4rf1

Structural highlights

Function

M4STU1_MERS Catalytic subunit of viral RNA capping enzyme which catalyzes the RNA guanylyltransferase reaction for genomic and sub-genomic RNAs. The kinase-like NiRAN domain of NSP12 transfers RNA to the amino terminus of NSP9, forming a covalent RNA-protein intermediate. Subsequently, the NiRAN domain transfers RNA to GDP, forming the core cap structure GpppA-RNA. The NSP14 and NSP16 methyltransferases then add methyl groups to form functional cap structures.[ARBA:ARBA00034461] 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.[ARBA:ARBA00002182] 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.[ARBA:ARBA00003443] 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.[ARBA:ARBA00003115] 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.[ARBA:ARBA00002840] 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.[ARBA:ARBA00002960] Participates in the assembly of virally-induced cytoplasmic double-membrane vesicles necessary for viral replication.[ARBA:ARBA00003070] 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.[ARBA:ARBA00002697] 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.[ARBA:ARBA00003748] 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.[ARBA:ARBA00025521] 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. 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. The kinase-like NiRAN domain of NSP12 transfers RNA to the amino terminus of NSP9, forming a covalent RNA-protein intermediate. Subsequently, the NiRAN domain transfers RNA to GDP, and forms the core cap structure GpppA-RNA.[ARBA:ARBA00034462] 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.[ARBA:ARBA00003368]

See Also

• Virus protease 3D structures

References

1. ↑ Bailey-Elkin BA, Knaap RC, Johnson GG, Dalebout TJ, Ninaber DK, van Kasteren PB, Bredenbeek PJ, Snijder EJ, Kikkert M, Mark BL. Crystal Structure of the MERS Coronavirus Papain-Like Protease Bound to Ubiquitin Facilitates Targeted Disruption of Deubiquitinating Activity to Demonstrate its Role in Innate Immune Suppression. J Biol Chem. 2014 Oct 15. pii: jbc.M114.609644. PMID:25320088 doi:http://dx.doi.org/10.1074/jbc.M114.609644