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1.
J Enzyme Inhib Med Chem ; 37(1): 1077-1082, 2022 Dec.
Article in English | MEDLINE | ID: covidwho-1788416

ABSTRACT

Despite a huge effort by the scientific community to determine the animal reservoir of SARS-CoV-2, which led to the identification of several SARS-CoV-2-related viruses both in bats and in pangolins, the origin of SARS-CoV-2 is still not clear. Recently, Temmam et al. reported the discovery of bat coronaviruses with a high degree of genome similarity with SARS-CoV-2, especially concerning the RBDs of the S protein, which mediates the capability of such viruses to enter and therefore infect human cells through a hACE2-dependent pathway. These viruses, especially the one named BANAL-236, showed a higher affinity for the hACE2 compared to the original strain of SARS-CoV-2. In the present work, we analyse the similarities and differences between the 3CL protease (main protease, Mpro) of these newly reported viruses and SARS-CoV-2, discussing their relevance relative to the efficacy of existing therapeutic approaches against COVID-19, particularly concerning the recently approved orally available Paxlovid, and the development of future ones.


Subject(s)
Chiroptera , Coronavirus 3C Proteases , Coronavirus , Animals , Chiroptera/virology , Coronavirus/enzymology , SARS-CoV-2
2.
J Virol ; 96(1): e0125321, 2022 01 12.
Article in English | MEDLINE | ID: covidwho-1639525

ABSTRACT

Over the past 20 years, the severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome CoV (MERS-CoV), and SARS-CoV-2 emerged, causing severe human respiratory diseases throughout the globe. Developing broad-spectrum drugs would be invaluable in responding to new, emerging coronaviruses and to address unmet urgent clinical needs. Main protease (Mpro; also known as 3CLpro) has a major role in the coronavirus life cycle and is one of the most important targets for anti-coronavirus agents. We show that a natural product, noncovalent inhibitor, shikonin, is a pan-main protease inhibitor of SARS-CoV-2, SARS-CoV, MERS-CoV, human coronavirus (HCoV)-HKU1, HCoV-NL63, and HCoV-229E with micromolar half maximal inhibitory concentration (IC50) values. Structures of the main protease of different coronavirus genus, SARS-CoV from the betacoronavirus genus and HCoV-NL63 from the alphacoronavirus genus, were determined by X-ray crystallography and revealed that the inhibitor interacts with key active site residues in a unique mode. The structure of the main protease inhibitor complex presents an opportunity to discover a novel series of broad-spectrum inhibitors. These data provide substantial evidence that shikonin and its derivatives may be effective against most coronaviruses as well as emerging coronaviruses of the future. Given the importance of the main protease for coronavirus therapeutic indication, insights from these studies should accelerate the development and design of safer and more effective antiviral agents. IMPORTANCE The current pandemic has created an urgent need for broad-spectrum inhibitors of SARS-CoV-2. The main protease is relatively conservative compared to the spike protein and, thus, is one of the most promising targets in developing anti-coronavirus agents. We solved the crystal structures of the main protease of SARS-CoV and HCoV-NL63 that bound to shikonin. The structures provide important insights, have broad implications for understanding the structural basis underlying enzyme activity, and can facilitate rational design of broad-spectrum anti-coronavirus ligands as new therapeutic agents.


Subject(s)
Antiviral Agents/chemistry , Coronavirus 3C Proteases/antagonists & inhibitors , Protease Inhibitors/chemistry , Catalytic Domain , Coronavirus/classification , Coronavirus/enzymology , Coronavirus 3C Proteases/chemistry , Crystallography, X-Ray , Molecular Docking Simulation , Naphthoquinones/chemistry , Protein Binding
3.
Nucleic Acids Res ; 50(2): 635-650, 2022 01 25.
Article in English | MEDLINE | ID: covidwho-1621653

ABSTRACT

Coronaviral methyltransferases (MTases), nsp10/16 and nsp14, catalyze the last two steps of viral RNA-cap creation that takes place in cytoplasm. This cap is essential for the stability of viral RNA and, most importantly, for the evasion of innate immune system. Non-capped RNA is recognized by innate immunity which leads to its degradation and the activation of antiviral immunity. As a result, both coronaviral MTases are in the center of scientific scrutiny. Recently, X-ray and cryo-EM structures of both enzymes were solved even in complex with other parts of the viral replication complex. High-throughput screening as well as structure-guided inhibitor design have led to the discovery of their potent inhibitors. Here, we critically summarize the tremendous advancement of the coronaviral MTase field since the beginning of COVID pandemic.


Subject(s)
Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Coronavirus/drug effects , Coronavirus/enzymology , Methyltransferases/antagonists & inhibitors , Methyltransferases/chemistry , Methyltransferases/metabolism , Amino Acid Sequence , Amino Acids/chemistry , Binding Sites , Coronavirus/genetics , Drug Discovery , Humans , Methylation , Models, Molecular , Molecular Conformation , Molecular Structure , Protein Binding , RNA, Viral/chemistry , RNA, Viral/genetics , RNA, Viral/metabolism , Structure-Activity Relationship
4.
Int J Mol Sci ; 22(22)2021 Nov 09.
Article in English | MEDLINE | ID: covidwho-1512384

ABSTRACT

Coronaviruses cause diseases in humans and livestock. The SARS-CoV-2 is infecting millions of human beings, with high morbidity and mortality worldwide. The main protease (Mpro) of coronavirus plays a pivotal role in viral replication and transcription, which, in theory, is an attractive drug target for antiviral drug development. It has been extensively discussed whether Xanthohumol is able to help COVID-19 patients. Here, we report that Xanthohumol, a small molecule in clinical trials from hops (Humulus lupulus), was a potent pan-inhibitor for various coronaviruses by targeting Mpro, for example, betacoronavirus SARS-CoV-2 (IC50 value of 1.53 µM), and alphacoronavirus PEDV (IC50 value of 7.51 µM). Xanthohumol inhibited Mpro activities in the enzymatical assays, while pretreatment with Xanthohumol restricted the SARS-CoV-2 and PEDV replication in Vero-E6 cells. Therefore, Xanthohumol is a potent pan-inhibitor of coronaviruses and an excellent lead compound for further drug development.


Subject(s)
3C Viral Proteases/antagonists & inhibitors , Flavonoids/chemistry , Propiophenones/chemistry , Protease Inhibitors/chemistry , SARS-CoV-2/enzymology , 3C Viral Proteases/chemistry , 3C Viral Proteases/metabolism , Alphacoronavirus/enzymology , Alphacoronavirus/physiology , Amino Acid Sequence , Animals , Binding Sites , Biological Products/chemistry , Biological Products/metabolism , Biological Products/pharmacology , Biological Products/therapeutic use , COVID-19/drug therapy , COVID-19/virology , Catalytic Domain , Chlorocebus aethiops , Coronavirus/enzymology , Coronavirus/physiology , Flavonoids/metabolism , Flavonoids/pharmacology , Flavonoids/therapeutic use , Humans , Molecular Docking Simulation , Propiophenones/metabolism , Propiophenones/pharmacology , Propiophenones/therapeutic use , Protease Inhibitors/metabolism , Protease Inhibitors/pharmacology , Protease Inhibitors/therapeutic use , SARS-CoV-2/isolation & purification , Sequence Alignment , Vero Cells , Virus Replication/drug effects
5.
Cell ; 184(1): 184-193.e10, 2021 01 07.
Article in English | MEDLINE | ID: covidwho-1385213

ABSTRACT

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 Replication
6.
J Gen Virol ; 102(3)2021 03.
Article in English | MEDLINE | ID: covidwho-1369236

ABSTRACT

Coronavirus protease nsp5 (Mpro, 3CLpro) remains a primary target for coronavirus therapeutics due to its indispensable and conserved role in the proteolytic processing of the viral replicase polyproteins. In this review, we discuss the diversity of known coronaviruses, the role of nsp5 in coronavirus biology, and the structure and function of this protease across the diversity of known coronaviruses, and evaluate past and present efforts to develop inhibitors to the nsp5 protease with a particular emphasis on new and mostly unexplored potential targets of inhibition. With the recent emergence of pandemic SARS-CoV-2, this review provides novel and potentially innovative strategies and directions to develop effective therapeutics against the coronavirus protease nsp5.


Subject(s)
Antiviral Agents/therapeutic use , COVID-19/drug therapy , Coronavirus 3C Proteases/antagonists & inhibitors , Coronavirus 3C Proteases/chemistry , SARS-CoV-2/enzymology , Viral Nonstructural Proteins/antagonists & inhibitors , Viral Protease Inhibitors/therapeutic use , Amino Acid Sequence , COVID-19/virology , Coronavirus/enzymology , Coronavirus/metabolism , Coronavirus 3C Proteases/genetics , Coronavirus 3C Proteases/metabolism , Humans , Phylogeny , SARS-CoV-2/metabolism , Viral Nonstructural Proteins/metabolism
7.
Expert Opin Ther Targets ; 25(6): 479-489, 2021 06.
Article in English | MEDLINE | ID: covidwho-1306504

ABSTRACT

Introduction: Enteroviruses are common viruses causing a huge number of acute and chronic infections and producing towering economic costs. Similarly, coronaviruses cause seasonal mild infections, epidemics, and even pandemics and can lead to severe respiratory symptoms. It is important to develop broadly acting antiviral molecules to efficiently tackle the infections caused by thes.Areas covered: This review illuminates the differences and similarities between enteroviruses and coronaviruses and examines the most appealing therapeutic targets to combat both virus groups. Publications of both virus groups and deposited structures discovered through PubMed to March 2021 for viral proteases have been evaluated.Expert opinion: The main protease of coronaviruses and enteroviruses share similarities in their structure and function. These proteases process their viral polyproteins and thus drugs that bind to the active site have potential to target both virus groups. It is important to develop drugs that target more evolutionarily conserved processes and proteins. Moreover, it is a wise strategy to concentrate on processes that are similar between several virus families.


Subject(s)
Antiviral Agents/pharmacology , Coronavirus/physiology , Enterovirus/physiology , Animals , Coronavirus/drug effects , Coronavirus/enzymology , Cysteine Endopeptidases/metabolism , Enterovirus/drug effects , Enterovirus/enzymology , Humans , Substrate Specificity
8.
Proc Natl Acad Sci U S A ; 118(2)2021 01 12.
Article in English | MEDLINE | ID: covidwho-1006583

ABSTRACT

Macrodomains are proteins that recognize and hydrolyze ADP ribose (ADPR) modifications of intracellular proteins. Macrodomains are implicated in viral genome replication and interference with host cell immune responses. They are important to the infectious cycle of Coronaviridae and Togaviridae viruses. We describe crystal structures of the conserved macrodomain from the bat coronavirus (CoV) HKU4 in complex with ligands. The structures reveal a binding cavity that accommodates ADPR and analogs via local structural changes within the pocket. Using a radioactive assay, we present evidence of mono-ADPR (MAR) hydrolase activity. In silico analysis presents further evidence on recognition of the ADPR modification for hydrolysis. Mutational analysis of residues within the binding pocket resulted in diminished enzymatic activity and binding affinity. We conclude that the common structural features observed in the macrodomain in a bat CoV contribute to a conserved function that can be extended to other known macrodomains.


Subject(s)
Adenosine Diphosphate Ribose/chemistry , Coronavirus/enzymology , Pyrophosphatases/chemistry , Viral Nonstructural Proteins/chemistry , Animals , Binding Sites , Chiroptera , Coronavirus/genetics , Crystallography, X-Ray , Hydrolysis , Pyrophosphatases/genetics , Viral Nonstructural Proteins/genetics
9.
Biomolecules ; 10(8)2020 08 01.
Article in English | MEDLINE | ID: covidwho-1023242

ABSTRACT

Posttranslational modifications of cellular proteins by covalent conjugation of ubiquitin and ubiquitin-like polypeptides regulate numerous cellular processes that are captured by viruses to promote infection, replication, and spreading. The importance of these protein modifications for the viral life cycle is underscored by the discovery that many viruses encode deconjugases that reverse their functions. The structural and functional characterization of these viral enzymes and the identification of their viral and cellular substrates is providing valuable insights into the biology of viral infections and the host's antiviral defense. Given the growing body of evidence demonstrating their key contribution to pathogenesis, the viral deconjugases are now recognized as attractive targets for the design of novel antiviral therapeutics.


Subject(s)
Antiviral Agents/pharmacology , Enzymes/metabolism , Host-Pathogen Interactions/physiology , Ubiquitin/metabolism , Viral Proteins/metabolism , Virus Diseases/metabolism , Adenoviridae/enzymology , Coronavirus/enzymology , Enzymes/chemistry , Herpesviridae/enzymology , Humans , Protein Processing, Post-Translational , Viral Proteins/chemistry , Virus Diseases/drug therapy
10.
Viruses ; 13(4)2021 03 24.
Article in English | MEDLINE | ID: covidwho-1154528

ABSTRACT

Several life-threatening viruses have recently appeared, including the coronavirus, infecting a variety of human and animal hosts and causing a range of diseases like human upper respiratory tract infections. They not only cause serious human and animal deaths, but also cause serious public health problems worldwide. Currently, seven species are known to infect humans, namely SARS-CoV-2, MERS-CoV, SARS-CoV, HCoV-229E, HCoV-NL63, HCoV-OC43, and HCoV-HKU1. The coronavirus nonstructural protein 16 (NSP16) structure is similar to the 5'-end capping system of mRNA used by eukaryotic hosts and plays a vital role in evading host immunity response and protects the nascent viral mRNA from degradation. NSP16 is also well-conserved among related coronaviruses and requires its binding partner NSP10 to activate its enzymatic activity. With the continued threat of viral emergence highlighted by human coronaviruses and SARS-CoV-2, mutant strains continue to appear, affecting the highly conserved NSP16: this provides a possible therapeutic approach applicable to any novel coronavirus. To this end, current information on the 2'-O-MTase activity mechanism, the differences between NSP16 and NSP10 in human coronaviruses, and the current potential prevention and treatment strategies related to NSP16 are summarized in this review.


Subject(s)
Coronavirus Infections/virology , Coronavirus/metabolism , Methyltransferases/metabolism , Viral Nonstructural Proteins/metabolism , Animals , COVID-19/virology , Coronavirus/enzymology , Coronavirus/genetics , Humans , Methyltransferases/genetics , SARS-CoV-2/enzymology , SARS-CoV-2/genetics , SARS-CoV-2/metabolism , Viral Nonstructural Proteins/genetics
11.
Clin Infect Dis ; 71(16): 2079-2088, 2020 11 19.
Article in English | MEDLINE | ID: covidwho-1153156

ABSTRACT

BACKGROUND: This study aimed to develop mortality-prediction models for patients with coronavirus disease-2019 (COVID-19). METHODS: The training cohort included consecutive COVID-19 patients at the First People's Hospital of Jiangxia District in Wuhan, China, from 7 January 2020 to 11 February 2020. We selected baseline data through the stepwise Akaike information criterion and ensemble XGBoost (extreme gradient boosting) model to build mortality-prediction models. We then validated these models by randomly collected COVID-19 patients in Union Hospital, Wuhan, from 1 January 2020 to 20 February 2020. RESULTS: A total of 296 COVID-19 patients were enrolled in the training cohort; 19 died during hospitalization and 277 discharged from the hospital. The clinical model developed using age, history of hypertension, and coronary heart disease showed area under the curve (AUC), 0.88 (95% confidence interval [CI], .80-.95); threshold, -2.6551; sensitivity, 92.31%; specificity, 77.44%; and negative predictive value (NPV), 99.34%. The laboratory model developed using age, high-sensitivity C-reactive protein, peripheral capillary oxygen saturation, neutrophil and lymphocyte count, d-dimer, aspartate aminotransferase, and glomerular filtration rate had a significantly stronger discriminatory power than the clinical model (P = .0157), with AUC, 0.98 (95% CI, .92-.99); threshold, -2.998; sensitivity, 100.00%; specificity, 92.82%; and NPV, 100.00%. In the subsequent validation cohort (N = 44), the AUC (95% CI) was 0.83 (.68-.93) and 0.88 (.75-.96) for the clinical model and laboratory model, respectively. CONCLUSIONS: We developed 2 predictive models for the in-hospital mortality of patients with COVID-19 in Wuhan that were validated in patients from another center.


Subject(s)
COVID-19/mortality , COVID-19/virology , Coronavirus/pathogenicity , Adult , Aspartate Aminotransferases/metabolism , COVID-19/epidemiology , China/epidemiology , Cohort Studies , Coronavirus/enzymology , Female , Glomerular Filtration Rate/physiology , Hospital Mortality , Humans , Male , Middle Aged
12.
J Virol ; 95(3)2021 01 13.
Article in English | MEDLINE | ID: covidwho-1039853

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other SARS-related CoVs encode 3 tandem macrodomains within nonstructural protein 3 (nsp3). The first macrodomain, Mac1, is conserved throughout CoVs and binds to and hydrolyzes mono-ADP-ribose (MAR) from target proteins. Mac1 likely counters host-mediated antiviral ADP-ribosylation, a posttranslational modification that is part of the host response to viral infections. Mac1 is essential for pathogenesis in multiple animal models of CoV infection, implicating it as a virulence factor and potential therapeutic target. Here, we report the crystal structure of SARS-CoV-2 Mac1 in complex with ADP-ribose. SARS-CoV-2, SARS-CoV, and Middle East respiratory syndrome coronavirus (MERS-CoV) Mac1 domains exhibit similar structural folds, and all 3 proteins bound to ADP-ribose with affinities in the low micromolar range. Importantly, using ADP-ribose-detecting binding reagents in both a gel-based assay and novel enzyme-linked immunosorbent assays (ELISAs), we demonstrated de-MARylating activity for all 3 CoV Mac1 proteins, with the SARS-CoV-2 Mac1 protein leading to a more rapid loss of substrate than the others. In addition, none of these enzymes could hydrolyze poly-ADP-ribose. We conclude that the SARS-CoV-2 and other CoV Mac1 proteins are MAR-hydrolases with similar functions, indicating that compounds targeting CoV Mac1 proteins may have broad anti-CoV activity.IMPORTANCE SARS-CoV-2 has recently emerged into the human population and has led to a worldwide pandemic of COVID-19 that has caused more than 1.2 million deaths worldwide. With no currently approved treatments, novel therapeutic strategies are desperately needed. All coronaviruses encode a highly conserved macrodomain (Mac1) that binds to and removes ADP-ribose adducts from proteins in a dynamic posttranslational process that is increasingly being recognized as an important factor that regulates viral infection. The macrodomain is essential for CoV pathogenesis and may be a novel therapeutic target. Thus, understanding its biochemistry and enzyme activity are critical first steps for these efforts. Here, we report the crystal structure of SARS-CoV-2 Mac1 in complex with ADP-ribose and describe its ADP-ribose binding and hydrolysis activities in direct comparison to those of SARS-CoV and MERS-CoV Mac1 proteins. These results are an important first step for the design and testing of potential therapies targeting this unique protein domain.


Subject(s)
N-Glycosyl Hydrolases/metabolism , SARS-CoV-2/enzymology , Viral Nonstructural Proteins/metabolism , Adenosine Diphosphate Ribose/chemistry , Adenosine Diphosphate Ribose/metabolism , Amino Acid Sequence , Coronavirus/chemistry , Coronavirus/enzymology , Coronavirus/metabolism , Crystallography, X-Ray , Humans , Hydrolysis , Kinetics , N-Glycosyl Hydrolases/chemistry , Protein Binding , Protein Domains , SARS-CoV-2/chemistry , SARS-CoV-2/metabolism , Viral Nonstructural Proteins/chemistry
13.
J Virol ; 95(3)2021 01 13.
Article in English | MEDLINE | ID: covidwho-1027782

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other SARS-related CoVs encode 3 tandem macrodomains within nonstructural protein 3 (nsp3). The first macrodomain, Mac1, is conserved throughout CoVs and binds to and hydrolyzes mono-ADP-ribose (MAR) from target proteins. Mac1 likely counters host-mediated antiviral ADP-ribosylation, a posttranslational modification that is part of the host response to viral infections. Mac1 is essential for pathogenesis in multiple animal models of CoV infection, implicating it as a virulence factor and potential therapeutic target. Here, we report the crystal structure of SARS-CoV-2 Mac1 in complex with ADP-ribose. SARS-CoV-2, SARS-CoV, and Middle East respiratory syndrome coronavirus (MERS-CoV) Mac1 domains exhibit similar structural folds, and all 3 proteins bound to ADP-ribose with affinities in the low micromolar range. Importantly, using ADP-ribose-detecting binding reagents in both a gel-based assay and novel enzyme-linked immunosorbent assays (ELISAs), we demonstrated de-MARylating activity for all 3 CoV Mac1 proteins, with the SARS-CoV-2 Mac1 protein leading to a more rapid loss of substrate than the others. In addition, none of these enzymes could hydrolyze poly-ADP-ribose. We conclude that the SARS-CoV-2 and other CoV Mac1 proteins are MAR-hydrolases with similar functions, indicating that compounds targeting CoV Mac1 proteins may have broad anti-CoV activity.IMPORTANCE SARS-CoV-2 has recently emerged into the human population and has led to a worldwide pandemic of COVID-19 that has caused more than 1.2 million deaths worldwide. With no currently approved treatments, novel therapeutic strategies are desperately needed. All coronaviruses encode a highly conserved macrodomain (Mac1) that binds to and removes ADP-ribose adducts from proteins in a dynamic posttranslational process that is increasingly being recognized as an important factor that regulates viral infection. The macrodomain is essential for CoV pathogenesis and may be a novel therapeutic target. Thus, understanding its biochemistry and enzyme activity are critical first steps for these efforts. Here, we report the crystal structure of SARS-CoV-2 Mac1 in complex with ADP-ribose and describe its ADP-ribose binding and hydrolysis activities in direct comparison to those of SARS-CoV and MERS-CoV Mac1 proteins. These results are an important first step for the design and testing of potential therapies targeting this unique protein domain.


Subject(s)
N-Glycosyl Hydrolases/metabolism , SARS-CoV-2/enzymology , Viral Nonstructural Proteins/metabolism , Adenosine Diphosphate Ribose/chemistry , Adenosine Diphosphate Ribose/metabolism , Amino Acid Sequence , Coronavirus/chemistry , Coronavirus/enzymology , Coronavirus/metabolism , Crystallography, X-Ray , Humans , Hydrolysis , Kinetics , N-Glycosyl Hydrolases/chemistry , Protein Binding , Protein Domains , SARS-CoV-2/chemistry , SARS-CoV-2/metabolism , Viral Nonstructural Proteins/chemistry
14.
Biophys Chem ; 269: 106510, 2021 02.
Article in English | MEDLINE | ID: covidwho-971712

ABSTRACT

The search for therapeutic drugs that can neutralize the effects of COVID-2019 (SARS-CoV-2) infection is the main focus of current research. The coronavirus main protease (Mpro) is an attractive target for anti-coronavirus drug design. Further, α-ketoamide is proved to be very effective as a reversible covalent-inhibitor against cysteine proteases. Herein, we report on the non-covalent to the covalent adduct formation mechanism of α-ketoamide-based inhibitor with the enzyme active site amino acids by QM/SQM model (QM = quantum mechanical, SQM = semi-empirical QM). To uncover the mechanism, we focused on two approaches: a concerted and a stepwise fashion. The concerted pathway proceeds via deprotonation of the thiol of cysteine (here, Cys145 SγH) and simultaneous reversible nucleophilic attack of sulfur onto the α-ketoamide warhead. In this work, we propose three plausible concerted pathways. On the contrary, in a traditional two-stage pathway, the first step is proton transfer from Cys145 SγH to His41 Nδ forming an ion pair, and consecutively, in the second step, the thiolate ion attacks the α-keto group to form a thiohemiketal. In this reaction, we find that the stability of the tetrahedral intermediate oxyanion/hydroxyl group plays an important role. Moreover, as the α-keto group has two faces Si or Re for the nucleophilic attack, we considered both possibilities of attack leading to S- and R-thiohemiketal. We computed the structural, electronic, and energetic parameters of all stationary points including transition states via ONIOM and pure DFT method. Additionally, to characterize covalent, weak noncovalent interaction (NCI) and hydrogen-bonds, we applied NCI-reduced density gradient (NCI-RDG) methods along with Bader's Quantum Theory of Atoms-in-Molecules (QTAIM) and natural bonding orbital (NBO) analysis.


Subject(s)
Amides/chemistry , Coronavirus/enzymology , Peptide Hydrolases/chemistry , Protease Inhibitors/chemistry , Viral Proteins/antagonists & inhibitors , Amides/metabolism , Binding Sites , Catalytic Domain , Coronavirus/isolation & purification , Coronavirus Infections/pathology , Coronavirus Infections/virology , Coronavirus M Proteins/antagonists & inhibitors , Coronavirus M Proteins/metabolism , Drug Design , Humans , Hydrogen Bonding , Molecular Docking Simulation , Peptide Hydrolases/metabolism , Protease Inhibitors/metabolism , Quantum Theory , Thermodynamics , Viral Proteins/metabolism
15.
Molecules ; 25(23)2020 Dec 03.
Article in English | MEDLINE | ID: covidwho-963646

ABSTRACT

The RNA-dependent RNA polymerase (RdRp) is an essential enzyme for the viral replication process, catalyzing the viral RNA synthesis using a metal ion-dependent mechanism. In recent years, RdRp has emerged as an optimal target for the development of antiviral drugs, as demonstrated by recent approvals of sofosbuvir and remdesivir against Hepatitis C virus (HCV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respectively. In this work, we overview the main sequence and structural features of the RdRp of emerging RNA viruses such as Coronaviruses, Flaviviruses, and HCV, as well as inhibition strategies implemented so far. While analyzing the structural information available on the RdRp of emerging RNA viruses, we provide examples of success stories such as for HCV and SARS-CoV-2. In contrast, Flaviviruses' story has raised attention about how the lack of structural details on catalytically-competent or ligand-bound RdRp strongly hampers the application of structure-based drug design, either in repurposing and conventional approaches.


Subject(s)
Antiviral Agents/chemistry , Antiviral Agents/pharmacology , RNA Viruses/enzymology , RNA-Dependent RNA Polymerase/chemistry , Amides/chemistry , Amides/pharmacology , Coronavirus/drug effects , Coronavirus/enzymology , Coronavirus/genetics , Drug Design , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Flavivirus/drug effects , Flavivirus/enzymology , Flavivirus/genetics , Hepacivirus/drug effects , Hepacivirus/enzymology , Hepacivirus/genetics , Humans , Pyrazines/chemistry , Pyrazines/pharmacology , RNA Virus Infections/epidemiology , RNA Viruses/drug effects , RNA-Dependent RNA Polymerase/antagonists & inhibitors , RNA-Dependent RNA Polymerase/metabolism , Small Molecule Libraries/chemistry , Small Molecule Libraries/pharmacology
16.
J Biol Chem ; 295(15): 4780-4781, 2020 04 10.
Article in English | MEDLINE | ID: covidwho-686585

ABSTRACT

The nucleotide analogue remdesivir is an investigational drug for the treatment of human coronavirus infection. Remdesivir is a phosphoramidate prodrug and is known to target viral RNA-dependent RNA polymerases. In this issue, Gordon et al. identify that remdesivir acts as a delayed RNA chain terminator for MERS-CoV polymerase complexes.


Subject(s)
Adenosine Monophosphate/analogs & derivatives , Alanine/analogs & derivatives , Antiviral Agents/pharmacology , Coronavirus Infections/drug therapy , Coronavirus/drug effects , Coronavirus/enzymology , RNA-Dependent RNA Polymerase/antagonists & inhibitors , Adenosine Monophosphate/pharmacology , Alanine/pharmacology , Animals , Coronavirus/physiology , Coronavirus Infections/virology , Exonucleases , Humans , Pandemics , Virus Replication/drug effects
17.
J Med Chem ; 63(9): 4562-4578, 2020 05 14.
Article in English | MEDLINE | ID: covidwho-613484

ABSTRACT

The main protease of coronaviruses and the 3C protease of enteroviruses share a similar active-site architecture and a unique requirement for glutamine in the P1 position of the substrate. Because of their unique specificity and essential role in viral polyprotein processing, these proteases are suitable targets for the development of antiviral drugs. In order to obtain near-equipotent, broad-spectrum antivirals against alphacoronaviruses, betacoronaviruses, and enteroviruses, we pursued a structure-based design of peptidomimetic α-ketoamides as inhibitors of main and 3C proteases. Six crystal structures of protease-inhibitor complexes were determined as part of this study. Compounds synthesized were tested against the recombinant proteases as well as in viral replicons and virus-infected cell cultures; most of them were not cell-toxic. Optimization of the P2 substituent of the α-ketoamides proved crucial for achieving near-equipotency against the three virus genera. The best near-equipotent inhibitors, 11u (P2 = cyclopentylmethyl) and 11r (P2 = cyclohexylmethyl), display low-micromolar EC50 values against enteroviruses, alphacoronaviruses, and betacoronaviruses in cell cultures. In Huh7 cells, 11r exhibits three-digit picomolar activity against the Middle East Respiratory Syndrome coronavirus.


Subject(s)
Antiviral Agents/pharmacology , Coronavirus/drug effects , Enterovirus/drug effects , Lactams/pharmacology , Peptidomimetics/pharmacology , Virus Replication/drug effects , 3C Viral Proteases , Animals , Antiviral Agents/chemical synthesis , Antiviral Agents/metabolism , Binding Sites , Cell Line, Tumor , Chlorocebus aethiops , Coronavirus/enzymology , Coronavirus 3C Proteases , Crystallography, X-Ray , Cysteine Endopeptidases/chemistry , Cysteine Endopeptidases/metabolism , Drug Design , Enterovirus/enzymology , Humans , Lactams/chemical synthesis , Lactams/metabolism , Peptidomimetics/chemical synthesis , Peptidomimetics/metabolism , Protease Inhibitors/chemical synthesis , Protease Inhibitors/metabolism , Protease Inhibitors/pharmacology , Protein Binding , Vero Cells , Viral Nonstructural Proteins/antagonists & inhibitors , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/metabolism , Viral Proteins/antagonists & inhibitors , Viral Proteins/chemistry , Viral Proteins/metabolism
18.
Int J Mol Sci ; 21(10)2020 May 15.
Article in English | MEDLINE | ID: covidwho-276931

ABSTRACT

Following the outbreak of novel severe acute respiratory syndrome (SARS)-coronavirus (CoV)2, the majority of nations are struggling with countermeasures to fight infection, prevent spread and improve patient survival. Considering that the pandemic is a recent event, no large clinical trials have been possible and since coronavirus specific drug are not yet available, there is no strong consensus on how to treat the coronavirus disease 2019 (COVID-19) associated viral pneumonia. Coronaviruses code for an important multifunctional enzyme named papain-like protease (PLP), that has many roles in pathogenesis. First, PLP is one of the two viral cysteine proteases, along with 3-chymotripsin-like protease, that is responsible for the production of the replicase proteins required for viral replication. Second, its intrinsic deubiquitinating and deISGylating activities serve to antagonize the host's immune response that would otherwise hinder infection. Both deubiquitinating and deISGylating functions involve the removal of the small regulatory polypeptides, ubiquitin and ISG15, respectively, from target proteins. Ubiquitin modifications can regulate the innate immune response by affecting regulatory proteins, either by altering their stability via the ubiquitin proteasome pathway or by directly regulating their activity. ISG15 is a ubiquitin-like modifier with pleiotropic effects, typically expressed during the host cell immune response. PLP inhibitors have been evaluated during past coronavirus epidemics, and have showed promising results as an antiviral therapy in vitro. In this review, we recapitulate the roles of PLPs in coronavirus infections, report a list of PLP inhibitors and suggest possible therapeutic strategies for COVID-19 treatment, using both clinical and preclinical drugs.


Subject(s)
Betacoronavirus/enzymology , Deubiquitinating Enzymes/antagonists & inhibitors , Animals , COVID-19 , Coronavirus/enzymology , Coronavirus 3C Proteases , Coronavirus Infections/drug therapy , Cysteine Endopeptidases , Humans , Pandemics , Pneumonia, Viral/drug therapy , SARS-CoV-2 , Viral Nonstructural Proteins/antagonists & inhibitors
19.
Protein Sci ; 29(5): 1228-1241, 2020 05.
Article in English | MEDLINE | ID: covidwho-244545

ABSTRACT

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a novel coronavirus that is involved in severe diarrhea disease in piglets, causing considerable agricultural and economic loss in China. The emergence of this new coronavirus increases the importance of understanding SADS-CoV as well as antivirals. Coronaviral proteases, including main proteases and papain-like proteases (PLP), are attractive antiviral targets because of their essential roles in polyprotein processing and thus viral maturation. Here, we describe the biochemical and structural identification of recombinant SADS papain-like protease 2 (PLP2) domain of nsp3. The SADS-CoV PLP2 was shown to cleave nsp1 proteins and also peptides mimicking the nsp2|nsp3 cleavage site and also had deubiquitinating and deISGynating activity by in vitro assays. The crystal structure adopts an architecture resembling that of PLPs from other coronaviruses. We characterize both conserved and unique structural features likely directing the interaction of PLP2 with the substrates, including the tentative mapping of active site and other essential residues. These results provide a foundation for understanding the molecular basis of coronaviral PLPs' catalytic mechanism and for the screening and design of therapeutics to combat infection by SADS coronavirus.


Subject(s)
Alphacoronavirus/enzymology , Diarrhea/veterinary , Papain/chemistry , Swine Diseases/virology , Viral Nonstructural Proteins/chemistry , Animals , Coronavirus/enzymology , Coronavirus Papain-Like Proteases , Crystallography, X-Ray , Diarrhea/virology , Models, Molecular , Papain/metabolism , Sus scrofa , Swine , Viral Nonstructural Proteins/metabolism
20.
Molecules ; 25(8)2020 Apr 14.
Article in English | MEDLINE | ID: covidwho-71998

ABSTRACT

The inhibition of viral protease is an important target in antiviral drug discovery and development. To date, protease inhibitor drugs, especially HIV-1 protease inhibitors, have been available for human clinical use in the treatment of coronaviruses. However, these drugs can have adverse side effects and they can become ineffective due to eventual drug resistance. Thus, the search for natural bioactive compounds that were obtained from bio-resources that exert inhibitory capabilities against HIV-1 protease activity is of great interest. Fungi are a source of natural bioactive compounds that offer therapeutic potential in the prevention of viral diseases and for the improvement of human immunomodulation. Here, we made a brief review of the current findings on fungi as producers of protease inhibitors and studies on the relevant candidate fungal bioactive compounds that can offer immunomodulatory activities as potential therapeutic agents of coronaviruses in the future.


Subject(s)
Biological Products/pharmacology , Coronavirus/drug effects , Fungi/chemistry , Immunologic Factors/pharmacology , Protease Inhibitors/pharmacology , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Biological Products/chemistry , Biological Products/isolation & purification , Coronavirus/enzymology , Coronavirus Infections/drug therapy , Coronavirus Infections/virology , Humans , Immunologic Factors/chemistry , Immunologic Factors/isolation & purification , Molecular Structure , Protease Inhibitors/chemistry , Protease Inhibitors/isolation & purification , Structure-Activity Relationship
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