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Jaiswal M, Tran TT, Guo J, Zhou M, Kundu S, Guo Z, Fanucci GE. Spin-labeling Insights into How Chemical Fixation Impacts Glycan Organization on Cells. APPLIED MAGNETIC RESONANCE 2024; 55:317-333. [PMID: 38469359 PMCID: PMC10927023 DOI: 10.1007/s00723-023-01624-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 09/21/2023] [Accepted: 09/22/2023] [Indexed: 03/13/2024]
Abstract
As new methods to interrogate glycan organization on cells develop, it is important to have a molecular level understanding of how chemical fixation can impact results and interpretations. Site-directed spin labeling technologies are well suited to study how the spin label mobility is impacted by local environmental conditions, such as those imposed by cross-linking effects of paraformaldehyde cell fixation methods. Here, we utilize three different azide-containing sugars for metabolic glycan engineering with HeLa cells to incorporate azido glycans that are modified with a DBCO-based nitroxide moiety via click reaction. Continuous wave X-band electron paramagnetic resonance spectroscopy is employed to characterize how the chronological sequence of chemical fixation and spin labeling impacts the local mobility and accessibility of the nitroxide-labeled glycans in the glycocalyx of HeLa cells. Results demonstrate that chemical fixation with paraformaldehyde can alter local glycan mobility and care should be taken in the analysis of data in any study where chemical fixation and cellular labeling occur.
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Affiliation(s)
- Mohit Jaiswal
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Trang T Tran
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Jiatong Guo
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Mingwei Zhou
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Sayan Kundu
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Zhongwu Guo
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Gail E Fanucci
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
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2
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Bogetti X, Saxena S. Integrating Electron Paramagnetic Resonance Spectroscopy and Computational Modeling to Measure Protein Structure and Dynamics. Chempluschem 2024; 89:e202300506. [PMID: 37801003 DOI: 10.1002/cplu.202300506] [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: 09/07/2023] [Revised: 10/05/2023] [Accepted: 10/06/2023] [Indexed: 10/07/2023]
Abstract
Electron paramagnetic resonance (EPR) has become a powerful probe of conformational heterogeneity and dynamics of biomolecules. In this Review, we discuss different computational modeling techniques that enrich the interpretation of EPR measurements of dynamics or distance restraints. A variety of spin labels are surveyed to provide a background for the discussion of modeling tools. Molecular dynamics (MD) simulations of models containing spin labels provide dynamical properties of biomolecules and their labels. These simulations can be used to predict EPR spectra, sample stable conformations and sample rotameric preferences of label sidechains. For molecular motions longer than milliseconds, enhanced sampling strategies and de novo prediction software incorporating or validated by EPR measurements are able to efficiently refine or predict protein conformations, respectively. To sample large-amplitude conformational transition, a coarse-grained or an atomistic weighted ensemble (WE) strategy can be guided with EPR insights. Looking forward, we anticipate an integrative strategy for efficient sampling of alternate conformations by de novo predictions, followed by validations by systematic EPR measurements and MD simulations. Continuous pathways between alternate states can be further sampled by WE-MD including all intermediate states.
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Affiliation(s)
- Xiaowei Bogetti
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA
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3
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Jaiswal M, Tran TT, Guo J, Zhou M, Kunda S, Guo Z, Fanucci G. Spin-labeling Insights into How Chemical Fixation Impacts Glycan Organization on Cells. RESEARCH SQUARE 2023:rs.3.rs-3039983. [PMID: 37398188 PMCID: PMC10312935 DOI: 10.21203/rs.3.rs-3039983/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
As new methods to interrogate glycan organization on cells develop, it is important to have a molecular level understanding of how chemical fixation can impact results and interpretations. Site-directed spin labeling technologies are well suited to study how the spin label mobility is impacted by local environmental conditions, such as those imposed by cross-linking effects of paraformaldehyde cell fixation methods. Here, we utilize three different azide-containing sugars for metabolic glycan engineering with HeLa cells to incorporate azido glycans that are modified with a DBCO-based nitroxide moiety via click reaction. Continuous wave X-band electron paramagnetic resonance spectroscopy is employed to characterize how the chronological sequence of chemical fixation and spin labeling impacts the local mobility and accessibility of the nitroxide-labeled glycans in the glycocalyx of HeLa cells. Results demonstrate that chemical fixation with paraformaldehyde can alter local glycan mobility and care should be taken in the analysis of data in any study where chemical fixation and cellular labeling occur.
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4
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Huang K, Fang X. A review on recent advances in methods for site-directed spin labeling of long RNAs. Int J Biol Macromol 2023; 239:124244. [PMID: 37001783 DOI: 10.1016/j.ijbiomac.2023.124244] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 01/12/2023] [Accepted: 03/15/2023] [Indexed: 03/31/2023]
Abstract
RNAs are important biomolecules that play essential roles in various cellular processes and are crucially linked with many human diseases. The key to elucidate the mechanisms underlying their biological functions and develop RNA-based therapeutics is to investigate RNA structure and dynamics and their connections to function in detail using a variety of approaches. Magnetic resonance techniques including paramagnetic nuclear magnetic resonance (NMR) and electron magnetic resonance (EPR) spectroscopies have proved to be powerful tools to gain insights into such properties. The prerequisites for paramagnetic NMR and EPR studies on RNAs are to achieve site-specific spin labeling of the intrinsically diamagnetic RNAs, which however is not trivial, especially for long ones. In this review, we present some covalent labeling strategies that allow site-specific introduction of electron spins to long RNAs. Generally, these strategies include assembly of long RNAs via enzymatic ligation of short oligonucleotides, co- and post-transcriptional site-specific labeling empowered with the unnatural base pair system, and direct enzymatic functionalization of natural RNAs. We introduce a few case studies to discuss the advantages and limitations of each strategy, and to provide a vision for the future development.
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5
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Zhao S, Li X, Wen Z, Zou M, Yu G, Liu X, Mao J, Zhang L, Xue Y, Fu R, Wang S. Dynamics of base pairs with low stability in RNA by solid-state nuclear magnetic resonance exchange spectroscopy. iScience 2022; 25:105322. [DOI: 10.1016/j.isci.2022.105322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 09/07/2022] [Accepted: 10/07/2022] [Indexed: 11/28/2022] Open
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6
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Segler ALJ, Sigurdsson ST. A Carbazole-Derived Nitroxide That Is an Analogue of Cytidine: A Rigid Spin Label for DNA and RNA. J Org Chem 2021; 86:11647-11659. [PMID: 34410721 DOI: 10.1021/acs.joc.1c01176] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
A variety of semirigid and rigid spin labels comprise a valuable arsenal for measurements of biomolecular structures and dynamics by electron paramagnetic resonance (EPR) spectroscopy. Here, we report the synthesis and characterization of rigid spin labels Ċ and Ċm for DNA and RNA, respectively, that are carbazole-derived nitroxides and analogues of cytidine. Ċ and Ċm were converted to their phosphoramidites and used for their incorporation into oligonucleotides by solid-phase synthesis. Analysis of Ċ and Ċm by single-crystal X-ray crystallography verified their identity and showed little deviation from planarity of the nucleobase. Analysis of the continuous-wave (CW) EPR spectra of the spin-labeled DNA and RNA duplexes confirmed their incorporation into the nucleic acids and the line-shape was characteristic of rigid spin labels. Circular dichroism (CD) and thermal denaturation studies of the Ċ-labeled DNAs and Ċm-labeled RNAs indicated that the labels are nonperturbing of duplex structure.
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Affiliation(s)
- Anna-Lena Johanna Segler
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
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7
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Nuthanakanti A, Srivatsan SG. Synthesis of DNA and RNA Oligonucleotides Containing a Dual-Purpose Selenium-Modified Fluorescent Nucleoside Probe. ACTA ACUST UNITED AC 2021; 81:e106. [PMID: 32311240 DOI: 10.1002/cpnc.106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Development of efficient tools that would enable direct correlation of nucleic acid structure and recognition in solution and in solid state at atomic resolution is highly desired. In this context, we recently developed dual-purpose nucleoside probes made of a 5-selenophene-modified uracil core, which serves both as a conformation-sensitive fluorophore and as an X-ray crystallography phasing agent. In this article, we provide a detailed synthetic procedure to synthesize the phosphoramidites of 5-selenophene-modified 2'-deoxyuridine and 5-selenophene-modified uridine analogs. We also describe their site-specific incorporation into therapeutically relevant DNA and RNA oligonucleotide motifs by an automated solid support synthesis protocol. The dual-purpose and minimally invasive nature of the probes enables efficient analysis of the conformation and ligand binding abilities of bacterial decoding site RNA (A-site) and G-quadruplex structures of the human telomeric overhang in real time by fluorescence and in 3D by X-ray crystallography. © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Synthesis of 5-selenophene-2'-deoxyuridine 2 and its phosphoramidite 5 Support Protocol 1: Synthesis of 2-(tri-n-butylstannyl) selenophene Support Protocol 2: Synthesis of 5'-O-DMT-protected 5-iodo-2'-deoxyuridine 3 Basic Protocol 2: Synthesis of 5-selenophene-modified uridine 7 and its phosphoramidite 11 Basic Protocol 3: Synthesis of DNA oligonucleotides containing 5-selenophene-modified 2'-deoxyuridine 2 Basic Protocol 4: Synthesis of an RNA oligonucleotide containing 5-selenophene-modified uridine 7.
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Affiliation(s)
- Ashok Nuthanakanti
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, India
| | - Seergazhi G Srivatsan
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, India
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8
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Mattay J, Dittmar M, Rentmeister A. Chemoenzymatic strategies for RNA modification and labeling. Curr Opin Chem Biol 2021; 63:46-56. [PMID: 33690011 DOI: 10.1016/j.cbpa.2021.01.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 01/20/2021] [Accepted: 01/31/2021] [Indexed: 12/17/2022]
Abstract
RNA is a central molecule in numerous cellular processes, including transcription, translation, and regulation of gene expression. To reveal the numerous facets of RNA function and metabolism in cells, labeling has become indispensable and enables the visualization, isolation, characterization, and even quantification of certain RNA species. In this review, we will cover chemoenzymatic approaches for covalent RNA labeling. These approaches rely on an enzymatic step to introduce an RNA modification before conjugation with a label for detection or isolation. We start with in vitro manipulation of RNA, sorted according to the enzymatic reaction exploited. Then, metabolic approaches for co- and post-transcriptional RNA labeling will be treated. We focus on recent advances in the field and highlight the most relevant applications for cellular imaging, RNA isolation and sequencing.
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Affiliation(s)
- Johanna Mattay
- Department of Chemistry, Institute of Biochemistry, University of Münster, Correnstr. 36, 48149, Münster, Germany
| | - Maria Dittmar
- Department of Chemistry, Institute of Biochemistry, University of Münster, Correnstr. 36, 48149, Münster, Germany
| | - Andrea Rentmeister
- Department of Chemistry, Institute of Biochemistry, University of Münster, Correnstr. 36, 48149, Münster, Germany; Cells in Motion Interfaculty Center, University of Münster, 48149, Münster, Germany.
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9
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Advanced approaches for elucidating structures of large RNAs using NMR spectroscopy and complementary methods. Methods 2020; 183:93-107. [DOI: 10.1016/j.ymeth.2020.01.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 11/11/2019] [Accepted: 01/16/2020] [Indexed: 11/23/2022] Open
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10
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Poncelet M, Driesschaert B. A 13 C-Labeled Triarylmethyl Radical as an EPR Spin Probe Highly Sensitive to Molecular Tumbling. Angew Chem Int Ed Engl 2020; 59:16451-16454. [PMID: 32542924 PMCID: PMC7901239 DOI: 10.1002/anie.202006591] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Indexed: 12/21/2022]
Abstract
A stable triarylmethyl spin probe whose electron paramagnetic resonance (EPR) spectrum is highly sensitive to molecular tumbling is reported. The strong anisotropy of the hyperfine coupling tensor with the central carbon of a 13 C1 -labeled triarylmethyl radical enables the measurement of the probe rotational correlation time with applications to measure microviscosity and molecular dynamics.
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Affiliation(s)
- Martin Poncelet
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, 26506, USA
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA
| | - Benoit Driesschaert
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, 26506, USA
- In Vivo Multifunctional Magnetic Resonance Center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV, 26506, USA
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11
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Poncelet M, Driesschaert B. A
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C‐Labeled Triarylmethyl Radical as an EPR Spin Probe Highly Sensitive to Molecular Tumbling. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202006591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Martin Poncelet
- Department of Pharmaceutical SciencesSchool of PharmacyWest Virginia University Morgantown WV 26506 USA
- In Vivo Multifunctional Magnetic Resonance CenterRobert C. Byrd Health Sciences CenterWest Virginia University Morgantown WV 26506 USA
| | - Benoit Driesschaert
- Department of Pharmaceutical SciencesSchool of PharmacyWest Virginia University Morgantown WV 26506 USA
- In Vivo Multifunctional Magnetic Resonance CenterRobert C. Byrd Health Sciences CenterWest Virginia University Morgantown WV 26506 USA
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12
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Ehrenberger MA, Vieyra A, Esquiaqui JM, Fanucci GE. Ion-dependent mobility effects of the Fusobacterium nucleatum glycine riboswitch aptamer II via site-directed spin-labeling (SDSL) electron paramagnetic resonance (EPR). Biochem Biophys Res Commun 2019; 516:839-844. [PMID: 31262445 DOI: 10.1016/j.bbrc.2019.06.105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 06/19/2019] [Indexed: 01/31/2023]
Abstract
Site-directed spin-labeling (SDSL) with continuous wave electron paramagnetic resonance (cw-EPR) spectroscopy was utilized to probe site-specific changes in backbone dynamics that accompany folding of the isolated 84 nucleotide aptamer II domain of the Fusobacterium nucleatum (FN) glycine riboswitch. Spin-labels were incorporated using splinted ligation strategies. Results show differential dynamics for spin-labels incorporated into the backbone at a base-paired and loop region. Additionally, the addition of a biologically relevant concentration of 5 mM Mg2+, to an RNA solution with 100 mM K+, folds and compacts the structure, inferred by a reduction in spin-label mobility. Furthermore, when controlling for ionic strength, Mg2+ added to the RNA induces more folding/less flexibility at the two sites than RNA with K+ alone. Addition of glycine does not alter the dynamics of this singlet aptamer II, indicating that the full length riboswitch construct may be needed for glycine binding and induced conformational changes. This work adds to our growing understanding of how splinted-ligation SDSL can be utilized to interrogate differential dynamics in large dynamic RNAs, providing insights into how RNA folding and structure is differentially stabilized by monovalent versus divalent cations.
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Affiliation(s)
- Michelle A Ehrenberger
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611, United States
| | - Aleida Vieyra
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611, United States
| | - Jackie M Esquiaqui
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611, United States
| | - Gail E Fanucci
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611, United States.
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13
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Zhang H, Keane SC. Advances that facilitate the study of large RNA structure and dynamics by nuclear magnetic resonance spectroscopy. WILEY INTERDISCIPLINARY REVIEWS-RNA 2019; 10:e1541. [PMID: 31025514 PMCID: PMC7169810 DOI: 10.1002/wrna.1541] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 01/18/2019] [Accepted: 04/02/2019] [Indexed: 12/22/2022]
Abstract
The characterization of functional yet nonprotein coding (nc) RNAs has expanded the role of RNA in the cell from a passive player in the central dogma of molecular biology to an active regulator of gene expression. The misregulation of ncRNA function has been linked with a variety of diseases and disorders ranging from cancers to neurodegeneration. However, a detailed molecular understanding of how ncRNAs function has been limited; due, in part, to the difficulties associated with obtaining high-resolution structures of large RNAs. Tertiary structure determination of RNA as a whole is hampered by various technical challenges, all of which are exacerbated as the size of the RNA increases. Namely, RNAs tend to be highly flexible and dynamic molecules, which are difficult to crystallize. Biomolecular nuclear magnetic resonance (NMR) spectroscopy offers a viable alternative to determining the structure of large RNA molecules that do not readily crystallize, but is itself hindered by some technical limitations. Recently, a series of advancements have allowed the biomolecular NMR field to overcome, at least in part, some of these limitations. These advances include improvements in sample preparation strategies as well as methodological improvements. Together, these innovations pave the way for the study of ever larger RNA molecules that have important biological function. This article is categorized under: RNA Structure and Dynamics > RNA Structure, Dynamics, and Chemistry Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems.
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Affiliation(s)
- Huaqun Zhang
- Biophysics Program, University of Michigan, Ann Arbor, Michigan
| | - Sarah C Keane
- Biophysics Program, University of Michigan, Ann Arbor, Michigan.,Department of Chemistry, University of Michigan, Ann Arbor, Michigan
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14
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Jassoy JJ, Meyer A, Spicher S, Wuebben C, Schiemann O. Synthesis of Nanometer Sized Bis- and Tris-trityl Model Compounds with Different Extent of Spin-Spin Coupling. Molecules 2018; 23:E682. [PMID: 29562622 PMCID: PMC6017437 DOI: 10.3390/molecules23030682] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 03/12/2018] [Accepted: 03/16/2018] [Indexed: 12/29/2022] Open
Abstract
Tris(2,3,5,6-tetrathiaaryl)methyl radicals, so-called trityl radicals, are emerging as spin labels for distance measurements in biological systems based on Electron Paramagnetic Resonance (EPR). Here, the synthesis and characterization of rigid model systems carrying either two or three trityl moieties is reported. The monofunctionalized trityl radicals are connected to the molecular bridging scaffold via an esterification reaction employing the Mukaiyama reagent 2-chloro-methylpyridinium iodide. The bis- and tris-trityl compounds exhibit different inter-spin distances, strength of electron-electron exchange and dipolar coupling and can give rise to multi-spin effects. They are to serve as benchmark systems in comparing EPR distance measurement methods.
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Affiliation(s)
- J Jacques Jassoy
- Institute of Physical and Theoretical Chemistry, University of Bonn, 53115 Bonn, Germany.
| | - Andreas Meyer
- Institute of Physical and Theoretical Chemistry, University of Bonn, 53115 Bonn, Germany.
| | - Sebastian Spicher
- Institute of Physical and Theoretical Chemistry, University of Bonn, 53115 Bonn, Germany.
| | - Christine Wuebben
- Institute of Physical and Theoretical Chemistry, University of Bonn, 53115 Bonn, Germany.
| | - Olav Schiemann
- Institute of Physical and Theoretical Chemistry, University of Bonn, 53115 Bonn, Germany.
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15
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Kamble NR, Sigurdsson ST. Purine-Derived Nitroxides for Noncovalent Spin-Labeling of Abasic Sites in Duplex Nucleic Acids. Chemistry 2018; 24:4157-4164. [DOI: 10.1002/chem.201705410] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Indexed: 12/27/2022]
Affiliation(s)
- Nilesh R. Kamble
- University of Iceland; Department of Chemistry; Science Institute; Dunhaga 3 107 Reykjavik Iceland
| | - Snorri Th. Sigurdsson
- University of Iceland; Department of Chemistry; Science Institute; Dunhaga 3 107 Reykjavik Iceland
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16
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Gmeiner C, Dorn G, Allain FHT, Jeschke G, Yulikov M. Spin labelling for integrative structure modelling: a case study of the polypyrimidine-tract binding protein 1 domains in complexes with short RNAs. Phys Chem Chem Phys 2018; 19:28360-28380. [PMID: 29034946 DOI: 10.1039/c7cp05822e] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A combined method, employing NMR and EPR spectroscopies, has demonstrated its strength in solving structures of protein/RNA and other types of biomolecular complexes. This method works particularly well when the large biomolecular complex consists of a limited number of rigid building blocks, such as RNA-binding protein domains (RBDs). A variety of spin labels is available for such studies, allowing for conventional as well as spectroscopically orthogonal double electron-electron resonance (DEER) measurements in EPR. In this work, we compare different types of nitroxide-based and Gd(iii)-based spin labels attached to isolated RBDs of the polypyrimidine-tract binding protein 1 (PTBP1) and to short RNA fragments. In particular, we demonstrate experiments on spectroscopically orthogonal labelled RBD/RNA complexes. For all experiments we analyse spin labelling, DEER method performance, resulting distance distributions, and their consistency with the predictions from the spin label rotamers analysis. This work provides a set of intra-domain calibration DEER data, which can serve as a basis to start structure determination of the full length PTBP1 complex with an RNA derived from encephalomycarditis virus (EMCV) internal ribosomal entry site (IRES). For a series of tested labelling sites, we discuss their particular advantages and drawbacks in such a structure determination approach.
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Affiliation(s)
- Christoph Gmeiner
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, 8093, Switzerland.
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17
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Grytz CM, Kazemi S, Marko A, Cekan P, Güntert P, Sigurdsson ST, Prisner TF. Determination of helix orientations in a flexible DNA by multi-frequency EPR spectroscopy. Phys Chem Chem Phys 2018; 19:29801-29811. [PMID: 29090294 DOI: 10.1039/c7cp04997h] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Distance measurements are performed between a pair of spin labels attached to nucleic acids using Pulsed Electron-Electron Double Resonance (PELDOR, also called DEER) spectroscopy which is a complementary tool to other structure determination methods in structural biology. The rigid spin label Ç, when incorporated pairwise into two helical parts of a nucleic acid molecule, allows the determination of both the mutual orientation and the distance between those labels, since Ç moves rigidly with the helix to which it is attached. We have developed a two-step protocol to investigate the conformational flexibility of flexible nucleic acid molecules by multi-frequency PELDOR. In the first step, a library with a broad collection of conformers, which are in agreement with topological constraints, NMR restraints and distances derived from PELDOR, was created. In the second step, a weighted structural ensemble of these conformers was chosen, such that it fits the multi-frequency PELDOR time traces of all doubly Ç-labelled samples simultaneously. This ensemble reflects the global structure and the conformational flexibility of the two-way DNA junction. We demonstrate this approach on a flexible bent DNA molecule, consisting of two short helical parts with a five adenine bulge at the center. The kink and twist motions between both helical parts were quantitatively determined and showed high flexibility, in agreement with a Förster Resonance Energy Transfer (FRET) study on a similar bent DNA motif. The approach presented here should be useful to describe the relative orientation of helical motifs and the conformational flexibility of nucleic acid structures, both alone and in complexes with proteins and other molecules.
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Affiliation(s)
- C M Grytz
- Institute of Physical and Theoretical Chemistry, Goethe University, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Germany.
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18
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Kuzhelev A, Akhmetzyanov D, Denysenkov V, Shevelev G, Krumkacheva O, Bagryanskaya E, Prisner T. High-frequency pulsed electron–electron double resonance spectroscopy on DNA duplexes using trityl tags and shaped microwave pulses. Phys Chem Chem Phys 2018; 20:26140-26144. [DOI: 10.1039/c8cp03951h] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Distances between trityl spin labels attached to DNA duplexes were determined by 180 GHz and 260 GHz PELDOR spectroscopy applying broadband pump pulse at higher frequency.
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Affiliation(s)
- A. Kuzhelev
- Novosibirsk State University
- 630090 Novosibirsk
- Russia
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS
- 630090 Novosibirsk
| | - D. Akhmetzyanov
- Goethe University Frankfurt am Main
- Institute of Physical and Theoretical Chemistry
- Center for Biomolecular Magnetic Resonance
- 60438 Frankfurt am Main
- Germany
| | - V. Denysenkov
- Goethe University Frankfurt am Main
- Institute of Physical and Theoretical Chemistry
- Center for Biomolecular Magnetic Resonance
- 60438 Frankfurt am Main
- Germany
| | - G. Shevelev
- Novosibirsk State University
- 630090 Novosibirsk
- Russia
- Institute of Chemical Biology and Fundamental Medicine SB RAS
- 630090 Novosibirsk
| | - O. Krumkacheva
- Novosibirsk State University
- 630090 Novosibirsk
- Russia
- International Tomography Center SB RAS
- Novosibirsk
| | - E. Bagryanskaya
- Novosibirsk State University
- 630090 Novosibirsk
- Russia
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS
- 630090 Novosibirsk
| | - T. Prisner
- Goethe University Frankfurt am Main
- Institute of Physical and Theoretical Chemistry
- Center for Biomolecular Magnetic Resonance
- 60438 Frankfurt am Main
- Germany
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Hollas MA, Webb SJ, Flitsch SL, Fielding AJ. A Bifunctional Spin Label for Ligand Recognition on Surfaces. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201703929] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Michael A. Hollas
- Department of Chemistry; Photon Science Institute; University of Manchester; Oxford Road Manchester M13 9PL UK
| | - Simon J. Webb
- Department of Chemistry; Manchester Institute of Biotechnology; University of Manchester; 131 Princess Street Manchester M1 7DN UK
| | - Sabine L. Flitsch
- Department of Chemistry; Manchester Institute of Biotechnology; University of Manchester; 131 Princess Street Manchester M1 7DN UK
| | - Alistair J. Fielding
- Department of Chemistry; Photon Science Institute; University of Manchester; Oxford Road Manchester M13 9PL UK
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20
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Hollas MA, Webb SJ, Flitsch SL, Fielding AJ. A Bifunctional Spin Label for Ligand Recognition on Surfaces. Angew Chem Int Ed Engl 2017; 56:9449-9453. [PMID: 28570782 PMCID: PMC5577508 DOI: 10.1002/anie.201703929] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Revised: 05/22/2017] [Indexed: 01/21/2023]
Abstract
In situ monitoring of biomolecular recognition, especially at surfaces, still presents a significant technical challenge. Electron paramagnetic resonance (EPR) of biomolecules spin-labeled with nitroxides can offer uniquely sensitive and selective insights into these processes, but new spin-labeling strategies are needed. The synthesis and study of a bromoacrylaldehyde spin label (BASL), which features two attachment points with orthogonal reactivity is reported. The first examples of mannose and biotin ligands coupled to aqueous carboxy-functionalized gold nanoparticles through a spin label are presented. EPR spectra were obtained for the spin-labeled ligands both free in solution and attached to nanoparticles. The labels were recognized by the mannose-binding lectin, Con A, and the biotin-binding protein avidin-peroxidase. Binding gave quantifiable changes in the EPR spectra from which binding profiles could be obtained that reflect the strength of binding in each case.
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Affiliation(s)
- Michael A Hollas
- Department of Chemistry, Photon Science Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Simon J Webb
- Department of Chemistry, Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Sabine L Flitsch
- Department of Chemistry, Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Alistair J Fielding
- Department of Chemistry, Photon Science Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
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21
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Seebald LM, DeMott CM, Ranganathan S, Asare-Okai PN, Glazunova A, Chen A, Shekhtman A, Royzen M. Cobalt-based paramagnetic probe to study RNA-protein interactions by NMR. J Inorg Biochem 2017; 170:202-208. [PMID: 28260679 PMCID: PMC5956527 DOI: 10.1016/j.jinorgbio.2017.02.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 12/16/2016] [Accepted: 02/10/2017] [Indexed: 11/16/2022]
Abstract
Paramagnetic resonance enhancement (PRE) is an NMR technique that allows studying three-dimensional structures of RNA-protein complexes in solution. RNA strands are typically spin labeled using nitroxide reagents, which provide minimal perturbation to the native structure. The current work describes an alternative approach, which is based on a Co2+-based probe that can be covalently attached to RNA in the vicinity of the protein's binding site using 'click' chemistry. Similar to nitroxide spin labels, the transition metal based probe is capable of attenuating NMR signal intensities from protein residues localized <40Å away. The extent of attenuation is related to the probe's distance, thus allowing for construction of the protein's contact surface map. This new paradigm has been applied to study binding of HIV-1 nucleocapsid protein 7, NCp7, to a model RNA pentanucleotide.
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Affiliation(s)
- Leah M Seebald
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave. Albany, NY 12222, United States
| | - Christopher M DeMott
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave. Albany, NY 12222, United States
| | - Srivathsan Ranganathan
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave. Albany, NY 12222, United States
| | - Papa Nii Asare-Okai
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave. Albany, NY 12222, United States
| | - Anastasia Glazunova
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave. Albany, NY 12222, United States
| | - Alan Chen
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave. Albany, NY 12222, United States
| | - Alexander Shekhtman
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave. Albany, NY 12222, United States
| | - Maksim Royzen
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave. Albany, NY 12222, United States.
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22
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Nuthanakanti A, Boerneke MA, Hermann T, Srivatsan SG. Structure of the Ribosomal RNA Decoding Site Containing a Selenium-Modified Responsive Fluorescent Ribonucleoside Probe. Angew Chem Int Ed Engl 2017; 56:2640-2644. [PMID: 28156044 PMCID: PMC5397316 DOI: 10.1002/anie.201611700] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 01/17/2017] [Indexed: 12/22/2022]
Abstract
Comprehensive understanding of the structure–function relationship of RNA both in real time and at atomic level will have a profound impact in advancing our understanding of RNA functions in biology. Here, we describe the first example of a multifunctional nucleoside probe, containing a conformation‐sensitive fluorophore and an anomalous X‐ray diffraction label (5‐selenophene uracil), which enables the correlation of RNA conformation and recognition under equilibrium and in 3D. The probe incorporated into the bacterial ribosomal RNA decoding site, fluorescently reports antibiotic binding and provides diffraction information in determining the structure without distorting native RNA fold. Further, by comparing solution binding data and crystal structure, we gained insight on how the probe senses ligand‐induced conformational change in RNA. Taken together, our nucleoside probe represents a new class of biophysical tool that would complement available tools for functional RNA investigations.
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Affiliation(s)
- Ashok Nuthanakanti
- Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, 411008, India
| | - Mark A Boerneke
- Department of Chemistry and Biochemistry, Center for Drug Discovery Innovation, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA
| | - Thomas Hermann
- Department of Chemistry and Biochemistry, Center for Drug Discovery Innovation, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA
| | - Seergazhi G Srivatsan
- Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, 411008, India
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23
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Nuthanakanti A, Boerneke MA, Hermann T, Srivatsan SG. Structure of the Ribosomal RNA Decoding Site Containing a Selenium-Modified Responsive Fluorescent Ribonucleoside Probe. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201611700] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Ashok Nuthanakanti
- Department of Chemistry; Indian Institute of Science Education and Research; Dr. Homi Bhabha Road, Pashan Pune 411008 India
| | - Mark A. Boerneke
- Department of Chemistry and Biochemistry; Center for Drug Discovery Innovation; University of California, San Diego; 9500 Gilman Drive La Jolla CA 92093 USA
| | - Thomas Hermann
- Department of Chemistry and Biochemistry; Center for Drug Discovery Innovation; University of California, San Diego; 9500 Gilman Drive La Jolla CA 92093 USA
| | - Seergazhi G. Srivatsan
- Department of Chemistry; Indian Institute of Science Education and Research; Dr. Homi Bhabha Road, Pashan Pune 411008 India
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24
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Nguyen JC, Dzowo YK, Wolfbrandt C, Townsend J, Kukatin S, Wang H, Resendiz MJE. Synthesis, Thermal Stability, Biophysical Properties, and Molecular Modeling of Oligonucleotides of RNA Containing 2'-O-2-Thiophenylmethyl Groups. J Org Chem 2016; 81:8947-8958. [PMID: 27584708 DOI: 10.1021/acs.joc.6b01615] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Dodecamers of RNA [CUACGGAAUCAU] were functionalized with C2'-O-2-thiophenylmethyl groups to obtain oligonucleotides 10-14 and 17. The modified nucleotides were incorporated into RNA strands via solid-phase synthesis. The biophysical properties of these ONs were used to quantify the effects of this modification on RNA:RNA and RNA:DNA duplexes. A combination of UV-vis and circular dichroism were used to determine thermal stabilities of all strands, which hybridized into A-form geometries. Destabilization of the double stranded RNA was measured as a function of number of consecutive modifications, reflected in decreased thermal denaturation values (ΔTm, ca. 2.5-11.5 °C). Van't Hoff plots on a duplex containing one modification (10:15) displayed a ca. ΔΔG° of +4 kcal/mol with respect to its canonical analogue. Interestingly, hybridization of two modified strands (13:17, containing a total of eight modifications) resulted in increased stability and a distinct secondary structure, reflected in its CD spectrum. Molecular modeling based on DFT calculations shed light on the nature of this stability, with induced changes in the torsional angle δ (C5'-C4'-C3'-O3) and phosphate-phosphate distances that are in agreement with a compacted structure. The described synthetic methodology and structural information will be useful in the design of thermodynamically stable structures containing chemically reactive modifications.
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Affiliation(s)
- Joseph C Nguyen
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Yannick Kokouvi Dzowo
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Carly Wolfbrandt
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Justin Townsend
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Stanislav Kukatin
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Haobin Wang
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Marino J E Resendiz
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
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25
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Babaylova ES, Malygin AA, Lomzov AA, Pyshnyi DV, Yulikov M, Jeschke G, Krumkacheva OA, Fedin MV, Karpova GG, Bagryanskaya EG. Complementary-addressed site-directed spin labeling of long natural RNAs. Nucleic Acids Res 2016; 44:7935-43. [PMID: 27269581 PMCID: PMC5027493 DOI: 10.1093/nar/gkw516] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 05/30/2016] [Indexed: 12/21/2022] Open
Abstract
Nanoscale distance measurements by pulse dipolar Electron paramagnetic resonance (EPR) spectroscopy allow new insights into the structure and dynamics of complex biopolymers. EPR detection requires site directed spin labeling (SDSL) of biomolecule(s), which remained challenging for long RNAs up-to-date. Here, we demonstrate that novel complementary-addressed SDSL approach allows efficient spin labeling and following structural EPR studies of long RNAs. We succeeded to spin-label Hepatitis C Virus RNA internal ribosome entry site consisting of ≈330 nucleotides and having a complicated spatial structure. Application of pulsed double electron–electron resonance provided spin–spin distance distribution, which agrees well with the results of molecular dynamics (MD) calculations. Thus, novel SDSL approach in conjunction with EPR and MD allows structural studies of long natural RNAs with nanometer resolution and can be applied to systems of biological and biomedical significance.
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Affiliation(s)
- Elena S Babaylova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk 630090, Russia Novosibirsk State University, Novosibirsk 630090, Russia
| | - Alexey A Malygin
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk 630090, Russia Novosibirsk State University, Novosibirsk 630090, Russia
| | - Alexander A Lomzov
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk 630090, Russia Novosibirsk State University, Novosibirsk 630090, Russia
| | - Dmitrii V Pyshnyi
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk 630090, Russia Novosibirsk State University, Novosibirsk 630090, Russia
| | - Maxim Yulikov
- Laboratory of Physical Chemistry, ETH Zurich, Zurich 8093, Switzerland
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zurich, Zurich 8093, Switzerland
| | - Olesya A Krumkacheva
- Novosibirsk State University, Novosibirsk 630090, Russia International Tomography Center SB RAS, Novosibirsk 630090, Russia
| | - Matvey V Fedin
- Novosibirsk State University, Novosibirsk 630090, Russia International Tomography Center SB RAS, Novosibirsk 630090, Russia
| | - Galina G Karpova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk 630090, Russia Novosibirsk State University, Novosibirsk 630090, Russia
| | - Elena G Bagryanskaya
- Novosibirsk State University, Novosibirsk 630090, Russia N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Novosibirsk 630090, Russia
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26
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Sun Y, Borbat PP, Grigoryants VM, Myers WK, Freed JH, Scholes CP. Pulse dipolar ESR of doubly labeled mini TAR DNA and its annealing to mini TAR RNA. Biophys J 2015; 108:893-902. [PMID: 25692594 DOI: 10.1016/j.bpj.2014.12.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 11/07/2014] [Accepted: 12/03/2014] [Indexed: 12/27/2022] Open
Abstract
Pulse dipolar electron-spin resonance in the form of double electron electron resonance was applied to strategically placed, site-specifically attached pairs of nitroxide spin labels to monitor changes in the mini TAR DNA stem-loop structure brought on by the HIV-1 nucleocapsid protein NCp7. The biophysical structural evidence was at Ångstrom-level resolution under solution conditions not amenable to crystallography or NMR. In the absence of complementary TAR RNA, double labels located in both the upper and the lower stem of mini TAR DNA showed in the presence of NCp7 a broadened distance distribution between the points of attachment, and there was evidence for several conformers. Next, when equimolar amounts of mini TAR DNA and complementary mini TAR RNA were present, NCp7 enhanced the annealing of their stem-loop structures to form duplex DNA-RNA. When duplex TAR DNA-TAR RNA formed, double labels initially located 27.5 Å apart at the 3'- and 5'-termini of the 27-base mini TAR DNA relocated to opposite ends of a 27 bp RNA-DNA duplex with 76.5 Å between labels, a distance which was consistent with the distance between the two labels in a thermally annealed 27-bp TAR DNA-TAR RNA duplex. Different sets of double labels initially located 26-27 Å apart in the mini TAR DNA upper stem, appropriately altered their interlabel distance to ~35 Å when a 27 bp TAR DNA-TAR RNA duplex formed, where the formation was caused either through NCp7-induced annealing or by thermal annealing. In summary, clear structural evidence was obtained for the fraying and destabilization brought on by NCp7 in its biochemical function as an annealing agent and for the detailed structural change from stem-loop to duplex RNA-DNA when complementary RNA was present.
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Affiliation(s)
- Yan Sun
- Department of Chemistry, University at Albany, State University of New York, Albany, New York
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology and ACERT, Cornell University, Ithaca, New York
| | - Vladimir M Grigoryants
- Department of Chemistry, University at Albany, State University of New York, Albany, New York
| | - William K Myers
- Department of Chemistry, University at Albany, State University of New York, Albany, New York
| | - Jack H Freed
- Department of Chemistry and Chemical Biology and ACERT, Cornell University, Ithaca, New York
| | - Charles P Scholes
- Department of Chemistry, University at Albany, State University of New York, Albany, New York.
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27
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Stein RA, Beth AH, Hustedt EJ. A Straightforward Approach to the Analysis of Double Electron-Electron Resonance Data. Methods Enzymol 2015; 563:531-67. [PMID: 26478498 PMCID: PMC5231402 DOI: 10.1016/bs.mie.2015.07.031] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Double electron-electron resonance (DEER) is now widely utilized to measure distance distributions in the 20-70Å range. DEER is frequently applied to biological systems that have multiple conformational states leading to complex distance distributions. These complex distributions raise issues regarding the best approach to analyze DEER data. A widely used method utilizes a priori background correction followed by Tikhonov regularization. Unfortunately, the underlying assumptions of this approach can impact the analysis. In this chapter, a method of analyzing DEER data is presented that is ideally suited to obtain these complex distance distributions. The approach allows the fitting of raw experimental data without a priori background correction as well as the rigorous determination of uncertainties for all fitting parameters. This same methodological approach can be used for the simultaneous or global analysis of multiple DEER data sets using variable ratios of a common set of components, thus allowing direct correlation of distance components with functionally relevant conformational and biochemical states. Examples are given throughout to highlight this robust fitting approach.
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Affiliation(s)
- Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Albert H Beth
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Eric J Hustedt
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA.
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28
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Saha S, Jagtap AP, Sigurdsson ST. Site-Directed Spin Labeling of RNA by Postsynthetic Modification of 2'-Amino Groups. Methods Enzymol 2015; 563:397-414. [PMID: 26478493 DOI: 10.1016/bs.mie.2015.07.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
To elucidate mechanisms that govern functions of nucleic acids, it is essential to understand their structure and dynamics. Electron paramagnetic resonance (EPR) spectroscopy is a valuable technique that is routinely used to study those aspects of nucleic acids. A prerequisite for most EPR studies of nucleic acids is incorporation of spin labels at specific sites, known as site-directed spin labeling (SDSL). There are two main strategies for SDSL through formation of covalent bonds, i.e., the phosphoramidite approach and postsynthetic spin-labeling. After describing briefly the advantages and disadvantages of these two strategies, postsynthetic labeling of 2'-amino groups in RNA is delineated. Postsynthetic labeling of 2'-amino groups in RNA using 4-isocyanato-TEMPO has long been established as a useful approach. However, this method has some drawbacks, both with regard to the spin-labeling protocol and the flexibility of the spin label itself. Recently reported isothiocyanate-substituted aromatic isoindoline-derived nitroxides can be used to quantitatively and selectively modify 2'-amino groups in RNA and do not have the drawbacks associated with 4-isocyanato-TEMPO. This chapter provides a detailed description of the postsynthetic spin-labeling methods of 2'-amino groups in RNA with a special focus on using the aromatic isothiocyanate spin labels.
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Affiliation(s)
- Subham Saha
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Anil P Jagtap
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland.
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29
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Shelke SA, Sandholt GB, Sigurdsson ST. Nitroxide-labeled pyrimidines for non-covalent spin-labeling of abasic sites in DNA and RNA duplexes. Org Biomol Chem 2015; 12:7366-74. [PMID: 25119508 DOI: 10.1039/c4ob01095g] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Non-covalent and site-directed spin labeling gives easy access to spin-labeled nucleic acids for the study of their structure and dynamics by electron paramagnetic resonance (EPR) spectroscopy. In a search for improved spin labels for non-covalent binding to abasic sites in duplex DNA and RNA, ten pyrimidine-derived spin labels were prepared in good yields and their binding was evaluated by continuous wave (CW)-EPR spectroscopy. Most of the spin labels showed lower binding affinity than the previously reported label ç towards abasic sites in DNA and RNA. The most promising labels were triazole-linked spin labels and a pyrrolocytosine label. In particular, the N1-ethylamino derivative of a triazole-linked uracil spin label binds fully to both DNA and RNA containing an abasic site. This is the first example of a spin label that binds fully through non-covalent interactions with an abasic site in RNA.
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Affiliation(s)
- Sandip A Shelke
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland.
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30
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Nguyen PH, Popova AM, Hideg K, Qin PZ. A nucleotide-independent cyclic nitroxide label for monitoring segmental motions in nucleic acids. BMC BIOPHYSICS 2015; 8:6. [PMID: 25897395 PMCID: PMC4404236 DOI: 10.1186/s13628-015-0019-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 03/16/2015] [Indexed: 01/07/2023]
Abstract
Background Spin labels, which are chemically stable radicals attached at specific sites of a bio-molecule, enable investigations on structure and dynamics of proteins and nucleic acids using techniques such as site-directed spin labeling and paramagnetic NMR. Among spin labels developed, the class of rigid labels have limited or no independent motions between the radical bearing moiety and the target, and afford a number of advantages in measuring distances and monitoring local dynamics within the parent bio-molecule. However, a general method for attaching a rigid label to nucleic acids in a nucleotide-independent manner has not been reported. Results We developed an approach for installing a nearly rigid nitroxide spin label, designated as R5c, at a specific site of the nucleic acid backbone in a nucleotide-independent manner. The method uses a post-synthesis approach to covalently attach the nitroxide moiety in a cyclic fashion to phosphorothioate groups introduced at two consecutive nucleotides of the target strand. R5c-labeled nucleic acids are capable of pairing with their respective complementary strands, and the cyclic nature of R5c attachment significantly reduced independence motions of the label with respect to the parent duplex, although it may cause distortion of the local environment at the site of labeling. R5c yields enhanced sensitivity to the collective motions of the duplex, as demonstrated by its capability to reveal changes in collective motions of the substrate recognition duplex of the 120-kDa Tetrahymena group I ribozyme, which elude detection by a flexible label. Conclusions The cyclic R5c nitroxide can be efficiently attached to a target nucleic acid site using a post-synthetic coupling approach conducted under mild biochemical conditions, and serves as a viable label for experimental investigation of segmental motions in nucleic acids, including large folded RNAs. Electronic supplementary material The online version of this article (doi:10.1186/s13628-015-0019-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Phuong H Nguyen
- Department of Chemistry, University of Southern California, 840 Downey Way, Los Angeles, CA 90089-0744 USA ; Current Address: Bachem Americas, Torrance, CA 90505 USA
| | - Anna M Popova
- Department of Chemistry, University of Southern California, 840 Downey Way, Los Angeles, CA 90089-0744 USA ; Current Address: Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037 USA
| | - Kálmán Hideg
- Institute of Organic and Medicinal Chemistry, University of Pécs, Szigetic Strasse 12, Pécs, Hungary
| | - Peter Z Qin
- Department of Chemistry, University of Southern California, 840 Downey Way, Los Angeles, CA 90089-0744 USA
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31
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Hennig J, Warner LR, Simon B, Geerlof A, Mackereth CD, Sattler M. Structural Analysis of Protein-RNA Complexes in Solution Using NMR Paramagnetic Relaxation Enhancements. Methods Enzymol 2015; 558:333-362. [PMID: 26068746 DOI: 10.1016/bs.mie.2015.02.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Biological activity in the cell is predominantly mediated by large multiprotein and protein-nucleic acid complexes that act together to ensure functional fidelity. Nuclear magnetic resonance (NMR) spectroscopy is the only method that can provide information for high-resolution three-dimensional structures and the conformational dynamics of these complexes in solution. Mapping of binding interfaces and molecular interactions along with the characterization of conformational dynamics is possible for very large protein complexes. In contrast, de novo structure determination by NMR becomes very time consuming and difficult for protein complexes larger than 30 kDa as data are noisy and sparse. Fortunately, high-resolution structures are often available for individual domains or subunits of a protein complex and thus sparse data can be used to define their arrangement and dynamics within the assembled complex. In these cases, NMR can therefore be efficiently combined with complementary solution techniques, such as small-angle X-ray or neutron scattering, to provide a comprehensive description of the structure and dynamics of protein complexes in solution. Particularly useful are NMR-derived paramagnetic relaxation enhancements (PREs), which provide long-range distance restraints (ca. 20Å) for structural analysis of large complexes and also report on conformational dynamics in solution. Here, we describe the use of PREs from sample production to structure calculation, focusing on protein-RNA complexes. On the basis of recent examples from our own research, we demonstrate the utility, present protocols, and discuss potential pitfalls when using PREs for studying the structure and dynamic features of protein-RNA complexes.
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Affiliation(s)
- Janosch Hennig
- Institute of Structural Biology, Helmholtz Zentrum München, Oberschleißheim, Germany; Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Garching, Germany
| | - Lisa R Warner
- Institute of Structural Biology, Helmholtz Zentrum München, Oberschleißheim, Germany; Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Garching, Germany
| | - Bernd Simon
- European Molecular Biology Laboratory, Heidelberg, Germany
| | - Arie Geerlof
- Institute of Structural Biology, Helmholtz Zentrum München, Oberschleißheim, Germany; Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Garching, Germany
| | - Cameron D Mackereth
- Institut Européen de Chimie et Biologie, IECB, Univ. Bordeaux, Pessac, France; Inserm, U869, ARNA Laboratory, Bordeaux, France
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Zentrum München, Oberschleißheim, Germany; Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, Garching, Germany.
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32
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Gophane DB, Sigurdsson ST. TEMPO-derived spin labels linked to the nucleobases adenine and cytosine for probing local structural perturbations in DNA by EPR spectroscopy. Beilstein J Org Chem 2015; 11:219-27. [PMID: 25815073 PMCID: PMC4362019 DOI: 10.3762/bjoc.11.24] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 01/15/2015] [Indexed: 02/04/2023] Open
Abstract
Three 2´-deoxynucleosides containing semi-flexible spin labels, namely (T)A, (U)A and (U)C, were prepared and incorporated into deoxyoligonucleotides using the phosphoramidite method. All three nucleosides contain 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) connected to the exocyclic amino group; (T)A directly and (U)A as well as (U)C through a urea linkage. (T)A and (U)C showed a minor destabilization of a DNA duplex, as registered by a small decrease in the melting temperature, while (U)A destabilized the duplex by more than 10 °C. Circular dichroism (CD) measurements indicated that all three labels were accommodated in B-DNA duplex. The mobility of the spin label (T)A varied with different base-pairing partners in duplex DNA, with the (T)A•T pair being the least mobile. Furthermore, (T)A showed decreased mobility under acidic conditions for the sequences (T)A•C and (T)A•G, to the extent that the EPR spectrum of the latter became nearly superimposable to that of (T)A•T. The reduced mobility of the (T)A•C and (T)A•G mismatches at pH 5 is consistent with the formation of (T)AH(+)•C and (T)AH(+)•G, in which protonation of N1 of A allows the formation of an additional hydrogen bond to N3 of C and N7 of G, respectively, with G in a syn-conformation. The urea-based spin labels (U)A and (U)C were more mobile than (T)A, but still showed a minor variation in their EPR spectra when paired with A, G, C or T in a DNA duplex. (U)A and (U)C had similar mobility order for the different base pairs, with the lowest mobility when paired with C and the highest when paired with T.
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Affiliation(s)
- Dnyaneshwar B Gophane
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
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Saha S, Jagtap AP, Sigurdsson ST. Site-directed spin labeling of 2′-amino groups in RNA with isoindoline nitroxides that are resistant to reduction. Chem Commun (Camb) 2015; 51:13142-5. [DOI: 10.1039/c5cc05014f] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
2'-Amino groups in RNA were selectively spin labeled with reductively stable isoindoline nitroxides through a high-yielding reaction with aromatic isothiocyanates.
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Affiliation(s)
- Subham Saha
- University of Iceland
- Department of Chemistry
- Science Institute
- 107 Reykjavik
- Iceland
| | - Anil P. Jagtap
- University of Iceland
- Department of Chemistry
- Science Institute
- 107 Reykjavik
- Iceland
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34
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Pawar MG, Nuthanakanti A, Srivatsan SG. Heavy atom containing fluorescent ribonucleoside analog probe for the fluorescence detection of RNA-ligand binding. Bioconjug Chem 2014; 24:1367-77. [PMID: 23841942 DOI: 10.1021/bc400194g] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Although numerous biophysical tools have provided effective systems to study nucleic acids, our current knowledge on how RNA structure complements its function is limited. Therefore, development of robust tools to study the structure–function relationship of RNA is highly desired. Toward this endeavor, we have developed a new ribonucleoside analog, based on a (selenophen-2-yl)pyrimidine core, which could serve as a fluorescence probe to study the function of RNA in real time and as an anomalous scattering label (selenium atom) for the phase determination in X-ray crystallography. The fluorescent selenophene-modified uridine analog is minimally perturbing and exhibits probe-like properties such as sensitivity to microenvironment and conformation changes. Utilizing these properties and amicability of the corresponding ribonucleotide analog to enzymatic incorporation, we have synthesized a fluorescent bacterial ribosomal decoding site (A-site) RNA construct and have developed a fluorescence binding assay to effectively monitor the binding of aminoglycoside antibiotics to the A-site. Our results demonstrate that this simple approach of building a dual probe could provide new avenues to study the structure–function relationship of not only nucleic acids, but also other biomacromolecules.
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35
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Gophane DB, Endeward B, Prisner TF, Sigurdsson ST. Conformationally restricted isoindoline-derived spin labels in duplex DNA: distances and rotational flexibility by pulsed electron-electron double resonance spectroscopy. Chemistry 2014; 20:15913-9. [PMID: 25296640 DOI: 10.1002/chem.201403726] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 07/10/2014] [Indexed: 12/25/2022]
Abstract
Three structurally related isoindoline-derived spin labels that have different mobilities were incorporated into duplex DNA to systematically study the effect of motion on orientation-dependent pulsed electron-electron double resonance (PELDOR) measurements. To that end, a new nitroxide spin label, (ExIm)U, was synthesized and incorporated into DNA oligonucleotides. (ExIm)U is the first example of a conformationally unambiguous spin label for nucleic acids, in which the nitroxide N-O bond lies on the same axis as the three single bonds used to attach the otherwise rigid isoindoline-based spin label to a uridine base. Continuous-wave (CW) EPR measurements of (ExIm)U confirm a very high rotational mobility of the spin label in duplex DNA relative to the structurally related spin label (Im)U, which has restricted mobility due to an intramolecular hydrogen bond. The X-band CW-EPR spectra of (ExIm)U can be used to identify mismatches in duplex DNA. PELDOR distance measurements between pairs of the spin labels (Im)U, (Ox)U, and (ExIm)U in duplex DNA showed a strong angular dependence for (Im)U, a medium dependence for (Ox)U, and no orientation effect for (ExIm)U. Thus, precise distances can be extracted from (ExIm)U without having to take orientational effects into account.
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Affiliation(s)
- Dnyaneshwar B Gophane
- Department of Chemistry, Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavik (Iceland), Fax: (+354)5528911
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36
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Lebars I, Vileno B, Bourbigot S, Turek P, Wolff P, Kieffer B. A fully enzymatic method for site-directed spin labeling of long RNA. Nucleic Acids Res 2014; 42:e117. [PMID: 24981512 PMCID: PMC4150755 DOI: 10.1093/nar/gku553] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Site-directed spin labeling is emerging as an essential tool to investigate the structural and dynamical features of RNA. We propose here an enzymatic method, which allows the insertion of a paramagnetic center at a specific position in an RNA molecule. The technique is based on a segmental approach using a ligation protocol with T4 RNA ligase 2. One transcribed acceptor RNA is ligated to a donor RNA in which a thio-modified nucleotide is introduced at its 5′-end by in vitro transcription with T7 RNA polymerase. The paramagnetic thiol-specific reagent is subsequently attached to the RNA ligation product. This novel strategy is demonstrated by introducing a paramagnetic probe into the 55 nucleotides long RNA corresponding to K-turn and Specifier Loop domains from the Bacillus subtilis tyrS T-Box leader RNA. The efficiency of the coupling reaction and the quality of the resulting spin-labeled RNA were assessed by Mass Spectrometry, Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR). This method enables various combinations of isotopic segmental labeling and spin labeling schemes, a strategy that will be of particular interest to investigate the structural and dynamical properties of large RNA complexes by NMR and EPR spectroscopies.
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Affiliation(s)
- Isabelle Lebars
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Département de Biologie Structurale, Centre National de la Recherche Scientifique (CNRS) UMR 7104/Institut National de la Santé et de la Recherche Médicale (INSERM) U964/Université de Strasbourg, 1 rue Laurent Fries, BP 10142, 67404 Illkirch cedex, France
| | - Bertrand Vileno
- Institut de Chimie, Laboratoire Propriétés Optiques & Magnétiques des Architectures Moléculaires, Université de Strasbourg, UMR 7177 CNRS, 4 rue Blaise Pascal, CS 90032, 67081 Strasbourg Cedex, France
| | - Sarah Bourbigot
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Département de Biologie Structurale, Centre National de la Recherche Scientifique (CNRS) UMR 7104/Institut National de la Santé et de la Recherche Médicale (INSERM) U964/Université de Strasbourg, 1 rue Laurent Fries, BP 10142, 67404 Illkirch cedex, France
| | - Philippe Turek
- Institut de Chimie, Laboratoire Propriétés Optiques & Magnétiques des Architectures Moléculaires, Université de Strasbourg, UMR 7177 CNRS, 4 rue Blaise Pascal, CS 90032, 67081 Strasbourg Cedex, France
| | - Philippe Wolff
- Institut de Biologie Moléculaire et Cellulaire, Plateforme Protéomique Strasbourg Esplanade, FRC 1589 CNRS, 15 rue René Descartes, 67084 Strasbourg Cedex, France Institut de Biologie Moléculaire et Cellulaire, Architecture et Réactivité des ARN, Université de Strasbourg, UPR 9002 CNRS, 15 rue René Descartes, 67084 Strasbourg Cedex, France
| | - Bruno Kieffer
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Département de Biologie Structurale, Centre National de la Recherche Scientifique (CNRS) UMR 7104/Institut National de la Santé et de la Recherche Médicale (INSERM) U964/Université de Strasbourg, 1 rue Laurent Fries, BP 10142, 67404 Illkirch cedex, France
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Casey TM, Liu Z, Esquiaqui JM, Pirman NL, Milshteyn E, Fanucci GE. Continuous wave W- and D-band EPR spectroscopy offer "sweet-spots" for characterizing conformational changes and dynamics in intrinsically disordered proteins. Biochem Biophys Res Commun 2014; 450:723-8. [PMID: 24950408 DOI: 10.1016/j.bbrc.2014.06.045] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 06/10/2014] [Indexed: 11/28/2022]
Abstract
Site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for characterizing conformational sampling and dynamics in biological macromolecules. Here we demonstrate that nitroxide spectra collected at frequencies higher than X-band (∼9.5 GHz) have sensitivity to the timescale of motion sampled by highly dynamic intrinsically disordered proteins (IDPs). The 68 amino acid protein IA3, was spin-labeled at two distinct sites and a comparison of X-band, Q-band (35 GHz) and W-band (95 GHz) spectra are shown for this protein as it undergoes the helical transition chemically induced by tri-fluoroethanol. Experimental spectra at W-band showed pronounced line shape dispersion corresponding to a change in correlation time from ∼0.3 ns (unstructured) to ∼0.6 ns (α-helical) as indicated by comparison with simulations. Experimental and simulated spectra at X- and Q-bands showed minimal dispersion over this range, illustrating the utility of SDSL EPR at higher frequencies for characterizing structural transitions and dynamics in IDPs.
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Affiliation(s)
- Thomas M Casey
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA
| | - Zhanglong Liu
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA
| | - Jackie M Esquiaqui
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA
| | - Natasha L Pirman
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA
| | - Eugene Milshteyn
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA
| | - Gail E Fanucci
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA.
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38
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Esquiaqui JM, Sherman EM, Ionescu SA, Ye JD, Fanucci GE. Characterizing the dynamics of the leader-linker interaction in the glycine riboswitch with site-directed spin labeling. Biochemistry 2014; 53:3526-8. [PMID: 24849816 PMCID: PMC4059530 DOI: 10.1021/bi500404b] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Site-directed
spin labeling with continuous wave electron paramagnetic
resonance (EPR) spectroscopy was utilized to characterize dynamic
features of the kink–turn motif formed through a leader–linker
interaction in the Vibrio cholerae glycine riboswitch.
Efficient incorporation of spin-labels into select sites within the
phosphate backbone of the leader–linker region proceeded via
splinted ligation of chemically synthesized spin-labeled oligonucleotides
to in vitro transcribed larger RNA fragments. The
resultant nitroxide EPR line shapes have spectral characteristics
consistent with a kink–turn motif and reveal differential backbone
dynamics that are modulated by the presence of magnesium, potassium,
and glycine.
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Affiliation(s)
- Jackie M Esquiaqui
- Department of Chemistry, University of Florida , P.O. Box 117200, Gainesville, Florida 32611, United States
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39
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Shi X, Bisaria N, Benz-Moy TL, Bonilla S, Pavlichin DS, Herschlag D. Roles of long-range tertiary interactions in limiting dynamics of the Tetrahymena group I ribozyme. J Am Chem Soc 2014; 136:6643-8. [PMID: 24738560 PMCID: PMC4021564 DOI: 10.1021/ja413033d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We determined the effects of mutating the long-range tertiary contacts of the Tetrahymena group I ribozyme on the dynamics of its substrate helix (referred to as P1) and on catalytic activity. Dynamics were assayed by fluorescence anisotropy of the fluorescent base analogue, 6-methyl isoxanthopterin, incorporated into the P1 helix, and fluorescence anisotropy and catalytic activity were measured for wild type and mutant ribozymes over a range of conditions. Remarkably, catalytic activity correlated with P1 anisotropy over 5 orders of magnitude of activity, with a correlation coefficient of 0.94. The functional and dynamic effects from simultaneous mutation of the two long-range contacts that weaken P1 docking are cumulative and, based on this RNA's topology, suggest distinct underlying origins for the mutant effects. Tests of mechanistic predictions via single molecule FRET measurements of rate constants for P1 docking and undocking suggest that ablation of the P14 tertiary interaction frees P2 and thereby enhances the conformational space explored by the undocked attached P1 helix. In contrast, mutation of the metal core tertiary interaction disrupts the conserved core into which the P1 helix docks. Thus, despite following a single correlation, the two long-range tertiary contacts facilitate P1 helix docking by distinct mechanisms. These results also demonstrate that a fluorescence anisotropy probe incorporated into a specific helix within a larger RNA can report on changes in local helical motions as well as differences in more global dynamics. This ability will help uncover the physical properties and behaviors that underlie the function of RNAs and RNA/protein complexes.
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Affiliation(s)
- Xuesong Shi
- Department of Biochemistry, ‡Department of Chemistry, §Department of Chemical Engineering, ∥Department of Physics, Stanford University , Stanford, California 94305, United States
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40
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From a structural average to the conformational ensemble of a DNA bulge. Proc Natl Acad Sci U S A 2014; 111:E1473-80. [PMID: 24706812 DOI: 10.1073/pnas.1317032111] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Direct experimental measurements of conformational ensembles are critical for understanding macromolecular function, but traditional biophysical methods do not directly report the solution ensemble of a macromolecule. Small-angle X-ray scattering interferometry has the potential to overcome this limitation by providing the instantaneous distance distribution between pairs of gold-nanocrystal probes conjugated to a macromolecule in solution. Our X-ray interferometry experiments reveal an increasing bend angle of DNA duplexes with bulges of one, three, and five adenosine residues, consistent with previous FRET measurements, and further reveal an increasingly broad conformational ensemble with increasing bulge length. The distance distributions for the AAA bulge duplex (3A-DNA) with six different Au-Au pairs provide strong evidence against a simple elastic model in which fluctuations occur about a single conformational state. Instead, the measured distance distributions suggest a 3A-DNA ensemble with multiple conformational states predominantly across a region of conformational space with bend angles between 24 and 85 degrees and characteristic bend directions and helical twists and displacements. Additional X-ray interferometry experiments revealed perturbations to the ensemble from changes in ionic conditions and the bulge sequence, effects that can be understood in terms of electrostatic and stacking contributions to the ensemble and that demonstrate the sensitivity of X-ray interferometry. Combining X-ray interferometry ensemble data with molecular dynamics simulations gave atomic-level models of representative conformational states and of the molecular interactions that may shape the ensemble, and fluorescence measurements with 2-aminopurine-substituted 3A-DNA provided initial tests of these atomistic models. More generally, X-ray interferometry will provide powerful benchmarks for testing and developing computational methods.
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41
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Pawar MG, Srivatsan SG. Environment-responsive fluorescent nucleoside analogue probe for studying oligonucleotide dynamics in a model cell-like compartment. J Phys Chem B 2013; 117:14273-82. [PMID: 24161106 DOI: 10.1021/jp4071168] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The majority of fluorescent nucleoside analogue probes that have been used in the in vitro study of nucleic acids are not suitable for cell-based biophysical assays because they exhibit excitation maxima in the UV region and low quantum yields within oligonucleotides. Therefore, we propose that the photophysical characterization of oligonucleotides labeled with a fluorescent nucleoside analogue in reverse micelles (RM), which are good biological membrane models and UV-transparent, could provide an alternative approach to studying the properties of nucleic acids in a cell-like confined environment. In this context, we describe the photophysical properties of an environment-sensitive fluorescent uridine analogue (1), based on the 5-(benzo[b]thiophen-2-yl)pyrimidine core, in micelles and RM. The emissive nucleoside, which is polarity- and viscosity-sensitive, reports the environment of the surfactant assemblies via changes in its fluorescence properties. The nucleoside analogue, incorporated into an RNA oligonucleotide and hybridized to its complementary DNA and RNA oligonucleotides, exhibits a significantly higher fluorescence intensity, lifetime, and anisotropy in RM than in aqueous buffer, which is consistent with the environment of RM. Collectively, our results demonstrate that nucleoside 1 could be utilized as a fluorescent label to study the function of nucleic acids in a model cellular milieu.
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Affiliation(s)
- Maroti G Pawar
- Department of Chemistry, Indian Institute of Science Education and Research, Pune , Dr. Homi Bhabha Road, Pashan, Pune 411008, India
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42
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Nguyen P, Shi X, Sigurdsson ST, Herschlag D, Qin PZ. A single-stranded junction modulates nanosecond motional ordering of the substrate recognition duplex of a group I ribozyme. Chembiochem 2013; 14:1720-3. [PMID: 23900919 DOI: 10.1002/cbic.201300376] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Indexed: 12/26/2022]
Abstract
Rigid spinning: Site-directed spin-labeling studies using a rigid nitroxide spin label (Ç) reveal that both length and sequence of a single-stranded junction (J1/2) modulate nanosecond motional ordering of the substrate-recognition duplex (P1) of the 120 kD group I ribozyme. The studies demonstrate an approach for experimental measurements of nanosecond dynamics in high-molecular-weight RNA complexes.
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Affiliation(s)
- Phuong Nguyen
- Department of Chemistry, University of Southern California, LJS-251, 840 Downey Way, Los Angeles, CA 90089-0744 (USA) http://pzqin.usc.edu/pzqhome
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43
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Bogart JA, Lee HB, Boreen MA, Jun M, Schelter EJ. Fine-Tuning the Oxidative Ability of Persistent Radicals: Electrochemical and Computational Studies of Substituted 2-Pyridylhydroxylamines. J Org Chem 2013; 78:6344-9. [DOI: 10.1021/jo400944r] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Justin A. Bogart
- P. Roy and Diana T. Vagelos Laboratories,
Department
of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United
States
| | - Heui Beom Lee
- P. Roy and Diana T. Vagelos Laboratories,
Department
of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United
States
| | - Michael A. Boreen
- P. Roy and Diana T. Vagelos Laboratories,
Department
of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United
States
| | - Minsik Jun
- P. Roy and Diana T. Vagelos Laboratories,
Department
of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United
States
| | - Eric J. Schelter
- P. Roy and Diana T. Vagelos Laboratories,
Department
of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United
States
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44
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Tanpure AA, Pawar MG, Srivatsan SG. Fluorescent Nucleoside Analogs: Probes for Investigating Nucleic Acid Structure and Function. Isr J Chem 2013. [DOI: 10.1002/ijch.201300010] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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45
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Synthesis of spin-labeled riboswitch RNAs using convertible nucleosides and DNA-catalyzed RNA ligation. Bioorg Med Chem 2013; 21:6171-80. [PMID: 23664496 DOI: 10.1016/j.bmc.2013.04.007] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/21/2013] [Accepted: 04/05/2013] [Indexed: 12/23/2022]
Abstract
Chemically stable nitroxide radicals that can be monitored by electron paramagnetic resonance (EPR) spectroscopy can provide information on structural and dynamic properties of functional RNA such as riboswitches. The convertible nucleoside approach is used to install 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and 2,2,5,5-tetramethylpyrrolidin-1-oxyl (proxyl) labels at the exocyclic N(4)-amino group of cytidine and 2'-O-methylcytidine nucleotides in RNA. To obtain site-specifically labeled long riboswitch RNAs beyond the limit of solid-phase synthesis, we report the ligation of spin-labeled RNA using an in vitro selected deoxyribozyme as catalyst, and demonstrate the synthesis of TEMPO-labeled 53 nt SAM-III and 118 nt SAM-I riboswitch domains (SAM=S-adenosylmethionine).
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46
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Höbartner C, Sicoli G, Wachowius F, Gophane DB, Sigurdsson ST. Synthesis and Characterization of RNA Containing a Rigid and Nonperturbing Cytidine-Derived Spin Label. J Org Chem 2012; 77:7749-54. [DOI: 10.1021/jo301227w] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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47
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Popova AM, Hatmal MM, Frushicheva M, Price EA, Qin PZ, Haworth IS. Nitroxide sensing of a DNA microenvironment: mechanistic insights from EPR spectroscopy and molecular dynamics simulations. J Phys Chem B 2012; 116:6387-96. [PMID: 22574834 PMCID: PMC3382087 DOI: 10.1021/jp303303v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The behavior of the nitroxide spin labels 1-oxyl-4-bromo-2,2,5,5-tetramethylpyrroline (R5a) and 1-oxyl-2,2,5,5-tetramethylpyrroline (R5) attached at a phosphorothioate-substituted site in a DNA duplex is modulated by the DNA in a site- and stereospecific manner. A better understanding of the mechanisms of R5a/R5 sensing of the DNA microenvironment will enhance our capability to relate information from nitroxide spectra to sequence-dependent properties of DNA. Toward this goal, electron paramagnetic resonance (EPR) spectroscopy and molecular dynamics (MD) simulations were used to investigate R5 and R5a attached as R(p) and S(p) diastereomers at phosphorothioate (pS)C(7) of d(CTACTG(pS)C(7)Y(8)TTAG). d(CTAAAGCAGTAG) (Y = T or U). X-band continuous-wave EPR spectra revealed that the dT(8) to dU(8) change alters nanosecond rotational motions of R(p)-R5a but produces no detectable differences for S(p)-R5a, R(p)-R5, and S(p)-R5. MD simulations were able to qualitatively account for these spectral variations and provide a plausible physical basis for the R5/R5a behavior. The simulations also revealed a correlation between DNA backbone B(I)/B(II) conformations and R5/R5a rotational diffusion, thus suggesting a direct connection between DNA local backbone dynamics and EPR-detectable R5/R5a motion. These results advance our understanding of how a DNA microenvironment influences nitroxide motion and the observed EPR spectra. This may enable use of R5/R5a for a quantitative description of the sequence-dependent properties of large biologically relevant DNA molecules.
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Affiliation(s)
- Anna M. Popova
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0744
| | - Ma’mon M. Hatmal
- Department of Biochemistry, University of Southern California, Los Angeles, California 90033-1039
| | - Maria Frushicheva
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0744
| | - Eric A. Price
- Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-0744
| | - Peter Z. Qin
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0744
| | - Ian S. Haworth
- Department of Biochemistry, University of Southern California, Los Angeles, California 90033-1039
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90089-9121
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48
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Shelke SA, Sigurdsson ST. Effect of N3 Modifications on the Affinity of Spin Label ç for Abasic Sites in Duplex DNA. Chembiochem 2012; 13:684-90. [DOI: 10.1002/cbic.201100728] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Indexed: 12/11/2022]
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49
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Zhang X, Tung CS, Sowa GZ, Hatmal MM, Haworth IS, Qin PZ. Global structure of a three-way junction in a phi29 packaging RNA dimer determined using site-directed spin labeling. J Am Chem Soc 2012; 134:2644-52. [PMID: 22229766 DOI: 10.1021/ja2093647] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The condensation of bacteriophage phi29 genomic DNA into its preformed procapsid requires the DNA packaging motor, which is the strongest known biological motor. The packaging motor is an intricate ring-shaped protein/RNA complex, and its function requires an RNA component called packaging RNA (pRNA). Current structural information on pRNA is limited, which hinders studies of motor function. Here, we used site-directed spin labeling to map the conformation of a pRNA three-way junction that bridges binding sites for the motor ATPase and the procapsid. The studies were carried out on a pRNA dimer, which is the simplest ring-shaped pRNA complex and serves as a functional intermediate during motor assembly. Using a nucleotide-independent labeling scheme, stable nitroxide radicals were attached to eight specific pRNA sites without perturbing RNA folding and dimer formation, and a total of 17 internitroxide distances spanning the three-way junction were measured using Double Electron-Electron Resonance spectroscopy. The measured distances, together with steric chemical constraints, were used to select 3662 viable three-way junction models from a pool of 65 billion. The results reveal a similar conformation among the viable models, with two of the helices (H(T) and H(L)) adopting an acute bend. This is in contrast to a recently reported pRNA tetramer crystal structure, in which H(T) and H(L) stack onto each other linearly. The studies establish a new method for mapping global structures of complex RNA molecules, and provide information on pRNA conformation that aids investigations of phi29 packaging motor and developments of pRNA-based nanomedicine and nanomaterial.
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Affiliation(s)
- Xiaojun Zhang
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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