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Vögele J, Duchardt-Ferner E, Bains JK, Knezic B, Wacker A, Sich C, Weigand J, Šponer J, Schwalbe H, Krepl M, Wöhnert J. Structure of an internal loop motif with three consecutive U•U mismatches from stem-loop 1 in the 3'-UTR of the SARS-CoV-2 genomic RNA. Nucleic Acids Res 2024; 52:6687-6706. [PMID: 38783391 PMCID: PMC11194097 DOI: 10.1093/nar/gkae349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 03/27/2024] [Accepted: 04/22/2024] [Indexed: 05/25/2024] Open
Abstract
The single-stranded RNA genome of SARS-CoV-2 is highly structured. Numerous helical stem-loop structures interrupted by mismatch motifs are present in the functionally important 5'- and 3'-UTRs. These mismatches modulate local helical geometries and feature unusual arrays of hydrogen bonding donor and acceptor groups. However, their conformational and dynamical properties cannot be directly inferred from chemical probing and are difficult to predict theoretically. A mismatch motif (SL1-motif) consisting of three consecutive U•U base pairs is located in stem-loop 1 of the 3'-UTR. We combined NMR-spectroscopy and MD-simulations to investigate its structure and dynamics. All three U•U base pairs feature two direct hydrogen bonds and are as stable as Watson-Crick A:U base pairs. Plasmodium falciparum 25S rRNA contains a triple U•U mismatch motif (Pf-motif) differing from SL1-motif only with respect to the orientation of the two closing base pairs. Interestingly, while the geometry of the outer two U•U mismatches was identical in both motifs the preferred orientation of the central U•U mismatch was different. MD simulations and potassium ion titrations revealed that the potassium ion-binding mode to the major groove is connected to the different preferred geometries of the central base pair in the two motifs.
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Affiliation(s)
- Jennifer Vögele
- Institute of Molecular Biosciences, Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
- Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Elke Duchardt-Ferner
- Institute of Molecular Biosciences, Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
- Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Jasleen Kaur Bains
- Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
- Institute of Organic Chemistry and Chemical Biology, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
| | - Bozana Knezic
- Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
- Institute of Organic Chemistry and Chemical Biology, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
| | - Anna Wacker
- Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
- Institute of Organic Chemistry and Chemical Biology, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
| | - Christian Sich
- Volkswagen AG, Brieffach 1617/0, 38436 Wolfsburg, Germany
| | - Julia E Weigand
- Institute of Pharmaceutical Chemistry, University of Marburg, Marbacher Weg 6, 35037 Marburg, Germany
| | - Jiří Šponer
- Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska 135, 612 00 Brno, Czech Republic
| | - Harald Schwalbe
- Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
- Institute of Organic Chemistry and Chemical Biology, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
| | - Miroslav Krepl
- Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska 135, 612 00 Brno, Czech Republic
| | - Jens Wöhnert
- Institute of Molecular Biosciences, Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
- Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
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2
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Yoon J, Conley BM, Shin M, Choi JH, Bektas CK, Choi JW, Lee KB. Ultrasensitive Electrochemical Detection of Mutated Viral RNAs with Single-Nucleotide Resolution Using a Nanoporous Electrode Array (NPEA). ACS NANO 2022; 16:5764-5777. [PMID: 35362957 DOI: 10.1021/acsnano.1c10824] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The detection of nucleic acids and their mutation derivatives is vital for biomedical science and applications. Although many nucleic acid biosensors have been developed, they often require pretreatment processes, such as target amplification and tagging probes to nucleic acids. Moreover, current biosensors typically cannot detect sequence-specific mutations in the targeted nucleic acids. To address the above problems, herein, we developed an electrochemical nanobiosensing system using a phenomenon comprising metal ion intercalation into the targeted mismatched double-stranded nucleic acids and a homogeneous Au nanoporous electrode array (Au NPEA) to obtain (i) sensitive detection of viral RNA without conventional tagging and amplifying processes, (ii) determination of viral mutation occurrence in a simple detection manner, and (iii) multiplexed detection of several RNA targets simultaneously. As a proof-of-concept demonstration, a SARS-CoV-2 viral RNA and its mutation derivative were used in this study. Our developed nanobiosensor exhibited highly sensitive detection of SARS-CoV-2 RNA (∼1 fM detection limit) without tagging and amplifying steps. In addition, a single point mutation of SARS-CoV-2 RNA was detected in a one-step analysis. Furthermore, multiplexed detection of several SARS-CoV-2 RNAs was successfully demonstrated using a single chip with four combinatorial NPEAs generated by a 3D printing technique. Collectively, our developed nanobiosensor provides a promising platform technology capable of detecting various nucleic acids and their mutation derivatives in highly sensitive, simple, and time-effective manners for point-of-care biosensing.
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Affiliation(s)
- Jinho Yoon
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey,123 Bevier Road, Piscataway, New Jersey 08854, United States
- Department of Chemical & Biomolecular Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Republic of Korea
| | - Brian M Conley
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey,123 Bevier Road, Piscataway, New Jersey 08854, United States
| | - Minkyu Shin
- Department of Chemical & Biomolecular Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Republic of Korea
| | - Jin-Ha Choi
- School of Chemical Engineering, Jeonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju, Jeollabuk-do 54896, Republic of Korea
| | - Cemile Kilic Bektas
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey,123 Bevier Road, Piscataway, New Jersey 08854, United States
| | - Jeong-Woo Choi
- Department of Chemical & Biomolecular Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Republic of Korea
| | - Ki-Bum Lee
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey,123 Bevier Road, Piscataway, New Jersey 08854, United States
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3
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Muya JT, Chung H, Lee SU. Theoretical investigation on the ground state properties of the hexaamminecobalt(iii) and nitro-nitrito linkage isomerism in pentaamminecobalt(iii) in vacuo. RSC Adv 2018; 8:3328-3342. [PMID: 35541161 PMCID: PMC9077707 DOI: 10.1039/c7ra11603a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 01/09/2018] [Indexed: 11/21/2022] Open
Abstract
Nitro-nitrito isomerization in Co(NH3)5NO2 2+ linkage isomers was investigated with a focus on the geometries, relative stabilities and chemical bonding using ωB97XD/6-31+G(d,p) to elucidate the photo-salient effect in [Co(NH3)5NO2]NO3Cl. Different techniques like atoms in molecules (AIM), electron localization function (ELF) and natural bonding orbital (NBO) were used to gain insight into the chemical bonds of the isomers and to identify the key factors influencing their relative stabilities. The study of the ground-state potential energy surface of [Co(NH3)5NO2]2+ reveals that the nitro/exo-nitrito isomerization reaction can proceed via the following two paths: (1) nitro → TS1 (38.16 kcal mol-1) → endo-nitrito → TS2 (9.68 kcal mol-1) → exo-nitrito and (2) nitro → TS3 (41.76 kcal mol-1) → exo-nitrito. Pathway (1) through endo-nitrito is the most likely isomerization mechanism because of a lower energy barrier than pathway (2). The intramolecular-resonance-assisted hydrogen bonds (N-H⋯O and N-H⋯N), the orientation of NO2, and the difference between Co-N and Co-O bond energies are identified as the key factors determining the relative stabilities of the linkage isomers. Co(NH3)6 3+ is less stable compared to Co(NH3)5NO2 2+ and undergoes a slight geometrical distortion from D 3d to either D 3 or S 6 characterized by a stabilization energy of ∼750 cm-1 at CCSD(T)/6-31+G(d,p).
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Affiliation(s)
| | - Hoeil Chung
- Hanyang University, Department of Chemistry Seoul South Korea
| | - Sang Uck Lee
- Hanyang University, Department of Chemical & Molecular Engineering Sangnok-gu Ansan 426-791 Korea
- Hanyang University, Department of Bionanotechnology Sangnok-gu Ansan 426-791 Korea
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4
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Specific phosphorothioate substitution within domain 6 of a group II intron ribozyme leads to changes in local structure and metal ion binding. J Biol Inorg Chem 2017; 23:167-177. [DOI: 10.1007/s00775-017-1519-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 11/14/2017] [Indexed: 10/18/2022]
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Abstract
Inspired by the recent success of scientific-discovery games for predicting protein tertiary and RNA secondary structures, we have developed an open software for coarse-grained RNA folding simulations, guided by human intuition. To determine the extent to which interactive simulations can accurately predict 3D RNA structures of increasing complexity and lengths (four RNAs with 22-47 nucleotides), an interactive experiment was conducted with 141 participants who had very little knowledge of nucleic acids systems and computer simulations, and had received only a brief description of the important forces stabilizing RNA structures. Their structures and full trajectories have been analyzed statistically and compared to standard replica exchange molecular dynamics simulations. Our analyses show that participants gain easily chemical intelligence to fold simple and nontrivial topologies, with little computer time, and this result opens the door for the use of human-guided simulations to RNA folding. Our experiment shows that interactive simulations have better chances of success when the user widely explores the conformational space. Interestingly, providing on-the-fly feedback of the root mean square deviation with respect to the experimental structure did not improve the quality of the proposed models.
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6
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Applications of NMR to structure determination of RNAs large and small. Arch Biochem Biophys 2017; 628:42-56. [PMID: 28600200 DOI: 10.1016/j.abb.2017.06.003] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 05/31/2017] [Accepted: 06/04/2017] [Indexed: 02/07/2023]
Abstract
Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool to investigate the structure and dynamics of RNA, because many biologically important RNAs have conformationally flexible structures, which makes them difficult to crystallize. Functional, independently folded RNA domains, range in size between simple stem-loops of as few as 10-20 nucleotides, to 50-70 nucleotides, the size of tRNA and many small ribozymes, to a few hundred nucleotides, the size of more complex RNA enzymes and of the functional domains of non-coding transcripts. In this review, we discuss new methods for sample preparation, assignment strategies and structure determination for independently folded RNA domains of up to 100 kDa in molecular weight.
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7
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Bartova S, Pechlaner M, Donghi D, Sigel RKO. Studying metal ion binding properties of a three-way junction RNA by heteronuclear NMR. J Biol Inorg Chem 2016; 21:319-28. [PMID: 26880094 DOI: 10.1007/s00775-016-1341-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 01/25/2016] [Indexed: 10/22/2022]
Abstract
Self-splicing group II introns are highly structured RNA molecules, containing a characteristic secondary and catalytically active tertiary structure, which is formed only in the presence of Mg(II). Mg(II) initiates the first folding step governed by the κζ element within domain 1 (D1κζ). We recently solved the NMR structure of D1κζ derived from the mitochondrial group II intron ribozyme Sc.ai5γ and demonstrated that Mg(II) is essential for its stabilization. Here, we performed a detailed multinuclear NMR study of metal ion interactions with D1κζ, using Cd(II) and cobalt(III)hexammine to probe inner- and outer-sphere coordination of Mg(II) and thus to better characterize its binding sites. Accordingly, we mapped (1)H, (15)N, (13)C, and (31)P spectral changes upon addition of different amounts of the metal ions. Our NMR data reveal a Cd(II)-assisted macrochelate formation at the 5'-end triphosphate, a preferential Cd(II) binding to guanines in a helical context, an electrostatic interaction in the ζ tetraloop receptor and various metal ion interactions in the GAAA tetraloop and κ element. These results together with our recently published data on Mg(II) interaction provide a much better understanding of Mg(II) binding to D1κζ, and reveal how intricate and complex metal ion interactions can be.
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Affiliation(s)
- Simona Bartova
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,Department of Analytical Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28, Prague, Czech Republic
| | - Maria Pechlaner
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,Institute for Molecular Modeling and Simulation, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18, 1190, Vienna, Austria
| | - Daniela Donghi
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
| | - Roland K O Sigel
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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8
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Abstract
![]()
Influenza A is an RNA virus with
a genome of eight negative sense
segments. Segment 7 mRNA contains a 3′ splice site for alternative
splicing to encode the essential M2 protein. On the basis of sequence
alignment and chemical mapping experiments, the secondary structure
surrounding the 3′ splice site has an internal loop, adenine
bulge, and hairpin loop when it is in the hairpin conformation that
exposes the 3′ splice site. We report structural features of
a three-dimensional model of the hairpin derived from nuclear magnetic
resonance spectra and simulated annealing with restrained molecular
dynamics. Additional insight was provided by modeling based on 1H chemical shifts. The internal loop containing the 3′
splice site has a dynamic guanosine and a stable imino (cis Watson–Crick/Watson–Crick) GA pair. The adenine bulge
also appears to be dynamic with the A either stacked in the stem or
forming a base triple with a Watson–Crick GC pair. The hairpin
loop is a GAAA tetraloop closed by an AC pair.
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Affiliation(s)
- Jonathan L Chen
- †Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Scott D Kennedy
- ‡Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, United States
| | - Douglas H Turner
- †Department of Chemistry, University of Rochester, Rochester, New York 14627, United States.,§Center for RNA Biology, University of Rochester, Rochester, New York 14627, United States
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9
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Marcia M, Pyle AM. Principles of ion recognition in RNA: insights from the group II intron structures. RNA (NEW YORK, N.Y.) 2014; 20:516-27. [PMID: 24570483 PMCID: PMC3964913 DOI: 10.1261/rna.043414.113] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 01/29/2014] [Indexed: 05/20/2023]
Abstract
Metal ions promote both RNA folding and catalysis, thus being essential in stabilizing the structure and determining the function of large RNA molecules, including group II introns. The latter are self-splicing metalloribozymes, containing a heteronuclear four-metal-ion center within the active site. In addition to these catalytic ions, group II introns bind many other structural ions, including delocalized ions that bind the RNA diffusively and well-ordered ions that bind the RNA tightly with high occupancy. The latter ions, which can be studied by biophysical methods, have not yet been analyzed systematically. Here, we compare crystal structures of the group IIC intron from Oceanobacillus iheyensis and classify numerous site-bound ions, which are primarily localized in the intron core and near long-range tertiary contacts. Certain ion-binding sites resemble motifs observed in known RNA structures, while others are idiosyncratic to the group II intron. Particularly interesting are (1) ions proximal to the active site, which may participate in splicing together with the catalytic four-metal-ion center, (2) organic ions that bind regions predicted to interact with intron-encoded proteins, and (3) unusual monovalent ions bound to GU wobble pairs, GA mismatches, the S-turn, the tetraloop-receptor, and the T-loop. Our analysis extends the general principles by which ions participate in RNA structural organization and it will aid in the determination and interpretation of future RNA structures.
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Affiliation(s)
- Marco Marcia
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06511, USA
| | - Anna Marie Pyle
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06511, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
- Corresponding authorE-mail
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10
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Solution structure and metal ion binding sites of the human CPEB3 ribozyme's P4 domain. J Biol Inorg Chem 2014; 19:903-12. [PMID: 24652468 DOI: 10.1007/s00775-014-1125-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Accepted: 03/05/2014] [Indexed: 01/18/2023]
Abstract
Three ribozymes are known to occur in humans, the CPEB3 ribozyme, the CoTC ribozyme, and the hammerhead ribozyme. Here, we present the NMR solution structure of a well-conserved motif within the CPEB3 ribozyme, the P4 domain. In addition, we discuss the binding sites and impact of Mg(2+) and [Co(NH3)6](3+), a spectroscopic probe for [Mg(H2O)6](2+), on the structure. The well-defined P4 region is a hairpin closed with a UGGU tetraloop that shows a distinct electrostatic surface potential and a characteristic, strongly curved backbone trajectory. The P4 hairpin contains two specific Mg(2+) binding sites: one outer-sphere binding site close to the proposed CPEB3 ribozyme active site with potential relevance for maintaining a compact fold of the ribozyme core, and one inner-sphere binding site, probably stabilizing the tetraloop structure. The structure of the tetraloop resembles an RNase III recognition structure, as previously described for an AGUU tetraloop. The detailed knowledge of the P4 domain and its metal ion binding preferences thus brings us closer to understanding the importance of Mg(2+) binding for the CPEB3 ribozyme's fold and function in the cell.
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11
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Bonneau E, Legault P. NMR localization of divalent cations at the active site of the Neurospora VS ribozyme provides insights into RNA-metal-ion interactions. Biochemistry 2014; 53:579-90. [PMID: 24364590 PMCID: PMC3906864 DOI: 10.1021/bi401484a] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Metal cations represent key elements of RNA structure and function. In the Neurospora VS ribozyme, metal cations play diverse roles; they are important for substrate recognition, formation of the active site, and shifting the pKa's of two key nucleobases that contribute to the general acid-base mechanism. Recently, we determined the NMR structure of the A730 loop of the VS ribozyme active site (SLVI) that contributes the general acid (A756) in the enzymatic mechanism of the cleavage reaction. Our studies showed that magnesium (Mg(2+)) ions are essential to stabilize the formation of the S-turn motif within the A730 loop that exposes the A756 nucleobase for catalysis. In this article, we extend these NMR investigations by precisely mapping the Mg(2+)-ion binding sites using manganese-induced paramagnetic relaxation enhancement and cadmium-induced chemical-shift perturbation of phosphorothioate RNAs. These experiments identify five Mg(2+)-ion binding sites within SLVI. Four Mg(2+) ions in SLVI are associated with known RNA structural motifs, including the G-U wobble pair and the GNRA tetraloop, and our studies reveal novel insights about Mg(2+) ion binding to these RNA motifs. Interestingly, one Mg(2+) ion is specifically associated with the S-turn motif, confirming its structural role in the folding of the A730 loop. This Mg(2+) ion is likely important for formation of the active site and may play an indirect role in catalysis.
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Affiliation(s)
- Eric Bonneau
- Département de Biochimie et Médecine Moléculaire, Université de Montréal , C.P. 6128, Succursale Centre-Ville, Montréal, Québec H3C 3J7, Canada
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12
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Kornyshev AA, Leikin S. Helical structure determines different susceptibilities of dsDNA, dsRNA, and tsDNA to counterion-induced condensation. Biophys J 2013; 104:2031-41. [PMID: 23663846 DOI: 10.1016/j.bpj.2013.03.033] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 03/06/2013] [Accepted: 03/18/2013] [Indexed: 11/18/2022] Open
Abstract
Recent studies of counterion-induced condensation of nucleic acid helices into aggregates produced several puzzling observations. For instance, trivalent cobalt hexamine ions condensed double-stranded (ds) DNA oligomers but not their more highly charged dsRNA counterparts. Divalent alkaline earth metal ions condensed triple-stranded (ts) DNA oligomers but not dsDNA. Here we show that these counterintuitive experimental results can be rationalized within the electrostatic zipper model of interactions between molecules with helical charge motifs. We report statistical mechanical calculations that reveal dramatic and nontrivial interplay between the effects of helical structure and thermal fluctuations on electrostatic interaction between oligomeric nucleic acids. Combining predictions for oligomeric and much longer helices, we also interpret recent experimental studies of the role of counterion charge, structure, and chemistry. We argue that an electrostatic zipper attraction might be a major or even dominant force in nucleic acid condensation.
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Affiliation(s)
- Alexei A Kornyshev
- Department of Chemistry, Imperial College London, London, United Kingdom
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13
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Rowinska-Zyrek M, Skilandat M, Sigel RKO. Hexaamminecobalt(III) - Probing Metal Ion Binding Sites in Nucleic Acids by NMR Spectroscopy. Z Anorg Allg Chem 2013. [DOI: 10.1002/zaac.201300123] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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14
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Korth MMT, Sigel RKO. Unusually high-affinity Mg(2+) binding at the AU-rich sequence within the antiterminator hairpin of a Mg(2+) riboswitch. Chem Biodivers 2013; 9:2035-49. [PMID: 22976989 DOI: 10.1002/cbdv.201200031] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mg(2+)-Responsive riboswitches represent a fascinating example of bifunctional RNAs that sense Mg(2+) ions with high selectivity and autonomously regulate the expression of Mg(2+)-transporter proteins. The mechanism of the mgtA riboswitch is scarcely understood, and a detailed structural analysis is called for to study how this RNA can selectively recognize Mg(2+) and respond by switching between two alternative stem loop structures. In this work, we investigated the structure and Mg(2+)-binding properties of the lower part of the antiterminator loop C from the mgtA riboswitch of Yersinia enterocolitica by solution NMR and report a discrete Mg(2+)-binding site embedded in the AU-rich sequence. At the position of Mg(2+) binding, the helical axis exhibits a distinct kink accompanied by a widening of the major groove, which accommodates the Mg(2+)-binding pocket. An unusually large overlap between two adenine residues on the opposite strands suggests that the bending may be sequence-induced by strong stacking interactions, enabling Mg(2+) to bind at this so-far not described metal-ion binding site.
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Affiliation(s)
- Maximiliane M T Korth
- Institute of Inorganic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, (phone: +41 44 635 4652; fax: +41 44 635 6802)
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15
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Donghi D, Pechlaner M, Finazzo C, Knobloch B, Sigel RKO. The structural stabilization of the κ three-way junction by Mg(II) represents the first step in the folding of a group II intron. Nucleic Acids Res 2012; 41:2489-504. [PMID: 23275550 PMCID: PMC3575829 DOI: 10.1093/nar/gks1179] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Folding of group II introns is characterized by a first slow compaction of domain 1 (D1) followed by the rapid docking of other domains to this scaffold. D1 compaction initiates in a small subregion encompassing the κ and ζ elements. These two tertiary elements are also the major interaction sites with domain 5 to form the catalytic core. Here, we provide the first characterization of the structure adopted at an early folding step and show that the folding control element can be narrowed down to the three-way junction with the κ motif. In our nuclear magnetic resonance studies of this substructure derived from the yeast mitochondrial group II intron Sc.ai5γ, we show that a high affinity Mg(II) ion stabilizes the κ element and enables coaxial stacking between helices d′ and d′′, favoring a rigid duplex across the three-way junction. The κ-element folds into a stable GAAA-tetraloop motif and engages in A-minor interactions with helix d′. The addition of cobalt(III)hexammine reveals three distinct binding sites. The Mg(II)-promoted structural rearrangement and rigidification of the D1 core can be identified as the first micro-step of D1 folding.
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Affiliation(s)
- Daniela Donghi
- Institute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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16
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Henriksen NM, Davis DR, Cheatham TE. Molecular dynamics re-refinement of two different small RNA loop structures using the original NMR data suggest a common structure. JOURNAL OF BIOMOLECULAR NMR 2012; 53:321-39. [PMID: 22714631 PMCID: PMC3405240 DOI: 10.1007/s10858-012-9642-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2012] [Accepted: 05/24/2012] [Indexed: 06/01/2023]
Abstract
Restrained molecular dynamics simulations are a robust, though perhaps underused, tool for the end-stage refinement of biomolecular structures. We demonstrate their utility-using modern simulation protocols, optimized force fields, and inclusion of explicit solvent and mobile counterions-by re-investigating the solution structures of two RNA hairpins that had previously been refined using conventional techniques. The structures, both domain 5 group II intron ribozymes from yeast ai5γ and Pylaiella littoralis, share a nearly identical primary sequence yet the published 3D structures appear quite different. Relatively long restrained MD simulations using the original NMR restraint data identified the presence of a small set of violated distance restraints in one structure and a possibly incorrect trapped bulge nucleotide conformation in the other structure. The removal of problematic distance restraints and the addition of a heating step yielded representative ensembles with very similar 3D structures and much lower pairwise RMSD values. Analysis of ion density during the restrained simulations helped to explain chemical shift perturbation data published previously. These results suggest that restrained MD simulations, with proper caution, can be used to "update" older structures or aid in the refinement of new structures that lack sufficient experimental data to produce a high quality result. Notable cautions include the need for sufficient sampling, awareness of potential force field bias (such as small angle deviations with the current AMBER force fields), and a proper balance between the various restraint weights.
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Affiliation(s)
- Niel M Henriksen
- Department of Medicinal Chemistry, College of Pharmacy, University of Utah, 2000 East 30 South Skaggs 201, Salt Lake City, UT 84112, USA.
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17
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Morgado CA, Svozil D, Turner DH, Šponer J. Understanding the role of base stacking in nucleic acids. MD and QM analysis of tandem GA base pairs in RNA duplexes. Phys Chem Chem Phys 2012; 14:12580-91. [PMID: 22722325 DOI: 10.1039/c2cp40556c] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Preceding NMR experiments show that the conformation of tandem GA base pairs, an important recurrent non-canonical building block in RNA duplexes, is context dependent. The GA base pairs adopt "sheared" N3(G)-N6(A), N2(G)-N7(A) geometry in the r(CGAG)(2) and r(iGGAiC)(2) contexts while switching to "imino" N1(G)-N1(A), O6(G)-N6(A) geometry in the r(GGAC)(2) and r(iCGAiG)(2) contexts (iC and iG stand for isocytosine and isoguanine, respectively). As base stacking is likely to be one of the key sources of the context dependence of the conformation of GA base pairs, we calculated base stacking energies in duplexes containing such base pairs, to see if this dependence can be predicted by stacking energy calculations. When investigating the context dependence of the GA geometry two different conformations of the same duplex were compared (imino vs. sheared). The geometries were generated via explicit solvent MD simulations of the respective RNA duplexes, while the subsequent QM energy calculations focused on base stacking interactions of the four internal base pairs. Geometrical relaxation of nucleobase atoms prior to the stacking energy computations has a non-negligible effect on the results. The stacking energies were derived at the DFT-D/6-311++G(3df,3pd) level. We show a rather good correspondence between the intrinsic gas-phase stacking energies and the NMR-determined GA geometries. The conformation with more favorable gas-phase stacking is in most cases the one observed in experiments. This correlation is not improved when including solvent effects via the COSMO method. On the other side, the stacking calculations do not predict the relative thermodynamic stability of duplex formation for different sequences.
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Affiliation(s)
- Claudio A Morgado
- Universidad Técnica Federico Santa María, Departamento de Química, Casilla 110-V, Valparaíso, Chile.
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18
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Moss WN, Dela-Moss LI, Kierzek E, Kierzek R, Priore SF, Turner DH. The 3' splice site of influenza A segment 7 mRNA can exist in two conformations: a pseudoknot and a hairpin. PLoS One 2012; 7:e38323. [PMID: 22685560 PMCID: PMC3369869 DOI: 10.1371/journal.pone.0038323] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 05/03/2012] [Indexed: 12/29/2022] Open
Abstract
The 3′ splice site of influenza A segment 7 is used to produce mRNA for the M2 ion-channel protein, which is critical to the formation of viable influenza virions. Native gel analysis, enzymatic/chemical structure probing, and oligonucleotide binding studies of a 63 nt fragment, containing the 3′ splice site, key residues of an SF2/ASF splicing factor binding site, and a polypyrimidine tract, provide evidence for an equilibrium between pseudoknot and hairpin structures. This equilibrium is sensitive to multivalent cations, and can be forced towards the pseudoknot by addition of 5 mM cobalt hexammine. In the two conformations, the splice site and other functional elements exist in very different structural environments. In particular, the splice site is sequestered in the middle of a double helix in the pseudoknot conformation, while in the hairpin it resides in a two-by-two nucleotide internal loop. The results suggest that segment 7 mRNA splicing can be controlled by a conformational switch that exposes or hides the splice site.
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Affiliation(s)
- Walter N. Moss
- Department of Chemistry, Center for RNA Biology, University of Rochester, Rochester, New York, United States of America
| | - Lumbini I. Dela-Moss
- Department of Chemistry, Center for RNA Biology, University of Rochester, Rochester, New York, United States of America
| | - Elzbieta Kierzek
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Noskowskiego, Poland
| | - Ryszard Kierzek
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Noskowskiego, Poland
| | - Salvatore F. Priore
- Department of Chemistry, Center for RNA Biology, University of Rochester, Rochester, New York, United States of America
| | - Douglas H. Turner
- Department of Chemistry, Center for RNA Biology, University of Rochester, Rochester, New York, United States of America
- * E-mail:
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20
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Abstract
Metal ions are inextricably involved with nucleic acids due to their polyanionic nature. In order to understand the structure and function of RNAs and DNAs, one needs to have detailed pictures on the structural, thermodynamic, and kinetic properties of metal ion interactions with these biomacromolecules. In this review we first compile the physicochemical properties of metal ions found and used in combination with nucleic acids in solution. The main part then describes the various methods developed over the past decades to investigate metal ion binding by nucleic acids in solution. This includes for example hydrolytic and radical cleavage experiments, mutational approaches, as well as kinetic isotope effects. In addition, spectroscopic techniques like EPR, lanthanide(III) luminescence, IR and Raman as well as various NMR methods are summarized. Aside from gaining knowledge about the thermodynamic properties on the metal ion-nucleic acid interactions, especially NMR can be used to extract information on the kinetics of ligand exchange rates of the metal ions applied. The final section deals with the influence of anions, buffers, and the solvent permittivity on the binding equilibria between metal ions and nucleic acids. Little is known on some of these aspects, but it is clear that these three factors have a large influence on the interaction between metal ions and nucleic acids.
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Affiliation(s)
- Maria Pechlaner
- Institute of Inorganic Chemistry, University of Zürich, Zürich, Switzerland
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21
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Denning EJ, Priyakumar UD, Nilsson L, MacKerell AD. Impact of 2'-hydroxyl sampling on the conformational properties of RNA: update of the CHARMM all-atom additive force field for RNA. J Comput Chem 2011; 32:1929-43. [PMID: 21469161 PMCID: PMC3082605 DOI: 10.1002/jcc.21777] [Citation(s) in RCA: 288] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Revised: 01/24/2011] [Accepted: 01/30/2011] [Indexed: 01/02/2023]
Abstract
Here, we present an update of the CHARMM27 all-atom additive force field for nucleic acids that improves the treatment of RNA molecules. The original CHARMM27 force field parameters exhibit enhanced Watson-Crick base pair opening which is not consistent with experiment, whereas analysis of molecular dynamics (MD) simulations show the 2'-hydroxyl moiety to almost exclusively sample the O3' orientation. Quantum mechanical (QM) studies of RNA related model compounds indicate the energy minimum associated with the O3' orientation to be too favorable, consistent with the MD results. Optimization of the dihedral parameters dictating the energy of the 2'-hydroxyl proton targeting the QM data yielded several parameter sets, which sample both the base and O3' orientations of the 2'-hydroxyl to varying degrees. Selection of the final dihedral parameters was based on reproduction of hydration behavior as related to a survey of crystallographic data and better agreement with experimental NMR J-coupling values. Application of the model, designated CHARMM36, to a collection of canonical and noncanonical RNA molecules reveals overall improved agreement with a range of experimental observables as compared to CHARMM27. The results also indicate the sensitivity of the conformational heterogeneity of RNA to the orientation of the 2'-hydroxyl moiety and support a model whereby the 2'-hydroxyl can enhance the probability of conformational transitions in RNA.
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Affiliation(s)
- Elizabeth J. Denning
- Department of Pharmaceutical Sciences, School of Pharmacy, University
of Maryland, Baltimore, MD 21201
| | - U. Deva Priyakumar
- Department of Pharmaceutical Sciences, School of Pharmacy, University
of Maryland, Baltimore, MD 21201
| | - Lennart Nilsson
- Department of Pharmaceutical Sciences, School of Pharmacy, University
of Maryland, Baltimore, MD 21201
| | - Alexander D. MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University
of Maryland, Baltimore, MD 21201
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22
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Spano MN, Walter NG. Solution structure of an alternate conformation of helix27 from Escherichia coli16S rRNA. Biopolymers 2011; 95:653-68. [PMID: 21442607 DOI: 10.1002/bip.21626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 03/08/2011] [Accepted: 03/09/2011] [Indexed: 11/09/2022]
Abstract
Helix (H)27 of 16S ribosomal (r)RNA from Escherichia coli was dubbed the "switch helix" when mutagenesis suggested that two alternative base pair registers may have distinct functional roles in the bacterial ribosome. Although more recent genetic analyses suggest that H27 conformational switching is not required for translation, previous solution studies demonstrated that the isolated E. coli H27 can dynamically convert between the 885 and 888 conformations. Here, we have solved the nuclear magnetic resonance solution structure of a locked 888 conformation. NOE and residual dipolar coupling restraints reveal an architecture that markedly differs from that of the 885 conformation found in crystal structures of the bacterial ribosome. In place of the loop E motif that characterizes the 885 conformer and that the 888 conformer cannot adopt, we find evidence for an asymmetrical A-rich internal loop stabilized by stacking interactions among the unpaired A's. Comparison of the isolated H27 888 solution structure with the 885 crystal structure within the context of the ribosome suggests a difference in overall length of H27 that presents one plausible reason for the absence of H27 conformational switching within the sterically confining ribosome.
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23
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Wilson RC, Smith AM, Fuchs RT, Kleckner IR, Henkin TM, Foster MP. Tuning riboswitch regulation through conformational selection. J Mol Biol 2011; 405:926-38. [PMID: 21075119 PMCID: PMC3019289 DOI: 10.1016/j.jmb.2010.10.056] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 10/27/2010] [Accepted: 10/28/2010] [Indexed: 01/20/2023]
Abstract
The S(MK) box riboswitch, which represents one of three known classes of S-adenosylmethionine (SAM)-responsive riboswitches, regulates gene expression in bacteria at the level of translation initiation. In contrast to most riboswitches, which contain separate domains responsible for ligand recognition and gene regulation, the ligand-binding and regulatory domains of the S(MK) box riboswitch are coincident. This property was exploited to allow the first atomic-level characterization of a functionally intact riboswitch in both the ligand-bound state and the ligand-free state. NMR spectroscopy revealed distinct mutually exclusive RNA conformations that are differentially populated in the presence or in the absence of the effector metabolite. Isothermal titration calorimetry and in vivo reporter assay results revealed the thermodynamic and functional consequences of this conformational equilibrium. We present a comprehensive model of the structural, thermodynamic, and functional properties of this compact RNA regulatory element.
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Affiliation(s)
- Ross C. Wilson
- Department of Biochemistry, Ohio State University, Columbus, OH 43210
- Center for RNA Biology, Ohio State University, Columbus, OH 43210
| | - Angela M. Smith
- Center for RNA Biology, Ohio State University, Columbus, OH 43210
- Department of Microbiology, Ohio State University, Columbus, OH 43210
| | - Ryan T. Fuchs
- Center for RNA Biology, Ohio State University, Columbus, OH 43210
- Department of Microbiology, Ohio State University, Columbus, OH 43210
| | - Ian R. Kleckner
- Department of Biochemistry, Ohio State University, Columbus, OH 43210
- Center for RNA Biology, Ohio State University, Columbus, OH 43210
| | - Tina M. Henkin
- Center for RNA Biology, Ohio State University, Columbus, OH 43210
- Department of Microbiology, Ohio State University, Columbus, OH 43210
| | - Mark P. Foster
- Department of Biochemistry, Ohio State University, Columbus, OH 43210
- Center for RNA Biology, Ohio State University, Columbus, OH 43210
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24
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Pasquali S, Derreumaux P. HiRE-RNA: a high resolution coarse-grained energy model for RNA. J Phys Chem B 2010; 114:11957-66. [PMID: 20795690 DOI: 10.1021/jp102497y] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Although RNAs play many cellular functions, the gap between their sequences and 3D structures is increasing and our knowledge of RNA thermodynamics and long time scale dynamics is still limited at an atomic level of detail. In principle, all-atom molecular dynamics (MD) and replica exchange molecular dynamics (REMD) simulations can investigate these issues, but with current computer facilities, these simulations in explicit solvent have been limited to small RNAs and to short times. To move to larger systems, we can resort to coarse-graining. In this study, we present HiRE-RNA, a generic high resolution coarse-grained model for RNA, and report MD and REMD simulations on two RNAs of 22 and 36 nucleotides. Starting from unfolded structures, the 22-mer folds within 1.8 A rmsd from the NMR structure, while the 36-mer folds within 4.6 A rmsd. Current results suggest that further optimization of the HiRE-RNA force field should open the door to a relevant model for studying large RNAs, such as riboswitches, and for predicting 3D structures from secondary structure information.
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Affiliation(s)
- Samuela Pasquali
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, Institut de Biologie Physico Chimique et Université Paris Diderot-Paris 7, 13 rue Pierre et Marie Curie, 75005 Paris, France
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25
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Cevec M, Thibaudeau C, Plavec J. NMR structure of the let-7 miRNA interacting with the site LCS1 of lin-41 mRNA from Caenorhabditis elegans. Nucleic Acids Res 2010; 38:7814-21. [PMID: 20660479 PMCID: PMC2995062 DOI: 10.1093/nar/gkq640] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
We have determined the 3D structure of a 34-nt RNA construct, herein named LCS1co, which mimics the interaction of let-7 microRNA (miRNA) to one of its complementary binding sites, LCS1, in the 3′-untranslated region of lin-41 mRNA by solution-state NMR spectroscopy. let-7 miRNAs control the timing of development of the nematode Caenorhabditis elegans and are highly conserved in mammals. The sequence and structure of the two conserved let-7 complementary sites, LCS1 and LCS2, in the 3′-untranslated region of lin-41 mRNA are important for a proper downregulation of lin-41. The high-resolution NMR structure reveals details of the binding of let-7 miRNA to lin-41 mRNA which involves formation of a complex with non-canonical structural elements within the seed region. LCS1co exhibits a stem-loop structure with two stems, an asymmetric internal loop and an adenine bulge. Comparison with the NMR solution-state structure of the let-7:lin-41 complex involving the LCS2-binding site shows that conformational freedom of the asymmetric internal loop of LCS1co correlates with a smaller bend between the upper and lower stems in comparison to the well-defined asymmetric loop of LCS2co.
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Affiliation(s)
- Mirko Cevec
- Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, Slovenia
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26
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Christian EL, Anderson VE, Carey PR, Harris ME. A quantitative Raman spectroscopic signal for metal-phosphodiester interactions in solution. Biochemistry 2010; 49:2869-79. [PMID: 20180599 DOI: 10.1021/bi901866u] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Accurate identification and quantification of metal ion-phosphodiester interactions are essential for understanding the role of metal ions as determinants of three-dimensional folding of large RNAs and as cofactors in the active sites of both RNA and protein phosphodiesterases. Accomplishing this goal is difficult due to the dynamic and complex mixture of direct and indirect interactions formed with nucleic acids and other phosphodiesters in solution. To address this issue, Raman spectroscopy has been used to measure changes in bond vibrational energies due to metal interactions. However, the contributions of inner-sphere, H-bonding, and electrostatic interactions to the Raman spectrum of phosphoryl oxygens have not been analyzed quantitatively. Here, we report that all three forms of metal ion interaction result in attenuation of the Raman signal for the symmetric vibration of the nonbridging phosphate oxygens (nu(s)PO(2)(-)), while only inner-sphere coordination gives rise to an apparent shift of nu(s)PO(2)(-) to higher wavenumbers (nu(s)PO(2)(-)M) in solution. Formation of nu(s)PO(2)(-)M is shown to be both dependent on metal ion identity and an accurate measure of site-specific metal ion binding. In addition, the spectroscopic parameter reflecting the energetic difference between nu(s)PO(2)(-) and nu(s)PO(2)(-)M (DeltanuM) is largely insensitive to changes in phosphodiester structure but strongly dependent on the absolute electronegativity and hardness of the interacting metal ion. Together, these studies provide strong experimental support for the use of nu(s)PO(2)(-)M and DeltanuM as general spectroscopic features for the quantitative analysis of metal binding affinity and the identification of metal ions associated with phosphodiesters in solution.
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Affiliation(s)
- Eric L Christian
- Center for RNA Molecular Biology, Case Western Reserve University School of Medicine,Cleveland, Ohio 44106, USA.
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27
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Priyakumar UD, Hyeon C, Thirumalai D, MacKerell AD. Urea destabilizes RNA by forming stacking interactions and multiple hydrogen bonds with nucleic acid bases. J Am Chem Soc 2009; 131:17759-61. [PMID: 19919063 PMCID: PMC2791195 DOI: 10.1021/ja905795v] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Urea titration of RNA by urea is an effective approach to investigate the forces stabilizing this biologically important molecule. We used all atom molecular dynamics simulations using two urea force fields and two RNA constructs to elucidate in atomic detail the destabilization mechanism of folded RNA in aqueous urea solutions. Urea denatures RNA by forming multiple hydrogen bonds with the RNA bases and has little influence on the phosphodiester backbone. Most significantly we discovered that urea engages in stacking interactions with the bases. We also estimate, for the first time, the m-value for RNA, which is a measure of the strength of urea-RNA interactions. Our work provides a conceptual understanding of the mechanism by which urea enhances RNA folding rates.
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Affiliation(s)
- U. Deva Priyakumar
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Changbong Hyeon
- Department of Chemistry, Chung-Ang University, Seoul 156-756, Republic of Korea
| | - D. Thirumalai
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742
| | - Alexander D. MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
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28
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B Staple D, Payne SH, Reddin ALC, Kreuzer HJ. Stretching and unfolding of multidomain biopolymers: a statistical mechanics theory of titin. Phys Biol 2009; 6:025005. [PMID: 19571360 DOI: 10.1088/1478-3975/6/2/025005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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29
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Bilbille Y, Vendeix FAP, Guenther R, Malkiewicz A, Ariza X, Vilarrasa J, Agris PF. The structure of the human tRNALys3 anticodon bound to the HIV genome is stabilized by modified nucleosides and adjacent mismatch base pairs. Nucleic Acids Res 2009; 37:3342-53. [PMID: 19324888 PMCID: PMC2691828 DOI: 10.1093/nar/gkp187] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Replication of human immunodeficiency virus (HIV) requires base pairing of the reverse transcriptase primer, human tRNALys3, to the viral RNA. Although the major complementary base pairing occurs between the HIV primer binding sequence (PBS) and the tRNA's 3′-terminus, an important discriminatory, secondary contact occurs between the viral A-rich Loop I, 5′-adjacent to the PBS, and the modified, U-rich anticodon domain of tRNALys3. The importance of individual and combined anticodon modifications to the tRNA/HIV-1 Loop I RNA's interaction was determined. The thermal stabilities of variously modified tRNA anticodon region sequences bound to the Loop I of viral sub(sero)types G and B were analyzed and the structure of one duplex containing two modified nucleosides was determined using NMR spectroscopy and restrained molecular dynamics. The modifications 2-thiouridine, s2U34, and pseudouridine, Ψ39, appreciably stabilized the interaction of the anticodon region with the viral subtype G and B RNAs. The structure of the duplex results in two coaxially stacked A-form RNA stems separated by two mismatched base pairs, U162•Ψ39 and G163•A38, that maintained a reasonable A-form helix diameter. The tRNA's s2U34 stabilized the interaction between the A-rich HIV Loop I sequence and the U-rich anticodon, whereas the tRNA's Ψ39 stabilized the adjacent mismatched pairs.
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Affiliation(s)
- Yann Bilbille
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695-7622, USA
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30
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Furler M, Knobloch B, Sigel RK. Influence of decreased solvent permittivity on the structure and magnesium(II)-binding properties of the catalytic domain 5 of a group II intron ribozyme. Inorganica Chim Acta 2009. [DOI: 10.1016/j.ica.2008.03.095] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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31
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Zhao Y, Knee JL, Baranger AM. Characterization of two adenosine analogs as fluorescence probes in RNA. Bioorg Chem 2008; 36:271-7. [PMID: 18707751 PMCID: PMC2661016 DOI: 10.1016/j.bioorg.2008.06.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 06/10/2008] [Accepted: 06/12/2008] [Indexed: 11/22/2022]
Abstract
The fluorescence properties of two adenosine analogs, 2-(3-phenylpropyl)adenosine [A-3CPh] and 2-(4-phenylbutyl)adenosine [A-4CPh], are reported. As monomers, the quantum yields and the mean lifetimes are 0.011 and 6.22 ns for A-3CPh and 0.007 and 7.13 ns for A-4CPh, respectively. Surprisingly, the quantum yields of the two probes are enhanced 11- to 82-fold upon incorporation into RNA, while the mean lifetimes decrease 23-40%. The data suggest that a subpopulation of molecules is responsible for the fluorescence characteristics and that the distribution of emitting and non-emitting structures is altered upon incorporation of the probes into RNA. Thus, although both adenosine analogs have low quantum yields as monomers, their fluorescence signals are significantly enhanced in RNA. Thermodenaturation experiments and CD spectroscopy indicate that incorporation of the adenosine analogs into three different RNAs does not alter their global structure or stability. Therefore, these probes should be useful for probing events occurring close to the site of modification.
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Affiliation(s)
- Ying Zhao
- Department of Chemistry, Wesleyan University, Middletown, CT 06459
| | - Joseph L. Knee
- Department of Chemistry, Wesleyan University, Middletown, CT 06459
| | - Anne M. Baranger
- Department of Chemistry, Wesleyan University, Middletown, CT 06459
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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32
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Hsiao C, Tannenbaum E, VanDeusen H, Hershkovitz E, Perng G, Tannenbaum AR, Williams LD. Complexes of Nucleic Acids with Group I and II Cations. NUCLEIC ACID–METAL ION INTERACTIONS 2008. [DOI: 10.1039/9781847558763-00001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Chiaolong Hsiao
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30332-0400 USA
| | | | - Halena VanDeusen
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30332-0400 USA
| | - Eli Hershkovitz
- School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332–0250 USA
- School of Biomedical Engineering Georgia Institute of Technology Atlanta, GA 30332–0250 USA
| | - Ginger Perng
- School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332–0250 USA
| | - Allen R. Tannenbaum
- School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332–0250 USA
- School of Biomedical Engineering Georgia Institute of Technology Atlanta, GA 30332–0250 USA
| | - Loren Dean Williams
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30332-0400 USA
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33
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Pincus DL, Hyeon C, Thirumalai D. Effects of trimethylamine N-oxide (TMAO) and crowding agents on the stability of RNA hairpins. J Am Chem Soc 2008; 130:7364-72. [PMID: 18479134 DOI: 10.1021/ja078326w] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We study the effect of the osmolyte, Trimethylamine N-Oxide (TMAO), which accumulates in cells in response to osmotic stress, on the stability of RNA hairpins. All atom molecular dynamics (MD) simulations of a nucleotide and the 22-nucleotide RNA hairpin P5GA in an aqueous TMAO solution show that TMAO preferentially interacts with the base through the formation of a single hydrogen bond. To circumvent the difficulties of adequately sampling the conformational space of polynucleotides, we used coarse-grained models (including one that is inspired by the results of all-atom MD simulations of a single nucleotide) to probe the effects of osmoyltes on the stability of P5GA. If, as revealed by our MD simulations, the cosolute specifically interacts with only one base at a time, then we find practically no change in hairpin stability as measured by Delta T m = T m(Phi) - T m, where T m(Phi) and T m are the melting temperatures at volume fraction Phi of the osmolyte and Phi = 0, respectively. This finding is in qualitative agreement with recent experiments. If the interactions between the RNA and osmolytes are repulsive, which is appropriate for mimicking the effects of crowding, Delta T m can vary from 5 to 15 K depending on the size of the osmolyte and the nature of RNA-osmolyte interactions. Cosolutes that interact favorably with multiple bases simultaneously can stabilize the hairpin more than a crowding agent of the same size. The implications of our predictions for experiments are briefly outlined.
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Affiliation(s)
- David L Pincus
- Biophysics Program, Institute for Physical Science and Technology, and Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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34
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Erat MC, Zerbe O, Fox T, Sigel RKO. Solution structure of domain 6 from a self-splicing group II intron ribozyme: a Mg(2+) binding site is located close to the stacked branch adenosine. Chembiochem 2008; 8:306-14. [PMID: 17200997 DOI: 10.1002/cbic.200600459] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Group II intron self-splicing is essential for the correct expression of organellar genes in plants, fungi, and yeast, as well as of bacterial genes. Self-excision of these autocatalytic introns from the primary RNA transcript is achieved in a two-step mechanism that is apparently analogous to that of the eukaryotic spliceosome. The 2'-OH of a conserved adenosine (the branch point) located within domain 6 (D6) acts as the nucleophile in the first step of splicing. Despite the biological importance of group II introns, little is known about their structural organization and usage of metal ions in catalysis. Here we report the first solution structure of a catalytically active D6 construct encompassing the branch point and the neighboring helical regions from the mitochondrial yeast intron ai5gamma. The branch adenosine is the single unpaired nucleotide, and, in contrast to the spliceosomal branch site, resides within the helix, being partially stacked between two flanking GU wobble pairs. We identified a novel prominent Mg(2+) binding site in the major groove of the branch site. Importantly, Mg(2+) addition does not impair the stacking of the branch adenosine, rather it strengthens the interaction with the flanking uridines, as shown by NMR and fluorescence studies. This means that domain 6 presents the branch adenosine in a stacked fashion to the core of group II introns upon folding to the active conformation.
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Affiliation(s)
- Michèle C Erat
- Institute of Inorganic Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
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35
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Erat MC, Sigel RKO. Determination of the Intrinsic Affinities of Multiple Site-Specific Mg2+ Ions Coordinated to Domain 6 of a Group II Intron Ribozyme. Inorg Chem 2007; 46:11224-34. [DOI: 10.1021/ic701627t] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Michèle C. Erat
- Institute of Inorganic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Roland K. O. Sigel
- Institute of Inorganic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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36
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Yan Z, Sikri S, Beveridge DL, Baranger AM. Identification of an aminoacridine derivative that binds to RNA tetraloops. J Med Chem 2007; 50:4096-104. [PMID: 17665894 DOI: 10.1021/jm070305p] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RNA folds into diverse structures that form unique targets for small molecules and thus provide significant potential for controlling biological processes involving RNA with small-molecule ligands. We are investigating molecular recognition of tetraloop RNA by small molecules. RNA tetraloops are four-nucleotide stem loops with unusual stability that are involved in biological processes involving RNA by forming binding sites for proteins and other RNAs. We have sequentially used the docking programs DOCK and AutoDock to screen 1990 small molecules in the NCI diversity set to identify molecules selective for RNA tetraloops over double-stranded RNA. The compounds predicted to bind to tetraloop RNA were evaluated for binding RNA tetraloops using 1H NMR spectroscopy and fluorescence techniques. An aminoacridine derivative (AD2) was identified that binds to a GAAA tetraloop in a 2:1 ratio with dissociation constants of 1.0 and 4.0 microM. AD2 binds with approximately 20-fold and 9-fold higher affinity to tetraloop RNA than to double- and single-stranded RNAs, respectively.
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Affiliation(s)
- Zhaohui Yan
- Department of Chemistry and Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459, USA
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Roychowdhury-Saha M, Burke DH. Distinct reaction pathway promoted by non-divalent-metal cations in a tertiary stabilized hammerhead ribozyme. RNA (NEW YORK, N.Y.) 2007; 13:841-8. [PMID: 17456566 PMCID: PMC1869042 DOI: 10.1261/rna.339207] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Divalent ion sensitivity of hammerhead ribozymes is significantly reduced when the RNA structure includes appropriate tertiary stabilization. Therefore, we investigated the activity of the tertiary stabilized "RzB" hammerhead ribozyme in several nondivalent ions. Ribozyme RzB is active in spermidine and Na(+) alone, although the cleavage rates are reduced by more than 1,000-fold relative to the rates observed in Mg(2+) and in transition metal ions. The trivalent cobalt hexammine (CoHex) ion is often used as an exchange-inert analog of hydrated magnesium ion. Trans-cleavage rates exceeded 8 min(-1) in 20 mM CoHex, which promoted cleavage through outersphere interactions. The stimulation of catalysis afforded by the tertiary structural interactions within RzB does not require Mg(2+), unlike other extended hammerhead ribozymes. Site-specific interaction with at least one Mg(2+) ion is suggested by CoHex competition experiments. In the presence of a constant, low concentration of Mg(2+), low concentrations of CoHex decreased the rate by two to three orders of magnitude relative to the rate in Mg(2+) alone. Cleavage rates increased as CoHex concentrations were raised further, but the final fraction cleaved was lower than what was observed in CoHex or Mg(2+) alone. These observations suggest that Mg(2+) and CoHex compete for binding and that they cause misfolded structures when they are together. The results of this study support the existence of an alternate catalytic mechanism used by nondivalent ions (especially CoHex) that is distinct from the one promoted by divalent metal ions, and they imply that divalent metals influence catalysis through a specific nonstructural role.
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38
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Tolbert BS, Kennedy SD, Schroeder SJ, Krugh TR, Turner DH. NMR structures of (rGCUGAGGCU)2 and (rGCGGAUGCU)2: probing the structural features that shape the thermodynamic stability of GA pairs. Biochemistry 2007; 46:1511-22. [PMID: 17279616 PMCID: PMC4032317 DOI: 10.1021/bi061350m] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The NMR structures of [see text] and [see text] are reported. The internal loop, [see text], is about 2 kcal/mol more stable than [see text] at 37 degrees C. The duplexes assemble into similar global folds characterized by the formation of tandem sheared GA pairs. The different stabilities of the loops are accompanied by differences in the local structure of the closing GU pairs. In the [see text] internal loop, the GU pairs form canonical wobble configurations with two hydrogen bonds, whereas in [see text], the GU pairs form a single hydrogen bond involving the amino group, GH22, and the carbonyl group, UO4. This pairing is similar to the GU closing pair of the 690 hairpin loop found in E. coli 16S rRNA. The [see text] and [see text] structures reveal how the subtle interplay between stacking and hydrogen bonding determines sequence dependent conformation and thermodynamic stability. Thus, this work provides structural and thermodynamic benchmarks for theoreticians in the ongoing effort to understand the sequence dependence of RNA physicochemical properties.
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Affiliation(s)
- Blanton S. Tolbert
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642
| | - Scott D. Kennedy
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642
| | - Susan J. Schroeder
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019-3051
| | - Thomas R. Krugh
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216
| | - Douglas H. Turner
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216
- Center for Pediatric Biomedical Research and Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642
- To whom correspondence should be addressed to: , (Phone) 585-275-3207, (Fax) 585-276-0205
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39
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Hyeon C, Thirumalai D. Mechanical unfolding of RNA: from hairpins to structures with internal multiloops. Biophys J 2006; 92:731-43. [PMID: 17028142 PMCID: PMC1779982 DOI: 10.1529/biophysj.106.093062] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mechanical unfolding of RNA structures, ranging from hairpins to ribozymes, using laser optical tweezer experiments have begun to reveal the features of the energy landscape that cannot be easily explored using conventional experiments. Upon application of constant force (f), RNA hairpins undergo cooperative transitions from folded to unfolded states whereas subdomains of ribozymes unravel one at a time. Here, we use a self-organized polymer model and Brownian dynamics simulations to probe mechanical unfolding at constant force and constant-loading rate of four RNA structures of varying complexity. For simple hairpins, such as P5GA, application of constant force or constant loading rate results in bistable cooperative transitions between folded and unfolded states without populating any intermediates. The transition state location (DeltaxFTS) changes dramatically as the loading rate is varied. At loading rates comparable to those used in laser optical tweezer experiments, the hairpin is plastic, with DeltaxFTS being midway between folded and unfolded states; whereas at high loading rates, DeltaxFTS moves close to the folded state, i.e., RNA is brittle. For the 29-nucleotide TAR RNA with the three-nucleotide bulge, unfolding occurs in a nearly two-state manner with an occasional pause in a high free energy metastable state. Forced unfolding of the 55 nucleotides of the Hepatitis IRES domain IIa, which has a distorted L-shaped structure, results in well-populated stable intermediates. The most stable force-stabilized intermediate represents straightening of the L-shaped structure. For these structures, the unfolding pathways can be predicted using the contact map of the native structures. Unfolding of a RNA motif with internal multiloop, namely, the 109-nucleotide prohead RNA that is part of the 29 DNA packaging motor, at constant value of rf occurs with three distinct rips that represent unraveling of the paired helices. The rips represent kinetic barriers to unfolding. Our work shows 1), the response of RNA to force is largely determined by the native structure; and 2), only by probing mechanical unfolding over a wide range of forces can the underlying energy landscape be fully explored.
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Affiliation(s)
- Changbong Hyeon
- Biophysics Program, Institute for Physical Science and Technology, Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, USA.
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Kieltyka JW, Chow CS. Probing RNA hairpins with cobalt(III)hexammine and electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:1376-1382. [PMID: 16904339 DOI: 10.1016/j.jasms.2006.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2006] [Revised: 07/03/2006] [Accepted: 07/06/2006] [Indexed: 05/11/2023]
Abstract
In this work, electrospray ionization mass spectrometry (ESI MS) was employed to study the interactions of cobalt(III) hexammine, Co(NH3)6(3+), with five RNA hairpins representing the 790 loop of 16S ribosomal RNA and 1920 loop of 23S ribosomal RNA. The RNAs varied in mismatch identity (G.U versus A.C) and level of base modification (pseudouridine versus uridine). Co(NH3)6(3+) binding was observed with the four RNA hairpins that contained a G.U wobble pair in the stem region. ESI MS revealed 1:1 and 1:2 complex formation with all RNAs. Weaker binding was observed with the fifth RNA hairpin that contained an A.C wobble pair in the stem region. The effects of pH on Co(NH3)6(3+) binding were also examined.
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Affiliation(s)
- Jason W Kieltyka
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, 48202, Detroit, MI, USA
| | - Christine S Chow
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, 48202, Detroit, MI, USA.
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Gudima SO, Chang J, Taylor JM. Restoration in vivo of defective hepatitis delta virus RNA genomes. RNA (NEW YORK, N.Y.) 2006; 12:1061-73. [PMID: 16618966 PMCID: PMC1464851 DOI: 10.1261/rna.2328806] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The 1679-nt single-stranded RNA genome of hepatitis delta virus (HDV) is circular in conformation. It is able to fold into an unbranched rodlike structure via intramolecular base-pairing. This RNA is replicated by host RNA polymerase II (Pol II). Such transcription is unique, because Pol II is known only for its ability to act on DNA templates. The present study addressed the ability of the HDV RNA replication to tolerate insertions of up to 1000 nt of non-HDV sequence either at an end of the rodlike RNA structure or at a site embedded within the rod. The insertions did not interfere with the ability of primary transcripts to be processed in vivo by ribozyme cleavage and ligation. The insertions greatly reduced the ability of genomes to replicate. However, when total RNA from such transfected cells was used to transfect new recipient cells, replicating HDV RNAs could be detected by Northern analyses. The size of the emerged RNAs was consistent with loss of the inserted sequences. RT-PCR, cloning, and sequencing showed that recovery involved removal of inserted sequences with or without small deletions of adjacent RNA sequences. Such restoration of the RNA genome is consistent with a model requiring intramolecular template-switching (RNA recombination) during RNA-directed transcription, in combination with biological selection for maintenance of the rodlike structure of the template.
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Abstract
Internal loops in RNA are important for folding and function. Consecutive noncanonical pairs can form in internal loops having at least two nucleotides on each side. Thermodynamic and structural insights into such internal loops should improve approximations for their stabilities and predictions of secondary and three-dimensional structures. Most natural internal loops are purine rich. A series of oligoribonucleotides that form purine-rich internal loops of 5-10 nucleotides, including kink-turn loops, were studied by UV melting, exchangeable proton and phosphorus NMR. Three consecutive GA pairs with the motif 5' Y GGA/3' R AAG or GGA R 3'/AAG Y 5' (i.e., 5' GGA 3'/3' AAG 5' closed on at least one side with a CG, UA, or UG pair with Y representing C or U and R representing A or G) stabilize internal loops having 6-10 nucleotides. Certain motifs with two consecutive GA pairs are also stabilizing. In internal loops with three or more nucleotides on each side, the motif 5' U G/3' G A has stability similar to 5' C G/3' G A. A revised model for predicting stabilities of internal loops with 6-10 nucleotides is derived by multiple linear regression. Loops with 2 x 3 nucleotides are predicted well by a previous thermodynamic model.
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Affiliation(s)
- Gang Chen
- Department of Chemistry, University of Rochester, Rochester, NY 14627
| | - Douglas H. Turner
- Department of Chemistry, University of Rochester, Rochester, NY 14627
- Center for Pediatric Biomedical Research and Department of Pediatrics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642
- To whom correspondence should be addressed. Phone: (585) 275-3207. Fax: (585) 276-0205.
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43
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Abstract
Nanomanipulation of individual RNA molecules, using laser optical tweezers, has made it possible to infer the major features of their energy landscape. Time-dependent mechanical unfolding trajectories, measured at a constant stretching force (f(S)) of simple RNA structures (hairpins and three-helix junctions) sandwiched between RNA/DNA hybrid handles show that they unfold in a reversible all-or-none manner. To provide a molecular interpretation of the experiments we use a general coarse-grained off-lattice Gō-like model, in which each nucleotide is represented using three interaction sites. Using the coarse-grained model we have explored forced-unfolding of RNA hairpin as a function of f(S) and the loading rate (r(f)). The simulations and theoretical analysis have been done both with and without the handles that are explicitly modeled by semiflexible polymer chains. The mechanisms and timescales for denaturation by temperature jump and mechanical unfolding are vastly different. The directed perturbation of the native state by f(S) results in a sequential unfolding of the hairpin starting from their ends, whereas thermal denaturation occurs stochastically. From the dependence of the unfolding rates on r(f) and f(S) we show that the position of the unfolding transition state is not a constant but moves dramatically as either r(f) or f(S) is changed. The transition-state movements are interpreted by adopting the Hammond postulate for forced-unfolding. Forced-unfolding simulations of RNA, with handles attached to the two ends, show that the value of the unfolding force increases (especially at high pulling speeds) as the length of the handles increases. The pathways for refolding of RNA from stretched initial conformation, upon quenching f(S) to the quench force f(Q), are highly heterogeneous. The refolding times, upon force-quench, are at least an order-of-magnitude greater than those obtained by temperature-quench. The long f(Q)-dependent refolding times starting from fully stretched states are analyzed using a model that accounts for the microscopic steps in the rate-limiting step, which involves the trans to gauche transitions of the dihedral angles in the GAAA tetraloop. The simulations with explicit molecular model for the handles show that the dynamics of force-quench refolding is strongly dependent on the interplay of their contour length and persistence length and the RNA persistence length. Using the generality of our results, we also make a number of precise experimentally testable predictions.
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Affiliation(s)
- Changbong Hyeon
- Biophysics Program Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, USA
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Grajcar L, El Amri C, Ghomi M, Fermandjian S, Huteau V, Mandel R, Lecomte S, Baron MH. Assessment of adenyl residue reactivity within model nucleic acids by surface enhanced Raman spectroscopy. Biopolymers 2006; 82:6-28. [PMID: 16425174 DOI: 10.1002/bip.20455] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We rank the reactivity of the adenyl residues (A) of model DNA and RNA molecules with electropositive subnano size [Ag]n+ sites as a function of nucleic acid primary sequences and secondary structures and in the presence of biological amounts of Cl- and Na+ or Mg2+ ions. In these conditions A is markedly more reactive than any other nucleic acid bases. A reactivity is higher in ribo (r) than in deoxyribo (d) species [pA>pdA and (pA)n>>(pdA)n]. Base pairing decreases A reactivity in corresponding duplexes but much less in r than in d. In linear single and paired dCAG or dGAC loci, base stacking inhibits A reactivity even if A is bulged or mispaired (A.A). dA tracts are highly reactive only when dilution prevents self-association and duplex structures. In d hairpins the solvent-exposed A residues are reactive in CAG and GAC triloops and even more in ATC loops. Among the eight rG1N2R3A4 loops, those bearing a single A (A4) are the least reactive. The solvent-exposed A2 is reactive, but synergistic structural transitions make the initially stacked A residues of any rGNAA loop much more reactive. Mg2+ cross-bridging single strands via phosphates may screen A reactivity. In contrast d duplexes cross-bridging enables "A flipping" much more in rA.U pairs than in dA.T. Mg2+ promotes A reactivity in unpaired strands. For hairpins Mg2+ binding stabilizes the stems, but according to A position in the loops, A reactivity may be abolished, reduced, or enhanced. It is emphasized that not only accessibility but also local flexibility, concerted docking, and cation and anion binding control A reactivity.
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Affiliation(s)
- Lydie Grajcar
- Laboratoire de Dynamique Interactions et Réactivité, UMR 7075, Université Paris 6 CNRS, 2 rue Henri Dunant, 94320, Thiais, France
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45
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Lambert MN, Hoerter JAH, Pereira MJB, Walter NG. Solution probing of metal ion binding by helix 27 from Escherichia coli 16S rRNA. RNA (NEW YORK, N.Y.) 2005; 11:1688-700. [PMID: 16244134 PMCID: PMC1370855 DOI: 10.1261/rna.2940705] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Helix (H)27 from Escherichia coli 16S ribosomal (r)RNA is centrally located within the small (30S) ribosomal subunit, immediately adjacent to the decoding center. Bacterial 30S subunit crystal structures depicting Mg(2+) binding sites resolve two magnesium ions within the vicinity of H27: one in the major groove of the G886-U911 wobble pair, and one within the GCAA tetraloop. Binding of such metal cations is generally thought to be crucial for RNA folding and function. To ask how metal ion-RNA interactions in crystals compare with those in solution, we have characterized, using solution NMR spectroscopy, Tb(3+) footprinting and time-resolved fluorescence resonance energy transfer (tr-FRET), location, and modes of metal ion binding in an isolated H27. NMR and Tb(3+) footprinting data indicate that solution secondary structure and Mg(2+) binding are generally consistent with the ribosomal crystal structures. However, our analyses also suggest that H27 is dynamic in solution and that metal ions localize within the narrow major groove formed by the juxtaposition of the loop E motif with the tandem G894-U905 and G895-U904 wobble pairs. In addition, tr-FRET studies provide evidence that Mg(2+) uptake by the H27 construct results in a global lengthening of the helix. We propose that only a subset of H27-metal ion interactions has been captured in the crystal structures of the 30S ribosomal subunit, and that small-scale structural dynamics afforded by solution conditions may contribute to these differences. Our studies thus highlight an example for differences between RNA-metal ion interactions observed in solution and in crystals.
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Zhao Q, Nagaswamy U, Lee H, Xia Y, Huang HC, Gao X, Fox GE. NMR structure and Mg2+ binding of an RNA segment that underlies the L7/L12 stalk in the E.coli 50S ribosomal subunit. Nucleic Acids Res 2005; 33:3145-53. [PMID: 15939932 PMCID: PMC1143578 DOI: 10.1093/nar/gki621] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Helix 42 of Domain II of Escherichia coli 23S ribosomal RNA underlies the L7/L12 stalk in the ribosome and may be significant in positioning this feature relative to the rest of the 50S ribosomal subunit. Unlike the Haloarcula marismortui and Deinococcus radiodurans examples, the lower portion of helix 42 in E.coli contains two consecutive G*A oppositions with both adenines on the same side of the stem. Herein, the structure of an analog of positions 1037-1043 and 1112-1118 in the helix 42 region is reported. NMR spectra and structure calculations support a cis Watson-Crick/Watson-Crick (cis W.C.) G*A conformation for the tandem (G*A)2 in the analog and a minimally perturbed helical duplex stem. Mg2+ titration studies imply that the cis W.C. geometry of the tandem (G*A)2 probably allows O6 of G20 and N1 of A4 to coordinate with a Mg2+ ion as indicated by the largest chemical shift changes associated with the imino group of G20 and the H8 of G20 and A4. A cross-strand bridging Mg2+ coordination has also been found in a different sequence context in the crystal structure of H.marismortui 23S rRNA, and therefore it may be a rare but general motif in Mg2+ coordination.
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Affiliation(s)
- Qin Zhao
- Department of Biology and Biochemistry, University of HoustonHouston, TX 77204-5001, USA
| | - Uma Nagaswamy
- Department of Biology and Biochemistry, University of HoustonHouston, TX 77204-5001, USA
| | - Hunjoong Lee
- Department of Chemistry, University of HoustonHouston, TX 77204-5001, USA
| | - Youlin Xia
- Department of Chemistry, University of HoustonHouston, TX 77204-5001, USA
| | - Hung-Chung Huang
- Department of Biology and Biochemistry, University of HoustonHouston, TX 77204-5001, USA
| | - Xiaolian Gao
- Department of Biology and Biochemistry, University of HoustonHouston, TX 77204-5001, USA
- Department of Chemistry, University of HoustonHouston, TX 77204-5001, USA
| | - George E. Fox
- Department of Biology and Biochemistry, University of HoustonHouston, TX 77204-5001, USA
- To whom correspondence should be addressed. Tel: +1 713 743 8363; Fax: +1 713 743 8351;
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47
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Wrzesinski J, Ciesiolka J. Characterization of structure and metal ions specificity of Co2+-binding RNA aptamers. Biochemistry 2005; 44:6257-68. [PMID: 15835914 DOI: 10.1021/bi047397u] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Studies on RNA motifs capable of binding metal ions have largely focused on Mg(2+)-specific motifs, therefore information concerning interactions of other metal ions with RNA is still very limited. Application of the in vitro selection approach allowed us to isolate two RNA aptamers that bind Co(2+) ions. Structural analysis of their secondary structures revealed the presence of two motifs, loop E and "kissing" loop complex, commonly occurring in RNA molecules. The Co(2+)-induced cleavage method was used for identification of Co(2+)-binding sites after the determination of the optimal cleavage conditions. In the aptamers, Co(2+) ions seem to bind to N7 atoms of purines, inducing cleavage of the adjacent phosphodiester bonds, similarly as is the case with yeast tRNA(Phe). Although the in vitro selection experiment was carried out in the presence of Co(2+) ions only, the aptamers displayed broader metal ions specificity. This was shown by inhibition of Co(2+)-induced cleavages in the presence of the following transition metal ions: Zn(2+), Cd(2+), Ni(2+), and Co(NH(3))(6)(3+) complex. On the other hand, alkaline metal ions such as Mg(2+), Ca(2+), Sr(2+), and Ba(2+) affected Co(2+)-induced cleavages only slightly. Multiple metal ions specificity of Co(2+)-binding sites has also been reported for other in vitro selected or natural RNAs. Among many factors that influence metal specificity of the Co(2+)-binding pocket, chemical properties of metal ions, such as their hardness as well as the structure of the coordination site, seem to be particularly important.
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Affiliation(s)
- Jan Wrzesinski
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
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48
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Abstract
Mechanical unfolding trajectories, generated by applying constant force in optical-tweezer experiments, show that RNA hairpins and the P5abc subdomain of the group I intron unfold reversibly. We use coarse-grained Go-like models for RNA hairpins to explore forced unfolding over a broad range of temperatures. A number of predictions that are amenable to experimental tests are made. At the critical force, the hairpin jumps between folded and unfolded conformations without populating any discernible intermediates. The phase diagram in the force-temperature (f, T) plane shows that the hairpin unfolds by an all-or-none process. The cooperativity of the unfolding transition increases dramatically at low temperatures. Free energy of stability, obtained from time averages of mechanical unfolding trajectories, coincides with ensemble averages, which establishes ergodicity. The hopping time between the native basin of attraction (NBA) and the unfolded basin increases dramatically along the phase boundary. Thermal unfolding is stochastic, whereas mechanical unfolding occurs in "quantized steps" with great variations in the step lengths. Refolding times, upon force quench, from stretched states to the NBA are at least an order of magnitude greater than folding times by temperature quench. Upon force quench from stretched states, the NBA is reached in at least three stages. In the initial stages, the mean end-to-end distance decreases nearly continuously, and there is a sudden transition to the NBA only in the last stage. Because of the generality of the results, we propose that similar behavior should be observed in force quench refolding of proteins.
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Affiliation(s)
- Changbong Hyeon
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA
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49
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Abstract
Nucleic acids possess several metal cation recognition sites, including phosphates, nucleobases and possibly riboses. This article focuses on the detection of nucleobase-metal interactions by NMR spectroscopy.
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Affiliation(s)
- Yoshiyuki Tanaka
- Laboratory of Molecular Transformation, Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Sendai, Miyagi 980-8578, Japan.
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50
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Schmitz M. Change of RNase P RNA function by single base mutation correlates with perturbation of metal ion binding in P4 as determined by NMR spectroscopy. Nucleic Acids Res 2004; 32:6358-66. [PMID: 15576680 PMCID: PMC535670 DOI: 10.1093/nar/gkh961] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The solution structures of two 27 nt RNA hairpins and their complexes with cobalt(III)-hexammine [Co(NH(3))(6)(3+)] were determined by NMR spectroscopy. The RNA hairpins are variants of the P4 region from Escherichia coli RNase P RNA: a U-to-A mutant changing the identity of the bulged nucleotide, and a U-to-C, C-to-U double mutant changing only the bulge position. Structures calculated from NMR constraints show that the RNA hairpins adopt different conformations. In the U-to-C, C-to-U double mutant, the conserved bulged uridine in the P4 wild-type stem is found to be shifted in the 3'-direction by one nucleotide when compared with the wild-type structure. Co(NH(3))(6)(3+) is used as a spectroscopic probe for Mg(H(2)O)(6)(2+) binding sites because both complexes have octahedral symmetry and have similar radii. Intermolecular NOE crosspeaks between Co(NH(3))(6)(3+) and RNA protons were used to locate the site of Co(NH(3))(6)(3+) binding to both RNA hairpins. The metal ion binds in the major groove near a bulge loop in both mutants, but is shifted 3' by about one base pair in the double mutant. The change of the metal ion binding site is compared with results obtained on corresponding mutant RNase P RNA molecules as reported by Harris and co-workers (RNA, 1, 210-218).
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Affiliation(s)
- Michael Schmitz
- Institut für Physikalische Biologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
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