1
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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: 0] [Impact Index Per Article: 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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2
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Resolving dynamics and function of transient states in single enzyme molecules. Nat Commun 2020; 11:1231. [PMID: 32144241 PMCID: PMC7060211 DOI: 10.1038/s41467-020-14886-w] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 02/08/2020] [Indexed: 11/23/2022] Open
Abstract
We use a hybrid fluorescence spectroscopic toolkit to monitor T4 Lysozyme (T4L) in action by unraveling the kinetic and dynamic interplay of the conformational states. In particular, by combining single-molecule and ensemble multiparameter fluorescence detection, EPR spectroscopy, mutagenesis, and FRET-positioning and screening, and other biochemical and biophysical tools, we characterize three short-lived conformational states over the ns-ms timescale. The use of 33 FRET-derived distance sets, to screen available T4L structures, reveal that T4L in solution mainly adopts the known open and closed states in exchange at 4 µs. A newly found minor state, undisclosed by, at present, more than 500 crystal structures of T4L and sampled at 230 µs, may be actively involved in the product release step in catalysis. The presented fluorescence spectroscopic toolkit will likely accelerate the development of dynamic structural biology by identifying transient conformational states that are highly abundant in biology and critical in enzymatic reactions. T4 Lysozyme (T4L) is a model protein whose structure is extensively studied. Here the authors combine single-molecule and ensemble FRET measurements, FRET-positioning and screening and EPR spectroscopy to study the structural dynamics of T4L and describe its conformational landscape during the catalytic cycle by an extended Michaelis–Menten mechanism and identify an excited conformational state of the enzyme.
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3
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Karunakaran I, Angamuthu A, Gopalan P. Impact of N-(2-aminoethyl) Glycine Unit on Watson-Crick Base Pairs. Z PHYS CHEM 2019. [DOI: 10.1515/zpch-2017-1095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Abstract
We aim to understand the structure and stability of the backbone tailored Watson-Crick base pairs, Guanine-Cytosine (GC), Adenine-Thymine (AT) and Adenine-Uracil (AU) by incorporating N-(2-aminoethyl) glycine units (linked by amide bonds) at the purine and pyrimidine sites of the nucleobases. Density functional theory (DFT) is employed in which B3LYP/6-311++G∗
∗ level of theory has been used to optimize all the structures. The peptide attached base pairs are compared with the natural deoxyribose nucleic acid (DNA)/ribonucleic acid (RNA) base pairs and the calculations are carried out in both the gas and solution phases. The structural propensities of the optimized base pairs are analyzed using base pair geometries, hydrogen bond distances and stabilization energies and, compared with the standard reference data. The structural parameters were found to correlate well with the available data. The addition of peptide chain at the back bone of the DNA/RNA base pairs results only with a minimal distortion and hence does not alter the structural configuration of the base pairs. Also enhanced stability of the base pairs is spotted while adding peptidic chain at the purine site rather than the pyrimidine site of the nucleobases. The stability of the complexes is further interpreted by considering the hydrogen bonded N–H stretching frequencies of the respective base pairs. The discrimination in the interaction energies observed in both gas and solution phases are resulted due to the existence of distinct lowest unoccupied molecular orbitals (LUMO) in the solution phase. The reactivity of the base pairs is also analyzed through the in-depth examinations on the highest occupied molecular orbital (HOMO)-LUMO orbitals.
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Affiliation(s)
- Indumathi Karunakaran
- Department of Physics , PSGR Krishnammal College for Women , Coimbatore 641004, Tamilnadu , India
| | - Abiram Angamuthu
- Department of Physics , Karunya Institute of Technology and Sciences , Coimbatore 641114, Tamilnadu , India
| | - Praveena Gopalan
- Department of Physics , PSGR Krishnammal College for Women , Coimbatore 641004, Tamilnadu , India , Tel.: +91-7812844344
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4
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Weinrich T, Jaumann EA, Scheffer U, Prisner TF, Göbel MW. A Cytidine Phosphoramidite with Protected Nitroxide Spin Label: Synthesis of a Full-Length TAR RNA and Investigation by In-Line Probing and EPR Spectroscopy. Chemistry 2018; 24:6202-6207. [PMID: 29485736 DOI: 10.1002/chem.201800167] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 02/23/2018] [Indexed: 01/20/2023]
Abstract
EPR studies on RNA are complicated by three major obstacles related to the chemical nature of nitroxide spin labels: Decomposition while oligonucleotides are chemically synthesized, further decay during enzymatic strand ligation, and undetected changes in conformational equilibria due to the steric demand of the label. Herein possible solutions for all three problems are presented: A 2-nitrobenzyloxymethyl protective group for nitroxides that is stable under all conditions of chemical RNA synthesis and can be removed photochemically. By careful selection of ligation sites and splint oligonucleotides, high yields were achieved in the assembly of a full-length HIV-1 TAR RNA labeled with two protected nitroxide groups. PELDOR measurements on spin-labeled TAR in the absence and presence of arginine amide indicated arrest of interhelical motions on ligand binding. Finally, even minor changes in conformation due to the presence of spin labels are detected with high sensitivity by in-line probing.
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Affiliation(s)
- Timo Weinrich
- Institute for Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
| | - Eva A Jaumann
- Institute for Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
| | - Ute Scheffer
- Institute for Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
| | - Thomas F Prisner
- Institute for Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
| | - Michael W Göbel
- Institute for Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt am Main, Germany
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5
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Dimura M, Peulen TO, Hanke CA, Prakash A, Gohlke H, Seidel CA. Quantitative FRET studies and integrative modeling unravel the structure and dynamics of biomolecular systems. Curr Opin Struct Biol 2016; 40:163-185. [PMID: 27939973 DOI: 10.1016/j.sbi.2016.11.012] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 11/11/2016] [Accepted: 11/11/2016] [Indexed: 01/11/2023]
Abstract
Förster Resonance Energy Transfer (FRET) combined with single-molecule spectroscopy probes macromolecular structure and dynamics and identifies coexisting conformational states. We review recent methodological developments in integrative structural modeling by satisfying spatial restraints on networks of FRET pairs (hybrid-FRET). We discuss procedures to incorporate prior structural knowledge and to obtain optimal distance networks. Finally, a workflow for hybrid-FRET is presented that automates integrative structural modeling and experiment planning to put hybrid-FRET on rails. To test this workflow, we simulate realistic single-molecule experiments and resolve three protein conformers, exchanging at 30μs and 10ms, with accuracies of 1-3Å RMSD versus the target structure. Incorporation of data from other spectroscopies and imaging is also discussed.
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Affiliation(s)
- Mykola Dimura
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Thomas O Peulen
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Christian A Hanke
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Aiswaria Prakash
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Claus Am Seidel
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany.
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6
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Lomzov AA, Sviridov EA, Shernuykov AV, Shevelev GY, Pyshnyi DV, Bagryanskaya EG. Study of a DNA Duplex by Nuclear Magnetic Resonance and Molecular Dynamics Simulations. Validation of Pulsed Dipolar Electron Paramagnetic Resonance Distance Measurements Using Triarylmethyl-Based Spin Labels. J Phys Chem B 2016; 120:5125-33. [PMID: 27195671 DOI: 10.1021/acs.jpcb.6b03193] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pulse dipole-dipole electron paramagnetic resonance (EPR) spectroscopy (double electron-electron resonance [DEER] or pulse electron-electron double resonance [PELDOR] and double quantum coherence [DQC]) allows for measurement of distances in biomolecules and can be used at low temperatures in a frozen solution. Recently, the possibility of distance measurement in a nucleic acid at a physiological temperature using pulse EPR was demonstrated. In these experiments, triarylmethyl (TAM) radicals with long memory time of the electron spin served as a spin label. In addition, the duplex was immobilized on modified silica gel particles (Nucleosil DMA); this approach enables measurement of interspin distances close to 4.5 nm. Nevertheless, the possible influence of TAM on the structure of a biopolymer under study and validity of the data obtained by DQC are debated. In this paper, a combination of molecular dynamics (MD) and nuclear magnetic resonance (NMR) methods was used for verification of interspin distances measured by the X-band DQC method. NMR is widely used for structural analysis of biomolecules under natural conditions (room temperature and an aqueous solution). The ultraviolet (UV) melting method and thermal series (1)H NMR in the range 5-95 °C revealed the presence of only the DNA duplex in solution at oligonucleotide concentrations 1 μM to 1.1 mM at temperatures below 40 °C. The duplex structures and conformation flexibility of native and TAM-labeled DNA complexes obtained by MD simulation were the same as the structure obtained by NMR refinement. Thus, we showed that distance measurements at physiological temperatures by the X-band DQC method allow researchers to obtain valid structural information on an unperturbed DNA duplex using terminal TAM spin labels.
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Affiliation(s)
- Alexander A Lomzov
- Institute of Chemical Biology and Fundamental Medicine, SB RAS , 8 Lavrentiev Avenue, Novosibirsk 630090, Russia.,Novosibirsk State University , Novosibirsk 630090, Russia
| | - Eugeniy A Sviridov
- Novosibirsk State University , Novosibirsk 630090, Russia.,N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS , 9 Lavrentiev Avenue, Novosibirsk 630090, Russia
| | - Andrey V Shernuykov
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS , 9 Lavrentiev Avenue, Novosibirsk 630090, Russia
| | - Georgiy Yu Shevelev
- Institute of Chemical Biology and Fundamental Medicine, SB RAS , 8 Lavrentiev Avenue, Novosibirsk 630090, Russia.,Novosibirsk State University , Novosibirsk 630090, Russia
| | - Dmitrii V Pyshnyi
- Institute of Chemical Biology and Fundamental Medicine, SB RAS , 8 Lavrentiev Avenue, 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 , 9 Lavrentiev Avenue, Novosibirsk 630090, Russia
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7
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Dolino DM, Rezaei Adariani S, Shaikh SA, Jayaraman V, Sanabria H. Conformational Selection and Submillisecond Dynamics of the Ligand-binding Domain of the N-Methyl-d-aspartate Receptor. J Biol Chem 2016; 291:16175-85. [PMID: 27226581 PMCID: PMC4965566 DOI: 10.1074/jbc.m116.721274] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Indexed: 01/22/2023] Open
Abstract
The N-methyl-d-aspartate (NMDA) receptors are heteromeric non-selective cation channels that require the binding of glycine and glutamate for gating. Based on crystal structures, the mechanism of partial agonism at the glycine-binding site is thought to be mediated by a shift in the conformational equilibrium between an open clamshell and a closed clamshell-like structure of the bilobed ligand-binding domain (LBD). Using single-molecule Förster resonance energy transfer (smFRET) and multiparameter fluorescence detection, which allows us to study the conformational states and dynamics in the submillisecond time scale, we show that there are at least three conformational states explored by the LBD: the low FRET, medium FRET, and high FRET states. The distance of the medium and low FRET states corresponds to what has been observed in crystallography structures. We show that the high FRET state, which would represent a more closed clamshell conformation than that observed in the crystal structure, is most likely the state initiating activation, as evidenced by the fact that the fraction of the protein in this state correlates well with the extent of activation. Furthermore, full agonist bound LBDs show faster dynamic motions between the medium and high FRET states, whereas they show slower dynamics when bound to weaker agonists or to antagonists.
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Affiliation(s)
- Drew M Dolino
- From the Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Graduate School for Biomedical Sciences, Houston, Texas 77030 and
| | | | - Sana A Shaikh
- From the Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Graduate School for Biomedical Sciences, Houston, Texas 77030 and
| | - Vasanthi Jayaraman
- From the Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Graduate School for Biomedical Sciences, Houston, Texas 77030 and
| | - Hugo Sanabria
- the Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634
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8
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Halbmair K, Seikowski J, Tkach I, Höbartner C, Sezer D, Bennati M. High-resolution measurement of long-range distances in RNA: pulse EPR spectroscopy with TEMPO-labeled nucleotides. Chem Sci 2016; 7:3172-3180. [PMID: 29997809 PMCID: PMC6005265 DOI: 10.1039/c5sc04631a] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/01/2016] [Indexed: 01/02/2023] Open
Abstract
Distance measurements in RNAs by pulse EPR with TEMPO-labeled nucleotides allow for model free conversion of distances into base-pair separation.
Structural information at atomic resolution of biomolecular assemblies, such as RNA and RNA protein complexes, is fundamental to comprehend biological function. Modern spectroscopic methods offer exceptional opportunities in this direction. Here we present the capability of pulse EPR to report high-resolution long-range distances in RNAs by means of a recently developed spin labeled nucleotide, which carries the TEMPO group directly attached to the nucleobase and preserves Watson–Crick base-pairing. In a representative RNA duplex with spin-label separations up to 28 base pairs (≈8 nm) we demonstrate that the label allows for a model-free conversion of inter-spin distances into base-pair separation (Δbp) if broad-band pulse excitation at Q band frequencies (34 GHz) is applied. The observed distance distribution increases from ±0.2 nm for Δbp = 10 to only ±0.5 nm for Δbp = 28, consistent with only small deviations from the “ideal” A-form RNA structure. Molecular dynamics (MD) simulations conducted at 20 °C show restricted conformational freedom of the label. MD-generated structural deviations from an “ideal” A-RNA geometry help disentangle the contributions of local flexibility of the label and its neighboring nucleobases and global deformations of the RNA double helix to the experimental distance distributions. The study demonstrates that our simple but strategic spin labeling procedure can access detailed structural information on RNAs at atomic resolution over distances that match the size of macromolecular RNA complexes.
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Affiliation(s)
- Karin Halbmair
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany .
| | - Jan Seikowski
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany .
| | - Igor Tkach
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany .
| | - Claudia Höbartner
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany . .,Department of Organic and Biomolecular Chemistry , University of Göttingen , 37077 Göttingen , Germany
| | - Deniz Sezer
- Faculty of Engineering and Natural Sciences , Sabanci University , 34956 Istanbul , Turkey .
| | - Marina Bennati
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany . .,Department of Organic and Biomolecular Chemistry , University of Göttingen , 37077 Göttingen , Germany
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9
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Zhang X, Xu CX, Di Felice R, Sponer J, Islam B, Stadlbauer P, Ding Y, Mao L, Mao ZW, Qin PZ. Conformations of Human Telomeric G-Quadruplex Studied Using a Nucleotide-Independent Nitroxide Label. Biochemistry 2015; 55:360-72. [PMID: 26678746 DOI: 10.1021/acs.biochem.5b01189] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Guanine-rich oligonucleotides can form a unique G-quadruplex (GQ) structure with stacking units of four guanine bases organized in a plane through Hoogsteen bonding. GQ structures have been detected in vivo and shown to exert their roles in maintaining genome integrity and regulating gene expression. Understanding GQ conformation is important for understanding its inherent biological role and for devising strategies to control and manipulate functions based on targeting GQ. Although a number of biophysical methods have been used to investigate structure and dynamics of GQs, our understanding is far from complete. As such, this work explores the use of the site-directed spin labeling technique, complemented by molecular dynamics simulations, for investigating GQ conformations. A nucleotide-independent nitroxide label (R5), which has been previously applied for probing conformations of noncoding RNA and DNA duplexes, is attached to multiple sites in a 22-nucleotide DNA strand derived from the human telomeric sequence (hTel-22) that is known to form GQ. The R5 labels are shown to minimally impact GQ folding, and inter-R5 distances measured using double electron-electron resonance spectroscopy are shown to adequately distinguish the different topological conformations of hTel-22 and report variations in their occupancies in response to changes of the environment variables such as salt, crowding agent, and small molecule ligand. The work demonstrates that the R5 label is able to probe GQ conformation and establishes the base for using R5 to study more complex sequences, such as those that may potentially form multimeric GQs in long telomeric repeats.
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Affiliation(s)
- Xiaojun Zhang
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Cui-Xia Xu
- School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, China
| | - Rosa Di Felice
- Department of Physics and Astronomy, University of Southern California , Los Angeles, California 90089, United States.,Center S3, CNR institute of Nanoscience , Modena, Italy
| | - Jiri Sponer
- Central European Institute of Technology (CEITEC), Masaryk University , Campus Bohunice, Kamenice 5, 625 00 Brno, Czech Republic.,Institute of Biophysics, Academy of Sciences of the Czech Republic , Kralovopolska 135, 612 65 Brno, Czech Republic
| | - Barira Islam
- Central European Institute of Technology (CEITEC), Masaryk University , Campus Bohunice, Kamenice 5, 625 00 Brno, Czech Republic
| | - Petr Stadlbauer
- Institute of Biophysics, Academy of Sciences of the Czech Republic , Kralovopolska 135, 612 65 Brno, Czech Republic
| | - Yuan Ding
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Lingling Mao
- School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, China
| | - Zong-Wan Mao
- School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, China
| | - Peter Z Qin
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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10
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Malygin AA, Graifer DM, Meschaninova MI, Venyaminova AG, Krumkacheva OA, Fedin MV, Karpova GG, Bagryanskaya EG. Doubly Spin-Labeled RNA as an EPR Reporter for Studying Multicomponent Supramolecular Assemblies. Biophys J 2015; 109:2637-2643. [PMID: 26682820 PMCID: PMC4699879 DOI: 10.1016/j.bpj.2015.10.042] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 10/21/2015] [Accepted: 10/30/2015] [Indexed: 02/06/2023] Open
Abstract
mRNAs are involved in complicated supramolecular complexes with human 40S and 80S ribosomes responsible for the protein synthesis. In this work, a derivative of nonaribonucleotide pUUCGUAAAA with nitroxide spin labels attached to the 5'-phosphate and to the C8 atom of the adenosine in sixth position (mRNA analog) was used for studying such complexes using double electron-electron resonance/pulsed electron-electron double resonance spectroscopy. The complexes were assembled with participation of tRNA(Phe), which targeted triplet UUC of the derivative to the ribosomal peptidyl site and predetermined location of the adjacent GUA triplet coding for Val at the aminoacyl (A) site. The interspin distances were measured between the two labels of mRNA analog attached to the first nucleotide of the peptidyl site bound codon and to the third nucleotide of the A site bound codon, in the absence/presence of second tRNA bound at the A site. The values of the obtained interspin distances agree with those calculated for available near-atomic structures of similar complexes of 40S and 80S ribosomes, showing that neither 60S subunit nor tRNA at the A site have a noticeable effect on arrangement of mRNA at the codon-anticodon interaction area. In addition, the shapes of distance distributions in four studied ribosomal complexes allowed conclusions on conformational flexibility of mRNA in these complexes. Overall, the results of this study are the first, to our knowledge, demonstration of double electron-electron resonance/pulsed electron-electron double resonance application for measurements of intramolecular distances in multicomponent supramolecular complexes involving intricate cellular machineries and for evaluating dynamic properties of ligands bound to these machineries.
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Affiliation(s)
- Alexey A Malygin
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia
| | - Dmitri M Graifer
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia
| | - Maria I Meschaninova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk, Russia
| | - Aliya G Venyaminova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk, Russia
| | - Olesya A Krumkacheva
- International Tomography Center SB RAS, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia
| | - Matvey V Fedin
- International Tomography Center SB RAS, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia.
| | - Galina G Karpova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia.
| | - Elena G Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia.
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11
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Yu H, Mu Y, Nordenskiöld L, Stock G. Influence of Nitroxide Spin Labels on RNA Structure: A Molecular Dynamics Simulation Study. J Chem Theory Comput 2015; 4:1781-7. [PMID: 26620180 DOI: 10.1021/ct800266e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pulsed electron double resonance (PELDOR) experiments on oligonucleotides provide a distance ruler that allows the measurement of nanometer distances accurately. The technique requires attachment of nitroxide spin labels to the nucleotides, which may possibly perturb its conformation. To study to what extent nitroxide spin labels may affect RNA structure, all-atom molecular dynamics simulations in explicit solvent are performed for six double-labeled RNA duplexes. A new parametrization of the force field for the nitroxide spin label is developed, which leads to intramolecular distances that are in good agreement with experimental results. Comparison of the results for spin-labeled and unlabeled RNA reveals that the conformational effect of the spin label depends significantly on whether the spin label is attached to the major or the minor groove of RNA. While major-groove spin labeling may to some extent affect the conformation of nearby base pairs, minor-groove spin labeling has the advantage of mostly preserving the RNA conformation.
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Affiliation(s)
- Hang Yu
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, and Institute of Physical and Theoretical Chemistry, J. W. Goethe University, D-60438 Frankfurt, Germany
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, and Institute of Physical and Theoretical Chemistry, J. W. Goethe University, D-60438 Frankfurt, Germany
| | - Lars Nordenskiöld
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, and Institute of Physical and Theoretical Chemistry, J. W. Goethe University, D-60438 Frankfurt, Germany
| | - Gerhard Stock
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, and Institute of Physical and Theoretical Chemistry, J. W. Goethe University, D-60438 Frankfurt, Germany
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12
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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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13
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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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14
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15
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Tangprasertchai NS, Zhang X, Ding Y, Tham K, Rohs R, Haworth IS, Qin PZ. An Integrated Spin-Labeling/Computational-Modeling Approach for Mapping Global Structures of Nucleic Acids. Methods Enzymol 2015; 564:427-53. [PMID: 26477260 PMCID: PMC4641853 DOI: 10.1016/bs.mie.2015.07.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The technique of site-directed spin labeling (SDSL) provides unique information on biomolecules by monitoring the behavior of a stable radical tag (i.e., spin label) using electron paramagnetic resonance (EPR) spectroscopy. In this chapter, we describe an approach in which SDSL is integrated with computational modeling to map conformations of nucleic acids. This approach builds upon a SDSL tool kit previously developed and validated, which includes three components: (i) a nucleotide-independent nitroxide probe, designated as R5, which can be efficiently attached at defined sites within arbitrary nucleic acid sequences; (ii) inter-R5 distances in the nanometer range, measured via pulsed EPR; and (iii) an efficient program, called NASNOX, that computes inter-R5 distances on given nucleic acid structures. Following a general framework of data mining, our approach uses multiple sets of measured inter-R5 distances to retrieve "correct" all-atom models from a large ensemble of models. The pool of models can be generated independently without relying on the inter-R5 distances, thus allowing a large degree of flexibility in integrating the SDSL-measured distances with a modeling approach best suited for the specific system under investigation. As such, the integrative experimental/computational approach described here represents a hybrid method for determining all-atom models based on experimentally-derived distance measurements.
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Affiliation(s)
| | - Xiaojun Zhang
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
| | - Yuan Ding
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
| | - Kenneth Tham
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
| | - Remo Rohs
- Department of Chemistry, University of Southern California, Los Angeles, California, USA,Molecular and Computational Biology Program, Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Ian S. Haworth
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA
| | - Peter Z. Qin
- Department of Chemistry, University of Southern California, Los Angeles, California, USA,Molecular and Computational Biology Program, Department of Biological Sciences, University of Southern California, Los Angeles, California, USA,Corresponding author:
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16
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Combining NMR and EPR to Determine Structures of Large RNAs and Protein–RNA Complexes in Solution. Methods Enzymol 2015; 558:279-331. [DOI: 10.1016/bs.mie.2015.02.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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17
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Duss O, Yulikov M, Jeschke G, Allain FHT. EPR-aided approach for solution structure determination of large RNAs or protein-RNA complexes. Nat Commun 2014; 5:3669. [PMID: 24828280 DOI: 10.1038/ncomms4669] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 03/14/2014] [Indexed: 12/18/2022] Open
Abstract
High-resolution structural information on RNA and its functionally important complexes with proteins is dramatically underrepresented compared with proteins but is urgently needed for understanding cellular processes at the molecular and atomic level. Here we present an EPR-based protocol to help solving large RNA and protein-RNA complex structures in solution by providing long-range distance constraints between rigid fragments. Using enzymatic ligation of smaller RNA fragments, large doubly spin-labelled RNAs can be obtained permitting the acquisition of long distance distributions (>80 Å) within a large protein-RNA complex. Using a simple and fast calculation in torsion angle space of the spin-label distributions with the program CYANA, we can derive simple distance constraints between the spin labels and use them together with short-range distance restraints derived from NMR to determine the structure of a 70 kDa protein-RNA complex composed of three subcomplexes.
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Affiliation(s)
- Olivier Duss
- Institute for Molecular Biology and Biophysics, ETH Zürich, Zürich 8093, Switzerland
| | - Maxim Yulikov
- Institute for Physical Chemistry, ETH Zürich, Zürich 8093, Switzerland
| | - Gunnar Jeschke
- Institute for Physical Chemistry, ETH Zürich, Zürich 8093, Switzerland
| | - Frédéric H-T Allain
- Institute for Molecular Biology and Biophysics, ETH Zürich, Zürich 8093, Switzerland
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18
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Magnus M, Matelska D, Łach G, Chojnowski G, Boniecki MJ, Purta E, Dawson W, Dunin-Horkawicz S, Bujnicki JM. Computational modeling of RNA 3D structures, with the aid of experimental restraints. RNA Biol 2014; 11:522-36. [PMID: 24785264 PMCID: PMC4152360 DOI: 10.4161/rna.28826] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/01/2014] [Accepted: 04/08/2014] [Indexed: 11/19/2022] Open
Abstract
In addition to mRNAs whose primary function is transmission of genetic information from DNA to proteins, numerous other classes of RNA molecules exist, which are involved in a variety of functions, such as catalyzing biochemical reactions or performing regulatory roles. In analogy to proteins, the function of RNAs depends on their structure and dynamics, which are largely determined by the ribonucleotide sequence. Experimental determination of high-resolution RNA structures is both laborious and difficult, and therefore, the majority of known RNAs remain structurally uncharacterized. To address this problem, computational structure prediction methods were developed that simulate either the physical process of RNA structure formation ("Greek science" approach) or utilize information derived from known structures of other RNA molecules ("Babylonian science" approach). All computational methods suffer from various limitations that make them generally unreliable for structure prediction of long RNA sequences. However, in many cases, the limitations of computational and experimental methods can be overcome by combining these two complementary approaches with each other. In this work, we review computational approaches for RNA structure prediction, with emphasis on implementations (particular programs) that can utilize restraints derived from experimental analyses. We also list experimental approaches, whose results can be relatively easily used by computational methods. Finally, we describe case studies where computational and experimental analyses were successfully combined to determine RNA structures that would remain out of reach for each of these approaches applied separately.
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Affiliation(s)
- Marcin Magnus
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
| | - Dorota Matelska
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
| | - Grzegorz Łach
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
| | - Grzegorz Chojnowski
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
| | - Michal J Boniecki
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
| | - Elzbieta Purta
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
| | - Wayne Dawson
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
| | - Stanislaw Dunin-Horkawicz
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
| | - Janusz M Bujnicki
- Laboratory of Bioinformatics and Protein Engineering; International Institute of Molecular and Cell Biology; Warsaw, Poland
- Laboratory of Structural Bioinformatics; Institute of Molecular Biology and Biotechnology; Faculty of Biology; Adam Mickiewicz University; Poznan, Poland
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19
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Ji M, Ruthstein S, Saxena S. Paramagnetic metal ions in pulsed ESR distance distribution measurements. Acc Chem Res 2014; 47:688-95. [PMID: 24289139 DOI: 10.1021/ar400245z] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The use of pulsed electron spin resonance (ESR) to measure interspin distance distributions has advanced biophysical research. The three major techniques that use pulsed ESR are relaxation rate based distance measurements, double quantum coherence (DQC), and double electron electron resonance (DEER). Among these methods, the DEER technique has become particularly popular largely because it is easy to implement on commercial instruments and because programs are available to analyze experimental data. Researchers have widely used DEER to measure the structure and conformational dynamics of molecules labeled with the methanethiosulfonate spin label (MTSSL). Recently, researchers have exploited endogenously bound paramagnetic metal ions as spin probes as a way to determine structural constraints in metalloproteins. In this context Cu(2+) has served as a useful paramagnetic metal probe at X-band for DEER based distance measurements. Sample preparation is simple, and a coordinated-Cu(2+) ion offers limited spatial flexibility, making it an attractive probe for DEER experiments. On the other hand, Cu(2+) has a broad absorption ESR spectrum at low temperature, which leads to two potential complications. First, the Cu(2+)-based DEER time domain data has lower signal to noise ratio compared with MTSSL. Second, accurate distance distribution analysis often requires high-quality experimental data at different external magnetic fields or with different frequency offsets. In this Account, we summarize characteristics of Cu(2+)-based DEER distance distribution measurements and data analysis methods. We highlight a novel application of such measurements in a protein-DNA complex to identify the metal ion binding site and to elucidate its chemical mechanism of function. We also survey the progress of research on other metal ions in high frequency DEER experiments.
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Affiliation(s)
- Ming Ji
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Sharon Ruthstein
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Chemistry, Faculty of Exact Science, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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20
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Zhang X, Dantas Machado AC, Ding Y, Chen Y, Lu Y, Duan Y, Tham KW, Chen L, Rohs R, Qin PZ. Conformations of p53 response elements in solution deduced using site-directed spin labeling and Monte Carlo sampling. Nucleic Acids Res 2013; 42:2789-97. [PMID: 24293651 PMCID: PMC3936745 DOI: 10.1093/nar/gkt1219] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The tumor suppressor protein p53 regulates numerous signaling pathways by specifically recognizing diverse p53 response elements (REs). Understanding the mechanisms of p53-DNA interaction requires structural information on p53 REs. However, such information is limited as a 3D structure of any RE in the unbound form is not available yet. Here, site-directed spin labeling was used to probe the solution structures of REs involved in p53 regulation of the p21 and Bax genes. Multiple nanometer distances in the p21-RE and BAX-RE, measured using a nucleotide-independent nitroxide probe and double-electron-electron-resonance spectroscopy, were used to derive molecular models of unbound REs from pools of all-atom structures generated by Monte-Carlo simulations, thus enabling analyses to reveal sequence-dependent DNA shape features of unbound REs in solution. The data revealed distinct RE conformational changes on binding to the p53 core domain, and support the hypothesis that sequence-dependent properties encoded in REs are exploited by p53 to achieve the energetically most favorable mode of deformation, consequently enhancing binding specificity. This work reveals mechanisms of p53-DNA recognition, and establishes a new experimental/computational approach for studying DNA shape in solution that has far-reaching implications for studying protein-DNA interactions.
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Affiliation(s)
- Xiaojun Zhang
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA and Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
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21
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de Vera IMS, Blackburn ME, Galiano L, Fanucci GE. Pulsed EPR distance measurements in soluble proteins by site-directed spin labeling (SDSL). ACTA ACUST UNITED AC 2013; 74:17.17.1-17.17.29. [PMID: 24510645 DOI: 10.1002/0471140864.ps1717s74] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The resurgence of pulsed electron paramagnetic resonance (EPR) in structural biology centers on recent improvements in distance measurements using the double electron-electron resonance (DEER) technique. This unit focuses on EPR-based distance measurements by site-directed spin labeling (SDSL) of engineered cysteine residues in soluble proteins, with HIV-1 protease used as a model. To elucidate conformational changes in proteins, experimental protocols were optimized and existing data analysis programs were employed to derive distance-distribution profiles. Experimental considerations, sample preparation, and error analysis for artifact suppression are also outlined herein.
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Affiliation(s)
| | - Mandy E Blackburn
- Department of Chemistry, University of Florida, Gainesville, Florida.,Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts
| | - Luis Galiano
- Department of Chemistry, University of Florida, Gainesville, Florida.,Syngenta Crop Protection, Minnetonka, Minnesota
| | - Gail E Fanucci
- Department of Chemistry, University of Florida, Gainesville, Florida
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22
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Jeschke G. Conformational dynamics and distribution of nitroxide spin labels. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2013; 72:42-60. [PMID: 23731861 DOI: 10.1016/j.pnmrs.2013.03.001] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 03/26/2013] [Accepted: 03/27/2013] [Indexed: 06/02/2023]
Abstract
Long-range distance measurements based on paramagnetic relaxation enhancement (PRE) in NMR, quantification of surface water dynamics near biomacromolecules by Overhauser dynamic nuclear polarization (DNP) and sensitivity enhancement by solid-state DNP all depend on introducing paramagnetic species into an otherwise diamagnetic NMR sample. The species can be introduced by site-directed spin labeling, which offers precise control for positioning the label in the sequence of a biopolymer. However, internal flexibility of the spin label gives rise to dynamic processes that potentially influence PRE and DNP behavior and leads to a spatial distribution of the electron spin even in solid samples. Internal dynamics of spin labels and their static conformational distributions have been studied mainly by electron paramagnetic resonance spectroscopy and molecular dynamics simulations, with a large body of results for the most widely applied methanethiosulfonate spin label MTSL. These results are critically discussed in a unifying picture based on rotameric states of the group that carries the spin label. Deficiencies in our current understanding of dynamics and conformations of spin labeled groups and of their influence on NMR observables are highlighted and directions for further research suggested.
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Affiliation(s)
- Gunnar Jeschke
- ETH Zürich, Laboratory Physical Chemistry, Zürich, Switzerland.
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23
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de Vera IMS, Smith AN, Dancel MCA, Huang X, Dunn BM, Fanucci GE. Elucidating a relationship between conformational sampling and drug resistance in HIV-1 protease. Biochemistry 2013; 52:3278-88. [PMID: 23566104 DOI: 10.1021/bi400109d] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Enzyme targets in rapidly replicating systems, such as retroviruses, commonly respond to drug-selective pressure with mutations arising in the active site pocket that limit inhibitor effectiveness by introducing steric hindrance or by eliminating essential molecular interactions. However, these primary mutations are disposed to compromising pathogenic fitness. Emerging secondary mutations, which are often found outside of the binding cavity, may or can restore fitness while maintaining drug resistance. The accumulated drug pressure selected mutations could have an indirect effect in the development of resistance, such as altering protein flexibility or the dynamics of protein-ligand interactions. Here, we show that accumulation of mutations in a drug-resistant HIV-1 protease (HIV-1 PR) variant, D30N/M36I/A71V, changes the fractional occupancy of the equilibrium conformational sampling ensemble. Correlations are made among populations of the conformational states, namely, closed-like, semiopen, and open-like, with inhibition constants, as well as kinetic parameters. Mutations that stabilize a closed-like conformation correlate with enzymes of lowered activity and with higher affinity for inhibitors, which is corroborated by a further increase in the fractional occupancy of the closed state upon addition of inhibitor or substrate-mimic. Cross-resistance is found to correlate with combinations of mutations that increase the population of the open-like conformations at the expense of the closed-like state while retaining native-like occupancy of the semiopen population. These correlations suggest that at least three states are required in the conformational sampling model to establish the emergence of drug resistance in HIV-1 PR. More importantly, these results shed light on a possible mechanism whereby mutations combine to impart drug resistance while maintaining catalytic activity.
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Affiliation(s)
- Ian Mitchelle S de Vera
- Department of Chemistry, P.O. Box 117200, University of Florida , Gainesville, Florida 32611-7200, United States
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24
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Fedorova OS, Tsvetkov YD. Pulsed electron double resonance in structural studies of spin-labeled nucleic acids. Acta Naturae 2013; 5:9-32. [PMID: 23556128 PMCID: PMC3612823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
This review deals with the application of the pulsed electron double resonance (PELDOR) method to studies of spin-labeled DNA and RNA with complicated spatial structures, such as tetramers, aptamers, riboswitches, and three- and four-way junctions. The use of this method for studying DNA damage sites is also described.
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Affiliation(s)
- O. S. Fedorova
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, Lavrentyev Ave., 8, Novosibirsk, 630090
| | - Yu. D. Tsvetkov
- Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, Institutskaya Str. 3, Novosibirsk, 630090
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25
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Kalinin S, Peulen T, Sindbert S, Rothwell PJ, Berger S, Restle T, Goody RS, Gohlke H, Seidel CAM. A toolkit and benchmark study for FRET-restrained high-precision structural modeling. Nat Methods 2012; 9:1218-25. [PMID: 23142871 DOI: 10.1038/nmeth.2222] [Citation(s) in RCA: 299] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Accepted: 10/05/2012] [Indexed: 12/17/2022]
Abstract
We present a comprehensive toolkit for Förster resonance energy transfer (FRET)-restrained modeling of biomolecules and their complexes for quantitative applications in structural biology. A dramatic improvement in the precision of FRET-derived structures is achieved by explicitly considering spatial distributions of dye positions, which greatly reduces uncertainties due to flexible dye linkers. The precision and confidence levels of the models are calculated by rigorous error estimation. The accuracy of this approach is demonstrated by docking a DNA primer-template to HIV-1 reverse transcriptase. The derived model agrees with the known X-ray structure with an r.m.s. deviation of 0.5 Å. Furthermore, we introduce FRET-guided 'screening' of a large structural ensemble created by molecular dynamics simulations. We used this hybrid approach to determine the formerly unknown configuration of the flexible single-strand template overhang.
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Affiliation(s)
- Stanislav Kalinin
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität (HHU), Düsseldorf, Germany.
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26
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Sun Y, Zhang Z, Grigoryants VM, Myers WK, Liu F, Earle KA, Freed JH, Scholes CP. The internal dynamics of mini c TAR DNA probed by electron paramagnetic resonance of nitroxide spin-labels at the lower stem, the loop, and the bulge. Biochemistry 2012; 51:8530-41. [PMID: 23009298 DOI: 10.1021/bi301058q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Electron paramagnetic resonance (EPR) at 236.6 and 9.5 GHz probed the tumbling of nitroxide spin probes in the lower stem, in the upper loop, and near the bulge of mini c TAR DNA. High-frequency 236.6 GHz EPR, not previously applied to spin-labeled oligonucleotides, was notably sensitive to fast, anisotropic, hindered local rotational motion of the spin probe, occurring approximately about the NO nitroxide axis. Labels attached to the 2'-aminocytidine sugar in the mini c TAR DNA showed such anisotropic motion, which was faster in the lower stem, a region previously thought to be partially melted. More flexible labels attached to phosphorothioates at the end of the lower stem tumbled isotropically in mini c TAR DNA, mini TAR RNA, and ψ(3) RNA, but at 5 °C, the motion became more anisotropic for the labeled RNAs, implying more order within the RNA lower stems. As observed by 9.5 GHz EPR, the slowing of nanosecond motions of large segments of the oligonucleotide was enhanced by increasing the ratio of the nucleocapsid protein NCp7 to mini c TAR DNA from 0 to 2. The slowing was most significant at labels in the loop and near the bulge. At a 4:1 ratio of NCp7 to mini c TAR DNA, all labels reported tumbling times of >5 ns, indicating a condensation of NCp7 and TAR DNA. At the 4:1 ratio, pulse dipolar EPR spectroscopy of bilabels attached near the 3' and 5' termini showed evidence of an NCp7-induced increase in the 3'-5' end-to-end distance distribution and a partially melted stem.
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Affiliation(s)
- Yan Sun
- Department of Chemistry, University at Albany, 1400 Washington Avenue, Albany, NY 12222, USA
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27
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Preus S, Wilhelmsson LM. Advances in quantitative FRET-based methods for studying nucleic acids. Chembiochem 2012; 13:1990-2001. [PMID: 22936620 DOI: 10.1002/cbic.201200400] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Indexed: 01/02/2023]
Abstract
Förster resonance energy transfer (FRET) is a powerful tool for monitoring molecular distances and interactions at the nanoscale level. The strong dependence of transfer efficiency on probe separation makes FRET perfectly suited for "on/off" experiments. To use FRET to obtain quantitative distances and three-dimensional structures, however, is more challenging. This review summarises recent studies and technological advances that have improved FRET as a quantitative molecular ruler in nucleic acid systems, both at the ensemble and at the single-molecule levels.
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Affiliation(s)
- Søren Preus
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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28
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Preparation and spectral characterization of fluorescence probes based on 4-N,N-dimethylamino benzoic acid and sterically hindered amines. J Fluoresc 2012; 22:1371-81. [PMID: 22730137 DOI: 10.1007/s10895-012-1076-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 06/11/2012] [Indexed: 10/28/2022]
Abstract
The adducts of simple chromophore 4-N,N-dimethylamino benzoic acid with 2,2,6,6-tetrametyl-4-hydroxy- or 4-amino-piperidine were examined as fluorescence probes (spin double sensors) to monitor radical processes. The links in the adducts were either an ester or amide group, and the sterically hindered amines were in the form of -NH, -NO• and -NOR. The spectral properties of the three related derivatives (esters or amides) were quite similar. The maxima of the absorption spectra were in the range of 295-315 nm, and the maximum of fluorescence was located in the range of 330-360 nm, depending on the polarity of the solvent. In polar solvents, a red-shifted fluorescence band at 460-475 nm was observed. The fluorescence of these derivatives was rather weak as compared to anthracene under the same conditions. The Stokes shift was large, as high as 6,000 cm(-1), indicating the formation of a twisted intra-molecular charge transfer (TICT) state. No large differences in Stokes shifts were observed in polymer matrices of poly(methyl methacrylate), polystyrene and poly(vinyl chloride). The extent of intramolecular quenching was expressed as Φ(NX)/Φ(NO) (X = H, NOR) and was in the range of 1-3 in solution and as high as 8 in polymer matrices. The low efficiency of intramolecular quenching limits the application of these new adducts as fluorescence probes for the monitoring of radical processes in solution but favors their application in polymer matrices.
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29
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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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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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Metal-Based Spin Labeling for Distance Determination. STRUCTURAL INFORMATION FROM SPIN-LABELS AND INTRINSIC PARAMAGNETIC CENTRES IN THE BIOSCIENCES 2012. [DOI: 10.1007/430_2011_63] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Structural Information from Oligonucleotides. STRUCTURAL INFORMATION FROM SPIN-LABELS AND INTRINSIC PARAMAGNETIC CENTRES IN THE BIOSCIENCES 2012. [DOI: 10.1007/430_2012_76] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Nguyen P, Qin PZ. RNA dynamics: perspectives from spin labels. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 3:62-72. [PMID: 21882345 DOI: 10.1002/wrna.104] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Dynamics are important and indispensible physical attributes that play essential roles in RNA function. RNA dynamics are complex, spanning vast timescales, and encompassing a large number of physical modes. The technique of site-directed spin labeling (SDSL), which derives information on local structural and dynamic features of a macromolecule by monitoring a chemically stable nitroxide radical using electron paramagnetic resonance spectroscopy, has been applied to monitor intrinsic dynamics at defined structural states as well as to probe conformational transition dynamics of RNAs. The current state of SDSL studies of RNA dynamics is summarized here. Further development and application of SDSL promise to open up many more opportunities for probing RNA dynamics and connecting dynamics to structure and function.
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Affiliation(s)
- Phuong Nguyen
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
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Song Y, Meade TJ, Astashkin A, Klein E, Enemark J, Raitsimring A. Pulsed dipolar spectroscopy distance measurements in biomacromolecules labeled with Gd(III) markers. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 210:59-68. [PMID: 21388847 PMCID: PMC3081411 DOI: 10.1016/j.jmr.2011.02.010] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 02/03/2011] [Accepted: 02/08/2011] [Indexed: 05/11/2023]
Abstract
This work demonstrates the feasibility of using Gd(III) tags for long-range Double Electron Electron Resonance (DEER) distance measurements in biomacromolecules. Double-stranded 14- base pair Gd(III)-DNA conjugates were synthesized and investigated at K(a) band. For the longest Gd(III) tag the average distance and average deviation between Gd(III) ions determined from the DEER time domains was about 59±12Å. This result demonstrates that DEER measurements with Gd(III) tags can be routinely carried out for distances of at least 60Å, and analysis indicates that distance measurements up to 100Å are possible. Compared with commonly used nitroxide labels, Gd(III)-based labels will be most beneficial for the detection of distance variations in large biomacromolecules, with an emphasis on large scale changes in shape or distance. Tracking the folding/unfolding and domain interactions of proteins and the conformational changes in DNA are examples of such applications.
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Affiliation(s)
- Y. Song
- Departments of Chemistry; Molecular Biosciences; Neurobiology & Physiology; and Radiology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - T. J. Meade
- Departments of Chemistry; Molecular Biosciences; Neurobiology & Physiology; and Radiology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - A.V. Astashkin
- Department of Chemistry and Biochemistry, University of Arizona, 1306 E. University Blvd., Tucson, Arizona 85721-0041, USA
| | - E.L. Klein
- Department of Chemistry and Biochemistry, University of Arizona, 1306 E. University Blvd., Tucson, Arizona 85721-0041, USA
| | - J.H. Enemark
- Department of Chemistry and Biochemistry, University of Arizona, 1306 E. University Blvd., Tucson, Arizona 85721-0041, USA
| | - A. Raitsimring
- Department of Chemistry and Biochemistry, University of Arizona, 1306 E. University Blvd., Tucson, Arizona 85721-0041, USA
- Corresponding Author: Arnold Raitsimring, Department of Chemistry and Biochemistry, University of Arizona, 1306 E. University Blvd., Tucson, Arizona 85721-0041, USA.
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Sindbert S, Kalinin S, Nguyen H, Kienzler A, Clima L, Bannwarth W, Appel B, Müller S, Seidel CAM. Accurate Distance Determination of Nucleic Acids via Förster Resonance Energy Transfer: Implications of Dye Linker Length and Rigidity. J Am Chem Soc 2011; 133:2463-80. [DOI: 10.1021/ja105725e] [Citation(s) in RCA: 210] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Simon Sindbert
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Universitätsstrasse 1, Geb 26.32, 40225 Düsseldorf, Germany
| | - Stanislav Kalinin
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Universitätsstrasse 1, Geb 26.32, 40225 Düsseldorf, Germany
| | - Hien Nguyen
- Institut für Biochemie, Bioorganische Chemie, Ernst-Moritz-Arndt-Universität Greifswald, Felix-Hausdorff-Strasse 4, 17487, Greifswald, Germany
| | - Andrea Kienzler
- Fakultät für Chemie und Biochemie, Albert-Ludwigs Universität Freiburg, AK Bannwarth, Albertstrasse 21, 79104, Freiburg, Germany
| | - Lilia Clima
- Fakultät für Chemie und Biochemie, Albert-Ludwigs Universität Freiburg, AK Bannwarth, Albertstrasse 21, 79104, Freiburg, Germany
| | - Willi Bannwarth
- Fakultät für Chemie und Biochemie, Albert-Ludwigs Universität Freiburg, AK Bannwarth, Albertstrasse 21, 79104, Freiburg, Germany
| | - Bettina Appel
- Institut für Biochemie, Bioorganische Chemie, Ernst-Moritz-Arndt-Universität Greifswald, Felix-Hausdorff-Strasse 4, 17487, Greifswald, Germany
| | - Sabine Müller
- Institut für Biochemie, Bioorganische Chemie, Ernst-Moritz-Arndt-Universität Greifswald, Felix-Hausdorff-Strasse 4, 17487, Greifswald, Germany
| | - Claus A. M. Seidel
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Universitätsstrasse 1, Geb 26.32, 40225 Düsseldorf, Germany
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A nucleotide-independent nitroxide probe reports on site-specific stereomeric environment in DNA. Biophys J 2011; 99:2180-9. [PMID: 20923652 DOI: 10.1016/j.bpj.2010.08.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 08/04/2010] [Accepted: 08/05/2010] [Indexed: 11/22/2022] Open
Abstract
In this report, stereospecific structural and dynamic features in DNA are studied using the site-directed spin labeling technique. A stable nitroxide radical, 1-oxyl-4-bromo-2,2,5,5-tetramethylpyrroline (R5a), was attached postsynthetically to phosphorothioates that were chemically introduced, one at a time, at five sites of a DNA duplex. The two phosphorothioate diastereomers (R(p) or S(p)) were separated, and nitroxide rotational motions were monitored using electron paramagnetic resonance spectroscopy. The resulting spectra vary according to diastereomer identity and location of the labeling site, with R(p)-R5a spectra effectively reporting on local DNA structural features and S(p)-R5a spectra sensing variations in local DNA motions. This establishes R(p)- and S(p)-R5a as unique probes for investigating nucleic acids in a site- and stereospecific manner, which may aid studies of stereospecific DNA/protein interactions. In addition, weighted averages of individual R(p) and S(p) spectra match those of R5a attached to mixed diastereomers. This suggests that R5a linked to mixed diastereomers reports on the composite behaviors of R(p)- and S(p)-R5a and is useful in initial probing of the DNA local environment. This work advances understanding of R5a/DNA coupling, and is a key step forward in developing a nucleotide-independent spectroscopic probe for studying nucleic acids.
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Cooke JA, Brown LJ. Distance measurements by continuous wave EPR spectroscopy to monitor protein folding. Methods Mol Biol 2011; 752:73-96. [PMID: 21713632 DOI: 10.1007/978-1-60327-223-0_6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Site-Directed Spin Labeling Electron Paramagnetic Resonance (SDSL-EPR) offers a powerful method for the structural analysis of protein folds. This method can be used to test and build secondary, tertiary, and quaternary structural models as well as measure protein conformational changes in solution. Insertion of two cysteine residues into the protein backbone using molecular biology methods and the subsequent labeling of the cysteine residues with a paramagnetic spin label enables the technique of EPR to be used as a molecular spectroscopic ruler. EPR measures the dipolar interaction between pairs of paramagnetic spin labels to yield internitroxide distances from which quantitative structural information on a protein fold can then be obtained. Interspin dipolar interaction between two spin labels at less than 25 Å are measured using continuous wave (CW) EPR methods. As for any low-resolution distance methods, the positioning of the spin labels and the number of distance constraints to be measured are dependent on the structural question being asked, thus a pattern approach for using distance sets to decipher structure mapping, including protein folds and conformational changes associated with biological activity, is essential. Practical guidelines and hints for the technique of SDSL-EPR are described in this chapter, including methods for spin labeling the protein backbone, CW-EPR data collection at physiological temperatures and two semiquantitative analysis methods to extract interspin distance information from the CW-EPR spectra.
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Affiliation(s)
- James A Cooke
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, Australia
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Krstić I, Endeward B, Margraf D, Marko A, Prisner TF. Structure and dynamics of nucleic acids. Top Curr Chem (Cham) 2011; 321:159-98. [PMID: 22160388 DOI: 10.1007/128_2011_300] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this chapter we describe the application of CW and pulsed EPR methods for the investigation of structural and dynamical properties of RNA and DNA molecules and their interaction with small molecules and proteins. Special emphasis will be given to recent applications of dipolar spectroscopy on nucleic acids.
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Affiliation(s)
- Ivan Krstić
- Goethe University Frankfurt, Frankfurt am Main, Germany
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40
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Kim NK, Bowman MK, DeRose VJ. Precise mapping of RNA tertiary structure via nanometer distance measurements with double electron-electron resonance spectroscopy. J Am Chem Soc 2010; 132:8882-4. [PMID: 20557039 DOI: 10.1021/ja101317g] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Divalent metal (Mg(2+)) ion-dependent folding of the hammerhead ribozyme from Schistosoma mansoni was monitored with double electron-electron resonance (DEER) pulsed electron paramagnetic resonance spectroscopy by measuring nanometer-scale distances between paramagnetic spin-labels attached to the RNA. DEER measurements detect global folding of the ribozyme with excellent agreement between predictions from experimental, modeled, and crystallographic measurements. These measurements demonstrate the use of DEER spectroscopy as a tool for structural analysis of complex RNAs.
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Affiliation(s)
- Nak-Kyoon Kim
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, USA
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41
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Potapov A, Song Y, Meade TJ, Goldfarb D, Astashkin A, Raitsimring A. Distance measurements in model bis-Gd(III) complexes with flexible "bridge". Emulation of biological molecules having flexible structure with Gd(III) labels attached. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 205:38-49. [PMID: 20418132 PMCID: PMC2885582 DOI: 10.1016/j.jmr.2010.03.019] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2009] [Revised: 03/30/2010] [Accepted: 03/30/2010] [Indexed: 05/18/2023]
Abstract
In this work, we continue to explore Gd(III) as a possible spin label for high-field Double Electron-Electron Resonance (DEER) based distance measurements in biological molecules with flexible geometry. For this purpose, a bis-Gd(III) complex with a flexible "bridge" was used as a model. The distances in the model were expected to be distributed in the range of 5-26 A, allowing us to probe the shortest limits of accessible distances which were found to be as small as 13 A. The upper distance limit for these labels was also evaluated and was found to be about 60 A. Various pulse duration setups can result in apparent differences in the distribution function derived from DEER kinetics due to short distance limit variations. The advantages, such as the ability to perform measurements at cryogenic temperatures and high repetition rates simultaneously, the use of very short pumping and observation pulses without mutual interference, the lack of orientational selectivity, as well as the shortcomings, such as the limited mw operational frequency range and intrinsically smaller amplitude of oscillation related to dipolar interaction as compared with nitroxide spin labels are discussed. Most probably the use of nitroxide and Gd-based labels for distance measurements will be complementary depending on the particulars of the problem and the availability of instrumentation.
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Affiliation(s)
- A. Potapov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Y. Song
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - T. J. Meade
- Department of Chemistry; Department of Biochemistry, Cell Biology, and Molecular Biology; Neurobiology & Physiology; Department of Radiology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - D. Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - A.V. Astashkin
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041, USA
| | - A. Raitsimring
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041, USA
- Corresponding author: Dr. A. Raitsimring, University of Arizona, Department of Chemistry, 1306 E. University Blvd, Tucson, AZ 85721. ; tel (520)621-9968; fax (520)621-8407
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Potapov A, Yagi H, Huber T, Jergic S, Dixon NE, Otting G, Goldfarb D. Nanometer-Scale Distance Measurements in Proteins Using Gd3+ Spin Labeling. J Am Chem Soc 2010; 132:9040-8. [DOI: 10.1021/ja1015662] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alexey Potapov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel, Research School of Chemistry, The Australian National University, Canberra ACT 0200, Australia, and School of Chemistry, University of Wollongong, NSW 2522, Australia
| | - Hiromasa Yagi
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel, Research School of Chemistry, The Australian National University, Canberra ACT 0200, Australia, and School of Chemistry, University of Wollongong, NSW 2522, Australia
| | - Thomas Huber
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel, Research School of Chemistry, The Australian National University, Canberra ACT 0200, Australia, and School of Chemistry, University of Wollongong, NSW 2522, Australia
| | - Slobodan Jergic
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel, Research School of Chemistry, The Australian National University, Canberra ACT 0200, Australia, and School of Chemistry, University of Wollongong, NSW 2522, Australia
| | - Nicholas E. Dixon
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel, Research School of Chemistry, The Australian National University, Canberra ACT 0200, Australia, and School of Chemistry, University of Wollongong, NSW 2522, Australia
| | - Gottfried Otting
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel, Research School of Chemistry, The Australian National University, Canberra ACT 0200, Australia, and School of Chemistry, University of Wollongong, NSW 2522, Australia
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel, Research School of Chemistry, The Australian National University, Canberra ACT 0200, Australia, and School of Chemistry, University of Wollongong, NSW 2522, Australia
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Krstić I, Frolow O, Sezer D, Endeward B, Weigand JE, Suess B, Engels JW, Prisner TF. PELDOR spectroscopy reveals preorganization of the neomycin-responsive riboswitch tertiary structure. J Am Chem Soc 2010; 132:1454-5. [PMID: 20078041 DOI: 10.1021/ja9077914] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Pulsed electron double resonance (PELDOR) spectroscopy reveals a prearranged tertiary structure of the 27 nucleotides long engineered neomycin-responsive riboswitch. Measured distances between spin labels at positions U4-U14, U4-U15, U14-U26, and U15-U26 were unchanged upon neomycin binding which implies that the global stem-loop architecture is preserved in the absence and presence of the ligand. On the basis of our results, we infer that low-temperature PELDOR data unambiguously demonstrate the existence of an enthalpically favorable set of RNA conformations ready to bind the ligand without major global rearrangement.
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Affiliation(s)
- Ivan Krstić
- Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Frankfurt am Main, Germany
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Abstract
The understanding of structure-dynamics-function relationships in oligonucleotides or oligonucleotide/protein complexes calls for biophysical methods that can resolve the structure and dynamics of such systems on the critical nanometer length scale. A modern electron paramagnetic resonance (EPR) method called pulsed electron-electron double resonance (PELDOR or DEER) has been shown to reliably and precisely provide distances and distance distributions in the range of 1.5-8nm. In addition, recent experiments proved that a PELDOR experiment also contains information on the orientation of labels, enables easy separation of coupling mechanisms and allows for counting the number of monomers in complexes. This chapter briefly summarizes the theory, describes how to perform and analyze such experiments and discusses the limitations.
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Popova AM, Kálai T, Hideg K, Qin PZ. Site-specific DNA structural and dynamic features revealed by nucleotide-independent nitroxide probes. Biochemistry 2009; 48:8540-50. [PMID: 19650666 DOI: 10.1021/bi900860w] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In site-directed spin labeling, a covalently attached nitroxide probe containing a chemically inert unpaired electron is utilized to obtain information on the local environment of the parent macromolecule. Studies presented here examine the feasibility of probing local DNA structural and dynamic features using a class of nitroxide probes that are linked to chemically substituted phosphorothioate positions at the DNA backbone. Two members of this family, designated as R5 and R5a, were attached to eight different sites of a dodecameric DNA duplex without severely perturbing the native B-form conformation. Measured X-band electron paramagnetic resonance (EPR) spectra, which report on nitroxide rotational motions, were found to vary depending on the location of the label (e.g., duplex center vs termini) and the surrounding DNA sequence. This indicates that R5 and R5a can provide information on the DNA local environment at the level of an individual nucleotide. As these probes can be attached to arbitrary nucleotides within a nucleic acid sequence, they may provide a means to "scan" a given DNA molecule in order to interrogate its local structural and dynamic features.
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Affiliation(s)
- Anna M Popova
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
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Kuznetsov NA, Milov AD, Koval VV, Samoilova RI, Grishin YA, Knorre DG, Tsvetkov YD, Fedorova OS, Dzuba SA. PELDOR study of conformations of double-spin-labeled single- and double-stranded DNA with non-nucleotide inserts. Phys Chem Chem Phys 2009; 11:6826-32. [PMID: 19639157 DOI: 10.1039/b904873a] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
DNA fragments were synthesized consisting of 12 nucleotides and containing non-nucleotide inserts of different length in the middle. Two nitroxide spin labels 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl were attached at the two ends of the molecules. Single-stranded DNAs and double-stranded DNAs (DNA duplexes) in frozen at 77 K glassy water/glycerol solutions were studied using pulsed electron-electron double resonance (PELDOR). The distance distributions between two spin labels in molecules were obtained from PELDOR data using Tikhonov regularization algorithm, and were found to be close to the Gaussian functions. Experimental PELDOR data were fitted by adjusting precisely the maximum position and the width of these functions. The obtained results show that duplexes possess a substantially narrower distribution, as compared to the single-stranded DNAs. Introduction of a non-nucleotide insert 2-hydroxymethyl-3-hydroxy-tetrahydrofuran leads to a slight but nevertheless detectable decrease of the mean distance between two spin labels. This decrease may be attributed to bending of the molecule around the insert site, by an angle of approximately 20 degrees . An introduction of a non-nucleotide insert bis-(di-ethyleneglycol)-phosphate results in a remarkable broadening of the distance distribution. The results evidence that PELDOR of spin-labeled DNA molecules may be used as a "molecular ruler" for studying the influence of local damages on the DNA conformations.
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Affiliation(s)
- Nikita A Kuznetsov
- Institute of Chemical Biology and Fundamental Medicine, Lavrentyev Ave. 8, 630090, Novosibirsk, Russia
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Galiano L, Blackburn ME, Veloro AM, Bonora M, Fanucci GE. Solute effects on spin labels at an aqueous-exposed site in the flap region of HIV-1 protease. J Phys Chem B 2009; 113:1673-80. [PMID: 19146430 DOI: 10.1021/jp8057788] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effects of solutes on spin-label mobility and protein conformation have been investigated with X-band continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopy for spin labels attached to an aqueous-exposed site in the beta-hairpin flap region of HIV-1 protease. Specifically, we examined the effects of glycerol, sucrose, PEG3000, and Ficoll400 for four commonly used nitroxide spin labels and found that the largest perturbations to the EPR line shapes occur for solutions containing PEG3000 and glycerol. From comparisons of the spectral line shapes and distance distribution profiles of spin-labeled HIV-1 protease with and without inhibitor, it was concluded that solutes such as glycerol and PEG3000 alter the line shapes of the spin label in the beta-hairpin flaps of HIV-1 PR by modulation of spin-label mobility through changes in preferential interactions with the solutes. It is noteworthy that the high osmolality of the 40% glycerol solution did not alter the conformation of the flaps as determined from pulsed EPR distance measurements.
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Affiliation(s)
- Luis Galiano
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, USA
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Xi X, Sun Y, Karim CB, Grigoryants VM, Scholes CP. HIV-1 nucleocapsid protein NCp7 and its RNA stem loop 3 partner: rotational dynamics of spin-labeled RNA stem loop 3. Biochemistry 2008; 47:10099-110. [PMID: 18729386 DOI: 10.1021/bi800602e] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The tumbling dynamics of a 20-mer HIV-1 RNA stem loop 3 spin-labeled at the 5' position were probed in the nanosecond time range. This RNA interacted with the HIV-1 nucleocapsid Zn-finger protein, 1-55 NCp7, and specialized stopped-flow EPR revealed concomitant kinetics of probe immobilization from milliseconds to seconds. RNA stem loop 3 is highly conserved in HIV, while NCp7 is critical to HIV-RNA packaging and annealing. The 5' probe did not perturb RNA melting or the NCp7/RNA interaction monitored by gel shift and fluorescence. The 5'-labeled RNA tumbled with a subnanosecond isotropic correlation time (approximately 0.60 ns at room temperature) reflecting both local viscosity-independent bond rotation of the probe and viscosity-dependent diffusion of 40-60% of the RNA. The binding of NCp7 to spin-labeled RNA stem loop 3 in a 1:1 ratio increased the spin-labeled tumbling time by about 40%. At low ionic strength with a ratio of NCp7 to RNA >or=3 (i.e., an NCp7 to nucleotide ratio <or=7, which is the threshold ratio for chaperone effects), the probe tumbling time markedly increased to several nanoseconds, signifying a NCP7/RNA complex with restricted motion even at the initially mobile 5' position. Increasing the ionic strength to shield the electrostatic attraction between polyanionic RNA and polycationic NCp7 eliminated this immobilization. Forming the immobilized >or=3:1 complex also required intact Zn fingers. Stopped-flow EPR kinetics with NCP7/RNA mixed at a 4:1 ratio showed the major phase of NCp7 interaction with RNA stem loop 3 occurred within 4 ms, a second phase occurred with a time constant of approximately 30 ms, and a slower immobilization, possibly concomitant with large complex formation, proceeded over seconds. This work points the way for spin-labeling to investigate oligonucleotide-protein complexes, notably those lacking precise stoichiometry, that are requisite for viral packaging and genome fabrication.
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Affiliation(s)
- Xiangmei Xi
- Department of Chemistry, University at Albany-SUNY, Albany, New York 12222, USA
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Grant GPG, Popova A, Qin PZ. Diastereomer characterizations of nitroxide-labeled nucleic acids. Biochem Biophys Res Commun 2008; 371:451-5. [PMID: 18442474 DOI: 10.1016/j.bbrc.2008.04.088] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2008] [Accepted: 04/17/2008] [Indexed: 11/19/2022]
Abstract
Site-directed spin labeling (SDSL) obtains structural and dynamic information of a macromolecule using a site-specifically attached stable nitroxide radical. SDSL studies of arbitrary DNA and RNA sequences can be achieved using an efficient phosphorothioate labeling scheme, where a nitroxide is attached to a phosphorothioate substituted at a target site during chemical synthesis. The chemically introduced phosphorothioate contains two diastereomers (Rp and Sp), and nitroxides attached to each diastereomer may experience different local environments. Here, we report work on using anion-exchange HPLC to separate and characterize diastereomers in three DNA oligonucleotides and one RNA oligonucleotide. In all oligonucleotides studied, the Rp diastereomer was found to elute earlier than the Sp in the unlabeled oligonucleotides, while a reversal in the elution order (Sp earlier than Rp) was observed for nitroxide-labeled oligonucleotides. The results enable a one-step purification procedure for preparing diastereomerically pure nitroxide-labeled oligonucleotides. This expands the score of nucleic acids SDSL.
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Affiliation(s)
- Gian Paola G Grant
- Department of Chemistry, University of Southern California, LJS-251, 840 Downey Way, Los Angeles, CA 90089-0744, USA
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Qin PZ, Haworth IS, Cai Q, Kusnetzow AK, Grant GPG, Price EA, Sowa GZ, Popova A, Herreros B, He H. Measuring nanometer distances in nucleic acids using a sequence-independent nitroxide probe. Nat Protoc 2008; 2:2354-65. [PMID: 17947978 DOI: 10.1038/nprot.2007.308] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This protocol describes the procedures for measuring nanometer distances in nucleic acids using a nitroxide probe that can be attached to any nucleotide within a given sequence. Two nitroxides are attached to phosphorothioates that are chemically substituted at specific sites of DNA or RNA. Inter-nitroxide distances are measured using a four-pulse double electron-electron resonance technique, and the measured distances are correlated to the parent structures using a Web-accessible computer program. Four to five days are needed for sample labeling, purification and distance measurement. The procedures described herein provide a method for probing global structures and studying conformational changes of nucleic acids and protein/nucleic acid complexes.
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Affiliation(s)
- Peter Z Qin
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0744, USA.
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