Your browser doesn't support javascript.
Show: 20 | 50 | 100
Results 1 - 20 de 486
Filter
1.
Nat Methods ; 19(11): 1376-1382, 2022 11.
Article in English | MEDLINE | ID: covidwho-2151063

ABSTRACT

Machine-learning prediction algorithms such as AlphaFold and RoseTTAFold can create remarkably accurate protein models, but these models usually have some regions that are predicted with low confidence or poor accuracy. We hypothesized that by implicitly including new experimental information such as a density map, a greater portion of a model could be predicted accurately, and that this might synergistically improve parts of the model that were not fully addressed by either machine learning or experiment alone. An iterative procedure was developed in which AlphaFold models are automatically rebuilt on the basis of experimental density maps and the rebuilt models are used as templates in new AlphaFold predictions. We show that including experimental information improves prediction beyond the improvement obtained with simple rebuilding guided by the experimental data. This procedure for AlphaFold modeling with density has been incorporated into an automated procedure for interpretation of crystallographic and electron cryo-microscopy maps.


Subject(s)
Algorithms , Proteins , Models, Molecular , Cryoelectron Microscopy/methods , Proteins/chemistry , Machine Learning , Protein Conformation
2.
Structure ; 28(8): 874-878, 2020 08 04.
Article in English | MEDLINE | ID: covidwho-2132441

ABSTRACT

During global pandemics, the spread of information needs to be faster than the spread of the virus in order to ensure the health and safety of human populations worldwide. In our current crisis, the demand for SARS-CoV-2 drugs and vaccines highlights the importance of biological targets and their three-dimensional shape. In particular, structural biology as a field was poised to quickly respond to crises due to previous experience and expertise and because of its early adoption of open access practices.


Subject(s)
Betacoronavirus/chemistry , Coronavirus Infections/epidemiology , Coronavirus Infections/virology , Pandemics , Pneumonia, Viral/epidemiology , Pneumonia, Viral/virology , Viral Proteins/chemistry , COVID-19 , Coronavirus 3C Proteases , Coronavirus RNA-Dependent RNA Polymerase , Cysteine Endopeptidases/chemistry , Databases, Protein , Humans , Models, Molecular , Molecular Biology , Protein Conformation , RNA-Dependent RNA Polymerase/chemistry , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/chemistry , Viral Nonstructural Proteins/chemistry
3.
J Phys Chem B ; 126(46): 9465-9475, 2022 Nov 24.
Article in English | MEDLINE | ID: covidwho-2106303

ABSTRACT

Markov state models (MSMs) play a key role in studying protein conformational dynamics. A sliding count window with a fixed lag time is widely used to sample sub-trajectories for transition counting and MSM construction. However, sub-trajectories sampled with a fixed lag time may not perform well under different selections of lag time, which requires strong prior practice and leads to less robust estimation. To alleviate it, we propose a novel stochastic method from a Poisson process to generate perturbative lag time for sub-trajectory sampling and utilize it to construct a Markov chain. Comprehensive evaluations on the double-well system, WW domain, BPTI, and RBD-ACE2 complex of SARS-CoV-2 reveal that our algorithm significantly increases the robustness and power of a constructed MSM without disturbing the Markovian properties. Furthermore, the superiority of our algorithm is amplified for slow dynamic modes in complex biological processes.


Subject(s)
COVID-19 , SARS-CoV-2 , Humans , Markov Chains , Protein Conformation , Algorithms , Molecular Dynamics Simulation
4.
Adv Protein Chem Struct Biol ; 132: 221-242, 2022.
Article in English | MEDLINE | ID: covidwho-2003777

ABSTRACT

Disordered proteins serve a crucial part in many biological processes that go beyond the capabilities of ordered proteins. A large number of virus-encoded proteins have extremely condensed proteomes and genomes, which results in highly disordered proteins. The presence of these IDPs allows them to rapidly adapt to changes in their biological environment and play a significant role in viral replication and down-regulation of host defense mechanisms. Since viruses undergo rapid evolution and have a high rate of mutation and accumulation in their proteome, IDPs' insights into viruses are critical for understanding how viruses hijack cells and cause disease. There are many conformational changes that IDPs can adopt in order to interact with different protein partners and thus stabilize the particular fold and withstand high mutation rates. This chapter explains the molecular mechanism behind viral IDPs, as well as the significance of recent research in the field of IDPs, with the goal of gaining a deeper comprehension of the essential roles and functions played by viral proteins.


Subject(s)
Intrinsically Disordered Proteins , Intrinsically Disordered Proteins/metabolism , Protein Conformation , Proteome/genetics , Viral Proteins
5.
Science ; 377(6608): 819-820, 2022 08 19.
Article in English | MEDLINE | ID: covidwho-2001760

ABSTRACT

Molecular structures provide a road map for understanding and controlling B cell receptor activation.


Subject(s)
CD79 Antigens , Immunoglobulin M , CD79 Antigens/chemistry , Cryoelectron Microscopy , Humans , Immunoglobulin M/chemistry , Protein Conformation
6.
Faraday Discuss ; 240(0): 184-195, 2022 Nov 08.
Article in English | MEDLINE | ID: covidwho-1984449

ABSTRACT

AlphaFold2 is a machine-learning based program that predicts a protein structure based on the amino acid sequence. In this article, we report on the current usages of this new tool and give examples from our work in the Coronavirus Structural Task Force. With its unprecedented accuracy, it can be utilized for the design of expression constructs, de novo protein design and the interpretation of Cryo-EM data with an atomic model. However, these methods are limited by their training data and are of limited use to predict conformational variability and fold flexibility; they also lack co-factors, post-translational modifications and multimeric complexes with oligonucleotides. They also are not always perfect in terms of chemical geometry. Nevertheless, machine learning-based fold prediction is a game changer for structural bioinformatics and experimentalists alike, with exciting developments ahead.


Subject(s)
Computational Biology , Proteins , Models, Molecular , Amino Acid Sequence , Proteins/chemistry , Machine Learning , Protein Conformation
7.
PLoS Pathog ; 18(7): e1010583, 2022 07.
Article in English | MEDLINE | ID: covidwho-1974332

ABSTRACT

The spike (S) protein of SARS-CoV-2 has been observed in three distinct pre-fusion conformations: locked, closed and open. Of these, the function of the locked conformation remains poorly understood. Here we engineered a SARS-CoV-2 S protein construct "S-R/x3" to arrest SARS-CoV-2 spikes in the locked conformation by a disulfide bond. Using this construct we determined high-resolution structures confirming that the x3 disulfide bond has the ability to stabilize the otherwise transient locked conformations. Structural analyses reveal that wild-type SARS-CoV-2 spike can adopt two distinct locked-1 and locked-2 conformations. For the D614G spike, based on which all variants of concern were evolved, only the locked-2 conformation was observed. Analysis of the structures suggests that rigidified domain D in the locked conformations interacts with the hinge to domain C and thereby restrains RBD movement. Structural change in domain D correlates with spike conformational change. We propose that the locked-1 and locked-2 conformations of S are present in the acidic high-lipid cellular compartments during virus assembly and egress. In this model, release of the virion into the neutral pH extracellular space would favour transition to the closed or open conformations. The dynamics of this transition can be altered by mutations that modulate domain D structure, as is the case for the D614G mutation, leading to changes in viral fitness. The S-R/x3 construct provides a tool for the further structural and functional characterization of the locked conformations of S, as well as how sequence changes might alter S assembly and regulation of receptor binding domain dynamics.


Subject(s)
COVID-19 , SARS-CoV-2 , Disulfides , Humans , Protein Binding , Protein Conformation , Spike Glycoprotein, Coronavirus/metabolism
8.
Faraday Discuss ; 240(0): 196-209, 2022 Nov 08.
Article in English | MEDLINE | ID: covidwho-1972674

ABSTRACT

Cryogenic electron microscopy (cryo-EM) has recently been established as a powerful technique for solving macromolecular structures. Although the best resolutions achievable are improving, a significant majority of data are still resolved at resolutions worse than 3 Å, where it is non-trivial to build or fit atomic models. The map reconstructions and atomic models derived from the maps are also prone to errors accumulated through the different stages of data processing. Here, we highlight the need to evaluate both model geometry and fit to data at different resolutions. Assessment of cryo-EM structures from SARS-CoV-2 highlights a bias towards optimising the model geometry to agree with the most common conformations, compared to the agreement with data. We present the CoVal web service which provides multiple validation metrics to reflect the quality of atomic models derived from cryo-EM data of structures from SARS-CoV-2. We demonstrate that further refinement can lead to improvement of the agreement with data without the loss of geometric quality. We also discuss the recent CCP-EM developments aimed at addressing some of the current shortcomings.


Subject(s)
COVID-19 , SARS-CoV-2 , Humans , Cryoelectron Microscopy/methods , Models, Molecular , Protein Conformation , Software
9.
Phys Chem Chem Phys ; 24(29): 17723-17743, 2022 Jul 27.
Article in English | MEDLINE | ID: covidwho-1947641

ABSTRACT

Dissecting the regulatory principles underlying function and activity of the SARS-CoV-2 spike protein at the atomic level is of paramount importance for understanding the mechanisms of virus transmissibility and immune escape. In this work, we introduce a hierarchical computational approach for atomistic modeling of allosteric mechanisms in the SARS-CoV-2 Omicron spike proteins and present evidence of a frustration-based allostery as an important energetic driver of the conformational changes and spike activation. By examining conformational landscapes and the residue interaction networks in the SARS-CoV-2 Omicron spike protein structures, we have shown that the Omicron mutational sites are dynamically coupled and form a central engine of the allosterically regulated spike machinery that regulates the balance and tradeoffs between conformational plasticity, protein stability, and functional adaptability. We have found that the Omicron mutational sites at the inter-protomer regions form regulatory hotspot clusters that control functional transitions between the closed and open states. Through perturbation-based modeling of allosteric interaction networks and diffusion analysis of communications in the closed and open spike states, we have quantified the allosterically regulated activation mechanism and uncover specific regulatory roles of the Omicron mutations. Atomistic reconstruction of allosteric communication pathways and kinetic modeling using Markov transient analysis reveal that the Omicron mutations form the inter-protomer electrostatic bridges that operate as a network of coupled regulatory switches that could control global conformational changes and signal transmission in the spike protein. The results of this study have revealed distinct and yet complementary roles of the Omicron mutation sites as a network of hotspots that enable allosteric modulation of structural stability and conformational changes which are central for spike activation and virus transmissibility.


Subject(s)
COVID-19 , Spike Glycoprotein, Coronavirus , Allosteric Regulation , Humans , Molecular Dynamics Simulation , Mutation , Protein Conformation , Protein Stability , Protein Subunits , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/metabolism
10.
Biophys Chem ; 288: 106843, 2022 09.
Article in English | MEDLINE | ID: covidwho-1944353

ABSTRACT

The nucleocapsid protein of the SARS-CoV-2 virus comprises two RNA-binding domains and three regions that are intrinsically disordered. While the structures of the RNA-binding domains have been solved using protein crystallography and NMR, current knowledge of the conformations of the full-length nucleocapsid protein is rather limited. To fill in this knowledge gap, we combined coarse-grained molecular simulations with data from small-angle X-ray scattering (SAXS) experiments using the ensemble refinement of SAXS (EROS) method. Our results show that the dimer of the full-length nucleocapsid protein exhibits large conformational fluctuations with its radius of gyration ranging from about 4 to 8 nm. The RNA-binding domains do not make direct contacts. The disordered region that links these two domains comprises a hydrophobic α-helix which makes frequent and nonspecific contacts with the RNA-binding domains. Each of the intrinsically disordered regions adopts conformations that are locally compact, yet on average, much more extended than Gaussian chains of equivalent lengths. We offer a detailed picture of the conformational ensemble of the nucleocapsid protein dimer under near-physiological conditions, which will be important for understanding the nucleocapsid assembly process.


Subject(s)
COVID-19 , SARS-CoV-2 , Humans , Nucleocapsid , Nucleocapsid Proteins/chemistry , Protein Conformation , Scattering, Small Angle , X-Ray Diffraction
11.
J Mol Biol ; 434(17): 167748, 2022 09 15.
Article in English | MEDLINE | ID: covidwho-1936840

ABSTRACT

Inhibiting the main protease of SARS-CoV-2 is of great interest in tackling the COVID-19 pandemic caused by the virus. Most efforts have been centred on inhibiting the binding site of the enzyme. However, considering allosteric sites, distant from the active or orthosteric site, broadens the search space for drug candidates and confers the advantages of allosteric drug targeting. Here, we report the allosteric communication pathways in the main protease dimer by using two novel fully atomistic graph-theoretical methods: Bond-to-bond propensity, which has been previously successful in identifying allosteric sites in extensive benchmark data sets without a priori knowledge, and Markov transient analysis, which has previously aided in finding novel drug targets in catalytic protein families. Using statistical bootstrapping, we score the highest ranking sites against random sites at similar distances, and we identify four statistically significant putative allosteric sites as good candidates for alternative drug targeting.


Subject(s)
Coronavirus 3C Proteases , Allosteric Site , Coronavirus 3C Proteases/chemistry , Molecular Docking Simulation , Protein Conformation
12.
J Mol Biol ; 434(17): 167696, 2022 09 15.
Article in English | MEDLINE | ID: covidwho-1926683

ABSTRACT

The family of coarse-grained models for protein dynamics known as Elastic Network Models (ENMs) require careful choice of parameters to represent well experimental measurements or fully-atomistic simulations. The most basic ENM that represents each protein residue by a node at the position of its C-alpha atom, all connected by springs of equal stiffness, up to a cut-off in distance. Even at this level a choice is required of the optimum cut-off distance and the upper limit of elastic normal modes taken in any sum for physical properties, such as dynamic correlation or allosteric effects on binding. Additionally, backbone-enhanced ENM (BENM) may improve the model by allocating a higher stiffness to springs that connect along the protein backbone. This work reports on the effect of varying these three parameters (distance and mode cutoffs, backbone stiffness) on the dynamical structure of three proteins, Catabolite Activator Protein (CAP), Glutathione S-transferase (GST), and the SARS-CoV-2 Main Protease (M pro ). Our main results are: (1) balancing B-factor and dispersion-relation predictions, a near-universal optimal value of 8.5 Å is advisable for ENMs; (2) inhomogeneity in elasticity brings the first mode containing spatial structure not well-resolved by the ENM typically within the first 20; (3) the BENM only affects modes in the upper third of the distribution, and, additionally to the ENM, is only able to model the dispersion curve better in this vicinity; (4) BENM does not typically affect fluctuation-allostery, which also requires careful treatment of the effector binding to the host protein to capture.


Subject(s)
Coronavirus 3C Proteases , Cyclic AMP Receptor Protein , Glutathione Transferase , Allosteric Regulation , Coronavirus 3C Proteases/chemistry , Cyclic AMP Receptor Protein/chemistry , Elasticity , Glutathione Transferase/chemistry , Humans , Molecular Dynamics Simulation , Protein Conformation
13.
PLoS One ; 17(2): e0263582, 2022.
Article in English | MEDLINE | ID: covidwho-1910522

ABSTRACT

The membrane protein M of the Porcine Epidemic Diarrhea Virus (PEDV) is the most abundant component of the viral envelope. The M protein plays a central role in the morphogenesis and assembly of the virus through protein interactions of the M-M, M-Spike (S) and M-nucleocapsid (N) type. The M protein is known to induce protective antibodies in pigs and to participate in the antagonistic response of the cellular antiviral system coordinated by the type I and type III interferon pathways. The 3D structure of the PEDV M protein is still unknown. The present work exposes a predicted 3D model of the M protein generated using the Robetta protocol. The M protein model is organized into a transmembrane and a globular region. The obtained 3D model of the PEDV M protein was compared with 3D models of the SARS-CoV-2 M protein created using neural networks and with initial machine learning-based models created using trRosetta. The 3D model of the present study predicted four linear B-cell epitopes (RSVNASSGTG and KHGDYSAVSNPSALT peptides are noteworthy), six discontinuous B-cell epitopes, forty weak binding and fourteen strong binding T-cell epitopes in the CV777 M protein. A high degree of conservation of the epitopes predicted in the PEDV M protein was observed among different PEDV strains isolated in different countries. The data suggest that the M protein could be a potential candidate for the development of new treatments or strategies that activate protective cellular mechanisms against viral diseases.


Subject(s)
Coronavirus Infections/virology , Coronavirus M Proteins/chemistry , Porcine epidemic diarrhea virus/chemistry , Swine Diseases/virology , Swine/virology , Amino Acid Sequence , Animals , Coronavirus Infections/immunology , Coronavirus Infections/veterinary , Coronavirus M Proteins/immunology , Epitopes, B-Lymphocyte/chemistry , Epitopes, B-Lymphocyte/immunology , Epitopes, T-Lymphocyte/chemistry , Epitopes, T-Lymphocyte/immunology , Models, Molecular , Porcine epidemic diarrhea virus/immunology , Protein Conformation , Swine Diseases/immunology
14.
J Phys Chem B ; 126(22): 3973-3984, 2022 06 09.
Article in English | MEDLINE | ID: covidwho-1873396

ABSTRACT

Dynamic hydrogen bonds and hydrogen-bond networks are ubiquitous in proteins and protein complexes. Functional roles that have been assigned to hydrogen-bond networks include structural plasticity for protein function, allosteric conformational coupling, long-distance proton transfers, and transient storage of protons. Advances in structural biology provide invaluable insights into architectures of large proteins and protein complexes of direct interest to human physiology and disease, including G Protein Coupled Receptors (GPCRs) and the SARS-Covid-19 spike protein S, and give rise to the challenge of how to identify those interactions that are more likely to govern protein dynamics. This Perspective discusses applications of graph-based algorithms to dissect dynamical hydrogen-bond networks of protein complexes, with illustrations for GPCRs and spike protein S. H-bond graphs provide an overview of sites in GPCR structures where hydrogen-bond dynamics would be required to assemble longer-distance networks between functionally important motifs. In the case of spike protein S, graphs identify regions of the protein where hydrogen bonds rearrange during the reaction cycle and where local hydrogen-bond networks likely change in a virus variant of concern.


Subject(s)
COVID-19 , Spike Glycoprotein, Coronavirus , Humans , Hydrogen Bonding , Protein Conformation , Protons
15.
Int J Biol Macromol ; 209(Pt A): 984-990, 2022 Jun 01.
Article in English | MEDLINE | ID: covidwho-1796725

ABSTRACT

MERS-CoV main protease (Mpro) is essential for the maturation of the coronavirus; therefore, considered a potential drug target. Detailed conformational information is essential to developing antiviral therapeutics. However, the conformation of MERS-CoV Mpro under different conditions is poorly characterized. In this study, MERS-CoV Mpro was recombinantly produced in E.coli and characterized its structural stability with respect to changes in pH and temperatures. The intrinsic and extrinsic fluorescence measurements revealed that MERS-CoV Mpro tertiary structure was exposed to the polar environment due to the unfolding of the tertiary structure. However, the secondary structure of MERS-CoV Mpro was gained at low pH because of charge-charge repulsion. Furthermore, differential scanning fluorometry studies of Mpro showed a single thermal transition at all pHs except at pH 2.0; no transitions were observed. The data from the spectroscopic studies suggest that the MERS-CoV Mpro forms a molten globule-like state at pH 2.0. Insilico studies showed that the covid-19 Mpro shows 96.08% and 50.65% similarity to that of SARS-CoV Mpro and MERS-CoV Mpro, respectively. This study provides a basic understanding of the thermodynamic and structural properties of MERS-CoV Mpro.


Subject(s)
Coronavirus 3C Proteases , Middle East Respiratory Syndrome Coronavirus , Coronavirus 3C Proteases/genetics , Coronavirus 3C Proteases/metabolism , Middle East Respiratory Syndrome Coronavirus/enzymology , Middle East Respiratory Syndrome Coronavirus/genetics , Protein Conformation , Recombinant Proteins
16.
J Biol Chem ; 298(4): 101814, 2022 04.
Article in English | MEDLINE | ID: covidwho-1788109

ABSTRACT

Within the last 2 decades, severe acute respiratory syndrome coronaviruses 1 and 2 (SARS-CoV-1 and SARS-CoV-2) have caused two major outbreaks; yet, for reasons not fully understood, the coronavirus disease 2019 pandemic caused by SARS-CoV-2 has been significantly more widespread than the 2003 SARS epidemic caused by SARS-CoV-1, despite striking similarities between these two viruses. The SARS-CoV-1 and SARS-CoV-2 spike proteins, both of which bind to host cell angiotensin-converting enzyme 2, have been implied to be a potential source of their differential transmissibility. However, the mechanistic details of prefusion spike protein binding to angiotensin-converting enzyme 2 remain elusive at the molecular level. Here, we performed an extensive set of equilibrium and nonequilibrium microsecond-level all-atom molecular dynamics simulations of SARS-CoV-1 and SARS-CoV-2 prefusion spike proteins to determine their differential dynamic behavior. Our results indicate that the active form of the SARS-CoV-2 spike protein is more stable than that of SARS-CoV-1 and the energy barrier associated with the activation is higher in SARS-CoV-2. These results suggest that not only the receptor-binding domain but also other domains such as the N-terminal domain could play a crucial role in the differential binding behavior of SARS-CoV-1 and SARS-CoV-2 spike proteins.


Subject(s)
SARS-CoV-2 , Spike Glycoprotein, Coronavirus , Angiotensin-Converting Enzyme 2/metabolism , COVID-19/virology , Humans , Molecular Dynamics Simulation , Protein Binding , Protein Conformation , Protein Domains , SARS Virus/chemistry , SARS Virus/metabolism , SARS-CoV-2/chemistry , SARS-CoV-2/metabolism , Severe Acute Respiratory Syndrome/virology , Spike Glycoprotein, Coronavirus/metabolism
17.
Viruses ; 14(2)2022 02 17.
Article in English | MEDLINE | ID: covidwho-1786043

ABSTRACT

Various adenoviruses are being used as viral vectors for the generation of vaccines against chronic and emerging diseases (e.g., AIDS, COVID-19). Here, we report the improved capsid structure for one of these vectors, human adenovirus D26 (HAdV-D26), at 3.4 Å resolution, by reprocessing the previous cryo-electron microscopy dataset and obtaining a refined model. In addition to overall improvements in the model, the highlights of the structure include (1) locating a segment of the processed peptide of VIII that was previously believed to be released from the mature virions, (2) reorientation of the helical appendage domain (APD) of IIIa situated underneath the vertex region relative to its counterpart observed in the cleavage defective (ts1) mutant of HAdV-C5 that resulted in the loss of interactions between the APD and hexon bases, and (3) the revised conformation of the cleaved N-terminal segments of pre-protein VI (pVIn), located in the hexon cavities, is highly conserved, with notable stacking interactions between the conserved His13 and Phe18 residues. Taken together, the improved model of HAdV-D26 capsid provides a better understanding of protein-protein interactions in HAdV capsids and facilitates the efforts to modify and/or design adenoviral vectors with altered properties. Last but not least, we provide some insights into clotting factors (e.g., FX and PF4) binding to AdV vectors.


Subject(s)
Adenoviruses, Human/chemistry , Capsid/chemistry , Capsid/ultrastructure , Cryoelectron Microscopy/methods , Adenoviruses, Human/genetics , Capsid Proteins/genetics , Humans , Models, Molecular , Protein Conformation , Protein Interaction Domains and Motifs , Virus Assembly , Virus Internalization
18.
Proc Natl Acad Sci U S A ; 119(16): e2117142119, 2022 04 19.
Article in English | MEDLINE | ID: covidwho-1774040

ABSTRACT

The main protease (Mpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a key enzyme, which extensively digests CoV replicase polyproteins essential for viral replication and transcription, making it an attractive target for antiviral drug development. However, the molecular mechanism of how Mpro of SARS-CoV-2 digests replicase polyproteins, releasing the nonstructural proteins (nsps), and its substrate specificity remain largely unknown. Here, we determine the high-resolution structures of SARS-CoV-2 Mpro in its resting state, precleavage state, and postcleavage state, constituting a full cycle of substrate cleavage. The structures show the delicate conformational changes that occur during polyprotein processing. Further, we solve the structures of the SARS-CoV-2 Mpro mutant (H41A) in complex with six native cleavage substrates from replicase polyproteins, and demonstrate that SARS-CoV-2 Mpro can recognize sequences as long as 10 residues but only have special selectivity for four subsites. These structural data provide a basis to develop potent new inhibitors against SARS-CoV-2.


Subject(s)
Coronavirus 3C Proteases , Coronavirus RNA-Dependent RNA Polymerase , SARS-CoV-2 , Antiviral Agents/chemistry , Coronavirus 3C Proteases/chemistry , Coronavirus RNA-Dependent RNA Polymerase/chemistry , Coronavirus RNA-Dependent RNA Polymerase/genetics , Polyproteins/chemistry , Protein Conformation , Proteolysis , SARS-CoV-2/enzymology , Substrate Specificity/genetics
19.
J Am Chem Soc ; 144(15): 6839-6850, 2022 04 20.
Article in English | MEDLINE | ID: covidwho-1773923

ABSTRACT

The envelope (E) protein of the SARS-CoV-2 virus is a membrane-bound viroporin that conducts cations across the endoplasmic reticulum Golgi intermediate compartment (ERGIC) membrane of the host cell to cause virus pathogenicity. The structure of the closed state of the E transmembrane (TM) domain, ETM, was recently determined using solid-state NMR spectroscopy. However, how the channel pore opens to mediate cation transport is unclear. Here, we use 13C and 19F solid-state NMR spectroscopy to investigate the conformation and dynamics of ETM at acidic pH and in the presence of calcium ions, which mimic the ERGIC and lysosomal environment experienced by the E protein in the cell. Acidic pH and calcium ions increased the conformational disorder of the N- and C-terminal residues and also increased the water accessibility of the protein, indicating that the pore lumen has become more spacious. ETM contains three regularly spaced phenylalanine (Phe) residues in the center of the peptide. 19F NMR spectra of para-fluorinated Phe20 and Phe26 indicate that both residues exhibit two sidechain conformations, which coexist within each channel. These two Phe conformations differ in their water accessibility, lipid contact, and dynamics. Channel opening by acidic pH and Ca2+ increases the population of the dynamic lipid-facing conformation. These results suggest an intricate aromatic network that regulates the opening of the ETM channel pore. This aromatic network may be a target for E inhibitors against SARS-CoV-2 and related coronaviruses.


Subject(s)
COVID-19 , Calcium , Calcium/metabolism , Humans , Hydrogen-Ion Concentration , Ions , Lipids , Protein Conformation , SARS-CoV-2 , Water
20.
Acta Crystallogr D Struct Biol ; 78(Pt 3): 363-378, 2022 Mar 01.
Article in English | MEDLINE | ID: covidwho-1758984

ABSTRACT

The SARS-CoV-2 main protease (Mpro) has a pivotal role in mediating viral genome replication and transcription of the coronavirus, making it a promising target for drugs against the COVID-19 pandemic. Here, a crystal structure is presented in which Mpro adopts an inactive state that has never been observed before, called new-inactive. It is shown that the oxyanion loop, which is involved in substrate recognition and enzymatic activity, adopts a new catalytically incompetent conformation and that many of the key interactions of the active conformation of the enzyme around the active site are lost. Solvation/desolvation energetic contributions play an important role in the transition from the inactive to the active state, with Phe140 moving from an exposed to a buried environment and Asn142 moving from a buried environment to an exposed environment. In new-inactive Mpro a new cavity is present near the S2' subsite, and the N-terminal and C-terminal tails, as well as the dimeric interface, are perturbed, with partial destabilization of the dimeric assembly. This novel conformation is relevant both for comprehension of the mechanism of action of Mpro within the catalytic cycle and for the successful structure-based drug design of antiviral drugs.


Subject(s)
COVID-19/virology , Coronavirus 3C Proteases/chemistry , SARS-CoV-2/chemistry , Catalytic Domain , Crystallography, X-Ray , Humans , Models, Molecular , Protein Conformation , Protein Multimerization
SELECTION OF CITATIONS
SEARCH DETAIL