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Baulin EF, Mukherjee S, Moafinejad SN, Wirecki TK, Badepally NG, Jaryani F, Stefaniak F, Amiri Farsani M, Ray A, Rocha de Moura T, Bujnicki JM. RNA tertiary structure prediction in CASP15 by the GeneSilico group: Folding simulations based on statistical potentials and spatial restraints. Proteins 2023; 91:1800-1810. [PMID: 37622458 DOI: 10.1002/prot.26575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 07/06/2023] [Accepted: 07/31/2023] [Indexed: 08/26/2023]
Abstract
Ribonucleic acid (RNA) molecules serve as master regulators of cells by encoding their biological function in the ribonucleotide sequence, particularly their ability to interact with other molecules. To understand how RNA molecules perform their biological tasks and to design new sequences with specific functions, it is of great benefit to be able to computationally predict how RNA folds and interacts in the cellular environment. Our workflow for computational modeling of the 3D structures of RNA and its interactions with other molecules uses a set of methods developed in our laboratory, including MeSSPredRNA for predicting canonical and non-canonical base pairs, PARNASSUS for detecting remote homology based on comparisons of sequences and secondary structures, ModeRNA for comparative modeling, the SimRNA family of programs for modeling RNA 3D structure and its complexes with other molecules, and QRNAS for model refinement. In this study, we present the results of testing this workflow in predicting RNA 3D structures in the CASP15 experiment. The overall high score of the computational models predicted by our group demonstrates the robustness of our workflow and its individual components in terms of predicting RNA 3D structures of acceptable quality that are close to the target structures. However, the variance in prediction quality is still quite high, and the results are still too far from the level of protein 3D structure predictions. This exercise led us to consider several improvements, especially to better predict and enforce stacking interactions and non-canonical base pairs.
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Affiliation(s)
- Eugene F Baulin
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Sunandan Mukherjee
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - S Naeim Moafinejad
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Tomasz K Wirecki
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Nagendar Goud Badepally
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Farhang Jaryani
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Filip Stefaniak
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Masoud Amiri Farsani
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Angana Ray
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Tales Rocha de Moura
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Janusz M Bujnicki
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
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Das S, Roy S, Bhattacharyya D. Understanding the role of non-Watson-Crick base pairs in DNA-protein recognition: Structural and energetic aspects using crystallographic database analysis and quantum chemical calculation. Biopolymers 2022; 113:e23492. [PMID: 35615897 DOI: 10.1002/bip.23492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 04/22/2022] [Accepted: 05/03/2022] [Indexed: 11/06/2022]
Abstract
Specific recognition of DNA base sequences by proteins is vital for life-cycles of all organisms. In a large number of crystal structures of protein-DNA complexes, DNA conformation significantly deviates from the canonical B-DNA structure. A key question is whether such alternate conformations exist prior to protein binding and one is selected for complexation or the structure observed is induced by protein binding. Non-canonical base pairs, such as Hoogsteen base pairs, are often observed in crystal structures of protein-DNA complexes. We decided to explore whether the occurrence of such non-canonical base pairs in protein-DNA complexes is induced by the protein or is selected from pre-existing conformations. Detailed quantum chemical calculations with dispersion-corrected density functional theory (DFT-D) indicated that most of the non-canonical base pairs with DNA bases are stable even in the absence of the interacting amino acids. However, the G:G Hoogsteen base pair, which also appears in the telomere structure, appears to be unstable in the absence of other stabilizing agents, such as positively charged amino acids. Thus, the stability of many of the non-canonical base pair containing duplexes may be close to the canonical B-DNA structure and hence energetically accessible in the ground state; suggesting that the selection from pre-existing conformations may be an important mechanism for observed non-canonical base pairs in protein-DNA complexes.
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Affiliation(s)
- Soumi Das
- Department of Biophysics, Bose Institute, Kolkata, India
| | - Siddhartha Roy
- Department of Biophysics, Bose Institute, Kolkata, India
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3
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Skeparnias I, Zhang J. Cooperativity and Interdependency between RNA Structure and RNA-RNA Interactions. Noncoding RNA 2021; 7:ncrna7040081. [PMID: 34940761 PMCID: PMC8704770 DOI: 10.3390/ncrna7040081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/09/2021] [Accepted: 12/10/2021] [Indexed: 11/16/2022] Open
Abstract
Complex RNA–RNA interactions are increasingly known to play key roles in numerous biological processes from gene expression control to ribonucleoprotein granule formation. By contrast, the nature of these interactions and characteristics of their interfaces, especially those that involve partially or wholly structured RNAs, remain elusive. Herein, we discuss different modalities of RNA–RNA interactions with an emphasis on those that depend on secondary, tertiary, or quaternary structure. We dissect recently structurally elucidated RNA–RNA complexes including RNA triplexes, riboswitches, ribozymes, and reverse transcription complexes. These analyses highlight a reciprocal relationship that intimately links RNA structure formation with RNA–RNA interactions. The interactions not only shape and sculpt RNA structures but also are enabled and modulated by the structures they create. Understanding this two-way relationship between RNA structure and interactions provides mechanistic insights into the expanding repertoire of noncoding RNA functions, and may inform the design of novel therapeutics that target RNA structures or interactions.
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Zhang Z, Yu S, Zuo H. DNA Ring-Opening Polymerization Driven by Base Stacking. Chembiochem 2021; 22:1621-1626. [PMID: 33404185 DOI: 10.1002/cbic.202000776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/01/2021] [Indexed: 11/06/2022]
Abstract
Supramolecular polymers, relying on reversible intermolecular interactions, promise a wide range of applications, including optoelectronic materials, self-healing materials, and biomedical delivery materials. Among potential molecular candidates, DNA strands act as an excellent platform. DNA has a well-established secondary structure (double helix), and its intermolecular interactions can be readily thermodynamically engineered and kinetically controlled. Extensive studies have demonstrated that various DNA motifs can polymerize/assemble into large polymers with different topology, geometry, and dimensionalities. Most of the reported polymerization is driven by hybridization of DNA strands. Herein, we report a novel system of DNA supramolecular polymerization that is driven by DNA base stacking. The polymerization has been confirmed by native polyacrylamide gel electrophoresis (PAGE) and atomic force microscopy (AFM). We believe that this work will expand the toolbox for DNA supramolecular polymerization and would, with further development, increase further control of DNA supramolecular polymerization.
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Affiliation(s)
- Zhe Zhang
- Key Laboratory of Luminescence Analysis and Molecular Sensing, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, Chongqing, 400715, P. R. China
| | - Shuang Yu
- Key Laboratory of Luminescence Analysis and Molecular Sensing, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, Chongqing, 400715, P. R. China
| | - Hua Zuo
- Key Laboratory of Luminescence Analysis and Molecular Sensing, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, Chongqing, 400715, P. R. China
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Takahashi S, Herdwijn P, Sugimoto N. Effect of Molecular Crowding on DNA Polymerase Reactions along Unnatural DNA Templates. Molecules 2020; 25:E4120. [PMID: 32927591 PMCID: PMC7571040 DOI: 10.3390/molecules25184120] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 09/08/2020] [Accepted: 09/08/2020] [Indexed: 11/17/2022] Open
Abstract
Unnatural nucleic acids are promising materials to expand genetic information beyond the natural bases. During replication, substrate nucleotide incorporation should be strictly controlled for optimal base pairing with template strand bases. Base-pairing interactions occur via hydrogen bonding and base stacking, which could be perturbed by the chemical environment. Although unnatural nucleobases and sugar moieties have undergone extensive structural improvement for intended polymerization, the chemical environmental effect on the reaction is less understood. In this study, we investigated how molecular crowding could affect native DNA polymerization along various templates comprising unnatural nucleobases and sugars. Under non-crowding conditions, the preferred incorporation efficiency of pyrimidine deoxynucleotide triphosphates (dNTPs) by the Klenow fragment (KF) was generally high with low fidelity, whereas that of purine dNTPs was the opposite. However, under crowding conditions, the efficiency remained almost unchanged with varying preferences in each case. These results suggest that hydrogen bonding and base-stacking interactions could be perturbed by crowding conditions in the bulk solution and polymerase active center during transient base pairing before polymerization. This study highlights that unintended dNTP incorporation against unnatural nucleosides could be differentiated in cases of intracellular reactions.
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Affiliation(s)
- Shuntaro Takahashi
- Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, 7-1-20 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan;
| | - Piet Herdwijn
- Medicinal Chemistry, KU Leuven, Rega Institute for Medical Research, Herestraat 49-box 1041, 3000 Leuven, Belgium;
| | - Naoki Sugimoto
- Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, 7-1-20 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan;
- Graduate School of Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, 7-1-20 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan
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Li G, Quan Y, Wang X, Liu R, Bie L, Gao J, Zhang HY. Trinucleotide Base Pair Stacking Free Energy for Understanding TF-DNA Recognition and the Functions of SNPs. Front Chem 2019; 6:666. [PMID: 30713839 PMCID: PMC6345724 DOI: 10.3389/fchem.2018.00666] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 12/21/2018] [Indexed: 01/03/2023] Open
Abstract
Single nucleotide polymorphisms (SNPs) affect base pair stacking, which is the primary factor for maintaining the stability of DNA. However, the mechanism of how SNPs lead to phenotype variations is still unclear. In this work, we connected SNPs and base pair stacking by a 3-mer base pair stacking free energy matrix. The SNPs with large base pair stacking free energy differences led to phenotype variations. A molecular dynamics (MD) simulation was then applied. Our results showed that base pair stacking played an important role in the transcription factor (TF)-DNA interaction. Changes in DNA structure mainly originate from TF-DNA interactions, and with the increased base pair stacking free energy, the structure of DNA approaches its free type, although its binding affinity was increased by the SNP. In addition, quantitative models using base pair stacking features revealed that base pair stacking can be used to predict TF binding specificity. As such, our work combined knowledge from bioinformatics and structural biology and provided a new understanding of the relationship between SNPs and phenotype variations. The 3-mer base pair stacking free energy matrix is useful in high-throughput screening of SNPs and predicting TF-DNA binding affinity.
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Affiliation(s)
- Gen Li
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, China
| | - Yuan Quan
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, China
| | - Xiaocong Wang
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, China
| | - Rong Liu
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, China
| | - Lihua Bie
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, China
| | - Jun Gao
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, China
| | - Hong-Yu Zhang
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, China
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Deb I, Sarzynska J, Nilsson L, Lahiri A. Rapid communication capturing the destabilizing effect of dihydrouridine through molecular simulations. Biopolymers 2016; 101:985-91. [PMID: 24729441 DOI: 10.1002/bip.22495] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Revised: 04/04/2014] [Accepted: 04/07/2014] [Indexed: 01/08/2023]
Abstract
The structural effects of the commonly occurring modified nucleoside dihydrouridine (D) observed experimentally in model oligonucleotides include a strong destabilization of the C3'-endo sugar conformation of D, the disruption of stacking interactions of neighboring residues with D and a possible destabilization of the C3'-endo sugar pucker of the 5'-neighboring nucleoside. Our simulations with a combination of a set of parameters for modified RNA residues with the recently developed AMBER FF99χ force field having reoptimized glycosidic torsion angle parameters for standard nucleosides was found to reproduce the destabilizing effect of dihydrouridine better than with the AMBER FF99 force field for nucleic acids for which the parameters for the modified residues were originally developed.
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Affiliation(s)
- Indrajit Deb
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, 700009, West Bengal, India
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Zhang J, Ferré-D'Amaré AR. The tRNA Elbow in Structure, Recognition and Evolution. Life (Basel) 2016; 6:E3. [PMID: 26771646 DOI: 10.3390/life6010003] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 01/04/2016] [Accepted: 01/06/2016] [Indexed: 01/07/2023] Open
Abstract
Prominent in the L-shaped three-dimensional structure of tRNAs is the "elbow" where their two orthogonal helical stacks meet. It has a conserved structure arising from the interaction of the terminal loops of the D- and T-stem-loops, and presents to solution a flat face of a tertiary base pair between the D- and T-loops. In addition to the ribosome, which interacts with the elbow in all three of its tRNA binding sites, several cellular RNAs and many proteins are known to recognize the elbow. At least three classes of non-coding RNAs, namely 23S rRNA, ribonuclease P, and the T-box riboswitches, recognize the tRNA elbow employing an identical structural motif consisting of two interdigitated T-loops. In contrast, structural solutions to tRNA-elbow recognition by proteins are varied. Some enzymes responsible for post-transcriptional tRNA modification even disrupt the elbow structure in order to access their substrate nucleotides. The evolutionary origin of the elbow is mysterious, but, because it does not explicitly participate in the flow of genetic information, it has been proposed to be a late innovation. Regardless, it is biologically essential. Even some viruses that hijack the cellular machinery using tRNA decoys have convergently evolved near-perfect mimics of the tRNA elbow.
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Jolley EA, Lewis M, Znosko BM. A Computational Model for Predicting Experimental RNA Nearest-Neighbor Free Energy Rankings: Inosine•Uridine Pairs. Chem Phys Lett 2015; 639:157-60. [PMID: 26525429 DOI: 10.1016/j.cplett.2015.09.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
A computational model for predicting RNA nearest neighbor free energy rankings has been expanded to include the nonstandard nucleotide inosine. The model uses average fiber diffraction data and molecular dynamic simulations to generate input geometries for Quantum mechanic calculations. This resulted in calculated intrastrand stacking, interstrand stacking, and hydrogen bonding energies that were combined to give total binding energies. Total binding energies for RNA dimer duplexes containing inosine were ranked and compared to experimentally determined free energy ranks for RNA duplexes containing inosine. Statistical analysis showed significant agreement between the computationally determined ranks and the experimentally determined ranks.
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Affiliation(s)
- Elizabeth A Jolley
- Department of Chemistry, Saint Louis University, 3501 Laclede Avenue, Saint Louis, Missouri, 63103, United States
| | - Michael Lewis
- Department of Chemistry, Saint Louis University, 3501 Laclede Avenue, Saint Louis, Missouri, 63103, United States
| | - Brent M Znosko
- Department of Chemistry, Saint Louis University, 3501 Laclede Avenue, Saint Louis, Missouri, 63103, United States
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Abstract
The insertion of a DNA base moiety at the end of a DNA duplex to form a Watson-Crick or wobble pair during DNA annealing or replication is a step of fundamental biological importance. Therefore, we investigated the energetics of a formation of the terminal G x C, G x T, and G x A base pairs in DNA containing a 5'-dangling G adjacent to the base insertion point using differential scanning calorimetry and computer simulations. The energies calculated along classical molecular dynamics trajectories in aqueous solution were analyzed in the framework of linear-response approximation (LRA) to obtain relative free energies for the base insertion and their electrostatic, van der Waals, and preorganization components. Using the generic set of LRA parameters, the calculated free energies disfavored the mispair formation by 2.5 (G x C --> G x T) and 1.7 (G x C --> G x A) kcal/mol, in reasonable agreement with the experimental free energy differences of 1.8 and 1.4 kcal/mol, respectively. The calculated preorganization components of these free energies of 0.6 (G x C --> G x T) and -0.1 (G x C --> G x A) kcal/mol show that electrostatic preorganization, which is an important source of DNA replication fidelity, plays a lesser role in the mispair destabilization in the absence of DNA polymerase.
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Affiliation(s)
- Urban Bren
- National Institute of Chemistry, Hajdrihova 19, 1001 Ljubljana, Slovenia
| | - Jurij Lah
- University of Ljubljana, Faculty of Chemistry and Chemical Technology, Aškerčeva 5, 1000 Ljubljana, Slovenia
| | - Matevž Bren
- Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana, Slovenia
| | - Václav Martínek
- Department of Chemistry, Loyola University Chicago, Chicago, IL 60626, USA
| | - Jan Florián
- Department of Chemistry, Loyola University Chicago, Chicago, IL 60626, USA
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Moran S, Ren RX, Kool ET. A thymidine triphosphate shape analog lacking Watson-Crick pairing ability is replicated with high sequence selectivity. Proc Natl Acad Sci U S A 1997; 94:10506-11. [PMID: 9380669 PMCID: PMC23390 DOI: 10.1073/pnas.94.20.10506] [Citation(s) in RCA: 267] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Compound 1 (F), a nonpolar nucleoside analog that is isosteric with thymidine, has been proposed as a probe for the importance of hydrogen bonds in biological systems. Consistent with its lack of strong H-bond donors or acceptors, F is shown here by thermal denaturation studies to pair very poorly and with no significant selectivity among natural bases in DNA oligonucleotides. We report the synthesis of the 5'-triphosphate derivative of 1 and the study of its ability to be inserted into replicating DNA strands by the Klenow fragment (KF, exo- mutant) of Escherichia coli DNA polymerase I. We find that this nucleotide derivative (dFTP) is a surprisingly good substrate for KF; steady-state measurements indicate it is inserted into a template opposite adenine with efficiency (Vmax/Km) only 40-fold lower than dTTP. Moreover, it is inserted opposite A (relative to C, G, or T) with selectivity nearly as high as that observed for dTTP. Elongation of the strand past F in an F-A pair is associated with a brief pause, whereas that beyond A in the inverted A-F pair is not. Combined with data from studies with F in the template strand, the results show that KF can efficiently replicate a base pair (A-F/F-A) that is inherently very unstable, and the replication occurs with very high fidelity despite a lack of inherent base-pairing selectivity. The results suggest that hydrogen bonds may be less important in the fidelity of replication than commonly believed and that nucleotide/template shape complementarity may play a more important role than previously believed.
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Affiliation(s)
- S Moran
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
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12
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Keepers JW, Kollman PA, Weiner PK, James TL. Molecular mechanical studies of DNA flexibility: coupled backbone torsion angles and base-pair openings. Proc Natl Acad Sci U S A 1982; 79:5537-41. [PMID: 6957879 PMCID: PMC346939 DOI: 10.1073/pnas.79.18.5537] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Molecular mechanics studies have been carried out on "B-DNA-like" structures of [d(C-G-C-G-A-A-T-T-C-G-C-G)](2) and [d(A)](12).[d(T)](12). Each of the backbone torsion angles (psi, phi, omega, omega', phi') has been "forced" to alternative values from the normal B-DNA values (g(+), t, g(-), g(-), t conformations). Compensating torsion angle changes preserve most of the base stacking energy in the double helix. In a second part of the study, one purine N3-pyrimidine N1 distance at a time has been forced to a value of 6 A in an attempt to simulate the base opening motions required to rationalize proton exchange data for DNA. When the 6-A constraint is removed, many of the structures revert to the normal Watson-Crick hydrogen-bonded structure, but a number are trapped in structures approximately 5 kcal/mol higher in energy than the starting B-DNA structure. The relative energy of these structures, some of which involve a non-Watson-Crick thymine C2(carbonyl)[unk]adenine 6NH(2) hydrogen bond, are qualitatively consistent with the DeltaH for a "base pair-open state" suggested by Mandal et al. of 4-6 kcal/mol [Mandal, C., Kallenbach, N. R. & Englander, S. W. (1979) J. Mol. Biol. 135, 391-411]. The picture of DNA flexibility emerging from this study depicts the backbone as undergoing rapid motion between local torsional minima on a nanosecond time scale. Backbone motion is mainly localized within a dinucleoside segment and generally not conformationally coupled along the chain or across the base pairs. Base motions are much smaller in magnitude than backbone motions. Base sliding allows imino N-H exchange, but it is localized, and only a small fraction of the N-H groups is exposed at any one time. Stacking and hydrogen bonding cause a rigid core of bases in the center of the molecule accounting for the hydrodynamic properties of DNA.
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Kim SH, Sussman JL, Suddath FL, Quigley GJ, McPherson A, Wang AH, Seeman NC, RICH A. The general structure of transfer RNA molecules. Proc Natl Acad Sci U S A 1974; 71:4970-4. [PMID: 4612535 PMCID: PMC434021 DOI: 10.1073/pnas.71.12.4970] [Citation(s) in RCA: 183] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The three-dimensional structure of yeast phenylalanine tRNA serves as a useful basis for understanding the tertiary structure of all tRNAs. A large number of tRNA sequences have been surveyed and some general conclusions are drawn. There are only a few regions in the molecule in which there are differences in the number of nucleotides; and the structure of yeast phenylalanine tRNA can accommodate these differences by forming or enlarging protuberances on the surface of the basic framework molecule. The nature and distribution of the differences in number of nucleotides are surveyed and possible hydrogen bonding interactions are discussed for a number of tRNA classes. The two most significant features of the molecule are the large number of stacking interactions which are seen to include most of the nucleotides in the molecule and the system of specific hydrogen bonding interactions. It is likely that these stabilizing elements are preserved in all tRNA structures.
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