ABSTRACT
Remdesivir (RDV), a nucleotide analog with broad-spectrum features, has exhibited effectiveness in COVID-19 treatment. However, the precise working mechanism of RDV when targeting the viral RNA-dependent RNA polymerase (RdRP) has not been fully elucidated. Here, we solve a 3.0-Å structure of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RdRP elongation complex (EC) and assess RDV intervention in polymerase elongation phase. Although RDV could induce an "i+3" delayed termination in meta-stable complexes, only pausing and subsequent elongation are observed in the EC. A comparative investigation using an enterovirus RdRP further confirms similar delayed intervention and demonstrates that steric hindrance of the RDV-characteristic 1'-cyano at the -4 position is responsible for the "i+3" intervention, although two representative Flaviviridae RdRPs do not exhibit similar behavior. A comparison of representative viral RdRP catalytic complex structures indicates that the product RNA backbone encounters highly conserved structural elements, highlighting the broad-spectrum intervention potential of 1'-modified nucleotide analogs in anti-RNA virus drug development.
Subject(s)
Adenosine Monophosphate/analogs & derivatives , Alanine/analogs & derivatives , Antiviral Agents/pharmacology , RNA-Dependent RNA Polymerase/drug effects , SARS-CoV-2/drug effects , Viral Proteins/drug effects , Adenosine Monophosphate/pharmacology , Alanine/pharmacology , Cryoelectron Microscopy , Humans , RNA, Viral/chemistry , RNA, Viral/drug effects , RNA-Dependent RNA Polymerase/chemistry , SARS-CoV-2/chemistry , Viral Proteins/chemistry , Virus Replication/drug effects , COVID-19 Drug TreatmentSubject(s)
COVID-19 , Protease Inhibitors , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Coronavirus 3C Proteases , Humans , Lactams , Leucine , Molecular Docking Simulation , Molecular Dynamics Simulation , Nitriles , Proline , Protease Inhibitors/chemistry , Protease Inhibitors/pharmacology , SARS-CoV-2ABSTRACT
Transcription of SARS-CoV-2 mRNA requires sequential reactions facilitated by the replication and transcription complex (RTC). Here, we present a structural snapshot of SARS-CoV-2 RTC as it transitions toward cap structure synthesis. We determine the atomic cryo-EM structure of an extended RTC assembled by nsp7-nsp82-nsp12-nsp132-RNA and a single RNA-binding protein, nsp9. Nsp9 binds tightly to nsp12 (RdRp) NiRAN, allowing nsp9 N terminus inserting into the catalytic center of nsp12 NiRAN, which then inhibits activity. We also show that nsp12 NiRAN possesses guanylyltransferase activity, catalyzing the formation of cap core structure (GpppA). The orientation of nsp13 that anchors the 5' extension of template RNA shows a remarkable conformational shift, resulting in zinc finger 3 of its ZBD inserting into a minor groove of paired template-primer RNA. These results reason an intermediate state of RTC toward mRNA synthesis, pave a way to understand the RTC architecture, and provide a target for antiviral development.
Subject(s)
Coronavirus RNA-Dependent RNA Polymerase/chemistry , Cryoelectron Microscopy , RNA, Messenger/chemistry , RNA, Viral/chemistry , SARS-CoV-2/chemistry , Viral Replicase Complex Proteins/chemistry , Amino Acid Sequence , Coronavirus/chemistry , Coronavirus/classification , Coronavirus/enzymology , Coronavirus RNA-Dependent RNA Polymerase/metabolism , Methyltransferases/metabolism , Models, Molecular , RNA Helicases/metabolism , RNA-Binding Proteins/chemistry , RNA-Binding Proteins/metabolism , SARS-CoV-2/enzymology , Sequence Alignment , Transcription, Genetic , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/metabolism , Virus ReplicationABSTRACT
Non-structural proteins (nsp) constitute the SARS-CoV-2 replication and transcription complex (RTC) to play a pivotal role in the virus life cycle. Here we determine the atomic structure of a SARS-CoV-2 mini RTC, assembled by viral RNA-dependent RNA polymerase (RdRp, nsp12) with a template-primer RNA, nsp7 and nsp8, and two helicase molecules (nsp13-1 and nsp13-2), by cryo-electron microscopy. Two groups of mini RTCs with different conformations of nsp13-1 are identified. In both of them, nsp13-1 stabilizes overall architecture of the mini RTC by contacting with nsp13-2, which anchors the 5'-extension of RNA template, as well as interacting with nsp7-nsp8-nsp12-RNA. Orientation shifts of nsp13-1 results in its variable interactions with other components in two forms of mini RTC. The mutations on nsp13-1:nsp12 and nsp13-1:nsp13-2 interfaces prohibit the enhancement of helicase activity achieved by mini RTCs. These results provide an insight into how helicase couples with polymerase to facilitate its function in virus replication and transcription.
Subject(s)
Betacoronavirus/chemistry , Betacoronavirus/physiology , Virus Replication , Betacoronavirus/genetics , Betacoronavirus/metabolism , Binding Sites , Cryoelectron Microscopy , Humans , Methyltransferases/chemistry , Methyltransferases/genetics , Methyltransferases/metabolism , Models, Molecular , Mutation , Protein Binding , Protein Conformation , RNA Helicases/chemistry , RNA Helicases/genetics , RNA Helicases/metabolism , RNA, Viral/metabolism , SARS-CoV-2 , Structure-Activity Relationship , Transcription, Genetic , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/genetics , Viral Nonstructural Proteins/metabolismABSTRACT
The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses an unprecedented global health crisis. It is particularly urgent to develop clinically effective therapies to contain the pandemic. The main protease (Mpro) and the RNA-dependent RNA polymerase (RdRP), which are responsible for the viral polyprotein proteolytic process and viral genome replication and transcription, respectively, are two attractive drug targets for SARS-CoV-2. This review summarizes up-to-date progress in the structural and pharmacological aspects of those two key targets above. Different classes of inhibitors individually targeting Mpro and RdRP are discussed, which could promote drug development to treat SARS-CoV-2 infection.
Subject(s)
Antiviral Agents/chemistry , Coronavirus 3C Proteases/antagonists & inhibitors , Coronavirus 3C Proteases/chemistry , Coronavirus Protease Inhibitors/chemistry , Coronavirus RNA-Dependent RNA Polymerase/antagonists & inhibitors , Coronavirus RNA-Dependent RNA Polymerase/chemistry , Enzyme Inhibitors/chemistry , SARS-CoV-2/enzymology , Antiviral Agents/pharmacology , Coronavirus Protease Inhibitors/pharmacology , Drug Design , Enzyme Inhibitors/pharmacology , Humans , Protein Conformation , SARS-CoV-2/drug effectsABSTRACT
Nucleotide analog inhibitors, including broad-spectrum remdesivir and favipiravir, have shown promise in in vitro assays and some clinical studies for COVID-19 treatment, this despite an incomplete mechanistic understanding of the viral RNA-dependent RNA polymerase nsp12 drug interactions. Here, we examine the molecular basis of SARS-CoV-2 RNA replication by determining the cryo-EM structures of the stalled pre- and post- translocated polymerase complexes. Compared with the apo complex, the structures show notable structural rearrangements happening to nsp12 and its co-factors nsp7 and nsp8 to accommodate the nucleic acid, whereas there are highly conserved residues in nsp12, positioning the template and primer for an in-line attack on the incoming nucleotide. Furthermore, we investigate the inhibition mechanism of the triphosphate metabolite of remdesivir through structural and kinetic analyses. A transition model from the nsp7-nsp8 hexadecameric primase complex to the nsp12-nsp7-nsp8 polymerase complex is also proposed to provide clues for the understanding of the coronavirus transcription and replication machinery.
Subject(s)
Betacoronavirus/chemistry , Betacoronavirus/enzymology , RNA-Dependent RNA Polymerase/chemistry , Viral Nonstructural Proteins/chemistry , Adenosine Monophosphate/analogs & derivatives , Adenosine Monophosphate/chemistry , Adenosine Monophosphate/metabolism , Adenosine Monophosphate/pharmacology , Alanine/analogs & derivatives , Alanine/chemistry , Alanine/metabolism , Alanine/pharmacology , Antiviral Agents/chemistry , Antiviral Agents/metabolism , Antiviral Agents/pharmacology , Catalytic Domain , Coronavirus RNA-Dependent RNA Polymerase , Cryoelectron Microscopy , Models, Chemical , Models, Molecular , RNA, Viral/metabolism , SARS-CoV-2 , Transcription, Genetic , Virus ReplicationABSTRACT
The antineoplastic drug carmofur is shown to inhibit the SARS-CoV-2 main protease (Mpro). Here, the X-ray crystal structure of Mpro in complex with carmofur reveals that the carbonyl reactive group of carmofur is covalently bound to catalytic Cys145, whereas its fatty acid tail occupies the hydrophobic S2 subsite. Carmofur inhibits viral replication in cells (EC50 = 24.30 µM) and is a promising lead compound to develop new antiviral treatment for COVID-19.
Subject(s)
Betacoronavirus/enzymology , Cysteine Endopeptidases/chemistry , Fluorouracil/analogs & derivatives , Viral Nonstructural Proteins/antagonists & inhibitors , Viral Nonstructural Proteins/chemistry , Animals , Betacoronavirus/drug effects , COVID-19 , Chlorocebus aethiops , Coronavirus 3C Proteases , Coronavirus Infections/virology , Cysteine Endopeptidases/genetics , Cysteine Endopeptidases/metabolism , Fluorouracil/chemistry , Fluorouracil/pharmacology , Models, Molecular , Pandemics , Pneumonia, Viral/virology , SARS-CoV-2 , Vero Cells , Viral Nonstructural Proteins/genetics , Viral Nonstructural Proteins/metabolismABSTRACT
SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is the etiological agent responsible for the global COVID-19 (coronavirus disease 2019) outbreak. The main protease of SARS-CoV-2, Mpro, is a key enzyme that plays a pivotal role in mediating viral replication and transcription. We designed and synthesized two lead compounds (11a and 11b) targeting Mpro Both exhibited excellent inhibitory activity and potent anti-SARS-CoV-2 infection activity. The x-ray crystal structures of SARS-CoV-2 Mpro in complex with 11a or 11b, both determined at a resolution of 1.5 angstroms, showed that the aldehyde groups of 11a and 11b are covalently bound to cysteine 145 of Mpro Both compounds showed good pharmacokinetic properties in vivo, and 11a also exhibited low toxicity, which suggests that these compounds are promising drug candidates.
Subject(s)
Antiviral Agents/chemistry , Betacoronavirus/enzymology , Drug Design , Viral Nonstructural Proteins/antagonists & inhibitors , Animals , Antiviral Agents/pharmacology , Betacoronavirus/drug effects , COVID-19 , Catalytic Domain , Chlorocebus aethiops , Coronavirus 3C Proteases , Coronavirus Infections/drug therapy , Cysteine Endopeptidases , Dogs , Drug Evaluation, Preclinical , Female , Humans , Male , Mice , Molecular Structure , Pandemics , Pneumonia, Viral/drug therapy , Protein Structure, Tertiary , Rats, Sprague-Dawley , SARS-CoV-2 , Toxicity Tests , Vero CellsABSTRACT
A novel coronavirus [severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2)] outbreak has caused a global coronavirus disease 2019 (COVID-19) pandemic, resulting in tens of thousands of infections and thousands of deaths worldwide. The RNA-dependent RNA polymerase [(RdRp), also named nsp12] is the central component of coronaviral replication and transcription machinery, and it appears to be a primary target for the antiviral drug remdesivir. We report the cryo-electron microscopy structure of COVID-19 virus full-length nsp12 in complex with cofactors nsp7 and nsp8 at 2.9-angstrom resolution. In addition to the conserved architecture of the polymerase core of the viral polymerase family, nsp12 possesses a newly identified ß-hairpin domain at its N terminus. A comparative analysis model shows how remdesivir binds to this polymerase. The structure provides a basis for the design of new antiviral therapeutics that target viral RdRp.