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Beton JG, Mulvaney T, Cragnolini T, Topf M. Cryo-EM structure and B-factor refinement with ensemble representation. Nat Commun 2024; 15:444. [PMID: 38200043 PMCID: PMC10781738 DOI: 10.1038/s41467-023-44593-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 12/20/2023] [Indexed: 01/12/2024] Open
Abstract
Cryo-EM experiments produce images of macromolecular assemblies that are combined to produce three-dimensional density maps. Typically, atomic models of the constituent molecules are fitted into these maps, followed by a density-guided refinement. We introduce TEMPy-ReFF, a method for atomic structure refinement in cryo-EM density maps. Our method represents atomic positions as components of a Gaussian mixture model, utilising their variances as B-factors, which are used to derive an ensemble description. Extensively tested on a substantial dataset of 229 cryo-EM maps from EMDB ranging in resolution from 2.1-4.9 Å with corresponding PDB and CERES atomic models, our results demonstrate that TEMPy-ReFF ensembles provide a superior representation of cryo-EM maps. On a single-model basis, it performs similarly to the CERES re-refinement protocol, although there are cases where it provides a better fit to the map. Furthermore, our method enables the creation of composite maps free of boundary artefacts. TEMPy-ReFF is useful for better interpretation of flexible structures, such as those involving RNA, DNA or ligands.
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Affiliation(s)
- Joseph G Beton
- Leibniz Institute of Virology (LIV) and Universitätsklinikum Hamburg Eppendorf (UKE), Centre for Structural Systems Biology (CSSB), 22607, Hamburg, Germany
| | - Thomas Mulvaney
- Leibniz Institute of Virology (LIV) and Universitätsklinikum Hamburg Eppendorf (UKE), Centre for Structural Systems Biology (CSSB), 22607, Hamburg, Germany
| | - Tristan Cragnolini
- Leibniz Institute of Virology (LIV) and Universitätsklinikum Hamburg Eppendorf (UKE), Centre for Structural Systems Biology (CSSB), 22607, Hamburg, Germany
- Institute of Structural and Molecular Biology, Birkbeck, University of London, London, UK
| | - Maya Topf
- Leibniz Institute of Virology (LIV) and Universitätsklinikum Hamburg Eppendorf (UKE), Centre for Structural Systems Biology (CSSB), 22607, Hamburg, Germany.
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2
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Malhotra S, Mulvaney T, Cragnolini T, Sidhu H, Joseph A, Beton J, Topf M. RIBFIND2: Identifying rigid bodies in protein and nucleic acid structures. Nucleic Acids Res 2023; 51:9567-9575. [PMID: 37670532 PMCID: PMC10570027 DOI: 10.1093/nar/gkad721] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 08/10/2023] [Accepted: 08/21/2023] [Indexed: 09/07/2023] Open
Abstract
Molecular structures are often fitted into cryo-EM maps by flexible fitting. When this requires large conformational changes, identifying rigid bodies can help optimize the model-map fit. Tools for identifying rigid bodies in protein structures exist, however an equivalent for nucleic acid structures is lacking. With the increase in cryo-EM maps containing RNA and progress in RNA structure prediction, there is a need for such tools. We previously developed RIBFIND, a program for clustering protein secondary structures into rigid bodies. In RIBFIND2, this approach is extended to nucleic acid structures. RIBFIND2 can identify biologically relevant rigid bodies in important groups of complex RNA structures, capturing a wide range of dynamics, including large rigid-body movements. The usefulness of RIBFIND2-assigned rigid bodies in cryo-EM model refinement was demonstrated on three examples, with two conformations each: Group II Intron complexed IEP, Internal Ribosome Entry Site and the Processome, using cryo-EM maps at 2.7-5 Å resolution. A hierarchical refinement approach, performed on progressively smaller sets of RIBFIND2 rigid bodies, was clearly shown to have an advantage over classical all-atom refinement. RIBFIND2 is available via a web server with structure visualization and as a standalone tool.
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Affiliation(s)
- Sony Malhotra
- Science and Technology Facilities Council, Scientific Computing, Research Complex at Harwell, Didcot OX11 0FA, UK
| | - Thomas Mulvaney
- Leibniz Institute of Virology, Hamburg 20251, Germany
- Centre for Structural Systems Biology, Hamburg D-22607, Germany
- Universitätsklinikum Hamburg Eppendorf (UKE), Hamburg 20246, Germany
| | - Tristan Cragnolini
- Leibniz Institute of Virology, Hamburg 20251, Germany
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, London WC1E 7HX, UK
| | - Haneesh Sidhu
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, London WC1E 7HX, UK
| | - Agnel P Joseph
- Science and Technology Facilities Council, Scientific Computing, Research Complex at Harwell, Didcot OX11 0FA, UK
| | - Joseph G Beton
- Leibniz Institute of Virology, Hamburg 20251, Germany
- Centre for Structural Systems Biology, Hamburg D-22607, Germany
| | - Maya Topf
- Leibniz Institute of Virology, Hamburg 20251, Germany
- Centre for Structural Systems Biology, Hamburg D-22607, Germany
- Universitätsklinikum Hamburg Eppendorf (UKE), Hamburg 20246, Germany
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3
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Beton JG, Cragnolini T, Kaleel M, Mulvaney T, Sweeney A, Topf M. Integrating model simulation tools and
cryo‐electron
microscopy. WIREs Comput Mol Sci 2022. [DOI: 10.1002/wcms.1642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Joseph George Beton
- Centre for Structural Systems Biology (CSSB) Leibniz‐Institut für Virologie (LIV) Hamburg Germany
| | - Tristan Cragnolini
- Institute of Structural and Molecular Biology, Birkbeck and University College London London UK
| | - Manaz Kaleel
- Centre for Structural Systems Biology (CSSB) Leibniz‐Institut für Virologie (LIV) Hamburg Germany
| | - Thomas Mulvaney
- Centre for Structural Systems Biology (CSSB) Leibniz‐Institut für Virologie (LIV) Hamburg Germany
| | - Aaron Sweeney
- Centre for Structural Systems Biology (CSSB) Leibniz‐Institut für Virologie (LIV) Hamburg Germany
| | - Maya Topf
- Centre for Structural Systems Biology (CSSB) Leibniz‐Institut für Virologie (LIV) Hamburg Germany
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Eldrid C, Cragnolini T, Ben-Younis A, Zou J, Raleigh DP, Thalassinos K. Linking Gas-Phase and Solution-Phase Protein Unfolding via Mobile Proton Simulations. Anal Chem 2022; 94:16113-16121. [DOI: 10.1021/acs.analchem.2c03352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Charles Eldrid
- School of Biological Sciences, University of Southampton, SouthamptonSO16 1BJ, U.K
- Institute of Structural and Molecular Biology, Division of Bioscience, University College London, LondonWC1E 6BT, U.K
| | - Tristan Cragnolini
- Institute of Structural and Molecular Biology, Birkbeck College, University of London, LondonWC1E 7HX, U.K
| | - Aisha Ben-Younis
- Institute of Structural and Molecular Biology, Division of Bioscience, University College London, LondonWC1E 6BT, U.K
| | - Junjie Zou
- Department of Chemistry, Stony Brook University, 100 Nicolls Rd., Stony Brook, New York11794, United States
| | - Daniel P. Raleigh
- Institute of Structural and Molecular Biology, Division of Bioscience, University College London, LondonWC1E 6BT, U.K
- Department of Chemistry, Stony Brook University, 100 Nicolls Rd., Stony Brook, New York11794, United States
| | - Konstantinos Thalassinos
- Institute of Structural and Molecular Biology, Division of Bioscience, University College London, LondonWC1E 6BT, U.K
- Institute of Structural and Molecular Biology, Birkbeck College, University of London, LondonWC1E 7HX, U.K
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Britt HM, Cragnolini T, Khatun S, Hatimy A, James J, Page N, Williams JP, Hughes C, Denny R, Thalassinos K, Vissers JPC. Evaluation of acquisition modes for semi-quantitative analysis by targeted and untargeted mass spectrometry. Rapid Commun Mass Spectrom 2022; 36:e9308. [PMID: 35353398 PMCID: PMC9287043 DOI: 10.1002/rcm.9308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/26/2022] [Accepted: 03/27/2022] [Indexed: 06/14/2023]
Abstract
RATIONALE Analyte quantitation by mass spectrometry underpins a diverse range of scientific endeavors. The fast-growing field of mass spectrometer development has resulted in several targeted and untargeted acquisition modes suitable for these applications. By characterizing the acquisition methods available on an ion mobility (IM)-enabled orthogonal acceleration time-of-flight (oa-ToF) instrument, the optimum modes for analyte semi-quantitation can be deduced. METHODS Serial dilutions of commercial metabolite, peptide, or cross-linked peptide analytes were prepared in matrices of human urine or Escherichia coli digest. Each analyte dilution was introduced into an IM separation-enabled oa-ToF mass spectrometer by reversed-phase liquid chromatography and electrospray ionization. Data were acquired for each sample in duplicate using nine different acquisition modes, including four IM-enabled acquisitions modes, available on the mass spectrometer. RESULTS Five (metabolite) or seven (peptide/cross-linked peptide) point calibration curves were prepared for analytes across each of the acquisition modes. A nonlinear response was observed at high concentrations for some modes, attributed to saturation effects. Two correction methods, one MS1 isotope-correction and one MS2 ion intensity-correction, were applied to address this observation, resulting in an up to twofold increase in dynamic range. By averaging the semi-quantitative results across analyte classes, two parameters, linear dynamic range (LDR) and lower limit of quantification (LLOQ), were determined to evaluate each mode. CONCLUSION A comparison of the acquisition modes revealed that data-independent acquisition and parallel reaction monitoring methods are most robust for semi-quantitation when considering achievable LDR and LLOQ. IM-enabled modes exhibited sensitivity increases, but a simultaneous reduction in dynamic range required correction methods to recover. These findings will assist users in identifying the optimum acquisition mode for their analyte quantitation needs, supporting a diverse range of applications and providing guidance for future acquisition mode developments.
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Affiliation(s)
- Hannah M. Britt
- Institute of Structural and Molecular Biology, Division of BiosciencesUniversity College LondonLondonUK
| | - Tristan Cragnolini
- Institute of Structural and Molecular Biology, Division of BiosciencesUniversity College LondonLondonUK
- Institute of Structural and Molecular Biology, Birkbeck CollegeUniversity of LondonLondonUK
| | - Suniya Khatun
- Institute of Structural and Molecular Biology, Division of BiosciencesUniversity College LondonLondonUK
| | - Abubakar Hatimy
- Institute of Structural and Molecular Biology, Division of BiosciencesUniversity College LondonLondonUK
| | - Juliette James
- Institute of Structural and Molecular Biology, Division of BiosciencesUniversity College LondonLondonUK
| | - Nathanael Page
- Institute of Structural and Molecular Biology, Division of BiosciencesUniversity College LondonLondonUK
- LGC GroupTeddingtonUK
| | | | | | | | - Konstantinos Thalassinos
- Institute of Structural and Molecular Biology, Division of BiosciencesUniversity College LondonLondonUK
- Institute of Structural and Molecular Biology, Birkbeck CollegeUniversity of LondonLondonUK
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6
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Abstract
Structures of seven CASP14 targets were determined using cryo-electron microscopy (cryo-EM) technique with resolution between 2.1 and 3.8 Å. We provide an evaluation of the submitted models versus the experimental data (cryo-EM density maps) and experimental reference structures built into the maps. The accuracy of models is measured in terms of coordinate-to-density and coordinate-to-coordinate fit. A-posteriori refinement of the most accurate models in their corresponding cryo-EM density resulted in structures that are close to the reference structure, including some regions with better fit to the density. Regions that were found to be less "refineable" correlate well with regions of high diversity between the CASP models and low goodness-of-fit to density in the reference structure.
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Affiliation(s)
- Tristan Cragnolini
- Institute of Structural and Molecular Biology, Birkbeck, University College London, London, UK
| | | | - Maya Topf
- Center for Structural Systems Biology, Leibniz-Institut für Experimentelle Virologie and Universitätsklinikum Hamburg-Eppendorf (UKE), Hamburg, Germany
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7
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Abstract
Mass spectrometry (MS) is increasingly being used to probe the structure and dynamics of proteins and the complexes they form with other macromolecules. There are now several specialized MS methods, each with unique sample preparation, data acquisition, and data processing protocols. Collectively, these methods are referred to as structural MS and include cross-linking, hydrogen-deuterium exchange, hydroxyl radical footprinting, native, ion mobility, and top-down MS. Each of these provides a unique type of structural information, ranging from composition and stoichiometry through to residue level proximity and solvent accessibility. Structural MS has proved particularly beneficial in studying protein classes for which analysis by classic structural biology techniques proves challenging such as glycosylated or intrinsically disordered proteins. To capture the structural details for a particular system, especially larger multiprotein complexes, more than one structural MS method with other structural and biophysical techniques is often required. Key to integrating these diverse data are computational strategies and software solutions to facilitate this process. We provide a background to the structural MS methods and briefly summarize other structural methods and how these are combined with MS. We then describe current state of the art approaches for the integration of structural MS data for structural biology. We quantify how often these methods are used together and provide examples where such combinations have been fruitful. To illustrate the power of integrative approaches, we discuss progress in solving the structures of the proteasome and the nuclear pore complex. We also discuss how information from structural MS, particularly pertaining to protein dynamics, is not currently utilized in integrative workflows and how such information can provide a more accurate picture of the systems studied. We conclude by discussing new developments in the MS and computational fields that will further enable in-cell structural studies.
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Affiliation(s)
- Hannah M Britt
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom
| | - Tristan Cragnolini
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom.,Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, United Kingdom
| | - Konstantinos Thalassinos
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom.,Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, United Kingdom
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8
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Eldrid C, Ben-Younis A, Ujma J, Britt H, Cragnolini T, Kalfas S, Cooper-Shepherd D, Tomczyk N, Giles K, Morris M, Akter R, Raleigh D, Thalassinos K. Cyclic Ion Mobility-Collision Activation Experiments Elucidate Protein Behavior in the Gas Phase. J Am Soc Mass Spectrom 2021; 32:1545-1552. [PMID: 34006100 PMCID: PMC8172447 DOI: 10.1021/jasms.1c00018] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Ion mobility coupled to mass spectrometry (IM-MS) is widely used to study protein dynamics and structure in the gas phase. Increasing the energy with which the protein ions are introduced to the IM cell can induce them to unfold, providing information on the comparative energetics of unfolding between different proteoforms. Recently, a high-resolution cyclic IM-mass spectrometer (cIM-MS) was introduced, allowing multiple, consecutive tandem IM experiments (IMn) to be carried out. We describe a tandem IM technique for defining detailed protein unfolding pathways and the dynamics of disordered proteins. The method involves multiple rounds of IM separation and collision activation (CA): IM-CA-IM and CA-IM-CA-IM. Here, we explore its application to studies of a model protein, cytochrome C, and dimeric human islet amyloid polypeptide (hIAPP), a cytotoxic and amyloidogenic peptide involved in type II diabetes. In agreement with prior work using single stage IM-MS, several unfolding events are observed for cytochrome C. IMn-MS experiments also show evidence of interconversion between compact and extended structures. IMn-MS data for hIAPP shows interconversion prior to dissociation, suggesting that the certain conformations have low energy barriers between them and transition between compact and extended forms.
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Affiliation(s)
- Charles Eldrid
- Institute
of Structural and Molecular Biology, Division of Bioscience, University College London, London, WC1E 6BT, U.K.
| | - Aisha Ben-Younis
- Institute
of Structural and Molecular Biology, Division of Bioscience, University College London, London, WC1E 6BT, U.K.
| | - Jakub Ujma
- Waters
Corporation, Wilmslow SK9 4AX, U.K.
| | - Hannah Britt
- Institute
of Structural and Molecular Biology, Division of Bioscience, University College London, London, WC1E 6BT, U.K.
| | - Tristan Cragnolini
- Institute
of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, U.K.
| | - Symeon Kalfas
- Institute
of Structural and Molecular Biology, Division of Bioscience, University College London, London, WC1E 6BT, U.K.
| | | | | | | | | | - Rehana Akter
- Department
of Chemistry, Stony Brook University, 100 Nicolls Road, Stony Brook, New York 11794, United States
| | - Daniel Raleigh
- Institute
of Structural and Molecular Biology, Division of Bioscience, University College London, London, WC1E 6BT, U.K.
- Department
of Chemistry, Stony Brook University, 100 Nicolls Road, Stony Brook, New York 11794, United States
| | - Konstantinos Thalassinos
- Institute
of Structural and Molecular Biology, Division of Bioscience, University College London, London, WC1E 6BT, U.K.
- Institute
of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, U.K.
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9
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Cragnolini T, Sahota H, Joseph AP, Sweeney A, Malhotra S, Vasishtan D, Topf M. TEMPy2: a Python library with improved 3D electron microscopy density-fitting and validation workflows. Acta Crystallogr D Struct Biol 2021; 77:41-47. [PMID: 33404524 PMCID: PMC7787107 DOI: 10.1107/s2059798320014928] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 11/10/2020] [Indexed: 11/10/2022] Open
Abstract
Structural determination of molecular complexes by cryo-EM requires large, often complex processing of the image data that are initially obtained. Here, TEMPy2, an update of the TEMPy package to process, optimize and assess cryo-EM maps and the structures fitted to them, is described. New optimization routines, comprehensive automated checks and workflows to perform these tasks are described.
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Affiliation(s)
- Tristan Cragnolini
- Institute of Structural and Molecular Biology, Birkbeck, University College London, London, United Kingdom
| | - Harpal Sahota
- Institute of Structural and Molecular Biology, Birkbeck, University College London, London, United Kingdom
| | - Agnel Praveen Joseph
- Institute of Structural and Molecular Biology, Birkbeck, University College London, London, United Kingdom
| | - Aaron Sweeney
- Institute of Structural and Molecular Biology, Birkbeck, University College London, London, United Kingdom
| | - Sony Malhotra
- Institute of Structural and Molecular Biology, Birkbeck, University College London, London, United Kingdom
| | - Daven Vasishtan
- Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Maya Topf
- Institute of Structural and Molecular Biology, Birkbeck, University College London, London, United Kingdom
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10
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Kryshtafovych A, Malhotra S, Monastyrskyy B, Cragnolini T, Joseph AP, Chiu W, Topf M. Cryo-electron microscopy targets in CASP13: Overview and evaluation of results. Proteins 2019; 87:1128-1140. [PMID: 31576602 PMCID: PMC7197460 DOI: 10.1002/prot.25817] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 08/30/2019] [Accepted: 09/13/2019] [Indexed: 11/07/2022]
Abstract
Structures of seven CASP13 targets were determined using cryo-electron microscopy (cryo-EM) technique with resolution between 3.0 and 4.0 Å. We provide an overview of the experimentally derived structures and describe results of the numerical evaluation of the submitted models. The evaluation is carried out by comparing coordinates of models to those of reference structures (CASP-style evaluation), as well as checking goodness-of-fit of modeled structures to the cryo-EM density maps. The performance of contributing research groups in the CASP-style evaluation is measured in terms of backbone accuracy, all-atom local geometry and similarity of inter-subunit interfaces. The results on the cryo-EM targets are compared with those on the whole set of eighty CASP13 targets. A posteriori refinement of the best models in their corresponding cryo-EM density maps resulted in structures that are very close to the reference structure, including some regions with better fit to the density.
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Affiliation(s)
- Andriy Kryshtafovych
- Genome Center, University of California, Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
| | - Sony Malhotra
- Institute of Structural and Molecular Biology, Birkbeck, University College London, Malet Street, London WC1E 7HX, UK
| | - Bohdan Monastyrskyy
- Genome Center, University of California, Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
| | - Tristan Cragnolini
- Institute of Structural and Molecular Biology, Birkbeck, University College London, Malet Street, London WC1E 7HX, UK
| | - Agnel-Praveen Joseph
- Institute of Structural and Molecular Biology, Birkbeck, University College London, Malet Street, London WC1E 7HX, UK
| | - Wah Chiu
- Department of Bioengineering, Microbiology and Immunology and Photon Science, Stanford University, James H. Clark Center, MC5447, 318 Campus Drive, Stanford, CA 94305, USA
| | - Maya Topf
- Institute of Structural and Molecular Biology, Birkbeck, University College London, Malet Street, London WC1E 7HX, UK
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11
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Kimchi O, Cragnolini T, Brenner MP, Colwell LJ. A Polymer Physics Framework for the Entropy of Arbitrary Pseudoknots. Biophys J 2019; 117:520-532. [PMID: 31353036 PMCID: PMC6697467 DOI: 10.1016/j.bpj.2019.06.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 06/21/2019] [Accepted: 06/27/2019] [Indexed: 11/18/2022] Open
Abstract
The accurate prediction of RNA secondary structure from primary sequence has had enormous impact on research from the past 40 years. Although many algorithms are available to make these predictions, the inclusion of non-nested loops, termed pseudoknots, still poses challenges arising from two main factors: 1) no physical model exists to estimate the loop entropies of complex intramolecular pseudoknots, and 2) their NP-complete enumeration has impeded their study. Here, we address both challenges. First, we develop a polymer physics model that can address arbitrarily complex pseudoknots using only two parameters corresponding to concrete physical quantities-over an order of magnitude fewer than the sparsest state-of-the-art phenomenological methods. Second, by coupling this model to exhaustive enumeration of the set of possible structures, we compute the entire free energy landscape of secondary structures resulting from a primary RNA sequence. We demonstrate that for RNA structures of ∼80 nucleotides, with minimal heuristics, the complete enumeration of possible secondary structures can be accomplished quickly despite the NP-complete nature of the problem. We further show that despite our loop entropy model's parametric sparsity, it performs better than or on par with previously published methods in predicting both pseudoknotted and non-pseudoknotted structures on a benchmark data set of RNA structures of ≤80 nucleotides. We suggest ways in which the accuracy of the model can be further improved.
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Affiliation(s)
- Ofer Kimchi
- Harvard Graduate Program in Biophysics, Harvard University, Cambridge, Massachusetts.
| | - Tristan Cragnolini
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Michael P Brenner
- School of Engineering and Applied Sciences, Cambridge, Massachusetts; Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, Massachusetts
| | - Lucy J Colwell
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
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12
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Kimchi O, Cragnolini T, Garmann R, Manoharan VN, Brenner MP, Colwell LJ. RNA Structure and Kinetics Including Pseudoknots through Complete Landscape Enumeration. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.1922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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13
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Cragnolini T, Chakraborty D, Šponer J, Derreumaux P, Pasquali S, Wales DJ. Multifunctional energy landscape for a DNA G-quadruplex: An evolved molecular switch. J Chem Phys 2017; 147:152715. [DOI: 10.1063/1.4997377] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Tristan Cragnolini
- University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Debayan Chakraborty
- University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Jiří Šponer
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 612 65 Brno, Czech Republic
| | - Philippe Derreumaux
- Laboratoire de Biochimie Théorique UPR 9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, IBPC 13 Rue Pierre et Marie Curie, 75005 Paris, France
- Institut Universitaire de France, Boulevard Saint-Michel, 75005 Paris, France
| | - Samuela Pasquali
- Laboratoire de Biochimie Théorique UPR 9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, IBPC 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - David J. Wales
- University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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14
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Martinez-Zapien D, Legrand P, McEwen AG, Proux F, Cragnolini T, Pasquali S, Dock-Bregeon AC. The crystal structure of the 5΄ functional domain of the transcription riboregulator 7SK. Nucleic Acids Res 2017; 45:3568-3579. [PMID: 28082395 PMCID: PMC5389472 DOI: 10.1093/nar/gkw1351] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 01/06/2017] [Indexed: 12/22/2022] Open
Abstract
In vertebrates, the 7SK RNA forms the scaffold of a complex, which regulates transcription pausing of RNA-polymerase II. By binding to the HEXIM protein, the complex comprising proteins LARP7 and MePCE captures the positive transcription elongation factor P-TEFb and prevents phosphorylation of pausing factors. The HEXIM-binding site embedded in the 5΄-hairpin of 7SK (HP1) encompasses a short signature sequence, a GAUC repeat framed by single-stranded uridines. The present crystal structure of HP1 shows a remarkably straight helical stack involving several unexpected triples formed at a central region. Surprisingly, two uridines of the signature sequence make triple interactions in the major groove of the (GAUC)2. The third uridine is turned outwards or inward, wedging between the other uridines, thus filling the major groove. A molecular dynamics simulation indicates that these two conformations of the signature sequence represent stable alternatives. Analyses of the interaction with the HEXIM protein confirm the importance of the triple interactions at the signature sequence. Altogether, the present structural analysis of 7SK HP1 highlights an original mechanism of swapping bases, which could represent a possible ‘7SK signature’ and provides new insight into the functional importance of the plasticity of RNA.
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Affiliation(s)
- Denise Martinez-Zapien
- Biotechnologie et signalisation cellulaire, CNRS UMR 7242, Ecole Supérieure de Biotechnologie de Strasbourg, F-67412 Illkirch, France
| | - Pierre Legrand
- Synchrotron SOLEIL, L'Orme des Merisiers, F-91190 Gif-sur-Yvette, France
| | - Alastair G McEwen
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Florence Proux
- Department of functional genomics, CNRS UMR 8197, Institut de Biologie de l΄Ecole Normale Supérieure F-75005 Paris, France.,Department of functional genomics, INSERM-U1024, Institut de Biologie de l΄Ecole Normale Supérieure F-75005 Paris, France
| | | | - Samuela Pasquali
- Laboratoire de Biochimie Théorique, IBPC, CNRS UPR 9080, Université Sorbonne Paris Cite, Paris Diderot, 75005 Paris, France
| | - Anne-Catherine Dock-Bregeon
- Department of functional genomics, CNRS UMR 8197, Institut de Biologie de l΄Ecole Normale Supérieure F-75005 Paris, France.,Department of functional genomics, INSERM-U1024, Institut de Biologie de l΄Ecole Normale Supérieure F-75005 Paris, France.,Sorbonne Universités UPMC, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff cedex, France.,CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff cedex, France
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15
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Stadlbauer P, Mazzanti L, Cragnolini T, Wales DJ, Derreumaux P, Pasquali S, Šponer J. Coarse-Grained Simulations Complemented by Atomistic Molecular Dynamics Provide New Insights into Folding and Unfolding of Human Telomeric G-Quadruplexes. J Chem Theory Comput 2016; 12:6077-6097. [DOI: 10.1021/acs.jctc.6b00667] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Petr Stadlbauer
- Institute
of Biophysics, Academy of Sciences of the Czech Republic, Královopolská
135, 612 65 Brno, Czech Republic
- Regional
Centre of Advanced Technologies and Materials, Departments of Physical
Chemistry, Faculty of Science, Palacký University, 17. listopadu
1192/12, 771 46 Olomouc, Czech Republic
| | - Liuba Mazzanti
- Laboratoire
de Biochimie Théorique, IBPC, CNRS UPR9080, Université Sorbonne Paris Cite, Paris Diderot, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Tristan Cragnolini
- Department
of Chemistry, Cambridge University, Lensfield Road, Cambridge CB2 1EW, U.K
| | - David J. Wales
- Department
of Chemistry, Cambridge University, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Philippe Derreumaux
- Laboratoire
de Biochimie Théorique, IBPC, CNRS UPR9080, Université Sorbonne Paris Cite, Paris Diderot, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Samuela Pasquali
- Laboratoire
de Biochimie Théorique, IBPC, CNRS UPR9080, Université Sorbonne Paris Cite, Paris Diderot, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Jiří Šponer
- Institute
of Biophysics, Academy of Sciences of the Czech Republic, Královopolská
135, 612 65 Brno, Czech Republic
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16
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Cragnolini T, Doutreligne S, Baaden M, Derreumaux P, Pasquali S. 44 Predicting and exploring complex nucleic acids architectures through a coarse-grained model. J Biomol Struct Dyn 2015. [DOI: 10.1080/07391102.2015.1032593] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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17
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Abstract
RNA molecules are essential cellular machines performing a wide variety of functions for which a specific three-dimensional structure is required. Over the last several years, the experimental determination of RNA structures through x-ray crystallography and NMR seems to have reached a plateau in the number of structures resolved each year, but as more and more RNA sequences are being discovered, the need for structure prediction tools to complement experimental data is strong. Theoretical approaches to RNA folding have been developed since the late nineties, when the first algorithms for secondary structure prediction appeared. Over the last 10 years a number of prediction methods for 3D structures have been developed, first based on bioinformatics and data-mining, and more recently based on a coarse-grained physical representation of the systems. In this review we are going to present the challenges of RNA structure prediction and the main ideas behind bioinformatic approaches and physics-based approaches. We will focus on the description of the more recent physics-based phenomenological models and on how they are built to include the specificity of the interactions of RNA bases, whose role is critical in folding. Through examples from different models, we will point out the strengths of physics-based approaches, which are able not only to predict equilibrium structures, but also to investigate dynamical and thermodynamical behavior, and the open challenges to include more key interactions ruling RNA folding.
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Affiliation(s)
- Tristan Cragnolini
- Laboratoire de Biochimie Théorique UPR 9080 CNRS, Université Paris Diderot, Sorbonne, Paris Cité, IBPC 13 rue Pierre et Marie Curie, 75005 Paris, France
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18
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Cragnolini T, Laurin Y, Derreumaux P, Pasquali S. Coarse-Grained HiRE-RNA Model for ab Initio RNA Folding beyond Simple Molecules, Including Noncanonical and Multiple Base Pairings. J Chem Theory Comput 2015; 11:3510-22. [PMID: 26575783 DOI: 10.1021/acs.jctc.5b00200] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
HiRE-RNA is a coarse-grained model for RNA structure prediction and the dynamical study of RNA folding. Using a reduced set of particles and detailed interactions accounting for base-pairing and stacking, we show that noncanonical and multiple base interactions are necessary to capture the full physical behavior of complex RNAs. In this paper, we give a full account of the model and present results on the folding, stability, and free energy surfaces of 16 systems with 12 to 76 nucleotides of increasingly complex architectures, ranging from monomers to dimers, using a total of 850 μs of simulation time.
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Affiliation(s)
- Tristan Cragnolini
- Laboratoire de Biochimie Théorique UPR 9080 CNRS, Université Paris Diderot , Sorbonne, Paris Cité, IBPC 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Yoann Laurin
- Laboratoire de Biochimie Théorique UPR 9080 CNRS, Université Paris Diderot , Sorbonne, Paris Cité, IBPC 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Philippe Derreumaux
- Laboratoire de Biochimie Théorique UPR 9080 CNRS, Université Paris Diderot , Sorbonne, Paris Cité, IBPC 13 rue Pierre et Marie Curie, 75005 Paris, France.,Institut Universitaire de France , Boulevard Saint-Michel, 75005 Paris, France
| | - Samuela Pasquali
- Laboratoire de Biochimie Théorique UPR 9080 CNRS, Université Paris Diderot , Sorbonne, Paris Cité, IBPC 13 rue Pierre et Marie Curie, 75005 Paris, France
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19
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Tiwari SP, Fuglebakk E, Hollup SM, Skjærven L, Cragnolini T, Grindhaug SH, Tekle KM, Reuter N. WEBnm@ v2.0: Web server and services for comparing protein flexibility. BMC Bioinformatics 2014; 15:427. [PMID: 25547242 PMCID: PMC4339738 DOI: 10.1186/s12859-014-0427-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Accepted: 12/11/2014] [Indexed: 11/10/2022] Open
Abstract
Background Normal mode analysis (NMA) using elastic network models is a reliable and cost-effective computational method to characterise protein flexibility and by extension, their dynamics. Further insight into the dynamics–function relationship can be gained by comparing protein motions between protein homologs and functional classifications. This can be achieved by comparing normal modes obtained from sets of evolutionary related proteins. Results We have developed an automated tool for comparative NMA of a set of pre-aligned protein structures. The user can submit a sequence alignment in the FASTA format and the corresponding coordinate files in the Protein Data Bank (PDB) format. The computed normalised squared atomic fluctuations and atomic deformation energies of the submitted structures can be easily compared on graphs provided by the web user interface. The web server provides pairwise comparison of the dynamics of all proteins included in the submitted set using two measures: the Root Mean Squared Inner Product and the Bhattacharyya Coefficient. The Comparative Analysis has been implemented on our web server for NMA, WEBnm@, which also provides recently upgraded functionality for NMA of single protein structures. This includes new visualisations of protein motion, visualisation of inter-residue correlations and the analysis of conformational change using the overlap analysis. In addition, programmatic access to WEBnm@ is now available through a SOAP-based web service. Webnm@ is available at http://apps.cbu.uib.no/webnma. Conclusion WEBnm@ v2.0 is an online tool offering unique capability for comparative NMA on multiple protein structures. Along with a convenient web interface, powerful computing resources, and several methods for mode analyses, WEBnm@ facilitates the assessment of protein flexibility within protein families and superfamilies. These analyses can give a good view of how the structures move and how the flexibility is conserved over the different structures. Electronic supplementary material The online version of this article (doi:10.1186/s12859-014-0427-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sandhya P Tiwari
- Department of Molecular Biology, University of Bergen, Bergen, Norway. .,Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway.
| | - Edvin Fuglebakk
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway.
| | - Siv M Hollup
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway.
| | - Lars Skjærven
- Department of Biomedicine, University of Bergen, Bergen, Norway. .,Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway.
| | - Tristan Cragnolini
- Department of Molecular Biology, University of Bergen, Bergen, Norway. .,Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway. .,Present address: University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
| | - Svenn H Grindhaug
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway.
| | - Kidane M Tekle
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway.
| | - Nathalie Reuter
- Department of Molecular Biology, University of Bergen, Bergen, Norway. .,Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway.
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20
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Laurent B, Chavent M, Cragnolini T, Dahl ACE, Pasquali S, Derreumaux P, Sansom MSP, Baaden M. Epock: rapid analysis of protein pocket dynamics. ACTA ACUST UNITED AC 2014; 31:1478-80. [PMID: 25505095 PMCID: PMC4410650 DOI: 10.1093/bioinformatics/btu822] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 12/08/2014] [Indexed: 11/12/2022]
Abstract
Summary: The volume of an internal protein pocket is fundamental to ligand accessibility. Few programs that compute such volumes manage dynamic data from molecular dynamics (MD) simulations. Limited performance often prohibits analysis of large datasets. We present Epock, an efficient command-line tool that calculates pocket volumes from MD trajectories. A plugin for the VMD program provides a graphical user interface to facilitate input creation, run Epock and analyse the results. Availability and implementation: Epock C++ source code, Python analysis scripts, VMD Tcl plugin, documentation and installation instructions are freely available at http://epock.bitbucket.org. Contact:benoist.laurent@gmail.com or baaden@smplinux.de Supplementary information:Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Benoist Laurent
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France and Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Matthieu Chavent
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France and Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Tristan Cragnolini
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France and Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Anna Caroline E Dahl
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France and Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Samuela Pasquali
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France and Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Philippe Derreumaux
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France and Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Mark S P Sansom
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France and Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Marc Baaden
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France and Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
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21
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Sterpone F, Melchionna S, Tuffery P, Pasquali S, Mousseau N, Cragnolini T, Chebaro Y, St-Pierre JF, Kalimeri M, Barducci A, Laurin Y, Tek A, Baaden M, Nguyen PH, Derreumaux P. The OPEP protein model: from single molecules, amyloid formation, crowding and hydrodynamics to DNA/RNA systems. Chem Soc Rev 2014; 43:4871-93. [PMID: 24759934 PMCID: PMC4426487 DOI: 10.1039/c4cs00048j] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The OPEP coarse-grained protein model has been applied to a wide range of applications since its first release 15 years ago. The model, which combines energetic and structural accuracy and chemical specificity, allows the study of single protein properties, DNA-RNA complexes, amyloid fibril formation and protein suspensions in a crowded environment. Here we first review the current state of the model and the most exciting applications using advanced conformational sampling methods. We then present the current limitations and a perspective on the ongoing developments.
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Affiliation(s)
- Fabio Sterpone
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, IBPC, 13 rue Pierre et Marie Curie, 75005, Paris, France.
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22
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Cragnolini T, Sutherland-Cash KH, Wales D, Pasquali S, Derreumaux P. Wide Exploration of OPEP Protein Energy Landscapes using Advanced Monte Carlo Methods. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.1505] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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23
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Abstract
Although RNAs play many cellular functions, little is known about the dynamics and thermodynamics of these molecules. In principle, all-atom molecular dynamics simulations can investigate these issues, but with current computer facilities, these simulations have been limited to small RNAs and to short times. HiRe-RNA, a recently proposed high-resolution coarse-grained RNA that captures many geometric details such as base pairing and stacking, is able to fold RNA molecules to near-native structures in a short computational time. So far, it had been applied to simple hairpins, and here we present its application to duplexes of a couple dozen nucleotides and show how with replica exchange molecular dynamics (REMD) we can easily predict the correct double helix from a completely random configuration and study the dissociation curve. To show the versatility of our model, we present an application to a double stranded DNA molecule as well. A reconstruction algorithm allows us to obtain full atom structures from the coarse-grained model. Through atomistic molecular dynamics (MD), we can compare the dynamics starting from a representative structure of a low temperature replica or from the experimental structure, and show how the two are statistically identical, highlighting the validity of a coarse-grained approach for structured RNAs and DNAs.
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Affiliation(s)
- Tristan Cragnolini
- Laboratoire de Biochimie Théorique UPR 9080 CNRS, Université Paris Diderot, Sorbonne, Paris Citè, IBPC 13 rue Pierre et Marie Curie, 75005 Paris, France
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Fuglebakk E, Tiwari S, Hollup SM, Skjaerven L, Cragnolini T, Tekle K, Grindhaug SH, Reuter N. Comparing Normal Modes of Protein Structures using Webnm@ 2.0. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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