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Strizzi S, Bernardo L, D'Ursi P, Urbinati C, Bianco A, Limanaqi F, Manconi A, Milanesi M, Macchi A, Di Silvestre D, Cavalleri A, Pareschi G, Rusnati M, Clerici M, Mauri P, Biasin M. An innovative strategy to investigate microbial protein modifications in a reliable fast and sensitive way: A therapy oriented proof of concept based on UV-C irradiation of SARS-CoV-2 spike protein. Pharmacol Res 2023; 194:106862. [PMID: 37479104 DOI: 10.1016/j.phrs.2023.106862] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 07/04/2023] [Accepted: 07/18/2023] [Indexed: 07/23/2023]
Abstract
The characterization of modifications of microbial proteins is of primary importance to dissect pathogen lifecycle mechanisms and could be useful in identifying therapeutic targets. Attempts to solve this issue yielded only partial and non-exhaustive results. We developed a multidisciplinary approach by coupling in vitro infection assay, mass spectrometry (MS), protein 3D modelling, and surface plasma resonance (SPR). As a proof of concept, the effect of low UV-C (273 nm) irradiation on SARS-CoV-2 spike (S) protein was investigated. Following UV-C exposure, MS analysis identified, among other modifications, the disruption of a disulphide bond within the conserved S2 subunit of S protein. Computational analyses revealed that this bond breakage associates with an allosteric effect resulting in the generation of a closed conformation with a reduced ability to bind the ACE2 receptor. The UV-C-induced reduced affinity of S protein for ACE2 was further confirmed by SPR analyses and in vitro infection assays. This comprehensive approach pinpoints the S2 domain of S protein as a potential therapeutic target to prevent SARS-CoV-2 infection. Notably, this workflow could be used to screen a wide variety of microbial protein domains, resulting in a precise molecular fingerprint and providing new insights to adequately address future epidemics.
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Affiliation(s)
- Sergio Strizzi
- Department of Biomedical and Clinical Sciences, University of Milan, Via G.B. Grassi, 20122 Milan, Italy
| | - Letizia Bernardo
- Institute for Biomedical Technologies, National Research Council (ITB-CNR), 20054 Segrate, MI, Italy
| | - Pasqualina D'Ursi
- Institute for Biomedical Technologies, National Research Council (ITB-CNR), 20054 Segrate, MI, Italy
| | - Chiara Urbinati
- Unit of Macromolecular Interaction Analysis, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Andrea Bianco
- Italian National Institute for Astrophysics (INAF) - Brera Astronomical Observatory, Via E. Bianchi, 46, Merate, 23807 Lecco, Italy
| | - Fiona Limanaqi
- Department of Biomedical and Clinical Sciences, University of Milan, Via G.B. Grassi, 20122 Milan, Italy; Department of Pathophysiology and Transplantation, University of Milan, Via Francesco Sforza, 20122 Milan, Italy
| | - Andrea Manconi
- Institute for Biomedical Technologies, National Research Council (ITB-CNR), 20054 Segrate, MI, Italy
| | - Maria Milanesi
- Institute for Biomedical Technologies, National Research Council (ITB-CNR), 20054 Segrate, MI, Italy; Unit of Macromolecular Interaction Analysis, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Alberto Macchi
- Italian National Institute for Astrophysics (INAF) - Brera Astronomical Observatory, Via E. Bianchi, 46, Merate, 23807 Lecco, Italy
| | - Dario Di Silvestre
- Institute for Biomedical Technologies, National Research Council (ITB-CNR), 20054 Segrate, MI, Italy
| | - Adalberto Cavalleri
- Epidemiology and Prevention Unit, IRCCS Foundation, Istituto Nazionale dei Tumori, Via Giacomo Venezian, 1, 20133 Milan, Italy
| | - Giovanni Pareschi
- Italian National Institute for Astrophysics (INAF) - Brera Astronomical Observatory, Via E. Bianchi, 46, Merate, 23807 Lecco, Italy
| | - Marco Rusnati
- Unit of Macromolecular Interaction Analysis, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Mario Clerici
- Department of Pathophysiology and Transplantation, University of Milan, Via Francesco Sforza, 20122 Milan, Italy; Don C. Gnocchi Foundation, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation, Via A. Capecelatro 66, 20148 Milan, íItaly
| | - PierLuigi Mauri
- Institute for Biomedical Technologies, National Research Council (ITB-CNR), 20054 Segrate, MI, Italy; Interdisciplinary Research Center "Health Science", Sant'Anna School of Advanced Studies, 56127 Pisa, Italy.
| | - Mara Biasin
- Department of Biomedical and Clinical Sciences, University of Milan, Via G.B. Grassi, 20122 Milan, Italy
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Roy S, Booth CE, Powell-Pierce AD, Schulz AM, Skare JT, Garcia BL. Conformational dynamics of complement protease C1r inhibitor proteins from Lyme disease- and relapsing fever-causing spirochetes. J Biol Chem 2023; 299:104972. [PMID: 37380082 PMCID: PMC10413161 DOI: 10.1016/j.jbc.2023.104972] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 06/16/2023] [Accepted: 06/19/2023] [Indexed: 06/30/2023] Open
Abstract
Borrelial pathogens are vector-borne etiological agents known to cause Lyme disease, relapsing fever, and Borrelia miyamotoi disease. These spirochetes each encode several surface-localized lipoproteins that bind components of the human complement system to evade host immunity. One borrelial lipoprotein, BBK32, protects the Lyme disease spirochete from complement-mediated attack via an alpha helical C-terminal domain that interacts directly with the initiating protease of the classical complement pathway, C1r. In addition, the B. miyamotoi BBK32 orthologs FbpA and FbpB also inhibit C1r, albeit via distinct recognition mechanisms. The C1r-inhibitory activities of a third ortholog termed FbpC, which is found exclusively in relapsing fever-causing spirochetes, remains unknown. Here, we report the crystal structure of the C-terminal domain of Borrelia hermsii FbpC to a limiting resolution of 1.5 Å. We used surface plasmon resonance and assays of complement function to demonstrate that FbpC retains potent BBK32-like anticomplement activities. Based on the structure of FbpC, we hypothesized that conformational dynamics of the complement inhibitory domains of borrelial C1r inhibitors may differ. To test this, we utilized the crystal structures of the C-terminal domains of BBK32, FbpA, FbpB, and FbpC to carry out molecular dynamics simulations, which revealed borrelial C1r inhibitors adopt energetically favored open and closed states defined by two functionally critical regions. Taken together, these results advance our understanding of how protein dynamics contribute to the function of bacterial immune evasion proteins and reveal a surprising plasticity in the structures of borrelial C1r inhibitors.
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Affiliation(s)
- Sourav Roy
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA
| | - Charles E Booth
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA
| | - Alexandra D Powell-Pierce
- Department of Microbial Pathogenesis and Immunology, School of Medicine, Texas A&M University, Bryan, Texas, USA
| | - Anna M Schulz
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA
| | - Jon T Skare
- Department of Microbial Pathogenesis and Immunology, School of Medicine, Texas A&M University, Bryan, Texas, USA.
| | - Brandon L Garcia
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA.
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3
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Roy S, Booth CE, Powell-Pierce AD, Schulz AM, Skare JT, Garcia BL. "Conformational dynamics of C1r inhibitor proteins from Lyme disease and relapsing fever spirochetes". BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.01.530473. [PMID: 36909632 PMCID: PMC10002728 DOI: 10.1101/2023.03.01.530473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
Abstract
Borrelial pathogens are vector-borne etiological agents of Lyme disease, relapsing fever, and Borrelia miyamotoi disease. These spirochetes each encode several surface-localized lipoproteins that bind to components of the human complement system. BBK32 is an example of a borrelial lipoprotein that protects the Lyme disease spirochete from complement-mediated attack. The complement inhibitory activity of BBK32 arises from an alpha helical C-terminal domain that interacts directly with the initiating protease of the classical pathway, C1r. Borrelia miyamotoi spirochetes encode BBK32 orthologs termed FbpA and FbpB, and these proteins also inhibit C1r, albeit via distinct recognition mechanisms. The C1r-inhibitory activities of a third ortholog termed FbpC, which is found exclusively in relapsing fever spirochetes, remains unknown. Here we report the crystal structure of the C-terminal domain of B. hermsii FbpC to a limiting resolution of 1.5 Å. Surface plasmon resonance studies and assays of complement function demonstrate that FbpC retains potent BBK32-like anti-complement activities. Based on the structure of FbpC, we hypothesized that conformational dynamics of the complement inhibitory domains of borrelial C1r inhibitors may differ. To test this, we utilized the crystal structures of the C-terminal domains of BBK32, FbpA, FbpB, and FbpC to carry out 1 µs molecular dynamics simulations, which revealed borrelial C1r inhibitors adopt energetically favored open and closed states defined by two functionally critical regions. This study advances our understanding of how protein dynamics contribute to the function of bacterial immune evasion proteins and reveals a surprising plasticity in the structures of borrelial C1r inhibitors.
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Affiliation(s)
- Sourav Roy
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Charles E. Booth
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Alexandra D. Powell-Pierce
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University, Bryan, TX, United States of America
| | - Anna M. Schulz
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Jon T. Skare
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University, Bryan, TX, United States of America
- Correspondence to Jon T. Skare and () and Brandon L. Garcia ()
| | - Brandon L. Garcia
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
- Correspondence to Jon T. Skare and () and Brandon L. Garcia ()
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Defective ORF8 dimerization in SARS-CoV-2 delta variant leads to a better adaptive immune response due to abrogation of ORF8-MHC1 interaction. Mol Divers 2023; 27:45-57. [PMID: 35243596 PMCID: PMC8893242 DOI: 10.1007/s11030-022-10405-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 02/08/2022] [Indexed: 02/08/2023]
Abstract
In India, during the second wave of the COVID-19 pandemic, the breakthrough infections were mainly caused by the SARS-COV-2 delta variant (B.1.617.2). It was reported that, among majority of the infections due to the delta variant, only 9.8% percent cases required hospitalization, whereas only 0.4% fatality was observed. Sudden dropdown in COVID-19 infections cases were observed within a short timeframe, suggesting better host adaptation with evolved delta variant. Downregulation of host immune response against SARS-CoV-2 by ORF8 induced MHC-I degradation has been reported earlier. The Delta variant carried mutations (deletion) at Asp119 and Phe120 amino acids which are critical for ORF8 dimerization. The deletions of amino acids Asp119 and Phe120 in ORF8 of delta variant resulted in structural instability of ORF8 dimer caused by disruption of hydrogen bonds and salt bridges as revealed by structural analysis and MD simulation studies. Further, flexible docking of wild type and mutant ORF8 dimer revealed reduced interaction of mutant ORF8 dimer with MHC-I as compared to wild-type ORF8 dimer with MHC-1, thus implicating its possible role in MHC-I expression and host immune response against SARS-CoV-2. We thus propose that mutant ORF8 of SARS-CoV-2 delta variant may not be hindering the MHC-I expression thereby resulting in a better immune response against the SARS-CoV-2 delta variant, which partly explains the possible reason for sudden drop of SARS-CoV-2 infection rate in the second wave of SARS-CoV-2 predominated by delta variant in India.
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Chaudhari AM, Joshi M, Kumar D, Patel A, Lokhande KB, Krishnan A, Hanack K, Filipek S, Liepmann D, Renugopalakrishnan V, Paulmurugan R, Joshi C. Evaluation of immune evasion in SARS-CoV-2 Delta and Omicron variants. Comput Struct Biotechnol J 2022; 20:4501-4516. [PMID: 35965661 PMCID: PMC9359593 DOI: 10.1016/j.csbj.2022.08.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/04/2022] [Accepted: 08/04/2022] [Indexed: 12/18/2022] Open
Abstract
Emerging SARS-CoV-2 variants with higher transmissibility and immune escape remain a persistent threat across the globe. This is evident from the recent outbreaks of the Delta (B.1.617.2) and Omicron variants. These variants have originated from different continents and spread across the globe. In this study, we explored the genomic and structural basis of these variants for their lineage defining mutations of the spike protein through computational analysis, protein modeling, and molecular dynamic (MD) simulations. We further experimentally validated the importance of these deletion mutants for their immune escape using a pseudovirus-based neutralization assay, and an antibody (4A8) that binds directly to the spike protein's NTD. Delta variant with the deletion and mutations in the NTD revealed a better rigidity and reduced flexibility as compared to the wild-type spike protein (Wuhan isolate). Furthermore, computational studies of 4A8 monoclonal antibody (mAb) revealed a reduced binding of Delta variant compared to the wild-type strain. Similarly, the MD simulation data and virus neutralization assays revealed that the Omicron also exhibits immune escape, as antigenic beta-sheets appear to be disrupted. The results of the present study demonstrate the higher possibility of immune escape and thereby achieved better fitness advantages by the Delta and Omicron variants, which warrants further demonstrations through experimental evidences. Our study, based on in-silico computational modelling, simulations, and pseudovirus-based neutralization assay, highlighted and identified the probable mechanism through which the Delta and Omicron variants are more pathogenically evolved with higher transmissibility as compared to the wild-type strain.
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Affiliation(s)
- Armi M Chaudhari
- Gujarat Biotechnology Research Centre (GBRC), Department of Science and Technology, Government of Gujarat, Gandhinagar 382011, India
| | - Madhvi Joshi
- Gujarat Biotechnology Research Centre (GBRC), Department of Science and Technology, Government of Gujarat, Gandhinagar 382011, India
| | - Dinesh Kumar
- Gujarat Biotechnology Research Centre (GBRC), Department of Science and Technology, Government of Gujarat, Gandhinagar 382011, India
| | - Amrutlal Patel
- Gujarat Biotechnology Research Centre (GBRC), Department of Science and Technology, Government of Gujarat, Gandhinagar 382011, India
| | - Kiran Bharat Lokhande
- Gujarat Biotechnology Research Centre (GBRC), Department of Science and Technology, Government of Gujarat, Gandhinagar 382011, India
| | - Anandi Krishnan
- Cellular Pathway Imaging Laboratory (CPIL), Department of Radiology, Stanford University School of Medicine, Palo Alto, CA 94304, United States
- Department of Pathology, Stanford University School of Medicine, Palo Alto, CA 94304, United States
| | - Katja Hanack
- Immunotechnology Group, Department of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Slawomir Filipek
- Faculty of Chemistry & Biological and Chemical Research, Centre, University of Warsaw, ul, Pasteura 1, 02-093 Warsaw, Poland
| | - Dorian Liepmann
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, United States
| | - Venkatesan Renugopalakrishnan
- Department of Chemistry, Northeastern University, Boston Children's Hospital, Harvard Medical School, Boston, MGB Center for COVID Innovation, MA 02115, United States
| | - Ramasamy Paulmurugan
- Cellular Pathway Imaging Laboratory (CPIL), Department of Radiology, Stanford University School of Medicine, Palo Alto, CA 94304, United States
| | - Chaitanya Joshi
- Gujarat Biotechnology Research Centre (GBRC), Department of Science and Technology, Government of Gujarat, Gandhinagar 382011, India
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6
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Tekpinar M, Neron B, Delarue M. Extracting Dynamical Correlations and Identifying Key Residues for Allosteric Communication in Proteins by correlationplus. J Chem Inf Model 2021; 61:4832-4838. [PMID: 34652149 DOI: 10.1021/acs.jcim.1c00742] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Extracting dynamical pairwise correlations and identifying key residues from large molecular dynamics trajectories or normal-mode analysis of coarse-grained models are important for explaining various processes like ligand binding, mutational effects, and long-distance interactions. Efficient and flexible tools to perform this task can provide new insights about residues involved in allosteric regulation and protein function. In addition, combining and comparing dynamical coupling information with sequence coevolution data can help to understand better protein function. To this aim, we developed a Python package called correlationplus to calculate, visualize, and analyze pairwise correlations. In this way, the package aids to identify key residues and interactions in proteins. The source code of correlationplus is available under LGPL version 3 at https://github.com/tekpinar/correlationplus. The current version of the package (0.2.0) can be installed with common installation methods like conda or pip in addition to source code installation. Moreover, docker images are also available for usage of the code without installation.
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Affiliation(s)
- Mustafa Tekpinar
- Unit of Architecture and Dynamics of Biological Macromolecules, Pasteur Institute, UMR 3528 CNRS, 25 Rue du Dr. Roux, 75015 Paris, France
| | - Bertrand Neron
- Computational Biology Department, Bioinformatics and Biostatistics Hub, 28 Rue du Dr. Roux, 75015 Paris, France
| | - Marc Delarue
- Unit of Architecture and Dynamics of Biological Macromolecules, Pasteur Institute, UMR 3528 CNRS, 25 Rue du Dr. Roux, 75015 Paris, France
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Shao Q, Gong W, Li C. A study on allosteric communication in U1A-snRNA binding interactions: network analysis combined with molecular dynamics data. Biophys Chem 2020; 264:106393. [PMID: 32653695 DOI: 10.1016/j.bpc.2020.106393] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 05/02/2020] [Accepted: 05/03/2020] [Indexed: 01/09/2023]
Abstract
The allosteric regulation during the binding interactions between small nuclear RNAs (snRNAs) and the associated protein factors is critical to the function of spliceosomes in alternative RNA splicing. Although network models combined with molecular dynamics simulations have shown to be powerful tools for the analysis of protein allostery, the atomic-level simulations are, however, too expensive and with limited accuracy for the large-size systems. In this work, we use a residual network model combined with a coarse-grained Gaussian network model (GNM) to investigate the binding interactions between the snRNA and the human U1A protein which is a major component of the spliceosomal U1 small nuclear ribonucleoprotein particle, and to identify the residues that play an important role in the allosteric communication in U1A during this process. We also utilize the Girvan-Newman method to detect the structural organization in U1A-snRNA recognition and interactions. Our results reveal that: (Ι) not only the residues at the binding sites that are traditionally considered to play a major role in U1A-snRNA association, but those residues that are far away from the RNA binding interface participate in the U1A's allosteric signal transmission induced by the RNA binding; (Π) the structure of U1A protein is well organized with different communities acting different roles for its RNA binding and allosteric regulation. The study demonstrates that the combination of the residual network and elastic network models is an effective and efficient method which can be readily extended to the investigation of the allosteric communication for other macromolecular interaction systems.
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Affiliation(s)
- Qi Shao
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, China
| | - Weikang Gong
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, China
| | - Chunhua Li
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, China.
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8
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Sharma M, Sharma S, Alawada A. Understanding the binding specificities of mRNA targets by the mammalian Quaking protein. Nucleic Acids Res 2020; 47:10564-10579. [PMID: 31602485 PMCID: PMC6847458 DOI: 10.1093/nar/gkz877] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 09/18/2019] [Accepted: 10/08/2019] [Indexed: 01/01/2023] Open
Abstract
Mammalian Quaking (QKI) protein, a member of STAR family of proteins is a mRNA-binding protein, which post-transcriptionally modulates the target RNA. QKI protein possesses a maxi-KH domain composed of single heterogeneous nuclear ribonucleoprotein K homology (KH) domain and C-terminal QUA2 domain, that binds a sequence-specific QKI RNA recognition element (QRE), CUAAC. To understand the binding specificities for different mRNA sequences of the KH-QUA2 domain of QKI protein, we introduced point mutations at different positions in the QRE resulting in twelve different mRNA sequences with single nucleotide change. We carried out long unbiased molecular dynamics simulations using two different sets of recently updated forcefield parameters: AMBERff14SB+RNAχOL3 and CHARMM36 (with CMAP correction). We analyzed the changes in intermolecular dynamics as a result of mutation. Our results show that AMBER forcefields performed better to model the interactions between mRNA and protein. We also calculated the binding affinities of different mRNA sequences and found that the relative order correlates to the reported experimental studies. Our study shows that the favorable binding with the formation of stable complex will occur when there is an increase of the total intermolecular contacts between mRNA and protein, but without the loss of native contacts within the KH-QUA domain.
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Affiliation(s)
- Monika Sharma
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Sector 81, Knowledge City, SAS Nagar, Punjab, India
| | - Shakshi Sharma
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Sector 81, Knowledge City, SAS Nagar, Punjab, India
| | - Apoorv Alawada
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Sector 81, Knowledge City, SAS Nagar, Punjab, India
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9
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Interpreting the Dynamics of Binding Interactions of snRNA and U1A Using a Coarse-Grained Model. Biophys J 2019; 116:1625-1636. [PMID: 30975455 DOI: 10.1016/j.bpj.2019.03.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 03/04/2019] [Accepted: 03/12/2019] [Indexed: 12/14/2022] Open
Abstract
The binding interactions of small nuclear RNAs (snRNA) and the associated protein factors are critical to the function of spliceosomes in alternatively splicing primary RNA transcripts. Although molecular dynamics simulations are a powerful tool to interpret the mechanism of biological processes, the atomic-level simulations are, however, too expensive and with limited accuracy for the large-size systems, such as snRNA-protein complexes. We extend the coarse-grained Gaussian network model, which models the RNA-protein complexes as a harmonic chain of Cα, P, and O4' atoms, to investigating the impact of the snRNA-binding interaction on the dynamic stability of the human U1A protein, which is a major component of the spliceosomal U1 small nuclear ribonucleoprotein particle. The results reveal that the first and third loops and the C-terminal helix regions of the U1A domain undergo a significant loss of flexibility upon the RNA binding due to the forming of mostly electrostatic and hydrogen bond interactions with RNA 5' stem and loop. By examining the residues whose mutations significantly change the binding free energy between U1A and snRNA, the Gaussian network model-based calculations show that not only the residues at the binding sites that are traditionally considered to play a major role in U1A-RNA association but also those residues that are far away from the RNA-binding interface can participate in the long-range allosteric signal transmission; these calculations are quantitatively consistent with the data observed in the recent snRNA binding experiments. The study demonstrates a useful avenue to utilize the simplified elastic network model to investigate the dynamics characteristics of the biologically important macromolecular interactions.
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Tekpinar M, Yildirim A. Only a Subset of Normal Modes is Sufficient to Identify Linear Correlations in Proteins. J Chem Inf Model 2018; 58:1947-1961. [DOI: 10.1021/acs.jcim.8b00486] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
| | - Ahmet Yildirim
- Department of Physics, Siirt University, 56100 Siirt, Turkey
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11
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Chattopadhyay A, Zheng M, Waller MP, Priyakumar UD. A Probabilistic Framework for Constructing Temporal Relations in Replica Exchange Molecular Trajectories. J Chem Theory Comput 2018; 14:3365-3380. [PMID: 29791153 DOI: 10.1021/acs.jctc.7b01245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Knowledge of the structure and dynamics of biomolecules is essential for elucidating the underlying mechanisms of biological processes. Given the stochastic nature of many biological processes, like protein unfolding, it is almost impossible that two independent simulations will generate the exact same sequence of events, which makes direct analysis of simulations difficult. Statistical models like Markov chains, transition networks, etc. help in shedding some light on the mechanistic nature of such processes by predicting long-time dynamics of these systems from short simulations. However, such methods fall short in analyzing trajectories with partial or no temporal information, for example, replica exchange molecular dynamics or Monte Carlo simulations. In this work, we propose a probabilistic algorithm, borrowing concepts from graph theory and machine learning, to extract reactive pathways from molecular trajectories in the absence of temporal data. A suitable vector representation was chosen to represent each frame in the macromolecular trajectory (as a series of interaction and conformational energies), and dimensionality reduction was performed using principal component analysis (PCA). The trajectory was then clustered using a density-based clustering algorithm, where each cluster represents a metastable state on the potential energy surface (PES) of the biomolecule under study. A graph was created with these clusters as nodes with the edges learned using an iterative expectation maximization algorithm. The most reactive path is conceived as the widest path along this graph. We have tested our method on RNA hairpin unfolding trajectory in aqueous urea solution. Our method makes the understanding of the mechanism of unfolding in the RNA hairpin molecule more tractable. As this method does not rely on temporal data, it can be used to analyze trajectories from Monte Carlo sampling techniques and replica exchange molecular dynamics (REMD).
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Affiliation(s)
- Aditya Chattopadhyay
- Centre for Computational Natural Sciences and Bioinformatics , International Institute of Information Technology , Hyderabad 500032 , India
| | - Min Zheng
- Centre for Multiscale Theory and Computation , Westfälische Wilhelms-Universität Münster , Münster , Germany
| | - Mark P Waller
- Department of Physics and International Centre for Quantum and Molecular Structures , Shanghai University , Shanghai , 200444 , People's Republic of China
| | - U Deva Priyakumar
- Centre for Computational Natural Sciences and Bioinformatics , International Institute of Information Technology , Hyderabad 500032 , India
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12
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Patra KK, Bhattacharya A, Bhattacharya S. Allosteric Signal Transduction in HIV-1 Restriction Factor SAMHD1 Proceeds via Reciprocal Handshake across Monomers. J Chem Inf Model 2017; 57:2523-2538. [PMID: 28956603 DOI: 10.1021/acs.jcim.7b00279] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The sterile alpha motif and histidine-aspartate domain-containing protein 1 (or SAMHD1), a human dNTP-triphosphohydrolase, contributes to HIV-1 restriction in select terminally differentiated cells of the immune system. The catalytically active form of the protein is an allosterically triggered tetramer, whose HIV-1 restriction properties are attributed to its dNTP-triphosphohydrolase activity. The tetramer itself is assembled by a GTP/dNTP combination. This enzyme uses the strategy of deoxynucleotide starvation, which is thought to prevent effective reverse transcription of the retroviral genome-hence, restricting HIV-1 propagation. HIV-2 and SIV have evolved defenses against SAMHD1, underscoring its role in restriction. Previous studies have provided high-resolution structures of GTP/dNTP-bound enzyme complexes but have not been able to provide information on dynamics. In this study, we have used correlation network analysis along with MD techniques to study the flow of allosteric information across the active complex. We have found evidence of a reciprocal allosteric "handshake" occurring across monomeric units. We have also uncovered a short linker region as the nexus for funnelling the regulatory signal from phosphorylation at T592 from the surface to the interior core of the protein.
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Affiliation(s)
- Kajwal Kumar Patra
- Department of Physics, Indian Institute of Technology Guwahati , Guwahati, Assam, India 781039
| | - Akash Bhattacharya
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio , San Antonio, Texas 78229-3900, United States
| | - Swati Bhattacharya
- Department of Physics, Indian Institute of Technology Guwahati , Guwahati, Assam, India 781039.,Department of Chemical Engineering, Indian Institute of Technology Bombay , Mumbai, India 400076
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13
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Sharma M, Anirudh CR. Mechanism of mRNA-STAR domain interaction: Molecular dynamics simulations of Mammalian Quaking STAR protein. Sci Rep 2017; 7:12567. [PMID: 28974714 PMCID: PMC5626755 DOI: 10.1038/s41598-017-12930-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 09/20/2017] [Indexed: 01/08/2023] Open
Abstract
STAR proteins are evolutionary conserved mRNA-binding proteins that post-transcriptionally regulate gene expression at all stages of RNA metabolism. These proteins possess conserved STAR domain that recognizes identical RNA regulatory elements as YUAAY. Recently reported crystal structures show that STAR domain is composed of N-terminal QUA1, K-homology domain (KH) and C-terminal QUA2, and mRNA binding is mediated by KH-QUA2 domain. Here, we present simulation studies done to investigate binding of mRNA to STAR protein, mammalian Quaking protein (QKI). We carried out conventional MD simulations of STAR domain in presence and absence of mRNA, and studied the impact of mRNA on the stability, dynamics and underlying allosteric mechanism of STAR domain. Our unbiased simulations results show that presence of mRNA stabilizes the overall STAR domain by reducing the structural deviations, correlating the ‘within-domain’ motions, and maintaining the native contacts information. Absence of mRNA not only influenced the essential modes of motion of STAR domain, but also affected the connectivity of networks within STAR domain. We further explored the dissociation of mRNA from STAR domain using umbrella sampling simulations, and the results suggest that mRNA binding to STAR domain occurs in multi-step: first conformational selection of mRNA backbone conformations, followed by induced fit mechanism as nucleobases interact with STAR domain.
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Affiliation(s)
- Monika Sharma
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Sector 81, Knowledge City, SAS Nagar, Punjab, India.
| | - C R Anirudh
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Sector 81, Knowledge City, SAS Nagar, Punjab, India
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14
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Foster CA, West AH. Use of restrained molecular dynamics to predict the conformations of phosphorylated receiver domains in two-component signaling systems. Proteins 2016; 85:155-176. [PMID: 27802580 PMCID: PMC5242315 DOI: 10.1002/prot.25207] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 10/22/2016] [Accepted: 10/25/2016] [Indexed: 01/22/2023]
Abstract
Two‐component signaling (TCS) is the primary means by which bacteria, as well as certain plants and fungi, respond to external stimuli. Signal transduction involves stimulus‐dependent autophosphorylation of a sensor histidine kinase and phosphoryl transfer to the receiver domain of a downstream response regulator. Phosphorylation acts as an allosteric switch, inducing structural and functional changes in the pathway's components. Due to their transient nature, phosphorylated receiver domains are challenging to characterize structurally. In this work, we provide a methodology for simulating receiver domain phosphorylation to predict conformations that are nearly identical to experimental structures. Using restrained molecular dynamics, phosphorylated conformations of receiver domains can be reliably sampled on nanosecond timescales. These simulations also provide data on conformational dynamics that can be used to identify regions of functional significance related to phosphorylation. We first validated this approach on several well‐characterized receiver domains and then used it to compare the upstream and downstream components of the fungal Sln1 phosphorelay. Our results demonstrate that this technique provides structural insight, obtained in the absence of crystallographic or NMR information, regarding phosphorylation‐induced conformational changes in receiver domains that regulate the output of their associated signaling pathway. To our knowledge, this is the first time such a protocol has been described that can be broadly applied to TCS proteins for predictive purposes. Proteins 2016; 85:155–176. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Clay A Foster
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma
| | - Ann H West
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma
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15
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Ghaemi Z, Guzman I, Baek JUJ, Gruebele M, Luthey-Schulten Z. Estimation of Relative Protein–RNA Binding Strengths from Fluctuations in the Bound State. J Chem Theory Comput 2016; 12:4593-9. [DOI: 10.1021/acs.jctc.6b00418] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Zhaleh Ghaemi
- Department of Chemistry, ‡Department of Biochemistry, ¶Department of Physics, §Center for the Physics of Living Cells, and ∥Center for Biophysics
and Quantitative Biology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Irisbel Guzman
- Department of Chemistry, ‡Department of Biochemistry, ¶Department of Physics, §Center for the Physics of Living Cells, and ∥Center for Biophysics
and Quantitative Biology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Jung-un Julia Baek
- Department of Chemistry, ‡Department of Biochemistry, ¶Department of Physics, §Center for the Physics of Living Cells, and ∥Center for Biophysics
and Quantitative Biology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Martin Gruebele
- Department of Chemistry, ‡Department of Biochemistry, ¶Department of Physics, §Center for the Physics of Living Cells, and ∥Center for Biophysics
and Quantitative Biology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Zaida Luthey-Schulten
- Department of Chemistry, ‡Department of Biochemistry, ¶Department of Physics, §Center for the Physics of Living Cells, and ∥Center for Biophysics
and Quantitative Biology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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16
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A compare-and-contrast NMR dynamics study of two related RRMs: U1A and SNF. Biophys J 2015; 107:208-19. [PMID: 24988355 DOI: 10.1016/j.bpj.2014.05.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 05/14/2014] [Accepted: 05/19/2014] [Indexed: 11/21/2022] Open
Abstract
The U1A/U2B″/SNF family of small nuclear ribonucleoproteins uses a phylogenetically conserved RNA recognition motif (RRM1) to bind RNA stemloops in U1 and/or U2 small nuclear RNA (snRNA). RRMs are characterized by their α/β sandwich topology, and these RRMs use their β-sheet as the RNA binding surface. Unique to this RRM family is the tyrosine-glutamine-phenylalanine (YQF) triad of solvent-exposed residues that are displayed on the β-sheet surface; the aromatic residues form a platform for RNA nucleobases to stack. U1A, U2B″, and SNF have very different patterns of RNA binding affinity and specificity, however, so here we ask how YQF in Drosophila SNF RRM1 contributes to RNA binding, as well as to domain stability and dynamics. Thermodynamic double-mutant cycles using tyrosine and phenylalanine substitutions probe the communication between those two residues in the free and bound states of the RRM. NMR experiments follow corresponding changes in the glutamine side-chain amide in both U1A and SNF, providing a physical picture of the RRM1 β-sheet surface. NMR relaxation and dispersion experiments compare fast (picosecond to nanosecond) and intermediate (microsecond-to-millisecond) dynamics of U1A and SNF RRM1. We conclude that there is a network of amino acid interactions involving Tyr-Gln-Phe in both SNF and U1A RRM1, but whereas mutations of the Tyr-Gln-Phe triad result in small local responses in U1A, they produce extensive microsecond-to-millisecond global motions throughout SNF that alter the conformational states of the RRM.
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17
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Williams SG, Hall KB. Binding affinity and cooperativity control U2B″/snRNA/U2A' RNP formation. Biochemistry 2014; 53:3727-37. [PMID: 24866816 PMCID: PMC4067145 DOI: 10.1021/bi500438e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
![]()
The U1A and U2B″ proteins
are components of the U1 and U2
snRNPs, respectively, where they bind to snRNA stemloops. While localization
of U1A and U2B″ to their respective snRNP is a well-known phenomenon,
binding of U2B″ to U2 snRNA is typically thought to be accompanied
by the U2A′ protein. The molecular mechanisms that lead to
formation of the RNA/U2B″/U2A′ complex and its localization
to the U2 snRNP are investigated here, using a combination of in vitro RNA–protein and protein–protein fluorescence
and isothermal titration calorimetry binding experiments. We find
that U2A′ protein binds to U2B″ with nanomolar affinity
but binds to U1A with only micromolar affinity. In addition, there
is RNA-dependent cooperativity (linkage) between protein–protein
and protein–RNA binding. The unique combination of tight binding
and cooperativity ensures that the U2A′/U2B″ complex
is partitioned only to the U2 snRNP.
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Affiliation(s)
- Sandra G Williams
- Department of Biochemistry and Molecular Biophysics, Washington University Medical School , St. Louis, Missouri 63110, United States
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18
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Kurisaki I, Takayanagi M, Nagaoka M. Combined mechanism of conformational selection and induced fit in U1A-RNA molecular recognition. Biochemistry 2014; 53:3646-57. [PMID: 24828852 DOI: 10.1021/bi401708q] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In this study, we demonstrate that U1A-RNA molecular recognition is mediated by a combined mechanism of conformational selection and induced fit. The binding of U1A to RNA has been discussed in the context of induced fit that involves the reorientation of the α-helix in the C-terminal region (Helix-C) of U1A to permit RNA access only when U1A correctly recognizes RNA. However, according to our molecular dynamics simulations, even in the absence of RNA, Helix-C spontaneously reoriented to permit RNA access. Nonetheless, such a conformational change was still incomplete. Helix-C was often partially or even fully unfolded and in an infrequent RNA-accessible conformation, which can be detected using state-of-the-art nuclear magnetic resonance methodology. These results suggest that the formation of an energetically stabilized complex is promoted by specific interactions between U1A and RNA. In conclusion, in the recognition of RNA by U1A protein, we propose a combined mechanism that requires the reorientation of Helix-C and the subsequent contact with RNA through conformational selection, although the stabilization of the U1A-RNA complex is caused by induced fit. We further propose a modification to the conventional assumption regarding the mechanism of U1A-RNA molecular recognition.
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Affiliation(s)
- Ikuo Kurisaki
- Graduate School of Information Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
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19
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Fratev F, Mihaylova E, Pajeva I. Combination of Genetic Screening and Molecular Dynamics as a Useful Tool for Identification of Disease-Related Mutations: ZASP PDZ Domain G54S Mutation Case. J Chem Inf Model 2014; 54:1524-36. [DOI: 10.1021/ci5001136] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Filip Fratev
- Institute
of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Block 105, 1113 Sofia, Bulgaria
- Micar21 Ltd., Persenk Str. 34B, 1407 Sofia, Bulgaria
| | | | - Ilza Pajeva
- Institute
of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Block 105, 1113 Sofia, Bulgaria
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20
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Abstract
A 3D atomistic model of a plant cellulose synthase (CESA) has remained elusive despite over forty years of experimental effort. Here, we report a computationally predicted 3D structure of 506 amino acids of cotton CESA within the cytosolic region. Comparison of the predicted plant CESA structure with the solved structure of a bacterial cellulose-synthesizing protein validates the overall fold of the modeled glycosyltransferase (GT) domain. The coaligned plant and bacterial GT domains share a six-stranded β-sheet, five α-helices, and conserved motifs similar to those required for catalysis in other GT-2 glycosyltransferases. Extending beyond the cross-kingdom similarities related to cellulose polymerization, the predicted structure of cotton CESA reveals that plant-specific modules (plant-conserved region and class-specific region) fold into distinct subdomains on the periphery of the catalytic region. Computational results support the importance of the plant-conserved region and/or class-specific region in CESA oligomerization to form the multimeric cellulose-synthesis complexes that are characteristic of plants. Relatively high sequence conservation between plant CESAs allowed mapping of known mutations and two previously undescribed mutations that perturb cellulose synthesis in Arabidopsis thaliana to their analogous positions in the modeled structure. Most of these mutation sites are near the predicted catalytic region, and the confluence of other mutation sites supports the existence of previously undefined functional nodes within the catalytic core of CESA. Overall, the predicted tertiary structure provides a platform for the biochemical engineering of plant CESAs.
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21
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Rau M, Stump WT, Hall KB. Intrinsic flexibility of snRNA hairpin loops facilitates protein binding. RNA (NEW YORK, N.Y.) 2012; 18:1984-1995. [PMID: 23012481 PMCID: PMC3479389 DOI: 10.1261/rna.035006.112] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 08/02/2012] [Indexed: 06/01/2023]
Abstract
Stem-loop II of U1 snRNA and Stem-loop IV of U2 snRNA typically have 10 or 11 nucleotides in their loops. The fluorescent nucleobase 2-aminopurine was used as a substitute for the adenines in each loop to probe the local and global structures and dynamics of these unusually long loops. Using steady-state and time-resolved fluorescence, we find that, while the bases in the loops are stacked, they are able to undergo significant local motion on the picosecond/nanosecond timescale. In addition, the loops have a global conformational change at low temperatures that occurs on the microsecond timescale, as determined using laser T-jump experiments. Nucleobase and loop motions are present at temperatures far below the melting temperature of the hairpin stem, which may facilitate the conformational change required for specific protein binding to these RNA loops.
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Affiliation(s)
- Michael Rau
- Department of Biochemistry and Molecular Biophysics, Washington University Medical School, St. Louis, Missouri 63110, USA
| | - W. Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University Medical School, St. Louis, Missouri 63110, USA
| | - Kathleen B. Hall
- Department of Biochemistry and Molecular Biophysics, Washington University Medical School, St. Louis, Missouri 63110, USA
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22
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Papaleo E, Renzetti G. Coupled motions during dynamics reveal a tunnel toward the active site regulated by the N-terminal α-helix in an acylaminoacyl peptidase. J Mol Graph Model 2012; 38:226-34. [PMID: 23085164 DOI: 10.1016/j.jmgm.2012.06.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Revised: 06/15/2012] [Accepted: 06/26/2012] [Indexed: 10/28/2022]
Abstract
Acylaminoacyl peptidase (AAP) subfamily belongs to the prolyl oligopeptidase (POP) family of serine-proteases. There is a great interest in the definition of molecular mechanisms related to the activity and substrate recognition of these complex multi-domain enzymes. The active site relies at the interface between the C-terminal catalytic domain and the β-propeller domain, whose N-terminal region acts as a bridge to the hydrolase domain. In AAP, the N-terminal extension is characterized by a structurally conserved α1-helix, which is known to affect thermal stability and thermal dependence of the catalytic activity. In the present contribution, results from hundreds nanosecond all-atom molecular dynamics simulations, along with analyses of the networks of cross-correlated motions of a member of the AAP subfamily are discussed. The MD investigation identifies a tunnel that from the surrounding of the N-terminal α1-helix bring to the catalytic site. This cavity seems to be regulated by conformational changes of the α1-helix itself during the dynamics. The evidence here provided can be a useful guide for a better understanding of the mechanistic aspects related to AAP activity, but also for drug design purposes.
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Affiliation(s)
- Elena Papaleo
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, P.zza della Scienza 2, 20126 Milan, Italy.
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23
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Negureanu L, Salsbury FR. The molecular origin of the MMR-dependent apoptosis pathway from dynamics analysis of MutSα-DNA complexes. J Biomol Struct Dyn 2012; 30:347-61. [PMID: 22712459 PMCID: PMC3389999 DOI: 10.1080/07391102.2012.680034] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The cellular response to DNA damage signaling by mismatch-repair (MMR) proteins is incompletely understood. It is generally accepted that MMR-dependent apoptosis pathway in response to DNA damage detection is independent of MMR's DNA repair function. In this study, we investigate correlated motions in response to the binding of mismatched and platinum cross-linked DNA fragments by MutSα, as derived from 50 ns molecular dynamics simulations. The protein dynamics in response to the mismatched and damaged DNA recognition suggests that MutSα signals their recognition through independent pathways providing evidence for the molecular origin of the MMR-dependent apoptosis. MSH2 subunit is indicated to play a key role in signaling both mismatched and damaged DNA recognition; localized and collective motions within the protein allow identifying sites on the MSH2 surface possible involved in recruiting proteins responsible for downstream events. Unlike in the mismatch complex, predicted key communication sites specific for the damage recognition are on the list of known cancer-causing mutations or deletions. This confirms MSH2's role in signaling DNA damage-induced apoptosis and suggests that defects in MMR alone is sufficient to trigger tumorigenesis, supporting the experimental evidence that MMR-damage response function could protect from the early occurrence of tumors. Identifying these particular communication sites may have implications for the treatment of cancers that are not defective for MMR, but are unable to function optimally for MMR-dependent responses following DNA damage such as the case of resistance to cisplatin.
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24
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Papaleo E, Renzetti G, Tiberti M. Mechanisms of intramolecular communication in a hyperthermophilic acylaminoacyl peptidase: a molecular dynamics investigation. PLoS One 2012; 7:e35686. [PMID: 22558199 PMCID: PMC3338720 DOI: 10.1371/journal.pone.0035686] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 03/21/2012] [Indexed: 11/25/2022] Open
Abstract
Protein dynamics and the underlying networks of intramolecular interactions and communicating residues within the three-dimensional (3D) structure are known to influence protein function and stability, as well as to modulate conformational changes and allostery. Acylaminoacyl peptidase (AAP) subfamily of enzymes belongs to a unique class of serine proteases, the prolyl oligopeptidase (POP) family, which has not been thoroughly investigated yet. POPs have a characteristic multidomain three-dimensional architecture with the active site at the interface of the C-terminal catalytic domain and a β-propeller domain, whose N-terminal region acts as a bridge to the hydrolase domain. In the present contribution, protein dynamics signatures of a hyperthermophilic acylaminoacyl peptidase (AAP) of the prolyl oligopeptidase (POP) family, as well as of a deletion variant and alanine mutants (I12A, V13A, V16A, L19A, I20A) are reported. In particular, we aimed at identifying crucial residues for long range communications to the catalytic site or promoting the conformational changes to switch from closed to open ApAAP conformations. Our investigation shows that the N-terminal α1-helix mediates structural intramolecular communication to the catalytic site, concurring to the maintenance of a proper functional architecture of the catalytic triad. Main determinants of the effects induced by α1-helix are a subset of hydrophobic residues (V16, L19 and I20). Moreover, a subset of residues characterized by relevant interaction networks or coupled motions have been identified, which are likely to modulate the conformational properties at the interdomain interface.
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Affiliation(s)
- Elena Papaleo
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy.
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25
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Dynamical allosterism in the mechanism of action of DNA mismatch repair protein MutS. Biophys J 2012; 101:1730-9. [PMID: 21961599 DOI: 10.1016/j.bpj.2011.08.039] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 07/19/2011] [Accepted: 08/17/2011] [Indexed: 11/21/2022] Open
Abstract
The multidomain protein Thermus aquaticus MutS and its prokaryotic and eukaryotic homologs recognize DNA replication errors and initiate mismatch repair. MutS actions are fueled by ATP binding and hydrolysis, which modulate its interactions with DNA and other proteins in the mismatch-repair pathway. The DNA binding and ATPase activities are allosterically coupled over a distance of ∼70 Å, and the molecular mechanism of coupling has not been clarified. To address this problem, all-atom molecular dynamics simulations of ∼150 ns including explicit solvent were performed on two key complexes--ATP-bound and ATP-free MutS⋅DNA(+T bulge). We used principal component analysis in fluctuation space to assess ATP ligand-induced changes in MutS structure and dynamics. The molecular dynamics-calculated ensembles of thermally accessible structures showed markedly small differences between the two complexes. However, analysis of the covariance of dynamical fluctuations revealed a number of potentially significant interresidue and interdomain couplings. Moreover, principal component analysis revealed clusters of correlated atomic fluctuations linking the DNA and nucleotide binding sites, especially in the ATP-bound MutS⋅DNA(+T) complex. These results support the idea that allosterism between the nucleotide and DNA binding sites in MutS can occur via ligand-induced changes in motion, i.e., dynamical allosterism.
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26
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HU JP, LIU W, TANG DY, ZHANG YQ, CHANG S. Study on The Binding Mode and Mobility of HIV-1 Integrase With L708, 906 Inhibitor*. PROG BIOCHEM BIOPHYS 2011. [DOI: 10.3724/sp.j.1206.2010.00438] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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27
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Kormos BL, Pieniazek SN, Beveridge DL, Baranger AM. U1A protein-stem loop 2 RNA recognition: prediction of structural differences from protein mutations. Biopolymers 2011; 95:591-606. [PMID: 21384338 DOI: 10.1002/bip.21616] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 01/01/2011] [Accepted: 02/07/2011] [Indexed: 01/02/2023]
Abstract
Molecular dynamics (MD) simulations were carried out to compare the free and bound structures of wild type U1A protein with several Phe56 mutant U1A proteins that bind the target stem loop 2 (SL2) RNA with a range of affinities. The simulations indicate the free U1A protein is more flexible than the U1A-RNA complex for both wild type and Phe56 mutant systems. A complete analysis of the hydrogen-bonding (HB) and non-bonded (VDW) interactions over the course of the MD simulations suggested that changes in the interactions in the free U1A protein caused by the Phe56Ala and Phe56Leu mutations may stabilize the helical character in loop 3, and contribute to the weak binding of these proteins to SL2 RNA. Compared with wild type, changes in HB and VDW interactions in Phe56 mutants of the free U1A protein are global, and include differences in β-sheet, loop 1 and loop 3 interactions. In the U1A-RNA complex, the Phe56Ala mutation leads to a series of differences in interactions that resonate through the complex, while the Phe56Leu and Phe56Trp mutations cause local differences around the site of mutation. The long-range networks of interactions identified in the simulations suggest that direct interactions and dynamic processes in both the free and bound forms contribute to complex stability.
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Affiliation(s)
- Bethany L Kormos
- Chemistry Department and Molecular Biophysics Program, Wesleyan University, Middletown, CT 06459, USA
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28
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Kurisaki I, Fukuzawa K, Nakano T, Mochizuki Y, Watanabe H, Tanaka S. Fragment molecular orbital (FMO) study on stabilization mechanism of neuro-oncological ventral antigen (NOVA)–RNA complex system. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.theochem.2010.09.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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29
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Spacková N, Réblová K, Sponer J. Structural dynamics of the box C/D RNA kink-turn and its complex with proteins: the role of the A-minor 0 interaction, long-residency water bridges, and structural ion-binding sites revealed by molecular simulations. J Phys Chem B 2010; 114:10581-93. [PMID: 20701388 DOI: 10.1021/jp102572k] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Kink-turns (K-turns) are recurrent elbow-like RNA motifs that participate in protein-assisted RNA folding and contribute to RNA dynamics. We carried out a set of molecular dynamics (MD) simulations using parm99 and parmbsc0 force fields to investigate structural dynamics of the box C/D RNA and its complexes with two proteins: native archaeal L7ae protein and human 15.5 kDa protein, originally bound to very similar structure of U4 snRNA. The box C/D RNA forms K-turn with A-minor 0 tertiary interaction between its canonical (C) and noncanonical (NC) stems. The local K-turn architecture is thus different from the previously studied ribosomal K-turns 38 and 42 having A-minor I interaction. The simulations reveal visible structural dynamics of this tertiary interaction involving altogether six substates which substantially contribute to the elbow-like flexibility of the K-turn. The interaction can even temporarily shift to the A-minor I type pattern; however, this is associated with distortion of the G/A base pair in the NC-stem of the K-turn. The simulations show reduction of the K-turn flexibility upon protein binding. The protein interacts with the apex of the K-turn and with the NC-stem. The protein-RNA interface includes long-residency hydration sites. We have also found long-residency hydration sites and major ion-binding sites associated with the K-turn itself. The overall topology of the K-turn remains stable in all simulations. However, in simulations of free K-turn, we observed instability of the key C16(O2')-A7(N1) H-bond, which is a signature interaction of K-turns and which was visibly more stable in simulations of K-turns possessing A-minor I interaction. It may reflect either some imbalance of the force field or it may be a correct indication of early stages of unfolding since this K-turn requires protein binding for its stabilization. Interestingly, the 16(O2')-7(N1) H- bond is usually not fully lost since it is replaced by a water bridge with a tightly bound water, which is adenine-specific similarly as the original interaction. The 16(O2')-7(N1) H-bond is stabilized by protein binding. The stabilizing effect is more visible with the human 15.5 kDa protein, which is attributed to valine to arginine substitution in the binding site. The behavior of the A-minor interaction is force-field-dependent because the parmbsc0 force field attenuates the A-minor fluctuations compared to parm99 simulations. Behavior of other regions of the box C/D RNA is not sensitive to the force field choice. Simulation with net-neutralizing Na(+) and 0.2 M excess salt conditions appear in all aspects equivalent. The simulations show loss of a hairpin tetraloop, which is not part of the K-turn. This was attributed to force field limitations.
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Affiliation(s)
- Nad'a Spacková
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic
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Qin F, Chen Y, Wu M, Li Y, Zhang J, Chen HF. Induced fit or conformational selection for RNA/U1A folding. RNA (NEW YORK, N.Y.) 2010; 16:1053-1061. [PMID: 20354153 PMCID: PMC2856877 DOI: 10.1261/rna.2008110] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2009] [Accepted: 02/07/2010] [Indexed: 05/29/2023]
Abstract
The hairpin II of U1 snRNA can bind U1A protein with high affinity and specificity. NMR spectra suggest that the loop region of apo-RNA is largely unstructured and undergoes a transition from unstructured to well-folded upon U1Abinding. However, the mechanism that RNA folding coupled protein binding is poorly understood. To get an insight into the mechanism, we have performed explicit-solvent molecular dynamics (MD) to study the folding kinetics of bound RNA and apo-RNA. Room-temperature MD simulations suggest that the conformation of bound RNA has significant adjustment and becomes more stable upon U1A binding. Kinetic analysis of high-temperature MD simulations shows that bound RNA and apo-RNA unfold via a two-state process, respectively. Both kinetics and free energy landscape analyses indicate that bound RNA folds in the order of RNA contracting, U1A binding, and tertiary folding. The predicted Phi-values suggest that A8, C10, A11, and G16 are key bases for bound RNA folding. Mutant Arg52Gln analysis shows that electrostatic interaction and hydrogen bonds between RNA and U1A (Arg52Gln) decrease. These results are in qualitative agreement with experiments. Furthermore, this method could be used in other studies about biomolecule folding upon receptor binding.
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Affiliation(s)
- Fang Qin
- College of Life Sciences and Biotechnology, Shanghai Jiaotong University, Shanghai, 200240, China
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31
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Hansia P, Ghosh A, Vishveshwara S. Ligand dependent intra and inter subunit communication in human tryptophanyl tRNA synthetase as deduced from the dynamics of structure networks. MOLECULAR BIOSYSTEMS 2009; 5:1860-72. [PMID: 19763332 DOI: 10.1039/b903807h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Homodimeric protein tryptophanyl tRNA synthetase (TrpRS) has a Rossmann fold domain and belongs to the 1c subclass of aminoacyl tRNA synthetases. This enzyme performs the function of acylating the cognate tRNA. This process involves a number of molecules (2 protein subunits, 2 tRNAs and 2 activated Trps) and thus it is difficult to follow the complex steps in this process. Structures of human TrpRS complexed with certain ligands are available. Based on structural and biochemical data, mechanism of activation of Trp has been speculated. However, no structure has yet been solved in the presence of both the tRNA(Trp) and the activated Trp (TrpAMP). In this study, we have modeled the structure of human TrpRS bound to the activated ligand and the cognate tRNA. In addition, we have performed molecular dynamics (MD) simulations on these models as well as other complexes to capture the dynamical process of ligand induced conformational changes. We have analyzed both the local and global changes in the protein conformation from the protein structure network (PSN) of MD snapshots, by a method which was recently developed in our laboratory in the context of the functionally monomeric protein, methionyl tRNA synthetase. From these investigations, we obtain important information such as the ligand induced correlation between different residues of this protein, asymmetric binding of the ligands to the two subunits of the protein as seen in the crystal structure analysis, and the path of communication between the anticodon region and the aminoacylation site. Here we are able to elucidate the role of dimer interface at a level of detail, which has not been captured so far.
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Affiliation(s)
- Priti Hansia
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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Beššeová I, Otyepka M, Réblová K, Šponer J. Dependence of A-RNA simulations on the choice of the force field and salt strength. Phys Chem Chem Phys 2009; 11:10701-11. [DOI: 10.1039/b911169g] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Anunciado D, Agumeh M, Kormos BL, Beveridge DL, Knee JL, Baranger AM. Characterization of the dynamics of an essential helix in the U1A protein by time-resolved fluorescence measurements. J Phys Chem B 2008; 112:6122-30. [PMID: 18293956 DOI: 10.1021/jp076896c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The RNA recognition motif (RRM), one of the most common RNA-binding domains, recognizes single-stranded RNA. A C-terminal helix that undergoes conformational changes upon binding is often an important contributor to RNA recognition. The N-terminal RRM of the U1A protein contains a C-terminal helix (helix C) that interacts with the RNA-binding surface of a beta-sheet in the free protein (closed conformation), but is directed away from this beta-sheet in the complex with RNA (open conformation). The dynamics of helix C in the free protein have been proposed to contribute to binding affinity and specificity. We report here a direct investigation of the dynamics of helix C in the free U1A protein on the nanosecond time scale using time-resolved fluorescence anisotropy. The results indicate that helix C is dynamic on a 2-3 ns time scale within a 20 degrees range of motion. Steady-state fluorescence experiments and molecular dynamics simulations suggest that the dynamical motion of helix C occurs within the closed conformation. Mutation of a residue on the beta-sheet that contacts helix C in the closed conformation dramatically destabilizes the complex (Phe56Ala) and alters the steady-state fluorescence, but not the time-resolved fluorescence anisotropy, of a Trp in helix C. Mutation of Asp90 in the hinge region between helix C and the remainder of the protein to Ala or Gly subtly alters the dynamics of the U1A protein and destabilizes the complex. Together these results show that helix C maintains a dynamic closed conformation that is stable to these targeted protein modifications and does not equilibrate with the open conformation on the nanosecond time scale.
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Affiliation(s)
- Divina Anunciado
- Department of Chemistry and Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459, USA
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Mackerell AD, Nilsson L. Molecular dynamics simulations of nucleic acid-protein complexes. Curr Opin Struct Biol 2008; 18:194-9. [PMID: 18281210 DOI: 10.1016/j.sbi.2007.12.012] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Revised: 12/17/2007] [Accepted: 12/21/2007] [Indexed: 10/22/2022]
Abstract
Molecular dynamics simulation studies of protein-nucleic acid complexes are more complicated than studies of either component alone-the force field has to be properly balanced, the systems tend to become very large, and a careful treatment of solvent and of electrostatic interactions is necessary. Recent investigations into several protein-DNA and protein-RNA systems have shown the feasibility of the simulation approach, yielding results of biological interest not readily accessible to experimental methods.
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Affiliation(s)
- Alexander D Mackerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201, USA.
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35
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Recognition of essential purines by the U1A protein. BMC BIOCHEMISTRY 2007; 8:22. [PMID: 17980039 PMCID: PMC2203988 DOI: 10.1186/1471-2091-8-22] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Accepted: 11/02/2007] [Indexed: 11/10/2022]
Abstract
Background The RNA recognition motif (RRM) is one of the largest families of RNA binding domains. The RRM is modulated so that individual proteins containing RRMs can specifically recognize RNA targets with diverse sequences and structures. Understanding the principles governing this specificity will be important for the rational modification and design of RRM-RNA complexes. Results In this paper we have investigated the origins of specificity of the N terminal RRM of the U1A protein for stem loop 2 (SL2) of U1 snRNA by substituting modified bases for essential purines in SL2 RNA. In one series of modified bases, hydrogen bond donors and acceptors were replaced by aliphatic groups to probe the importance of these functional groups to binding. In a second series of modified bases, hydrogen bond donors and acceptors were incorrectly placed on the purine bases to analyze the origins of discrimination between cognate and non-cognate RNA. The results of these experiments show that three different approaches are used by the U1A protein to gain specificity for purines. Specificity for the first base in the loop, A1, is based primarily on discrimination against RNA containing the incorrect base, specificity for the fourth base in the loop, G4, is based largely on recognition of the donors and acceptors of G4, while specificity for the sixth base in the loop, A6, results from a combination of direct recognition of the base and discrimination against incorrectly placed functional groups. Conclusion These investigations identify different roles that hydrogen bond donors and acceptors on bases in both cognate and non-cognate RNA play in the specific recognition of RNA by the U1A protein. Taken together with investigations of other RNA-RRM complexes, the results contribute to a general understanding of the origins of RNA-RRM specificity and highlight, in particular, the contribution of steric and electrostatic repulsion to binding specificity.
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Shao J, Tanner SW, Thompson N, Cheatham TE. Clustering Molecular Dynamics Trajectories: 1. Characterizing the Performance of Different Clustering Algorithms. J Chem Theory Comput 2007; 3:2312-34. [DOI: 10.1021/ct700119m] [Citation(s) in RCA: 614] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jianyin Shao
- Departments of Medicinal Chemistry, Pharmaceutics and Pharmaceutical Chemistry, and Bioengineering, College of Pharmacy, University of Utah, 2000 East 30 South, Skaggs Hall 201, Salt Lake City, Utah 84112
| | - Stephen W. Tanner
- Departments of Medicinal Chemistry, Pharmaceutics and Pharmaceutical Chemistry, and Bioengineering, College of Pharmacy, University of Utah, 2000 East 30 South, Skaggs Hall 201, Salt Lake City, Utah 84112
| | - Nephi Thompson
- Departments of Medicinal Chemistry, Pharmaceutics and Pharmaceutical Chemistry, and Bioengineering, College of Pharmacy, University of Utah, 2000 East 30 South, Skaggs Hall 201, Salt Lake City, Utah 84112
| | - Thomas E. Cheatham
- Departments of Medicinal Chemistry, Pharmaceutics and Pharmaceutical Chemistry, and Bioengineering, College of Pharmacy, University of Utah, 2000 East 30 South, Skaggs Hall 201, Salt Lake City, Utah 84112
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Ghosh A, Vishveshwara S. A study of communication pathways in methionyl- tRNA synthetase by molecular dynamics simulations and structure network analysis. Proc Natl Acad Sci U S A 2007; 104:15711-6. [PMID: 17898174 PMCID: PMC2000407 DOI: 10.1073/pnas.0704459104] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The enzymes of the family of tRNA synthetases perform their functions with high precision by synchronously recognizing the anticodon region and the aminoacylation region, which are separated by approximately 70 A in space. This precision in function is brought about by establishing good communication paths between the two regions. We have modeled the structure of the complex consisting of Escherichia coli methionyl-tRNA synthetase (MetRS), tRNA, and the activated methionine. Molecular dynamics simulations have been performed on the modeled structure to obtain the equilibrated structure of the complex and the cross-correlations between the residues in MetRS have been evaluated. Furthermore, the network analysis on these simulated structures has been carried out to elucidate the paths of communication between the activation site and the anticodon recognition site. This study has provided the detailed paths of communication, which are consistent with experimental results. Similar studies also have been carried out on the complexes (MetRS + activated methonine) and (MetRS + tRNA) along with ligand-free native enzyme. A comparison of the paths derived from the four simulations clearly has shown that the communication path is strongly correlated and unique to the enzyme complex, which is bound to both the tRNA and the activated methionine. The details of the method of our investigation and the biological implications of the results are presented in this article. The method developed here also could be used to investigate any protein system where the function takes place through long-distance communication.
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Affiliation(s)
- Amit Ghosh
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Saraswathi Vishveshwara
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
- *To whom correspondence may be addressed. E-mail:
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Kormos BL, Benitex Y, Baranger AM, Beveridge DL. Affinity and specificity of protein U1A-RNA complex formation based on an additive component free energy model. J Mol Biol 2007; 371:1405-19. [PMID: 17603075 PMCID: PMC2034351 DOI: 10.1016/j.jmb.2007.06.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 06/02/2007] [Accepted: 06/04/2007] [Indexed: 11/26/2022]
Abstract
An MM-GBSA computational protocol was used to investigate wild-type U1A-RNA and F56 U1A mutant experimental binding free energies. The trend in mutant binding free energies compared to wild-type is well-reproduced. Following application of a linear-response-like equation to scale the various energy components, the binding free energies agree quantitatively with observed experimental values. Conformational adaptation contributes to the binding free energy for both the protein and the RNA in these systems. Small differences in DeltaGs are the result of different and sometimes quite large relative contributions from various energetic components. Residual free energy decomposition indicates differences not only at the site of mutation, but throughout the entire protein. MM-GBSA and ab initio calculations performed on model systems suggest that stacking interactions may nearly, but not completely, account for observed differences in mutant binding affinities. This study indicates that there may be different underlying causes of ostensibly similar experimentally observed binding affinities of different mutants, and thus recommends caution in the interpretation of binding affinities and specificities purely by inspection.
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Affiliation(s)
- Bethany L Kormos
- Chemistry Department and Molecular Biophysics Program, Wesleyan University, Middletown, CT 06459, USA.
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