Papain-like Protease Research Articles

Benzocarbazoledinones as SARS-CoV-2 Replication Inhibitors: Synthesis, Cell-Based Studies, Enzyme Inhibition, Molecular Modeling, and Pharmacokinetics Insights

Endemic and pandemic viruses represent significant public health challenges, leading to substantial morbidity and mortality over time. The COVID-19 pandemic has underscored the urgent need for the development and discovery of new, potent antiviral agents. In this study, we present the synthesis and anti-SARS-CoV-2 activity of a series of benzocarbazoledinones, assessed using cell-based screening assays. Our results indicate that four compounds (4a, 4b, 4d, and 4i) exhibit EC50 values below 4 μM without cytotoxic effects in Calu-3 cells. Mechanistic investigations focused on the inhibition of the SARS-CoV-2 main protease (Mpro) and papain-like protease (PLpro) have used enzymatic assays. Notably, compounds 4a and 4b showed Mpro inhibition activity with IC50 values of 0.11 ± 0.05 and 0.37 ± 0.05 µM, respectively. Furthermore, in silico molecular docking, physicochemical, and pharmacokinetic studies were conducted to validate the mechanism and assess bioavailability. Compound 4a was selected for preliminary drug-likeness analysis and in vivo pharmacokinetics investigations, which yielded promising results and corroborated the in vitro and in silico findings, reinforcing its potential as an anti-SARS-CoV-2 lead compound.

Structure-Based Design of Covalent SARS-CoV-2 Papain-like Protease Inhibitors.

The COVID-19 pandemic is caused by SARS-CoV-2, a highly transmissible and pathogenic RNA betacoronavirus. Like other RNA viruses, SARS-CoV-2 continues to evolve with or without drug selection pressure, and many variants have emerged since the beginning of the pandemic. The papain-like protease, PLpro, is a cysteine protease that cleaves viral polyproteins as well as ubiquitin and ISG15 modifications from host proteins. Leveraging our recently discovered Val70Ub binding site in PLpro, we designed covalent PLpro inhibitors by connecting cysteine reactive warheads to the biarylphenyl PLpro inhibitors via flexible linkers. Several leads displayed potent enzymatic inhibition (IC50 = 0.1-0.3 μM) and antiviral activity (EC50 = 0.09-0.96 μM). Fumaramide inhibitors Jun13567 (15), Jun13728 (16), and Jun13714 (18) showed favorable in vivo pharmacokinetic properties with intraperitoneal injection. The X-ray crystal structure of PLpro with Jun13567 (15) validated our design strategy, revealing covalent conjugation between the catalytic Cys111 and the fumaramide warhead. The results suggest these covalent PLpro inhibitors are promising SARS-CoV-2 antiviral drug candidates.

Discovery of potential FDA-approved SARS-CoV-2 Papain-like protease inhibitors: A multi-phase in silico approach

Papain-like protease (PLpro) is a crucial enzyme for SARS-CoV-2 replication and immune evasion. Inhibiting PLpro could be a promising strategy to fight against COVID-19. This study aimed to identify potent inhibitors of PLpro among FDA-approved drugs using an in silico approach. The study also aimed to examine and confirm the binding of the selected compounds to the active pocket of PLpro using a multi-phased in silico approach, involving the screening of 3009 FDA-approved drugs to pinpoint the most similar compounds to, TTT, the co-crystallized ligand TTT of PLpro. The selected compounds were subjected to further analysis, including molecular docking, molecular dynamics simulations, MM-GPSA (molecular mechanics generalized Born surface area), and PLIP (Protein-Ligand Interaction Profiler) studies, to examine and confirm their binding to the active pocket of PLpro. Seven candidates (Vismodegib, Celecoxib, Ketoprofen, Indomethacin, Naphazoline, Valdecoxib, and Eslicarbazepine) showed promising in silico activities against the PLpro. The computational analysis confirmed the binding of Celecoxib to the active pocket of PLpro, suggesting its potential in the fight against COVID-19. This study identified seven FDA-approved drugs as potential inhibitors of PLpro, providing a feasible approach for drug repurposing against COVID-19. The results obtained from the in silico approach hold promise, but further in vitro and in vivo studies are warranted to validate the potential of these compounds.

Naphthalen-1-ylethanamine–containing small molecule inhibitors of the papain-like protease of SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has not yet been eradicated. SARS-CoV-2 has two types of proteases, a main protease (Mpro) and a papain-like protease (PLpro), which together process two translated non-structural polyproteins, pp1a and pp1ab, to produce functional viral proteins. In this study, effective inhibitors against PLpro of SARS-CoV-2 were designed and synthesized using GRL-0048 as a lead. A docking simulation of GRL-0048 and SARS-CoV-2 PLpro showed that GRL-0048 noncovalently interacts with PLpro, and there is a newly identified binding pocket in PLpro. Structure-activity relationship studies were next performed on GRL-0048, resulting in the development of several inhibitors, specifically compounds 1, 2b, and 3h, that have more potent inhibitory activity than GRL-0048.

Novel Papain-Like Protease Inhibitors for Treating Viral Infections, in Particular Coronavirus Infections

Novel Papain-Like Protease Inhibitors for Treating Viral Infections, in Particular Coronavirus Infections

Diacerein reduces inflammasome activation and SARS-CoV-2 virus replication: a proof-of-concept translational study.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is linked to high mortality, primarily through an intense inflammatory response. Diacerein has emerged as a potential therapy for COVID-19 due to its potential impact in decreasing the inflammasome activation and coronavirus replication. This study aims to explore diacerein's influence in inhibiting both viral replication and the inflammatory response after SARS-CoV-2 infection. Human peripheral blood mononuclear cells (PBMCs) were obtained from healthy volunteers and infected in vitro with SARS-CoV-2. Additionally, we carried out a pilot randomized, double-blind, placebo-controlled study with 14 participants allocated to diacerein (n = 7) or placebo (n = 7) therapies every 12h for 10 days. The primary endpoint was change in plasma markers of inflammasome activation (NLRP3, caspase-1, and gasdermin-D). In vitro protocols have shown that rhein, diacerein's primary metabolite, decreased IL-1β secretion caused by SARS-CoV-2 infection in human PBMCs (p < 0.05), and suppressed viral replication when administered either before or after the virus incubation (p < 0.05). This later effect was, at least partially, attributed to its inhibitory effect on 3-chymotrypsin-like protease (SARS-CoV-2 3CLpro) and papain-like protease in the SARS-CoV-2 (SARS-CoV-2 PLpro) virus and in the phosphorylation of proteins related cytoskeleton network (p < 0.05). Diacerein-treated COVID-19 patients presented a smaller area under the curve for NLRP3, caspase-1 and GSDM-D measured on days 2, 5, and 10 after hospitalization compared to those receiving a placebo (p < 0.05). The indicated mechanisms of action of diacerein/rhein can reduce viral replication and mitigate the inflammatory response related to SARS-CoV-2. These findings are preliminary and require confirmation in clinical trials.

Exploring Niclosamide as a Multi-target Drug Against SARS-CoV-2: Molecular Dynamics Simulation Studies on Host and Viral Proteins.

Niclosamide has emerged as a promising repurposed drug against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In vitro studies suggested that niclosamide inhibits the host transmembrane protein 16F (hTMEM16F), crucial for lipid scramblase activity, which consequently reduces syncytia formation that aids viral spread. Based on other in vitro reports, niclosamide may also target viral proteases such as papain-like protease (PLpro) and main protease (Mpro), essential for viral replication and maturation. However, the precise interactions by which niclosamide interacts with these multiple targets remain largely unclear. Docking and molecular dynamics (MD) simulation studies were undertaken based on a homology model of the hTMEM16F and available crystal structures of SARS-CoV-2 PLpro and Mpro. Niclosamide was observed to bind stably throughout a 400ns MD simulation at the extracellular exit gate of the hTMEM16F tunnel, forming crucial interactions with residues spanning the TM1-TM2 loop (Gln350), TM3 (Phe481), and TM5-TM6 loop (Lys573, Glu594, and Asp596). Among the SARS-CoV-2 proteases, niclosamide was found to interact effectively with conserved active site residues of PLpro (Tyr268), exhibiting better stability in comparison to the control inhibitor, GRL0617. In conclusion, our in silico analyses support niclosamide as a multi-targeted drug inhibiting viral and host proteins involved in SARS-CoV-2 infections.

Thiol-Reactive or Redox-Active: Revising a Repurposing Screen Led to a New Invalidation Pipeline and Identified a True Noncovalent Inhibitor Against Papain-like Protease from SARS-CoV-2

Thiol-Reactive or Redox-Active: Revising a Repurposing Screen Led to a New Invalidation Pipeline and Identified a True Noncovalent Inhibitor Against Papain-like Protease from SARS-CoV-2

Integrated Exploration of Pyranocoumarin Derivatives as Synergistic Inhibitors of Dual-target for Mpro and PLpro Proteins of SARS-CoV-2 through Molecular Docking, ADMET Analysis, and Molecular Dynamics Simulation.

This study aimed to explore the potential of natural anticoagulant compounds as synergistic inhibitors of the main protease (Mpro) and papain-like protease (PLpro) of SARS-CoV-2 and find effective therapies against SARS-CoV-2 by investigating the inhibitory effects of natural anticoagulant compounds on key viral proteases. The objectives of this study were to conduct rigorous virtual screening and molecular docking analyses to evaluate the binding affinities and interactions of selected anticoagulant compounds with Mpro and PLpro, to assess the pharmacokinetic and pharmacodynamic profiles of the compounds to determine their viability for therapeutic use, and to employ molecular dynamics simulations to understand the stability of the identified compounds over time. In this study, a curated collection of natural anticoagulant compounds was conducted. Virtual screening and molecular docking analyses were performed to assess binding affinities and interactions with Mpro and PLpro. Furthermore, pharmacokinetic and pharmacodynamic analyses were carried out to evaluate absorption, distribution, metabolism, and excretion profiles. Molecular dynamics simulations were performed to elucidate compound stability. Natural compounds exhibiting significant inhibitory activity against Mpro and PLpro were identified. A dual-target approach was established as a promising strategy for attenuating viral replication and addressing coagulopathic complications associated with SARS-CoV-2 infection. The study lays a solid foundation for experimental validation and optimization of identified compounds, potentially leading to the development of precise treatments for SARS-CoV-2.

Integrated computational and experimental approaches to identify new papain-like protease inhibitors

SARS-CoV-2 papain-like protease (PLpro), a key viral protease, plays a crucial role in the viral replication and pathogenesis, making it an attractive target for the development of antiviral therapies. Thus to target PLpro, the chlorogenic acid was chosen based on its well-established characteristics as a natural compound with inhibitory properties against viral proteases. The research strategy involved a synergistic combination of in-silico and in-vitro techniques, enabled successful identification of a natural inhibitor for PLpro. In the docking analysis, it was observed that chlorogenic acid exhibited a more pronounced interaction energy with PLpro compared to GRL0617. Additionally, the molecular dynamics simulations demonstrated remarkable stability of the chlorogenic acid-PLpro complex, along with close proximity in conformational dynamics. The assessment of post-processing end-state free energies indicated comparable affinities for both molecules. Furthermore, the enzymatic inhibition assay performed for dose-response analysis provided validation for chlorogenic acid as a potential inhibitor of PLpro. This experimental assessment strengthens the evidence supporting the inhibitory activity of chlorogenic acid against PLpro. Overall, this comprehensive analysis serves as a valuable platform for the development of potential therapeutic candidates targeting PLpro, offering promising prospects for combating SARS-CoV-2.

Papain-like cysteine protease gene family in fig (Ficus carica L.): genome-wide analysis and expression patterns

Papain-like cysteine protease gene family in fig (<i>Ficus carica</i> L.): genome-wide analysis and expression patterns

Advances in the Search for SARS-CoV-2 Mpro and PLpro Inhibitors.

SARS-CoV-2 is a spherical, positive-sense, single-stranded RNA virus with a large genome, responsible for encoding both structural proteins, vital for the viral particle's architecture, and non-structural proteins, critical for the virus's replication cycle. Among the non-structural proteins, two cysteine proteases emerge as promising molecular targets for the design of new antiviral compounds. The main protease (Mpro) is a homodimeric enzyme that plays a pivotal role in the formation of the viral replication-transcription complex, associated with the papain-like protease (PLpro), a cysteine protease that modulates host immune signaling by reversing post-translational modifications of ubiquitin and interferon-stimulated gene 15 (ISG15) in host cells. Due to the importance of these molecular targets for the design and development of novel anti-SARS-CoV-2 drugs, the purpose of this review is to address aspects related to the structure, mechanism of action and strategies for the design of inhibitors capable of targeting the Mpro and PLpro. Examples of covalent and non-covalent inhibitors that are currently being evaluated in preclinical and clinical studies or already approved for therapy will be also discussed to show the advances in medicinal chemistry in the search for new molecules to treat COVID-19.

N-phenethyl-2-(1H-1,2,3-triazol-1-yl)acetamide derivatives: Synthesis, crystal structure and molecular docking studies against SARS-CoV-2

Novel N-phenethyl-2-(1H-1,2,3-triazol-1-yl)acetamide derivatives were synthesized via Copper(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition, commonly known as CuAAC. These triazoles were then characterized using Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), and Mass Spectrometry (MS). The crystal structures of ten compounds were elucidated through single-crystal X-ray diffraction (SCXRD). Computational calculations, based on Density Functional Theory (DFT), were employed to optimize the molecular structures. The energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were also determined. Additionally, molecular docking studies revealed the binding interactions of the most potent triazole with the active sites of key molecular targets. The findings indicated that the newly synthesized triazoles exhibit promising inhibitory activity against SARS-CoV-2 proteases 3-chymotrypsin-like protease (3CLpro), papain-like protease (PLpro), and helicase, outperforming the co-crystallized ligand.

Mechanistic Insights into Targeting SARS-CoV-2 Papain-like Protease in the Evolution and Management of COVID-19

Mechanistic Insights into Targeting SARS-CoV-2 Papain-like Protease in the Evolution and Management of COVID-19

SARS-CoV-2 papain-like protease inhibits ISGylation of the viral nucleocapsid protein to evade host anti-viral immunity.

A severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes mild-to-severe respiratory symptoms, including acute respiratory distress. Despite remarkable efforts to investigate the virological and pathological impacts of SARS-CoV-2, many of the characteristics of SARS-CoV-2 infection still remain unknown. The interferon-inducible ubiquitin-like protein ISG15 is covalently conjugated to several viral proteins to suppress their functions. It was reported that SARS-CoV-2 utilizes its papain-like protease (PLpro) to impede ISG15 conjugation, ISGylation. However, the role of ISGylation in SARS-CoV-2 infection remains unclear. We aimed to elucidate the role of ISGylation in SARS-CoV-2 replication. We observed that the SARS-CoV-2 nucleocapsid protein is a target protein for the HERC5 E3 ligase-mediated ISGylation in cultured cells. Site-directed mutagenesis reveals that the residue K374 within the C-terminal spacer B-N3 (SB/N3) domain is required for nucleocapsid-ISGylation, alongside conserved lysine residue in MERS-CoV (K372) and SARS-CoV (K375). We also observed that the nucleocapsid-ISGylation results in the disruption of nucleocapsid oligomerization, thereby inhibiting viral replication. Knockdown of ISG15 mRNA enhanced SARS-CoV-2 replication in the SARS-CoV-2 reporter replicon cells, while exogenous expression of ISGylation components partially hampered SARS-CoV-2 replication. Taken together, these results suggest that SARS-CoV-2 PLpro inhibits ISGylation of the nucleocapsid protein to promote viral replication by evading ISGylation-mediated disruption of the nucleocapsid oligomerization.IMPORTANCEISG15 is an interferon-inducible ubiquitin-like protein that is covalently conjugated to the viral protein via specific Lys residues and suppresses viral functions and viral propagation in many viruses. However, the role of ISGylation in SARS-CoV-2 infection remains largely unclear. Here, we demonstrated that the SARS-CoV-2 nucleocapsid protein is a target protein for the HERC5 E3 ligase-mediated ISGylation. We also found that the residue K374 within the C-terminal spacer B-N3 (SB/N3) domain is required for nucleocapsid-ISGylation. We obtained evidence suggesting that nucleocapsid-ISGylation results in the disruption of nucleocapsid-oligomerization, thereby suppressing SARS-CoV-2 replication. We discovered that SARS-CoV-2 papain-like protease inhibits ISG15 conjugation of nucleocapsid protein via its de-conjugating enzyme activity. The present study may contribute to gaining new insight into the roles of ISGylation-mediated anti-viral function in SARS-CoV-2 infection and may lead to the development of more potent and selective inhibitors targeted to SARS-CoV-2 nucleocapsid protein.

ISGylation of the SARS-CoV-2 N protein by HERC5 impedes N oligomerization and thereby viral RNA synthesis.

Interferon (IFN)-stimulated gene 15 (ISG15), a ubiquitin-like protein, is covalently conjugated to host immune proteins such as MDA5 and IRF3 in a process called ISGylation, thereby promoting type I IFN induction to limit the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, whether SARS-CoV-2 proteins can be directly targeted for ISGylation remains elusive. In this study, we identified the nucleocapsid (N) protein of SARS-CoV-2 as a major substrate of ISGylation catalyzed by the host E3 ligase HERC5; however, N ISGylation is readily removed through deISGylation by the papain-like protease (PLpro) activity of NSP3. Mass spectrometry analysis identified that the N protein undergoes ISGylation at four lysine residues (K266, K355, K387, and K388), and mutational analysis of these sites in the context of a SARS-CoV-2 replicon (N-4KR) abolished N ISGylation and alleviated ISGylation-mediated inhibition of viral RNA synthesis. Furthermore, our results indicated that HERC5 targets preferentially phosphorylated N protein for ISGylation to regulate its oligomeric assembly. These findings reveal a novel mechanism by which the host ISGylation machinery directly targets SARS-CoV-2 proteins to restrict viral replication and illuminate how an intricate interplay of host (HERC5) and viral (PLpro) enzymes coordinates viral protein ISGylation and thereby regulates virus replication.IMPORTANCEThe role of protein ISGylation in regulating host cellular processes has been studied extensively; however, how ISG15 conjugation influences the activity of viral proteins, particularly coronaviral proteins, is largely unknown. Our study uncovered that the nucleocapsid (N) protein of SARS-CoV-2 is ISGylated by the HERC5 ISGylation machinery and that this modification impedes the functional assembly of N into oligomers ultimately inhibiting viral RNA synthesis. This antiviral restriction mechanism is antagonized by the PLpro deISGylation activity of SARS-CoV-2 NSP3. This study deepens our understanding of SARS-CoV-2 protein regulation by posttranslational modifications and may open new avenues for designing antiviral strategies for COVID-19.

SARS-CoV-2 Genotyping Highlights the Challenges in Spike Protein Drift Independent of Other Essential Proteins.

As of 2024, SARS-CoV-2 continues to propagate and drift as an endemic virus, impacting healthcare for years. The largest sequencing initiative for any species was initiated to combat the virus, tracking changes over time at a full virus base-pair resolution. The SARS-CoV-2 sequencing represents a unique opportunity to understand selective pressures and viral evolution but requires cross-disciplinary approaches from epidemiology to functional protein biology. Within this work, we integrate a two-year genotyping window with structural biology to explore the selective pressures of SARS-CoV-2 on protein insights. Although genotype and the Spike (Surface Glycoprotein) protein continue to drift, most SARS-CoV-2 proteins have had few amino acid alterations. Within Spike, the high drift rate of amino acids involved in antibody evasion also corresponds to changes within the ACE2 binding pocket that have undergone multiple changes that maintain functional binding. The genotyping suggests selective pressure for receptor specificity that could also confer changes in viral risk. Mapping of amino acid changes to the structures of the SARS-CoV-2 co-transcriptional complex (nsp7-nsp14), nsp3 (papain-like protease), and nsp5 (cysteine protease) proteins suggest they remain critical factors for drug development that will be sustainable, unlike those strategies targeting Spike.

Repurposing FDA-Approved Drugs as Potential Inhibitors of SARS-CoV-2 PLpro: A Comprehensive Computational Study

This study explores the repurposing of Food and Drug Administration (FDA)-approved drugs as potential inhibitors of SARS-CoV-2 papain-like protease (PLpro), a critical enzyme for viral replication. Initially, 3009 FDA approved drugs were screened to identify candidates structurally similar to the co-crystallized ligand XT7 in the SARS-CoV-2 PLpro complex (PDB ID: 7LBR). A fingerprint analysis narrowed the selection to the top 5% )150 drugs) most structurally akin to XT7, followed by a more refined structural similarity test that identified the top 1% (30 drugs). Molecular docking studies highlighted several compounds with strong binding affinities to the SARS-CoV-2 PLpro. Notably, Fedratinib exhibited a particularly robust binding energy of [Formula: see text]kcal/mol and was chosen for further investigation. Subsequent molecular dynamics (MD) simulations over 100 ns confirmed the stability and efficacy of Fedratinib’s binding, as evidenced by favorable energetic and dynamic profiles. The molecular mechanics-generalized born surface area (MM-GBSA) calculations corroborated these findings, revealing a binding energy of [Formula: see text]kcal/mol. Additionally, PLIP, ProLIF, and PCAT analyses further validated the stability and interactions of the PLpro-Fedratinib complex observed during the MD simulations. Overall, our results indicate that Fedratinib, an FDA-approved drug, demonstrates promising potential as an inhibitor of SARS-CoV-2 PLpro, warranting further in vitro and in vivo experimental validation as well as potential clinical evaluation.

Rosmarinic Acid as a Potential Multi-targeted Inhibitor for SAR-CoV-2: An In silico Virtual Screening Approach

Background: Rosmarinic acid, a natural compound found in various plants like rosemary and lemon balm, may have potential as a multi-targeted inhibitor for SARS-CoV-2, a strain of virus responsible for COVID-19. SARS-CoV-2, a fusion protein of S1 and S2 subunits, has multiple precursors angiotensin-converting enzyme2 (ACE2), transmembrane serine protease 2 (TMPRSS2), papain-like protease (PLpro), and 3-chymotrypsin-like protease (3CLpro). The chemical interaction of Rosmarinic acid with SARS-CoV-2 is of major interest reported here. Objective:: The quantitative study of Rosmarinic acid with various precursors of SARS-CoV-2 has been accounted for in detail. Furthermore, the conformational flexibility of Rosmarinic acid has also been investigated during the interaction with four different precursors of SARS-CoV-2. Methods: This investigation delves deeply into the analysis of various aspects, including geometric parameters, atomic charge, the energy gap between the highest occupied and lowest unoccupied molecular orbitals, dipole moments, and the analysis of non-covalent interactions (NCI). Furthermore, the study incorporates molecular docking techniques in conjunction with thorough quantum chemical calculations to provide comprehensive insights. Results: Rosmarinic acid shows promise as a versatile inhibitor of SARS-CoV-2, the virus responsible for COVID-19. It can target multiple key precursors of the virus, including TMPRSS2, angiotensin- converting enzyme2, 3CLpro, and PLpro, found in the fusion protein comprising S1 and S2 subunits. This study delves into the quantitative analysis of Rosmarinic acid's interactions with these precursors. Its adaptable structure allows it to engage with them effectively. Various molecular parameters, including atomic charge, energy gap between molecular orbitals, dipole moment, and noncovalent interactions, are comprehensively explored. Conclusion: Combining molecular docking and quantum mechanics, the findings suggest Rosmarinic acid's potential as a multi-targeted SARS-CoV-2 inhibitor.

Identification of novel allosteric sites of SARS-CoV-2 papain-like protease (PLpro) for the development of COVID-19 antivirals

Coronaviruses such as SARS-CoV-2 encode a conserved papain-like protease (PLpro) that is crucial for viral replication and immune evasion, making it a prime target for antiviral drug development. In this study, three surface pockets on SARS-CoV-2 PLpro that may function as sites for allosteric inhibition were computationally identified. To evaluate the effects of these pockets on proteolytic activity, 52 residues were separately mutated to alanine. In Pocket 1, located between the Ubl and thumb domains, the introduction of alanine at T10, D12, T54, Y72, or Y83 reduced PLpro activity to <12% of that of WT. In Pocket 2, situated at the interface of the thumb, fingers, and palm domains, Q237A, S239A, H275A, and S278A inactivated PLpro. Finally, introducing alanine at five residues in Pocket 3, between the fingers and palm domains, inactivated PLpro: S212, Y213, Y251, K254, and Y305. Pocket 1 has a higher druggability score than Pockets 2 and 3. MD simulations showed that interactions within and between domains play critical roles in PLpro activity and thermal stability. The essential residues in Pockets 1 and 2 participate in a combination of intra- and inter-domain interactions. By contrast, the essential residues in Pocket 3 predominantly participate in inter-domain interactions. The most promising targets for therapeutic development are Pockets 1 and 3, which have the highest druggability score and the largest number of essential residues, respectively. Non-competitive inhibitors targeting these pockets may be antiviral agents against COVID-19 and related coronaviruses.