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Structure of a Core Papain-like Protease of MERS Coronavirus with utility for structure-based drug design
Structural highlights
FunctionR1AB_MERS1 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] Promotes the degradation of host mRNAs by inducing an endonucleolytic RNA cleavage in template mRNAs, and inhibits of host mRNA translation, a function that is separable from its RNA cleavage activity. By suppressing host gene expression, nsp1 facilitates efficient viral gene expression in infected cells and evasion from host immune response.[1] 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] 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][2] Participates in the assembly of virally-induced cytoplasmic double-membrane vesicles necessary for viral replication.[UniProtKB:P0C6X7] Cleaves the C-terminus of replicase polyprotein at 11 sites. Recognizes substrates containing the core sequence [ILMVF]-Q-|-[SGACN] (By similarity). May cleave human NLRP1 in lung epithelial cells, thereby activating the NLRP1 inflammasome pathway (PubMed:35594856). Also able to bind an ADP-ribose-1-phosphate (ADRP) (By similarity).[UniProtKB:P0C6X7][PROSITE-ProRule:PRU00772][3] 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] Forms a 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] Forms a 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] Forms a primer, NSP9-pU, which is utilized by the polymerase for the initiation of RNA chains. Interacts with ribosome signal recognition particle RNA (SRP). Together with NSP8, suppress protein integration into the cell membrane, thereby disrupting host immune defenses.[UniProtKB:P0DTD1] 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 that catalyzes the transcription of viral genomic and subgenomic RNAs. Acts in complex with nsp7 and nsp8 to transcribe both the minus and positive strands of genomic RNA. The kinase-like NiRAN domain of NSP12 attaches one or more nucleotides to the amino terminus of NSP9, forming a covalent RNA-protein intermediate that serves as transcription/replication primer. Subgenomic RNAs (sgRNAs) are formed by discontinuous transcription: The polymerase has the ability to pause at transcription-regulating sequences (TRS) and jump to the leader TRS, resulting in a major deletion. This creates a series of subgenomic RNAs that are replicated, transcribed and translated. In addition, Nsp12 is a subunit of the viral RNA capping enzyme that catalyzes the RNA guanylyltransferase reaction for genomic and sub-genomic RNAs. Subsequently, the NiRAN domain transfers RNA to GDP, and forms the core cap structure GpppA-RNA.[UniProtKB:P0DTD1] 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] Plays a role in viral RNA synthesis through two distinct activities: an N7-guanine methyltransferase activity involved in the formation of the cap structure GpppA-RNA; a proofreading exoribonuclease for RNA replication that reduces the sensitivity of the virus to RNA mutagens. This activity acts on both ssRNA and dsRNA in a 3'-5' direction.[UniProtKB:P0C6X7] Plays a role in viral transcription/replication and prevents the simultaneous activation of host cell dsRNA sensors, such as MDA5/IFIH1, OAS, and PKR (By similarity). Acts by degrading the 5'-polyuridines generated during replication of the poly(A) region of viral genomic and subgenomic RNAs. Catalyzes a two-step reaction in which a 2'3'-cyclic phosphate (2'3'-cP) is first generated by 2'-O transesterification, which is then hydrolyzed to a 3'-phosphate (3'-P) (By similarity). If not degraded, poly(U) RNA would hybridize with poly(A) RNA tails and activate host dsRNA sensors (By similarity).[UniProtKB:P0C6X7] 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] Publication Abstract from PubMedUbiquitin-like domain 2 (Ubl2) is immediately adjacent to the N-terminus of the papain-like protease (PLpro) domain in coronavirus polyproteins, and it may play a critical role in protease regulation and stability as well as in viral infection. However, our recent cellular studies reveal that removing the Ubl2 domain from MERS PLpro has no effect on its ability to process the viral polyprotein or act as an interferon antagonist, which involves deubiquitinating and deISGylating cellular proteins. Here, we test the hypothesis that the Ubl2 domain is not required for the catalytic function of MERS PLpro in vitro. The X-ray structure of MERS PLpro-Ubl2 was determined to 1.9 A and compared to PLpro containing the N-terminal Ubl2 domain. While the structures were nearly identical, the PLpro-Ubl2 enzyme revealed the intact structure of the substrate-binding loop. Moreover, PLpro-Ubl2 catalysis against different substrates and a purported inhibitor revealed no differences in catalytic efficiency, substrate specificity, and inhibition. Further, no changes in thermal stability were observed between enzymes. We conclude that the catalytic core of MERS PLpro, i.e. without the Ubl2 domain, is sufficient for catalysis and stability in vitro with utility to evaluate potential inhibitors as a platform for structure-based drug design. X-ray Structure and Enzymatic Activity Profile of a Core Papain-like Protease of MERS Coronavirus with utility for structure-based drug design.,Clasman JR, Baez-Santos YM, Mettelman RC, O'Brien A, Baker SC, Mesecar AD Sci Rep. 2017 Jan 12;7:40292. doi: 10.1038/srep40292. PMID:28079137[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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