confer processivity to the polymerase, maybe by binding to dsRNA or by producing primers utilized by the latter.[7] [8] [9]   Nsp9 is a ssRNA-binding protein.[10] [11] [12]  
 
  Publication Abstract from PubMed Pathogenic coronaviruses are a major threat to global public health, as exemplified by Severe Acute Respiratory Syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV) and the newly emerged SARS-CoV-2, the causative agent of coronavirus disease 2019 (COVID-19). We describe herein the structure-guided optimization of a series of inhibitors of the coronavirus 3C-like protease (3CLpro), an enzyme essential for viral replication. The optimized compounds were effective against several human coronaviruses including MERS-CoV, SARS-CoV and SARS-CoV-2 in an enzyme assay and in cell-based assays using Huh-7 and Vero E6 cell lines. Two selected compounds showed antiviral effects against SARS-CoV-2 in cultured primary human airway epithelial cells. In a mouse model of MERS-CoV infection, administration of a lead compound one day after virus infection increased survival from 0 to 100% and reduced lung viral titers and lung histopathology. These results suggest that this series of compounds has the potential to be developed further as antiviral drugs against human coronaviruses.
 3C-like protease inhibitors block coronavirus replication in vitro and improve survival in MERS-CoV-infected mice.,Rathnayake AD, Zheng J, Kim Y, Perera KD, Mackin S, Meyerholz DK, Kashipathy MM, Battaile KP, Lovell S, Perlman S, Groutas WC, Chang KO Sci Transl Med. 2020 Aug 3. pii: scitranslmed.abc5332. doi:, 10.1126/scitranslmed.abc5332. PMID:32747425[13]
 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
   References ↑ Imbert I, Guillemot JC, Bourhis JM, Bussetta C, Coutard B, Egloff MP, Ferron F, Gorbalenya AE, Canard B. A second, non-canonical RNA-dependent RNA polymerase in SARS coronavirus. EMBO J. 2006 Oct 18;25(20):4933-42. Epub 2006 Oct 5. PMID:17024178 doi:7601368↑ Lindner HA, Lytvyn V, Qi H, Lachance P, Ziomek E, Menard R. Selectivity in ISG15 and ubiquitin recognition by the SARS coronavirus papain-like protease. Arch Biochem Biophys. 2007 Oct 1;466(1):8-14. Epub 2007 Jul 14. PMID:17692280 doi:10.1016/j.abb.2007.07.006↑ Frieman M, Ratia K, Johnston RE, Mesecar AD, Baric RS. Severe acute respiratory syndrome coronavirus papain-like protease ubiquitin-like domain and catalytic domain regulate antagonism of IRF3 and NF-kappaB signaling. J Virol. 2009 Jul;83(13):6689-705. doi: 10.1128/JVI.02220-08. Epub 2009 Apr 15. PMID:19369340 doi:10.1128/JVI.02220-08↑ Imbert I, Guillemot JC, Bourhis JM, Bussetta C, Coutard B, Egloff MP, Ferron F, Gorbalenya AE, Canard B. A second, non-canonical RNA-dependent RNA polymerase in SARS coronavirus. EMBO J. 2006 Oct 18;25(20):4933-42. Epub 2006 Oct 5. PMID:17024178 doi:7601368↑ Lindner HA, Lytvyn V, Qi H, Lachance P, Ziomek E, Menard R. Selectivity in ISG15 and ubiquitin recognition by the SARS coronavirus papain-like protease. Arch Biochem Biophys. 2007 Oct 1;466(1):8-14. Epub 2007 Jul 14. PMID:17692280 doi:10.1016/j.abb.2007.07.006↑ Frieman M, Ratia K, Johnston RE, Mesecar AD, Baric RS. Severe acute respiratory syndrome coronavirus papain-like protease ubiquitin-like domain and catalytic domain regulate antagonism of IRF3 and NF-kappaB signaling. J Virol. 2009 Jul;83(13):6689-705. doi: 10.1128/JVI.02220-08. Epub 2009 Apr 15. PMID:19369340 doi:10.1128/JVI.02220-08↑ Imbert I, Guillemot JC, Bourhis JM, Bussetta C, Coutard B, Egloff MP, Ferron F, Gorbalenya AE, Canard B. A second, non-canonical RNA-dependent RNA polymerase in SARS coronavirus. EMBO J. 2006 Oct 18;25(20):4933-42. Epub 2006 Oct 5. PMID:17024178 doi:7601368↑ Lindner HA, Lytvyn V, Qi H, Lachance P, Ziomek E, Menard R. Selectivity in ISG15 and ubiquitin recognition by the SARS coronavirus papain-like protease. Arch Biochem Biophys. 2007 Oct 1;466(1):8-14. Epub 2007 Jul 14. PMID:17692280 doi:10.1016/j.abb.2007.07.006↑ Frieman M, Ratia K, Johnston RE, Mesecar AD, Baric RS. Severe acute respiratory syndrome coronavirus papain-like protease ubiquitin-like domain and catalytic domain regulate antagonism of IRF3 and NF-kappaB signaling. J Virol. 2009 Jul;83(13):6689-705. doi: 10.1128/JVI.02220-08. Epub 2009 Apr 15. PMID:19369340 doi:10.1128/JVI.02220-08↑ Imbert I, Guillemot JC, Bourhis JM, Bussetta C, Coutard B, Egloff MP, Ferron F, Gorbalenya AE, Canard B. A second, non-canonical RNA-dependent RNA polymerase in SARS coronavirus. EMBO J. 2006 Oct 18;25(20):4933-42. Epub 2006 Oct 5. PMID:17024178 doi:7601368↑ Lindner HA, Lytvyn V, Qi H, Lachance P, Ziomek E, Menard R. Selectivity in ISG15 and ubiquitin recognition by the SARS coronavirus papain-like protease. Arch Biochem Biophys. 2007 Oct 1;466(1):8-14. Epub 2007 Jul 14. PMID:17692280 doi:10.1016/j.abb.2007.07.006↑ Frieman M, Ratia K, Johnston RE, Mesecar AD, Baric RS. Severe acute respiratory syndrome coronavirus papain-like protease ubiquitin-like domain and catalytic domain regulate antagonism of IRF3 and NF-kappaB signaling. J Virol. 2009 Jul;83(13):6689-705. doi: 10.1128/JVI.02220-08. Epub 2009 Apr 15. PMID:19369340 doi:10.1128/JVI.02220-08↑ Rathnayake AD, Zheng J, Kim Y, Perera KD, Mackin S, Meyerholz DK, Kashipathy MM, Battaile KP, Lovell S, Perlman S, Groutas WC, Chang KO. 3C-like protease inhibitors block coronavirus replication in vitro and improve survival in MERS-CoV-infected mice. Sci Transl Med. 2020 Aug 3. pii: scitranslmed.abc5332. doi:, 10.1126/scitranslmed.abc5332. PMID:32747425 doi:http://dx.doi.org/10.1126/scitranslmed.abc5332
 
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