1
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Abstract
Glycans, carbohydrate molecules in the realm of biology, are present as biomedically important glycoconjugates and a characteristic aspect is that their structures in many instances are branched. In determining the primary structure of a glycan, the sugar components including the absolute configuration and ring form, anomeric configuration, linkage(s), sequence, and substituents should be elucidated. Solution state NMR spectroscopy offers a unique opportunity to resolve all these aspects at atomic resolution. During the last two decades, advancement of both NMR experiments and spectrometer hardware have made it possible to unravel carbohydrate structure more efficiently. These developments applicable to glycans include, inter alia, NMR experiments that reduce spectral overlap, use selective excitations, record tilted projections of multidimensional spectra, acquire spectra by multiple receivers, utilize polarization by fast-pulsing techniques, concatenate pulse-sequence modules to acquire several spectra in a single measurement, acquire pure shift correlated spectra devoid of scalar couplings, employ stable isotope labeling to efficiently obtain homo- and/or heteronuclear correlations, as well as those that rely on dipolar cross-correlated interactions for sequential information. Refined computer programs for NMR spin simulation and chemical shift prediction aid the structural elucidation of glycans, which are notorious for their limited spectral dispersion. Hardware developments include cryogenically cold probes and dynamic nuclear polarization techniques, both resulting in enhanced sensitivity as well as ultrahigh field NMR spectrometers with a 1H NMR resonance frequency higher than 1 GHz, thus improving resolution of resonances. Taken together, the developments have made and will in the future make it possible to elucidate carbohydrate structure in great detail, thereby forming the basis for understanding of how glycans interact with other molecules.
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Affiliation(s)
- Carolina Fontana
- Departamento
de Química del Litoral, CENUR Litoral Norte, Universidad de la República, Paysandú 60000, Uruguay
| | - Göran Widmalm
- Department
of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden,
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2
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Krishnarjuna B, Ravula T, Faison EM, Tonelli M, Zhang Q, Ramamoorthy A. Polymer-Nanodiscs as a Novel Alignment Medium for High-Resolution NMR-Based Structural Studies of Nucleic Acids. Biomolecules 2022; 12:1628. [PMID: 36358983 PMCID: PMC9687133 DOI: 10.3390/biom12111628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 10/28/2022] [Accepted: 10/31/2022] [Indexed: 11/06/2022] Open
Abstract
Residual dipolar couplings (RDCs) are increasingly used for high-throughput NMR-based structural studies and to provide long-range angular constraints to validate and refine structures of various molecules determined by X-ray crystallography and NMR spectroscopy. RDCs of a given molecule can be measured in an anisotropic environment that aligns in an external magnetic field. Here, we demonstrate the first application of polymer-based nanodiscs for the measurement of RDCs from nucleic acids. Polymer-based nanodiscs prepared using negatively charged SMA-EA polymer and zwitterionic DMPC lipids were characterized by size-exclusion chromatography, 1H NMR, dynamic light-scattering, and 2H NMR. The magnetically aligned polymer-nanodiscs were used as an alignment medium to measure RDCs from a 13C/15N-labeled fluoride riboswitch aptamer using 2D ARTSY-HSQC NMR experiments. The results showed that the alignment of nanodiscs is stable for nucleic acids and nanodisc-induced RDCs fit well with the previously determined solution structure of the riboswitch. These results demonstrate that SMA-EA-based lipid-nanodiscs can be used as a stable alignment medium for high-resolution structural and dynamical studies of nucleic acids, and they can also be applicable to study various other biomolecules and small molecules in general.
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Affiliation(s)
- Bankala Krishnarjuna
- Biophysics Program, Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Thirupathi Ravula
- Biophysics Program, Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA
- National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Edgar M. Faison
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Marco Tonelli
- National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Qi Zhang
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program, Department of Chemistry, Biomedical Engineering, and Macromolecular Science and Engineering, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA
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3
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Omar H, Hein A, Cole CA, Valafar H. Concurrent Identification and Characterization of Protein Structure and Continuous Internal Dynamics with REDCRAFT. Front Mol Biosci 2022; 9:806584. [PMID: 35187082 PMCID: PMC8856112 DOI: 10.3389/fmolb.2022.806584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 01/10/2022] [Indexed: 11/13/2022] Open
Abstract
Internal dynamics of proteins can play a critical role in the biological function of some proteins. Several well documented instances have been reported such as MBP, DHFR, hTS, DGCR8, and NSP1 of the SARS-CoV family of viruses. Despite the importance of internal dynamics of proteins, there currently are very few approaches that allow for meaningful separation of internal dynamics from structural aspects using experimental data. Here we present a computational approach named REDCRAFT that allows for concurrent characterization of protein structure and dynamics. Here, we have subjected DHFR (PDB-ID 1RX2), a 159-residue protein, to a fictitious, mixed mode model of internal dynamics. In this simulation, DHFR was segmented into 7 regions where 4 of the fragments were fixed with respect to each other, two regions underwent rigid-body dynamics, and one region experienced uncorrelated and melting event. The two dynamical and rigid-body segments experienced an average orientational modification of 7° and 12° respectively. Observable RDC data for backbone C′-N, N-HN, and C′-HN were generated from 102 uniformly sampled frames that described the molecular trajectory. The structure calculation of DHFR with REDCRAFT by using traditional Ramachandran restraint produced a structure with 29 Å of structural difference measured over the backbone atoms (bb-rmsd) over the entire length of the protein and an average bb-rmsd of more than 4.7 Å over each of the dynamical fragments. The same exercise repeated with context-specific dihedral restraints generated by PDBMine produced a structure with bb-rmsd of 21 Å over the entire length of the protein but with bb-rmsd of less than 3 Å over each of the fragments. Finally, utilization of the Dynamic Profile generated by REDCRAFT allowed for the identification of different dynamical regions of the protein and the recovery of individual fragments with bb-rmsd of less than 1 Å. Following the recovery of the fragments, our assembly procedure of domains (larger segments consisting of multiple fragments with a common dynamical profile) correctly assembled the four fragments that are rigid with respect to each other, categorized the two domains that underwent rigid-body dynamics, and identified one dynamical region for which no conserved structure could be defined. In conclusion, our approach was successful in identifying the dynamical domains, recovery of structure where it is meaningful, and relative assembly of the domains when possible.
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4
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Bezerra FF, Vignovich WP, Aderibigbe AO, Liu H, Sharp JS, Doerksen RJ, Pomin VH. Conformational properties of l-fucose and the tetrasaccharide building block of the sulfated l-fucan from Lytechinus variegatus. J Struct Biol 2019; 209:107407. [PMID: 31698075 DOI: 10.1016/j.jsb.2019.107407] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 10/07/2019] [Accepted: 10/23/2019] [Indexed: 01/19/2023]
Abstract
Although the 3D structure of carbohydrates is known to contribute to their biological roles, conformational studies of sugars are challenging because their chains are flexible in solution and consequently the number of 3D structural restraints is limited. Here, we investigate the conformational properties of the tetrasaccharide building block of the Lytechinus variegatus sulfated fucan composed of the following structure [l-Fucp4(SO3-)-α(1-3)-l-Fucp2,4(SO3-)-α(1-3)-l-Fucp2(SO3-)-α(1-3)-l-Fucp2(SO3-)] and the composing monosaccharide unit Fucp, primarily by nuclear magnetic resonance (NMR) experiments performed at very low temperatures and using H2O as the solvent for the sugars rather than using the conventional deuterium oxide. By slowing down the fast chemical exchange rates and forcing the protonation of labile sites, we increased the number of through-space 1H-1H distances that could be measured by NMR spectroscopy. Following this strategy, additional conformational details of the tetrasaccharide and l-Fucp in solution were obtained. Computational molecular dynamics was performed to complement and validate the NMR-based measurements. A model of the NMR-restrained 3D structure is offered for the tetrasaccharide.
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Affiliation(s)
- Francisco F Bezerra
- Institute of Medical Biochemistry Leopoldo de Meis, University Hospital Clementino Fraga Filho, Federal University of Rio de Janeiro, Rio de Janeiro 21941, RJ, Brazil
| | - William P Vignovich
- BioMolecular Sciences Department, School of Pharmacy, University of Mississippi, University, 38677 MS, USA
| | - AyoOluwa O Aderibigbe
- BioMolecular Sciences Department, School of Pharmacy, University of Mississippi, University, 38677 MS, USA
| | - Hao Liu
- BioMolecular Sciences Department, School of Pharmacy, University of Mississippi, University, 38677 MS, USA
| | - Joshua S Sharp
- BioMolecular Sciences Department, School of Pharmacy, University of Mississippi, University, 38677 MS, USA; Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, 38677 MS, USA
| | - Robert J Doerksen
- BioMolecular Sciences Department, School of Pharmacy, University of Mississippi, University, 38677 MS, USA; Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, 38677 MS, USA
| | - Vitor H Pomin
- Institute of Medical Biochemistry Leopoldo de Meis, University Hospital Clementino Fraga Filho, Federal University of Rio de Janeiro, Rio de Janeiro 21941, RJ, Brazil; BioMolecular Sciences Department, School of Pharmacy, University of Mississippi, University, 38677 MS, USA; Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, 38677 MS, USA.
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5
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Zhang W, Meredith R, Yoon MK, Wang X, Woods RJ, Carmichael I, Serianni AS. Synthesis and O-Glycosidic Linkage Conformational Analysis of 13C-Labeled Oligosaccharide Fragments of an Antifreeze Glycolipid. J Org Chem 2019; 84:1706-1724. [PMID: 30624062 DOI: 10.1021/acs.joc.8b01411] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
NMR studies of two 13C-labeled disaccharides and a tetrasaccharide were undertaken that comprise the backbone of a novel thermal hysteresis glycolipid containing a linear glycan sequence of alternating [βXyl p-(1→4)-βMan p-(1→4)] n dimers. Experimental trans-glycoside NMR J-couplings, parameterized equations obtained from density functional theory (DFT) calculations, and an in-house circular statistics package ( MA'AT) were used to derive conformational models of linkage torsion angles ϕ and ψ in solution, which were compared to those obtained from molecular dynamics simulations. Modeling using different probability distribution functions showed that MA'AT models of ϕ in βMan(1→4)βXyl and βXyl(1→4)βMan linkages are very similar in the disaccharide building blocks, whereas MA'AT models of ψ differ. This pattern is conserved in the tetrasaccharide, showing that linkage context does not influence linkage geometry in this linear system. Good agreement was observed between the MA'AT and MD models of ψ with respect to mean values and circular standard deviations. Significant differences were observed for ϕ, indicating that revision of the force-field employed by GLYCAM is probably needed. Incorporation of the experimental models of ϕ and ψ into the backbone of an octasaccharide fragment leads to a helical amphipathic topography that may affect the thermal hysteresis properties of the glycolipid.
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Affiliation(s)
| | | | | | - Xiaocong Wang
- Complex Carbohydrate Research Center , University of Georgia , Athens , Georgia 30602 , United States
| | - Robert J Woods
- Complex Carbohydrate Research Center , University of Georgia , Athens , Georgia 30602 , United States
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6
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Zhang W, Meredith R, Pan Q, Wang X, Woods RJ, Carmichael I, Serianni AS. Use of Circular Statistics To Model αMan-(1→2)-αMan and αMan-(1→3)-α/βMan O-Glycosidic Linkage Conformation in 13C-Labeled Disaccharides and High-Mannose Oligosaccharides. Biochemistry 2019; 58:546-560. [PMID: 30605318 DOI: 10.1021/acs.biochem.8b01050] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A new experimental method, MA' AT analysis, has been applied to investigate the conformational properties of O-glycosidic linkages in several biologically important mannose-containing di- and oligosaccharides. Methyl α-d-mannopyranosyl-(1→2)-α-d-mannopyranoside (2), methyl α-d-mannopyranosyl-(1→3)-α-d-mannopyranoside (3), and methyl α-d-mannopyranosyl-(1→3)-β-d-mannopyranoside (4) were prepared with selective 13C-enrichment to enable the measurement of NMR scalar couplings across their internal O-glycosidic linkages. Density functional theory (DFT) was used to parameterize equations for JCH and JCC values in 2-4 that are sensitive to phi (ϕ) and psi (ψ). The experimental J-couplings and parameterized equations were treated using a circular statistics algorithm encoded in the MA' AT program. Conformations about ϕ and ψ treated using single-state von Mises models gave excellent fits to the ensembles of redundant J-couplings. Mean values and circular standard deviations (CSDs) for each linkage torsion angle ϕ (CSD) and ψ (CSD) in 2, -29° (25°) and 20° (22°); in 3, -36° (36°) and 8° (27°); in 4, -37° (34°) and 10° (26°); ϕ = H1'-C1'-O1'-CX and ψ = C1'-O1'-CX-HX (CX = aglycone carbon) were compared to histograms obtained from 1 μs aqueous molecular dynamics (MD) simulations and X-ray database statistical analysis. MA' AT-derived models of ψ were in very good agreement with the MD and X-ray data, but not those of ϕ, suggesting a need for force field revision. The effect of structural context on linkage conformation was also investigated in four selectively 13C-labeled homomannose tri- and tetrasaccharides using the MA' AT method. In the cases examined, context effects were found to be small.
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Affiliation(s)
| | | | | | - Xiaocong Wang
- Complex Carbohydrate Research Center , University of Georgia , Athens , Georgia 30602 United States
| | - Robert J Woods
- Complex Carbohydrate Research Center , University of Georgia , Athens , Georgia 30602 United States
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7
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Abstract
Complex carbohydrates are ubiquitous in nature, and together with proteins and nucleic acids they comprise the building blocks of life. But unlike proteins and nucleic acids, carbohydrates form nonlinear polymers, and they are not characterized by robust secondary or tertiary structures but rather by distributions of well-defined conformational states. Their molecular flexibility means that oligosaccharides are often refractory to crystallization, and nuclear magnetic resonance (NMR) spectroscopy augmented by molecular dynamics (MD) simulation is the leading method for their characterization in solution. The biological importance of carbohydrate-protein interactions, in organismal development as well as in disease, places urgency on the creation of innovative experimental and theoretical methods that can predict the specificity of such interactions and quantify their strengths. Additionally, the emerging realization that protein glycosylation impacts protein function and immunogenicity places the ability to define the mechanisms by which glycosylation impacts these features at the forefront of carbohydrate modeling. This review will discuss the relevant theoretical approaches to studying the three-dimensional structures of this fascinating class of molecules and interactions, with reference to the relevant experimental data and techniques that are key for validation of the theoretical predictions.
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Affiliation(s)
- Robert J Woods
- Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology , University of Georgia , 315 Riverbend Road , Athens , Georgia 30602 , United States
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8
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Zhang W, Turney T, Meredith R, Pan Q, Sernau L, Wang X, Hu X, Woods RJ, Carmichael I, Serianni AS. Conformational Populations of β-(1→4) O-Glycosidic Linkages Using Redundant NMR J-Couplings and Circular Statistics. J Phys Chem B 2017; 121:3042-3058. [PMID: 28296420 DOI: 10.1021/acs.jpcb.7b02252] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Twelve disaccharides containing β-(1→4) linkages and displaying systematic structural variations in the vicinity of these linkages were selectively labeled with 13C to facilitate measurements of multiple NMR spin-spin (scalar; J) coupling constants (JCH and JCC values) across their O-glycosidic linkages. Ensembles of spin-couplings (2JCOC, 3JCOCH, 3JCOCC) sensitive to the two linkage torsion angles, phi (ϕ) and psi (ψ), were analyzed by using parametrized equations obtained from density functional theory (DFT) calculations, Fredholm theory, and circular statistics to calculate experiment-based rotamer populations for ϕ and ψ in each disaccharide. With the statistical program MA'AT, torsion angles ϕ and ψ were modeled as a single von Mises distribution, which yielded two parameters, the mean position and the circular standard deviation (CSD) for each angle. The NMR-derived rotamer populations were compared to those obtained from 1 μs aqueous molecular dynamics (MD) simulations and crystallographic database statistical analyses. Conformer populations obtained exclusively from the MA'AT treatment of redundant J-couplings were in very good agreement with those obtained from the MD simulations, providing evidence that conformational populations can be determined by NMR for mobile molecular elements such as O-glycosidic linkages with minimal input from theory. The approach also provides an experimental means to validate the conformational preferences predicted from MD simulations. The conformational behaviors of ϕ in the 12 disaccharides were very similar, but those of ψ varied significantly, allowing a classification of the 12 disaccharides based on preferred linkage conformation in solution.
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Affiliation(s)
- Wenhui Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Toby Turney
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Reagan Meredith
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Qingfeng Pan
- Omicron Biochemicals Inc. , South Bend, Indiana 46617-2701, United States
| | - Luke Sernau
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Xiaocong Wang
- Complex Carbohydrate Research Center, University of Georgia , Athens, Georgia 30602, United States
| | - Xiaosong Hu
- Department of Chemistry, Wuhan University of Technology , Wuhan 430070, China
| | - Robert J Woods
- Complex Carbohydrate Research Center, University of Georgia , Athens, Georgia 30602, United States
| | - Ian Carmichael
- Radiation Laboratory, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
| | - Anthony S Serianni
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556-5670, United States
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9
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Fontana C, Zaccheus M, Weintraub A, Ansaruzzaman M, Widmalm G. Structural studies of a polysaccharide from Vibrio parahaemolyticus strain AN-16000. Carbohydr Res 2016; 432:41-9. [PMID: 27392309 DOI: 10.1016/j.carres.2016.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 06/08/2016] [Accepted: 06/09/2016] [Indexed: 11/17/2022]
Abstract
The structure of a polysaccharide from Vibrio parahaemolyticus strain AN-16000 has been investigated. The sugar and absolute configuration analysis revealed d-Glc, d-GalN, d-QuiN and l-FucN as major components. The PS was subjected to dephosphorylation with aqueous 40% HF to obtain an oligosaccharide that was analyzed by (1)H and (13)C NMR spectroscopy. The HR-MS spectrum of the oligosaccharide revealed a pentasaccharide composed of two Glc residues, one QuiNAc and one GalNAc, one FucNAc, as well as a glycerol moiety. The structure of the PS was determined using (1)H, (13)C, (15)N and (31)P NMR spectroscopy; inter-residue correlations were identified by (1)H,(13)C-heteronuclear multiple-bond correlation, (1)H,(1)H-NOESY and (1)H,(31)P-hetero-TOCSY experiments. The PS backbone has the following teichoic acid-like structure: →3)-d-Gro-(1-P-6)-β-d-Glcp-(1→4)-α-l-FucpNAc-(1→3)-β-d-QuipNAc-(1→ with a side-chain consisting of α-d-Glcp-(1→6)-α-d-GalpNAc-(1→ linked to the O3 position of the FucNAc residue.
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Affiliation(s)
- Carolina Fontana
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden
| | - Mona Zaccheus
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden
| | - Andrej Weintraub
- Karolinska Institute, Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska University Hospital, S-141 86 Stockholm, Sweden
| | | | - Göran Widmalm
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
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10
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Soares PA, Queiroz IN, Pomin VH. NMR structural biology of sulfated glycans. J Biomol Struct Dyn 2016; 35:1069-1084. [DOI: 10.1080/07391102.2016.1171165] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Paulo A.G. Soares
- Program of Glycobiology, Institute of Medical Biochemistry Leopoldo de Meis, and University Hospital Clementino Fraga Filho, Federal University of Rio de Janeiro , Rio de Janeiro, RJ 21941-913, Brazil
| | - Ismael N.L. Queiroz
- Program of Glycobiology, Institute of Medical Biochemistry Leopoldo de Meis, and University Hospital Clementino Fraga Filho, Federal University of Rio de Janeiro , Rio de Janeiro, RJ 21941-913, Brazil
| | - Vitor H. Pomin
- Program of Glycobiology, Institute of Medical Biochemistry Leopoldo de Meis, and University Hospital Clementino Fraga Filho, Federal University of Rio de Janeiro , Rio de Janeiro, RJ 21941-913, Brazil
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11
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Cole CA, Mukhopadhyay R, Omar H, Hennig M, Valafar H. Structure Calculation and Reconstruction of Discrete-State Dynamics from Residual Dipolar Couplings. J Chem Theory Comput 2016; 12:1408-22. [PMID: 26984680 DOI: 10.1021/acs.jctc.5b01091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Residual dipolar couplings (RDCs) acquired by nuclear magnetic resonance (NMR) spectroscopy are an indispensable source of information in investigation of molecular structures and dynamics. Here, we present a comprehensive strategy for structure calculation and reconstruction of discrete-state dynamics from RDC data that is based on the singular value decomposition (SVD) method of order tensor estimation. In addition to structure determination, we provide a mechanism of producing an ensemble of conformations for the dynamical regions of a protein from RDC data. The developed methodology has been tested on simulated RDC data with ±1 Hz of error from an 83 residue α protein (PDB ID 1A1Z ) and a 213 residue α/β protein DGCR8 (PDB ID 2YT4 ). In nearly all instances, our method reproduced the structure of the protein including the conformational ensemble to within less than 2 Å. On the basis of our investigations, arc motions with more than 30° of rotation are identified as internal dynamics and are reconstructed with sufficient accuracy. Furthermore, states with relative occupancies above 20% are consistently recognized and reconstructed successfully. Arc motions with a magnitude of 15° or relative occupancy of less than 10% are consistently unrecognizable as dynamical regions within the context of ±1 Hz of error.
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Affiliation(s)
- Casey A Cole
- Department of Computer Science & Engineering, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Rishi Mukhopadhyay
- Department of Computer Science & Engineering, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Hanin Omar
- Department of Computer Science & Engineering, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Mirko Hennig
- Nutrition Research Institute, University of North Carolina at Chapel Hill , Kannapolis, North Carolina 27514, United States
| | - Homayoun Valafar
- Department of Computer Science & Engineering, University of South Carolina , Columbia, South Carolina 29208, United States
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12
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Salmon L, Blackledge M. Investigating protein conformational energy landscapes and atomic resolution dynamics from NMR dipolar couplings: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2015; 78:126601. [PMID: 26517337 DOI: 10.1088/0034-4885/78/12/126601] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Nuclear magnetic resonance spectroscopy is exquisitely sensitive to protein dynamics. In particular inter-nuclear dipolar couplings, that become measurable in solution when the protein is dissolved in a dilute liquid crystalline solution, report on all conformations sampled up to millisecond timescales. As such they provide the opportunity to describe the Boltzmann distribution present in solution at atomic resolution, and thereby to map the conformational energy landscape in unprecedented detail. The development of analytical methods and approaches based on numerical simulation and their application to numerous biologically important systems is presented.
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Affiliation(s)
- Loïc Salmon
- Université Grenoble Alpes, Institut de Biologie Structurale (IBS), F-38027 Grenoble, France. CEA, DSV, IBS, F-38027 Grenoble, France. CNRS, IBS, F-38027 Grenoble, France
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13
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Kapla J, Engström O, Stevensson B, Wohlert J, Widmalm G, Maliniak A. Molecular dynamics simulations and NMR spectroscopy studies of trehalose-lipid bilayer systems. Phys Chem Chem Phys 2015; 17:22438-47. [PMID: 26252429 DOI: 10.1039/c5cp02472b] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The disaccharide trehalose (TRH) strongly affects the physical properties of lipid bilayers. We investigate interactions between lipid membranes formed by 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and TRH using NMR spectroscopy and molecular dynamics (MD) computer simulations. We compare dipolar couplings derived from DMPC/TRH trajectories with those determined (i) experimentally in TRH using conventional high-resolution NMR in a weakly ordered solvent (bicelles), and (ii) by solid-state NMR in multilamellar vesicles (MLV) formed by DMPC. Analysis of the experimental and MD-derived couplings in DMPC indicated that the force field used in the simulations reasonably well describes the experimental results with the exception for the glycerol fragment that exhibits significant deviations. The signs of dipolar couplings, not available from the experiments on highly ordered systems, were determined from the trajectory analysis. The crucial step in the analysis of residual dipolar couplings (RDCs) in TRH determined in a bicelle-environment was access to the conformational distributions derived from the MD trajectory. Furthermore, the conformational behavior of TRH, investigated by J-couplings, in the ordered and isotropic phases is essentially identical, indicating that the general assumptions in the analyses of RDCs are well founded.
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Affiliation(s)
- Jon Kapla
- Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden.
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14
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Simin M, Irausquin S, Cole CA, Valafar H. Improvements to REDCRAFT: a software tool for simultaneous characterization of protein backbone structure and dynamics from residual dipolar couplings. JOURNAL OF BIOMOLECULAR NMR 2014; 60:241-264. [PMID: 25403759 DOI: 10.1007/s10858-014-9871-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 10/30/2014] [Indexed: 06/04/2023]
Abstract
Within the past two decades, there has been an increase in the acquisition of residual dipolar couplings (RDC) for investigations of biomolecular structures. Their use however is still not as widely adopted as the traditional methods of structure determination by NMR, despite their potential for extending the limits in studies that examine both the structure and dynamics of biomolecules. This is in part due to the difficulties associated with the analysis of this information-rich data type. The software analysis tool REDCRAFT was previously introduced to address some of these challenges. Here we describe and evaluate a number of additional features that have been incorporated in order to extend its computational and analytical capabilities. REDCRAFT's more traditional enhancements integrate a modified steric collision term, as well as structural refinement in the rotamer space. Other, non-traditional improvements include: the filtering of viable structures based on relative order tensor estimates, decimation of the conformational space based on structural similarity, and forward/reverse folding of proteins. Utilizing REDCRAFT's newest features we demonstrate de-novo folding of proteins 1D3Z and 1P7E to within less than 1.6 Å of the corresponding X-ray structures, using as many as four RDCs per residue and as little as two RDCs per residue, in two alignment media. We also show the successful folding of a structure to less than 1.6 Å of the X-ray structure using {C(i-1)-N(i), N(i)-H(i), and C(i-1)-H(i)} RDCs in one alignment medium, and only {N(i)-H(i)} in the second alignment medium (a set of data which can be collected on deuterated samples). The program is available for download from our website at http://ifestos.cse.sc.edu .
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Affiliation(s)
- Mikhail Simin
- Department of Computer Science and Engineering, University of South Carolina, Columbia, SC, 29208, USA
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15
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Camilloni C, Vendruscolo M. A tensor-free method for the structural and dynamical refinement of proteins using residual dipolar couplings. J Phys Chem B 2014; 119:653-61. [PMID: 24824082 DOI: 10.1021/jp5021824] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Residual dipolar couplings (RDCs) are parameters measured in nuclear magnetic resonance spectroscopy that can provide exquisitely detailed information about the structure and dynamics of biological macromolecules. We describe here a method of using RDCs for the structural and dynamical refinement of proteins that is based on the observation that the RDC between two atomic nuclei depends directly on the angle ϑ between the internuclear vector and the external magnetic field. For every pair of nuclei for which an RDC is available experimentally, we introduce a structural restraint to minimize the deviation from the value of the angle ϑ derived from the measured RDC and that calculated in the refinement protocol. As each restraint involves only the calculation of the angle ϑ of the corresponding internuclear vector, the method does not require the definition of an overall alignment tensor to describe the preferred orientation of the protein with respect to the alignment medium. Application to the case of ubiquitin demonstrates that this method enables an accurate refinement of the structure and dynamics of this protein to be obtained.
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Affiliation(s)
- Carlo Camilloni
- Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, U.K
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16
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Bell NGA, Rigg G, Masters S, Bella J, Uhrín D. Detecting low-level flexibility using residual dipolar couplings: a study of the conformation of cellobiose. Phys Chem Chem Phys 2014; 15:18223-34. [PMID: 24064673 DOI: 10.1039/c3cp52987h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have developed novel NMR methods for the measurement of heteronuclear residual dipolar couplings (RDCs) in molecules with severely overlapping NMR resonances. These and other methods enabled us to obtain 31 RDCs for α-D-cellobiose and 24 RDCs for β-D-cellobiose. The interpretation of the data in the approximation of a rigid disaccharide structure, using RDCs and interglycosidic (3)J coupling constants, yielded conformation that is very close to that determined using X-ray crystallography. However, depending on which ring was used to calculate the order parameters, the dihedral angle ψH varied up to 30° or 40°, while the φH angle was always the same. This indicates residual flexibility of the glycosidic linkage between the two monosaccharide rings and was observed for both α- and β-D-cellobiose. The RDC analysis using rigid fragments rather than a complete molecule has thus shown that the glycosidic bond of cellobiose is not completely rigid and exhibits low-level flexibility. The sources of this flexibility are discussed and evidence presented to support a hypothesis that it is associated with the ψ more than the φ angle.
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Affiliation(s)
- Nicholle G A Bell
- EastChem School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, UK.
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17
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Battistel MD, Azurmendi HF, Yu B, Freedberg DI. NMR of glycans: shedding new light on old problems. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2014; 79:48-68. [PMID: 24815364 DOI: 10.1016/j.pnmrs.2014.01.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 01/10/2014] [Indexed: 06/03/2023]
Abstract
The diversity in molecular arrangements and dynamics displayed by glycans renders traditional NMR strategies, employed for proteins and nucleic acids, insufficient. Because of the unique properties of glycans, structural studies often require the adoption of a different repertoire of tailor-made experiments and protocols. We present an account of recent developments in NMR techniques that will deepen our understanding of structure-function relations in glycans. We open with a survey and comparison of methods utilized to determine the structure of proteins, nucleic acids and carbohydrates. Next, we discuss the structural information obtained from traditional NMR techniques like chemical shifts, NOEs/ROEs, and coupling-constants, along with the limitations imposed by the unique intrinsic characteristics of glycan structure on these approaches: flexibility, range of conformers, signal overlap, and non-first-order scalar (strong) coupling. Novel experiments taking advantage of isotopic labeling are presented as an option for overcoming spectral overlap and raising sensitivity. Computational tools used to explore conformational averaging in conjunction with NMR parameters are described. In addition, recent developments in hydroxyl detection and hydrogen bond detection in protonated solvents, in contrast to traditional sample preparations in D2O for carbohydrates, further increase the tools available for both structure information and chemical shift assignments. We also include previously unpublished data in this context. Accurate determination of couplings in carbohydrates has been historically challenging due to the common presence of strong-couplings. We present new strategies proposed for dealing with their influence on NMR signals. We close with a discussion of residual dipolar couplings (RDCs) and the advantages of using (13)C isotope labeling that allows gathering one-bond (13)C-(13)C couplings with a recently improved constant-time COSY technique, in addition to the commonly measured (1)H-(13)C RDCs.
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Affiliation(s)
- Marcos D Battistel
- Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, Rockville, MD 20852-1448, United States
| | - Hugo F Azurmendi
- Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, Rockville, MD 20852-1448, United States
| | - Bingwu Yu
- Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, Rockville, MD 20852-1448, United States
| | - Darón I Freedberg
- Laboratory of Bacterial Polysaccharides, Center for Biologics Evaluation and Research, Food and Drug Administration, 1401 Rockville Pike, Rockville, MD 20852-1448, United States.
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18
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Mukhopadhyay R, Irausquin S, Schmidt C, Valafar H. Dynafold: a dynamic programming approach to protein backbone structure determination from minimal sets of Residual Dipolar Couplings. J Bioinform Comput Biol 2014; 12:1450002. [PMID: 24467760 DOI: 10.1142/s0219720014500024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Residual Dipolar Couplings (RDCs) are a source of NMR data that can provide a powerful set of constraints on the orientation of inter-nuclear vectors, and are quickly becoming a larger part of the experimental toolset for molecular biologists. However, few reliable protocols exist for the determination of protein backbone structures from small sets of RDCs. DynaFold is a new dynamic programming algorithm designed specifically for this task, using minimal sets of RDCs collected in multiple alignment media. DynaFold was first tested utilizing synthetic data generated for the N--H , C(α)--H(α), and C--N vectors of 1BRF, 1F53, 110M, and 3LAY proteins, with up to ±1 Hz error in three alignment media, and was able to produce structures with less than 1.9 Å of the original structures. DynaFold was then tested using experimental data, obtained from the Biological Magnetic Resonance Bank, for proteins PDBID:1P7E and 1D3Z using RDC data from two alignment media. This exercise yielded structures within 1.0 Å of their respective published structures in segments with high data density, and less than 1.9 Å over the entire protein. The same sets of RDC data were also used in comparisons with traditional methods for analysis of RDCs, which failed to match the accuracy of DynaFold's approach to structure determination.
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Affiliation(s)
- Rishi Mukhopadhyay
- Department of Computer Science and Engineering, University of South Carolina, Columbia, SC 29208, USA
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19
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Barry C, Cocinero EJ, Çarçabal P, Gamblin D, Stanca-Kaposta EC, Remmert SM, Fernández-Alonso MC, Rudić S, Simons JP, Davis BG. 'Naked' and hydrated conformers of the conserved core pentasaccharide of N-linked glycoproteins and its building blocks. J Am Chem Soc 2013; 135:16895-903. [PMID: 24127839 PMCID: PMC3901393 DOI: 10.1021/ja4056678] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Indexed: 12/11/2022]
Abstract
N-glycosylation of eukaryotic proteins is widespread and vital to survival. The pentasaccharide unit -Man3GlcNAc2- lies at the protein-junction core of all oligosaccharides attached to asparagine side chains during this process. Although its absolute conservation implies an indispensable role, associated perhaps with its structure, its unbiased conformation and the potential modulating role of solvation are unknown; both have now been explored through a combination of synthesis, laser spectroscopy, and computation. The proximal -GlcNAc-GlcNAc- unit acts as a rigid rod, while the central, and unusual, -Man-β-1,4-GlcNAc- linkage is more flexible and is modulated by the distal Man-α-1,3- and Man-α-1,6- branching units. Solvation stiffens the 'rod' but leaves the distal residues flexible, through a β-Man pivot, ensuring anchored projection from the protein shell while allowing flexible interaction of the distal portion of N-glycosylation with bulk water and biomolecular assemblies.
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Affiliation(s)
- Conor
S. Barry
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Emilio J. Cocinero
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ United Kingdom
| | - Pierre Çarçabal
- Institut
des Sciences Moléculaire d’Orsay-CNRS, Université Paris Sud, Bâtiment 210, 91405 Orsay Cedex, France
| | - David
P. Gamblin
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - E. Cristina Stanca-Kaposta
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ United Kingdom
| | - Sarah M. Remmert
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ United Kingdom
| | | | - Svemir Rudić
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ United Kingdom
| | - John P. Simons
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ United Kingdom
| | - Benjamin G. Davis
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
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20
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Schmidt C, Irausquin SJ, Valafar H. Advances in the REDCAT software package. BMC Bioinformatics 2013; 14:302. [PMID: 24098943 PMCID: PMC3840585 DOI: 10.1186/1471-2105-14-302] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 09/13/2013] [Indexed: 12/24/2022] Open
Abstract
Background Residual Dipolar Couplings (RDCs) have emerged in the past two decades as an informative source of experimental restraints for the study of structure and dynamics of biological macromolecules and complexes. The REDCAT software package was previously introduced for the analysis of molecular structures using RDC data. Here we report additional features that have been included in this software package in order to expand the scope of its analyses. We first discuss the features that enhance REDCATs user-friendly nature, such as the integration of a number of analyses into one single operation and enabling convenient examination of a structural ensemble in order to identify the most suitable structure. We then describe the new features which expand the scope of RDC analyses, performing exercises that utilize both synthetic and experimental data to illustrate and evaluate different features with regard to structure refinement and structure validation. Results We establish the seamless interaction that takes place between REDCAT, VMD, and Xplor-NIH in demonstrations that utilize our newly developed REDCAT-VMD and XplorGUI interfaces. These modules enable visualization of RDC analysis results on the molecular structure displayed in VMD and refinement of structures with Xplor-NIH, respectively. We also highlight REDCAT’s Error-Analysis feature in reporting the localized fitness of a structure to RDC data, which provides a more effective means of recognizing local structural anomalies. This allows for structurally sound regions of a molecule to be identified, and for any refinement efforts to be focused solely on locally distorted regions. Conclusions The newly engineered REDCAT software package, which is available for download via the WWW from http://ifestos.cse.sc.edu, has been developed in the Object Oriented C++ environment. Our most recent enhancements to REDCAT serve to provide a more complete RDC analysis suite, while also accommodating a more user-friendly experience, and will be of great interest to the community of researchers and developers since it hides the complications of software development.
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Affiliation(s)
- Chris Schmidt
- Department of Computer Science & Engineering, University of South Carolina, Columbia, SC 29208, USA.
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21
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Affiliation(s)
- Vitor H. Pomin
- Program of
Glycobiology, Institute of Medical Biochemistry,
and University Hospital Clementino Fraga Filho, Federal University of Rio de Janeiro, Rio de Janeiro, 21941-913,
Brazil
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22
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Protein structure validation and identification from unassigned residual dipolar coupling data using 2D-PDPA. Molecules 2013; 18:10162-88. [PMID: 23973992 PMCID: PMC4090686 DOI: 10.3390/molecules180910162] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 08/10/2013] [Accepted: 08/13/2013] [Indexed: 11/22/2022] Open
Abstract
More than 90% of protein structures submitted to the PDB each year are homologous to some previously characterized protein structure. The extensive resources that are required for structural characterization of proteins can be justified for the 10% of the novel structures, but not for the remaining 90%. This report presents the 2D-PDPA method, which utilizes unassigned residual dipolar coupling in order to address the economics of structure determination of routine proteins by reducing the data acquisition and processing time. 2D-PDPA has been demonstrated to successfully identify the correct structure of an array of proteins that range from 46 to 445 residues in size from a library of 619 decoy structures by using unassigned simulated RDC data. When using experimental data, 2D-PDPA successfully identified the correct NMR structures from the same library of decoy structures. In addition, the most homologous X-ray structure was also identified as the second best structural candidate. Finally, success of 2D-PDPA in identifying and evaluating the most appropriate structure from a set of computationally predicted structures in the case of a previously uncharacterized protein Pf2048.1 has been demonstrated. This protein exhibits less than 20% sequence identity to any protein with known structure and therefore presents a compelling and practical application of our proposed work.
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23
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Aguirre C, ten Brink T, Walker O, Guillière F, Davesne D, Krimm I. BcL-xL conformational changes upon fragment binding revealed by NMR. PLoS One 2013; 8:e64400. [PMID: 23717610 PMCID: PMC3662666 DOI: 10.1371/journal.pone.0064400] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 04/12/2013] [Indexed: 11/19/2022] Open
Abstract
Protein-protein interactions represent difficult but increasingly important targets for the design of therapeutic compounds able to interfere with biological processes. Recently, fragment-based strategies have been proposed as attractive approaches for the elaboration of protein-protein surface inhibitors from fragment-like molecules. One major challenge in targeting protein-protein interactions is related to the structural adaptation of the protein surface upon molecular recognition. Methods capable of identifying subtle conformational changes of proteins upon fragment binding are therefore required at the early steps of the drug design process. In this report we present a fast NMR method able to probe subtle conformational changes upon fragment binding. The approach relies on the comparison of experimental fragment-induced Chemical Shift Perturbation (CSP) of amine protons to CSP simulated for a set of docked fragment poses, considering the ring-current effect from fragment binding. We illustrate the method by the retrospective analysis of the complex between the anti-apoptotic Bcl-xL protein and the fragment 4′-fluoro-[1,1′-biphenyl]-4-carboxylic acid that was previously shown to bind one of the Bcl-xL hot spots. The CSP-based approach shows that the protein undergoes a subtle conformational rearrangement upon interaction, for residues located in helices 2, 3 and the very beginning of 5. Our observations are corroborated by residual dipolar coupling measurements performed on the free and fragment-bound forms of the Bcl-xL protein. These NMR-based results are in total agreement with previous molecular dynamic calculations that evidenced a high flexibility of Bcl-xL around the binding site. Here we show that CSP of protein amine protons are useful and reliable structural probes. Therefore, we propose to use CSP simulation to assess protein conformational changes upon ligand binding in the fragment-based drug design approach.
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Affiliation(s)
- Clémentine Aguirre
- UMR5280/Université de Lyon/Université Lyon 1, Institut des Sciences Analytiques, Villeurbanne, France
| | - Tim ten Brink
- UMR5280/Université de Lyon/Université Lyon 1, Institut des Sciences Analytiques, Villeurbanne, France
| | - Olivier Walker
- UMR5280/Université de Lyon/Université Lyon 1, Institut des Sciences Analytiques, Villeurbanne, France
| | - Florence Guillière
- UMR5280/Université de Lyon/Université Lyon 1, Institut des Sciences Analytiques, Villeurbanne, France
| | - Dany Davesne
- UMR5822/IN2P3/F-69622 Lyon, Université de Lyon, IPNL, Villeurbanne, France
| | - Isabelle Krimm
- UMR5280/Université de Lyon/Université Lyon 1, Institut des Sciences Analytiques, Villeurbanne, France
- * E-mail:
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24
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Yu B, van Ingen H, Freedberg DI. Constant time INEPT CT-HSQC (CTi-CT-HSQC) - A new NMR method to measure accurate one-bond J and RDCs with strong 1H-1H couplings in natural abundance. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 228:159-165. [PMID: 23294631 DOI: 10.1016/j.jmr.2012.11.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Revised: 11/06/2012] [Accepted: 11/08/2012] [Indexed: 05/28/2023]
Abstract
Strong (1)H-(1)H coupling can significantly reduce the accuracy of (1)J(CH) measured from frequency differences in coupled HSQC spectra. Although accurate (1)J(CH) values can be extracted from spectral simulation, it would be more convenient if the same accurate (1)J(CH) values can be obtained experimentally. Furthermore, simulations reach their limit for residual dipolar coupling (RDC) measurement, as many significant, but immeasurable RDCs are introduced into the spin system when a molecule is weakly aligned, thus it is impossible to have a model spin system that truly represents the real spin system. Here we report a new J modulated method, constant-time INEPT CT-HSQC (CTi-CT-HSQC), to accurately measure one-bond scalar coupling constant and RDCs without strong coupling interference. In this method, changing the spacing between the two 180° pulses during a constant time INEPT period selectively modulates heteronuclear coupling in quantitative J fashion. Since the INEPT delays for measuring one-bond carbon-proton spectra are short compared to (3)J(HH), evolution due to (strong) (1)H-(1)H coupling is marginal. The resulting curve shape is practically independent of (1)H-(1)H coupling and only correlated to the heteronuclear coupling evolution. Consequently, an accurate (1)J(CH) can be measured even in the presence of strong coupling. We tested this method on N-acetyl-glucosamine and mannose whose apparent isotropic (1)J(CH) values are significantly affected by strong coupling with other methods. Agreement to within 0.5Hz or better is found between (1)J(CH) measured by this method and previously published simulation data. We further examined the strong coupling effects on RDC measurements and observed an error up to 100% for one bond RDCs using coupled HSQC in carbohydrates. We demonstrate that RDCs can be obtained with higher accuracy by CTi-CT-HSQC, which compensates the limitation of simulation method.
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Affiliation(s)
- Bingwu Yu
- Laboratory of Bacterial Polysaccharides, CBER/FDA, Bethesda, MD 20892, United States
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25
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Widmalm G. A perspective on the primary and three-dimensional structures of carbohydrates. Carbohydr Res 2013; 378:123-32. [PMID: 23522728 DOI: 10.1016/j.carres.2013.02.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 02/13/2013] [Indexed: 10/27/2022]
Abstract
Carbohydrates, in more biologically oriented areas referred to as glycans, constitute one of the four groups of biomolecules. The glycans, often present as glycoproteins or glycolipids, form highly complex structures. In mammals ten monosaccharides are utilized in building glycoconjugates in the form of oligo- (up to about a dozen monomers) and polysaccharides. Subsequent modifications and additions create a large number of different compounds. In bacteria, more than a hundred monosaccharides have been reported to be constituents of lipopolysaccharides, capsular polysaccharides, and exopolysaccharides. Thus, the number of polysaccharide structures possible to create is huge. NMR spectroscopy plays an essential part in elucidating the primary structure, that is, monosaccharide identity and ring size, anomeric configuration, linkage position, and sequence, of the sugar residues. The structural studies may also employ computational approaches for NMR chemical shift predictions (CASPER program). Once the components and sequence of sugar residues have been unraveled, the three-dimensional arrangement of the sugar residues relative to each other (conformation), their flexibility (transitions between and populations of conformational states), together with the dynamics (timescales) should be addressed. To shed light on these aspects we have utilized a combination of experimental liquid state NMR techniques together with molecular dynamics simulations. For the latter a molecular mechanics force field such as our CHARMM-based PARM22/SU01 has been used. The experimental NMR parameters acquired are typically (1)H,(1)H cross-relaxation rates (related to NOEs), (3)JCH and (3)JCCtrans-glycosidic coupling constants and (1)H,(13)C- and (1)H,(1)H-residual dipolar couplings. At a glycosidic linkage two torsion angles ϕ and ψ are defined and for 6-substituted residues also the ω torsion angle is required. Major conformers can be identified for which highly populated states are present. Thus, in many cases a well-defined albeit not rigid structure can be identified. However, on longer timescales, oligosaccharides must be considered as highly flexible molecules since also anti-conformations have been shown to exist with H-C-O-C torsion angles of ∼180°, compared to syn-conformations in which the protons at the carbon atoms forming the glycosidic linkage are in close proximity. The accessible conformational space governs possible interactions with proteins and both minor changes and significant alterations occur for the oligosaccharides in these interaction processes. Transferred NOE NMR experiments give information on the conformation of the glycan ligand when bound to the proteins whereas saturation transfer difference NMR experiments report on the carbohydrate part in contact with the protein. It is anticipated that the subtle differences in conformational preferences for glycan structures facilitate a means to regulate biochemical processes in different environments. Further developments in the analysis of glycan structure and in particular its role in interactions with other molecules, will lead to clarifications of the importance of structure in biochemical regulation processes essential to health and disease.
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Affiliation(s)
- Göran Widmalm
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
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26
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Canales A, Jiménez-Barbero J, Martín-Pastor M. Review: Use of residual dipolar couplings to determine the structure of carbohydrates. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2012; 50 Suppl 1:S80-S85. [PMID: 23280664 DOI: 10.1002/mrc.3888] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 09/08/2012] [Accepted: 09/20/2012] [Indexed: 05/28/2023]
Abstract
Solution nuclear magnetic resonance spectroscopy is especially useful in the carbohydrate field. The measurement of residual dipolar couplings provides long-range structural information, a valuable complement for the structural study of carbohydrates either in its free form or in the bound state to proteins. They permit to deduce the geometry and the flexibility of the glycosidic linkages, which have a major influence on the conformation of carbohydrates and their overall shape. This article reviews the current application of the residual dipolar couplings methodology to carbohydrates.
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Affiliation(s)
- A Canales
- Department Organic Chemistry, Universidad Complutense de Madrid, Madrid, Spain
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27
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Abstract
Nuclear Magnetic Resonance (NMR) techniques are widely used in the drug discovery process. The primary feature exploited in these investigations is the large difference in mass between drugs and receptors (usually proteins) and the effect this has on the rotational or translational correlation times for drugs bound to their targets. Many NMR parameters, such as the diffusion coefficient, spin diffusion, nuclear Overhauser enhancement, and transverse and longitudinal relaxation times, are strong functions of either the overall tumbling or translation of molecules in solution. This has led to the development of a wide variety of NMR techniques applicable to the elucidation of protein and nucleic acid structure in solution, the screening of drug candidates for binding to a target of choice, and the study of the conformational changes which occur in a target upon drug binding. High-throughput screening by NMR methods has recently received a boost from the introduction of sophisticated computational techniques for reducing the time needed for the acquisition of the primary NMR data for multidimensional studies.
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Affiliation(s)
- Laurel O Sillerud
- Department of Biochemistry and Molecular Biology, UNM HDC, University of New Mexico, Albuquerque, NM, USA.
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28
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Xia J, Margulis CJ, Case DA. Searching and optimizing structure ensembles for complex flexible sugars. J Am Chem Soc 2011; 133:15252-5. [PMID: 21863822 DOI: 10.1021/ja205251j] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
NMR restrictions are suitable to specify the geometry of a molecule when a single well-defined global free energy minimum exists that is significantly lower than other local minima. Carbohydrates are quite flexible, and therefore, NMR observables do not always correlate with a single conformer but instead with an ensemble of low free energy conformers that can be accessed by thermal fluctuations. In this communication, we describe a novel procedure to identify and weight the contribution to the ensemble of local minima conformers based on comparison to residual dipolar couplings (RDCs) or other NMR observables, such as scalar couplings. A genetic algorithm is implemented to globally minimize the R factor comparing calculated RDCs to experiment. This is done by optimizing the weights of different conformers derived from the exhaustive local minima conformational search program, fast sugar structure prediction software (FSPS). We apply this framework to six human milk sugars, LND-1, LNF-1, LNF-2, LNF-3, LNnT, and LNT, and are able to determine corresponding population weights for the ensemble of conformers. Interestingly, our results indicate that in all cases the RDCs can be well represented by only a few most important conformers. This confirms that several, but not all of the glycosidic linkages in histo-blood group "epitopes" are quite rigid.
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Affiliation(s)
- Junchao Xia
- BioMaPS Institute and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States.
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Kramer M, Kleinpeter E. A conformational study of N-acetyl glucosamine derivatives utilizing residual dipolar couplings. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 212:174-185. [PMID: 21802325 DOI: 10.1016/j.jmr.2011.06.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 06/22/2011] [Accepted: 06/25/2011] [Indexed: 05/31/2023]
Abstract
The conformational analyses of six non-rigid N-acetyl glucosamine (NAG) derivatives employing residual dipolar couplings (RDCs) and NOEs together with molecular dynamics (MD) simulations are presented. Due to internal dynamics we had to consider different conformer ratios existing in solution. The good quality of the correlation between theoretically and experimentally obtained RDCs show the correctness of the calculated conformers even if the ratios derived from the MD simulations do not exactly meet the experimental data. If possible, the results were compared to former published data and commented.
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Affiliation(s)
- Markus Kramer
- University of Potsdam, Department of Chemistry, Karl-Liebknecht-Str. 24-25, 14476 Potsdam/Golm, Germany
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30
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Erdélyi M, d'Auvergne E, Navarro-Vázquez A, Leonov A, Griesinger C. Dynamics of the glycosidic bond: conformational space of lactose. Chemistry 2011; 17:9368-76. [PMID: 21755545 DOI: 10.1002/chem.201100854] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2011] [Indexed: 11/11/2022]
Abstract
The dynamics of the glycosidic bond of lactose was studied by a paramagnetic tagging-based NMR technique, which allowed the collection of an unusually large series of NMR data for a single compound. By the use of distance- and orientation-dependent residual dipolar couplings and pseudocontact shifts, the simultaneous fitting of the probabilities of computed conformations and the orientation of the magnetic susceptibility tensor of a series of lanthanide complexes of lactose show that its glycosidic bond samples syn/syn, anti/syn and syn/anti ϕ/ψ regions of the conformational space in water. The analysis indicates a higher reliability of pseudocontact shift data as compared to residual dipolar couplings with the presently available weakly orienting paramagnetic tagging technique. The method presented herein allows for an improved understanding of the dynamic behaviour of oligosaccharides.
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Affiliation(s)
- Máté Erdélyi
- NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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31
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Salmon L, Bouvignies G, Markwick P, Blackledge M. Nuclear magnetic resonance provides a quantitative description of protein conformational flexibility on physiologically important time scales. Biochemistry 2011; 50:2735-47. [PMID: 21388216 DOI: 10.1021/bi200177v] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A complete description of biomolecular activity requires an understanding of the nature and the role of protein conformational dynamics. In recent years, novel nuclear magnetic resonance-based techniques that provide hitherto inaccessible detail concerning biomolecular motions occurring on physiologically important time scales have emerged. Residual dipolar couplings (RDCs) provide precise information about time- and ensemble-averaged structural and dynamic processes with correlation times up to the millisecond and thereby encode key information for understanding biological activity. In this review, we present the application of two very different approaches to the quantitative description of protein motion using RDCs. The first is purely analytical, describing backbone dynamics in terms of diffusive motions of each peptide plane, using extensive statistical analysis to validate the proposed dynamic modes. The second is based on restraint-free accelerated molecular dynamics simulation, providing statistically sampled free energy-weighted ensembles that describe conformational fluctuations occurring on time scales from pico- to milliseconds, at atomic resolution. Remarkably, the results from these two approaches converge closely in terms of distribution and absolute amplitude of motions, suggesting that this kind of combination of analytical and numerical models is now capable of providing a unified description of protein conformational dynamics in solution.
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Affiliation(s)
- Loïc Salmon
- Protein Dynamics and Flexibility, Institut de Biologie Structurale Jean-Pierre Ebel, CEA, CNRS, UJF UMR 5075, 41 Rue Jules Horowitz, Grenoble 38027, France
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32
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Shealy P, Simin M, Park SH, Opella SJ, Valafar H. Simultaneous structure and dynamics of a membrane protein using REDCRAFT: membrane-bound form of Pf1 coat protein. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 207:8-16. [PMID: 20829084 PMCID: PMC3970221 DOI: 10.1016/j.jmr.2010.07.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 07/18/2010] [Accepted: 07/25/2010] [Indexed: 05/11/2023]
Abstract
A strategy for simultaneous study of the structure and internal dynamics of a membrane protein is described using the REDCRAFT algorithm. The membrane-bound form of the Pf1 major coat protein (mbPf1) was used as an example. First, synthetic data is utilized to validate the simultaneous study of structure and dynamics with REDCRAFT using dihedral restraints and backbone N-H RDCs from two different alignments. Subsequently, the validated analysis is applied to experimental data and confirms that REDCRAFT produces meaningful structures from sparse RDC data. Furthermore, simulated data from a two-state jump motion is used to illustrate the necessity for simultaneous consideration of structure and dynamics. Disregarding internal dynamics during the course of structure determination is shown to produce an average-state that is not related to the two intermediate states. During the analysis of RDC data from the dynamic model, REDCRAFT appropriately identifies the region separating the static and dynamic domains of the protein. Finally, analysis of experimental data strongly suggests the existence of internal motion between the amphipathic and the transmembrane helices of the membrane-bound form of the protein. The ability to perform fragmented structure determination of each domain without a priori assumption of the order tensors allows an independent determination of the order tensors, which yields a more comprehensive description of protein structure and dynamics and is particularly relevant to the study of membrane proteins.
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Affiliation(s)
- Paul Shealy
- Department of Computer Science & Engineering, University of South Carolina, 315 Main Street, Columbia, SC 29208, United States
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33
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Ganguly S, Xia J, Margulis C, Stanwyck L, Bush CA. Measuring the magnitude of internal motion in a complex hexasaccharide. Biopolymers 2010; 95:39-50. [DOI: 10.1002/bip.21532] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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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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35
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Kövér KE, Szilágyi L, Batta G, Uhrín D, Jiménez-Barbero J. Biomolecular Recognition by Oligosaccharides and Glycopeptides: The NMR Point of View. COMPREHENSIVE NATURAL PRODUCTS II 2010:197-246. [DOI: 10.1016/b978-008045382-8.00193-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
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36
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Abstract
More than half of all human proteins are glycosylated. Glycosylation defines the adhesive properties of glycoconjugates and it is largely through glycan-protein interactions that cell-cell and cell-pathogen contacts occur. Not surprisingly, considering the central role they play in molecular encounters, glycoprotein and carbohydrate-based drugs and therapeutics represent a greater than $20 billion market. Glycomics, the study of glycan expression in biological systems, relies on effective analytical techniques for correlation of glycan structure with function. This overview summarizes techniques developed historically for glycan characterization as well as recent trends. Derivatization methods key to both traditional and modern approaches for glycoanalysis are described. Monosaccharide compositional analysis is fundamental to any effort to understand glycan structure-function relationships. Chromatographic and electrophoretic separations are key parts of any glycoanalytical workflow. Mass spectrometry and nuclear magnetic resonance are complementary instrumental techniques for glycan analysis. Finally, microarrays are emerging as powerful new tools for dynamic analysis of glycan expression.
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Affiliation(s)
- Alicia M Bielik
- Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
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37
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Ferner J, Suhartono M, Breitung S, Jonker HRA, Hennig M, Wöhnert J, Göbel M, Schwalbe H. Structures of HIV TAR RNA-ligand complexes reveal higher binding stoichiometries. Chembiochem 2009; 10:1490-4. [PMID: 19444830 DOI: 10.1002/cbic.200900220] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Target TAR by NMR: Tripeptides containing arginines as terminal residues and non-natural amino acids as central residues are good leads for drug design to target the HIV trans-activation response element (TAR). The structural characterization of the RNA-ligand complex by NMR spectroscopy reveals two specific binding sites that are located at bulge residue U23 and around the pyrimidine-stretch U40-C41-U42 directly adjacent to the bulge.
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Affiliation(s)
- Jan Ferner
- Institut für Organische Chemie und Chemische Biologie, Zentrum für Biomolekulare Magnetische Resonanz (BMRZ), Johann Wolfgang Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
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38
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Jin L, Hricovíni M, Deakin JA, Lyon M, Uhrín D. Residual dipolar coupling investigation of a heparin tetrasaccharide confirms the limited effect of flexibility of the iduronic acid on the molecular shape of heparin. Glycobiology 2009; 19:1185-96. [PMID: 19648354 PMCID: PMC2757574 DOI: 10.1093/glycob/cwp105] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The solution conformation of a fully sulfated heparin-derived tetrasaccharide, I, was studied in the presence of a 4-fold excess of Ca2+. Proton–proton and proton–carbon residual dipolar couplings (RDCs) were measured in a neutral aligning medium. The order parameters of two rigid hexosamine rings of I were determined separately using singular value decomposition and ab initio structures of disaccharide fragments of I. The order parameters were very similar implying that a common order tensor can be used to analyze the structure of I. Using one order tensor, RDCs of both hexosamine rings were used as restraints in molecular dynamics simulations. RDCs of the inner iduronic acid were calculated for every point of the molecular dynamics trajectory. The fitting of the calculated RDCs of the two forms of the iduronic acid to the experimental values yielded a population of 1C4 and 2So conformers of iduronic acid that agreed well with the analysis based on proton–proton scalar coupling constants. The glycosidic linkage torsion angles in RDC-restrained molecular dynamics (MD) structures of I are consistent with the interglycosidic three-bond proton–carbon coupling constants. These structures also show that the shape of heparin is not affected dramatically by the conformational flexibility of the iduronic acid ring. This is in line with conclusions of previous studies based on MD simulations and the analysis of 1H-1H NOEs. Our work therefore demonstrates the effectiveness of RDCs in the conformational analysis of glycosaminoglycans.
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Affiliation(s)
- Lan Jin
- School of Chemistry, University of Edinburgh, Edinburgh, Scotland
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39
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40
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Fisher CK, Zhang Q, Stelzer A, Al-Hashimi HM. Ultrahigh resolution characterization of domain motions and correlations by multialignment and multireference residual dipolar coupling NMR. J Phys Chem B 2009; 112:16815-22. [PMID: 19367865 DOI: 10.1021/jp806188j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Nuclear magnetic resonance (NMR) residual dipolar couplings (RDCs) provide a unique opportunity for spatially characterizing complex motions in biomolecules with time scale sensitivity extending up to milliseconds. Up to five motionally averaged Wigner rotation elements, (D(0k)2(alphaalpha)), can be determined experimentally using RDCs measured in five linearly independent alignment conditions and applied to define motions of axially symmetric bond vectors. Here, we show that up to 25 motionally averaged Wigner rotation elements, (D(mk)2(alphabetagamma)), can be determined experimentally from multialignment RDCs and used to characterize rigid-body motions of chiral domains. The 25 (D(mk)2(alphabetagamma)) elements form a basis set that allows one to measure motions of a domain relative to an isotropic distribution of reference frames anchored on a second domain (and vice versa), thus expanding the 3D spatial resolution with which motions can be characterized. The 25 (D(mk)2(alphabetagamma)) elements can also be used to fit an ensemble consisting of up to eight equally or six unequally populated states. For more than two domains, changing the identity of the domain governing alignment allows access to new information regarding the correlated nature of the domain fluctuations. Example simulations are provided that validate the theoretical derivation and illustrate the high spatial resolution with which rigid-body domain motions can be characterized using multialignment and multireference RDCs. Our results further motivate the development of experimental approaches for both modulating alignment and anchoring it on specifically targeted domains.
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Affiliation(s)
- Charles K Fisher
- Department of Chemistry & Biophysics, The University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA
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41
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Mackeen MM, Almond A, Deschamps M, Cumpstey I, Fairbanks AJ, Tsang C, Rudd PM, Butters TD, Dwek RA, Wormald MR. The conformational properties of the Glc3Man unit suggest conformational biasing within the chaperone-assisted glycoprotein folding pathway. J Mol Biol 2009; 387:335-47. [PMID: 19356590 DOI: 10.1016/j.jmb.2009.01.043] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 01/19/2009] [Accepted: 01/23/2009] [Indexed: 11/16/2022]
Abstract
A major puzzle is: are all glycoproteins routed through the ER calnexin pathway irrespective of whether this is required for their correct folding? Calnexin recognizes the terminal Glcalpha1-3Manalpha linkage, formed by trimming of the Glcalpha1-2Glcalpha1-3Glcalpha1-3Manalpha (Glc3Man) unit in Glc3Man9GlcNAc2. Different conformations of this unit have been reported. We have addressed this problem by studying the conformation of a series of N-glycans; i.e. Glc3ManOMe, Glc3Man(4,5,7)GlcNAc2 and Glc1Man9GlcNAc2 using 2D NMR NOESY, ROESY, T-ROESY and residual dipolar coupling experiments in a range of solvents, along with solution molecular dynamics simulations of Glc3ManOMe. Our results show a single conformation for the Glcalpha1-2Glcalpha and Glcalpha1-3Glcalpha linkages, and a major (65%) and a minor (30%) conformer for the Glcalpha1-3Manalpha linkage. Modeling of the binding of Glc1Man9GlcNAc2 to calnexin suggests that it is the minor conformer that is recognized by calnexin. This may be one of the mechanisms for controlling the rate of recruitment of proteins into the calnexin/calreticulin chaperone system and enabling proteins that do not require such assistance for folding to bypass the system. This is the first time evidence has been presented on glycoprotein folding that suggests the process may be optimized to balance the chaperone-assisted and chaperone-independent pathways.
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Affiliation(s)
- Mukram M Mackeen
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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42
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Miao X, Mukhopadhyay R, Valafar H. Estimation of relative order tensors, and reconstruction of vectors in space using unassigned RDC data and its application. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 194:202-11. [PMID: 18692422 PMCID: PMC2669903 DOI: 10.1016/j.jmr.2008.07.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 06/27/2008] [Accepted: 07/02/2008] [Indexed: 05/11/2023]
Abstract
Advances in NMR instrumentation and pulse sequence design have resulted in easier acquisition of Residual Dipolar Coupling (RDC) data. However, computational and theoretical analysis of this type of data has continued to challenge the international community of investigators because of their complexity and rich information content. Contemporary use of RDC data has required a-priori assignment, which significantly increases the overall cost of structural analysis. This article introduces a novel algorithm that utilizes unassigned RDC data acquired from multiple alignment media (nD-RDC, n3) for simultaneous extraction of the relative order tensor matrices and reconstruction of the interacting vectors in space. Estimation of the relative order tensors and reconstruction of the interacting vectors can be invaluable in a number of endeavors. An example application has been presented where the reconstructed vectors have been used to quantify the fitness of a template protein structure to the unknown protein structure. This work has other important direct applications such as verification of the novelty of an unknown protein and validation of the accuracy of an available protein structure model in drug design. More importantly, the presented work has the potential to bridge the gap between experimental and computational methods of structure determination.
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Affiliation(s)
- Xijiang Miao
- Computer Science and Engineering, Swearingen Engineering Center, University of South Carolina, Columbia, SC 29308, USA
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43
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Celebre G, Cinacchi G, De Luca G. Solvent smectic order parameters from solute nematic order parameters. J Chem Phys 2008; 129:094509. [PMID: 19044879 DOI: 10.1063/1.2970074] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In liquid crystals, while the second and fourth rank orientational order parameters characterizing a nematic phase can be experimentally determined via several techniques, there is no straightforward experiment rendering the positional order parameters characterizing a smectic A phase. This work illustrates a novel method to estimate the positional order parameters of a smectogenic liquid crystal solvent from knowledge of the orientational order parameters of a number of solutes dissolved therein. The latter order parameters can be experimentally determined via liquid crystal NMR spectroscopy. These data can be then analyzed with a statistical-thermodynamic density functional theory, whose basic ingredient is a model for solute-solvent intermolecular interactions. Its parametrization and the subsequent fitting procedure eventually permit one to obtain the positional order parameters of the solvent besides the positional-orientational distribution function of the solutes. The method is applied to the smectogen 4,4(')-di-n-heptyl-azoxybenzene, in which the solutes 1,4-dichlorobenzene and naphthalene have been dissolved. With the help of this exploratory practical example, pros and cons of the method are pointed out and further developments prospected.
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Affiliation(s)
- Giorgio Celebre
- Dipartimento di Chimica, Universita della Calabria, Via Pietro Bucci Cubo 14C, I-87036 Rende, Cosenza, Italy.
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Stanca-Kaposta EC, Gamblin DP, Cocinero EJ, Frey J, Kroemer RT, Fairbanks AJ, Davis BG, Simons JP. Solvent Interactions and Conformational Choice in a Core N-Glycan Segment: Gas Phase Conformation of the Central, Branching Trimannose Unit and its Singly Hydrated Complex. J Am Chem Soc 2008; 130:10691-6. [DOI: 10.1021/ja801892h] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- E. Cristina Stanca-Kaposta
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ Oxford, United Kingdom, Sanofi-Aventis, CRVA, 13 quai Jules Guesde, BP14, 94403 Vitry-sur-Seine, France, and the Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - David P. Gamblin
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ Oxford, United Kingdom, Sanofi-Aventis, CRVA, 13 quai Jules Guesde, BP14, 94403 Vitry-sur-Seine, France, and the Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Emilio J. Cocinero
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ Oxford, United Kingdom, Sanofi-Aventis, CRVA, 13 quai Jules Guesde, BP14, 94403 Vitry-sur-Seine, France, and the Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Jann Frey
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ Oxford, United Kingdom, Sanofi-Aventis, CRVA, 13 quai Jules Guesde, BP14, 94403 Vitry-sur-Seine, France, and the Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Romano T. Kroemer
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ Oxford, United Kingdom, Sanofi-Aventis, CRVA, 13 quai Jules Guesde, BP14, 94403 Vitry-sur-Seine, France, and the Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Antony J. Fairbanks
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ Oxford, United Kingdom, Sanofi-Aventis, CRVA, 13 quai Jules Guesde, BP14, 94403 Vitry-sur-Seine, France, and the Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Benjamin G. Davis
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ Oxford, United Kingdom, Sanofi-Aventis, CRVA, 13 quai Jules Guesde, BP14, 94403 Vitry-sur-Seine, France, and the Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - John P. Simons
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ Oxford, United Kingdom, Sanofi-Aventis, CRVA, 13 quai Jules Guesde, BP14, 94403 Vitry-sur-Seine, France, and the Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
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45
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Cevec M, Thibaudeau C, Plavec J. Solution structure of a let-7 miRNA:lin-41 mRNA complex from C. elegans. Nucleic Acids Res 2008; 36:2330-7. [PMID: 18296482 PMCID: PMC2367737 DOI: 10.1093/nar/gkn088] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Let-7 microRNA (miRNA) regulates heterochronic genes in developmental timing of the nematode Caenorhabditis elegans. Binding of miRNA to messenger RNA (mRNA) and structural features of the complex are crucial for gene silencing. We herein present the NMR solution structure of a model mimicking the interaction of let-7 miRNA with its complementary site (LCS 2) in the 3' untranslated region (3'-UTR) of the lin-41 mRNA. A structural study was performed by NMR spectroscopy using NOE restraints, torsion angle restraints and residual dipolar couplings. The 33-nt RNA construct folds into a stem-loop structure that features two stem regions which are separated by an asymmetric internal loop. One of the stems comprises a GU wobble base pair, which does not alter its overall A-form RNA conformation. The asymmetric internal loop adopts a single, well-defined structure in which three uracils form a base triple, while two adenines form a base pair. The 3D structure of the construct gives insight into the structural aspects of interactions between let-7 miRNA and lin-41 mRNA.
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Affiliation(s)
- Mirko Cevec
- Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
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46
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Mari S, Sánchez-Medina I, Mereghetti P, Belvisi L, Jiménez-Barbero J, Bernardi A. Synthesis and conformational analysis of an α-d-mannopyranosyl-(1→2)-α-d-mannopyranosyl-(1→6)-α-d-mannopyranose mimic. Carbohydr Res 2007; 342:1859-68. [PMID: 17420008 DOI: 10.1016/j.carres.2007.03.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 03/13/2007] [Accepted: 03/17/2007] [Indexed: 11/24/2022]
Abstract
A mimic of a (1-->2),(1-->6)-mannotrioside was synthesized by replacing the central mannose unit with an enantiomerically pure, conformationally stable trans-diaxial cyclohexanediol. The three-dimensional structure of the molecule was investigated by NMR spectroscopy supported by molecular modelling and was compared to the known features of the natural mannotrioside.
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Affiliation(s)
- Silvia Mari
- Centro de Investigaciones Biológicas, Departamento de Estructura y Functión de Proteínas, CSIC, c/Ramiro de Maeztu 9, 28040 Madrid, Spain
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47
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Jin L, Pham TN, Uhrín D. Measurement of1H–1H Residual Dipolar Coupling Constants for Structural Studies of Medium Size Molecules. Chemphyschem 2007; 8:1228-35. [PMID: 17457790 DOI: 10.1002/cphc.200700071] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Residual dipolar coupling constants (RDCs) are being increasingly applied to elucidate the configuration and conformation of small organic molecules, peptides and oligosaccharides. In this paper we describe a set of robust 1D NMR methods for accurate and precise measurement of proton-proton RDCs of small and medium size molecules. The performance of these techniques is not impeded by the presence of overlapping and broad (1)H multiplets that are typically observed for such molecules in weakly aligned media. The use of these techniques provides access to a large pool of proton-proton RDCs opening new avenues for the solution structure elucidation of medium size molecules by NMR. The techniques are illustrated on the determination of the alignment tensor of the reducing monosaccharide ring of cellobiose and the determination of the relative configuration of sodium cholate.
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Affiliation(s)
- Lan Jin
- School of Chemistry, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3JJ, UK
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Seidel RD, Zhuang T, Prestegard JH. Bound-state residual dipolar couplings for rapidly exchanging ligands of His-tagged proteins. J Am Chem Soc 2007; 129:4834-9. [PMID: 17385862 PMCID: PMC2542485 DOI: 10.1021/ja069145h] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The study of bound-state conformations of ligands interacting with proteins is important to the understanding of protein function and the design of drugs that alter function. Traditionally, transferred nuclear Overhauser effects (trNOEs), measured from NMR spectra of ligands in rapid exchange between bound and free states, have been used in these studies, owing to the inherent heavy weighting of bound-state data in the averaged ligand signals. In principle, residual dipolar couplings (RDCs) provide a useful complement to NOE data in that they provide orientational constraints as opposed to distance constraints, but use in ligand-binding applications has been limited due to the absence of heavy weighting of bound-state data. A widely applicable approach to increasing the weighting of bound-state data in averaged RDCs measured on ligands is presented. The approach rests on association of a His-tagged protein with a nickel-chelate-carrying lipid inserted into the lipid bilayer-like alignment media used in the acquisition of RDCs. The approach is validated through the observation of bound-state RDCs for the disaccharide, lactose, bound to the carbohydrate recognition domain of the mammalian lectin, galectin-3.
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Affiliation(s)
- Ronald D Seidel
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602-4712, USA
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Yu F, Prestegard JH. Structural monitoring of oligosaccharides through 13C enrichment and NMR observation of acetyl groups. Biophys J 2006; 91:1952-9. [PMID: 16782783 PMCID: PMC1544292 DOI: 10.1529/biophysj.105.079913] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Structural characterization of biomolecules by NMR methods frequently requires the enrichment of magnetically active isotopes at particular molecular sites. Introduction is usually achieved biosynthetically through the use of bacterial cultures grown on isotopically enriched media, but for certain types of molecules-cell-surface carbohydrates of mammalian origin, for example-this is not practical. Here we explore a means of introducing 13C-enriched sites, postisolation in natural carbohydrate products, and illustrate an ability to acquire sufficient information to select appropriate conformational models from among energetically allowed sets. The application presented involves replacement of native N-acetyl groups with 13C-labeled acetyl groups in a simple disaccharide derivative, (GlcNAc)2-OBu, or O-butyl-chitobiose. The assignment of the two acetyl groups introduced is based on a novel combination of NMR and mass spectrometry data. Structural information is obtained from chemical shift anisotropy offsets of 13C carbonyl resonances and 13C-13C dipolar couplings between the labeled methyl and carbonyl carbons of the acetyl groups. Although the application is to a relatively simple system, it lays the groundwork for application to biologically important complex carbohydrate systems.
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Affiliation(s)
- Fei Yu
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, USA
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Yuriev E, Farrugia W, Scott AM, Ramsland PA. Three-dimensional structures of carbohydrate determinants of Lewis system antigens: implications for effective antibody targeting of cancer. Immunol Cell Biol 2005; 83:709-17. [PMID: 16266323 DOI: 10.1111/j.1440-1711.2005.01374.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Lewis system carbohydrate antigens have been shown to be expressed at high levels in many cancers of epithelial cell origin, including those of colon, breast, lung, prostate and ovary. The type 1 (Le(a) and Le(b)) antigens are important histo-blood groups, while type 2 (Le(x) and Le(y)) antigens in healthy individuals are only expressed, at relatively low levels, by a few tissues, including some epithelial cells. Thus, the type 2 antigens are considered to be tumour-associated antigens and are promising targets for cancer treatment, including antibody-based immunotherapy. In this review, we discuss the conformational characteristics of the free and bound forms of Lewis oligosaccharides and the 3D structures of antibodies in complex with Le(y) and Le(x) antigens. Collectively, the structural studies have demonstrated that the Lewis determinants are rigid structures, which generally maintain the same conformation in the free and bound states. The rigid nature and similarities in shape of type 1 and 2 Lewis oligosaccharides appear to make them perfectly suited to driving a structurally convergent immune response (at least in the case of Le(y) specific antibodies) toward a highly specific recognition of individual carbohydrate determinants, which is a goal in the development of effective antibody-based cancer treatments.
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Affiliation(s)
- Elizabeth Yuriev
- Department of Medicinal Chemistry, Victorian College of Pharmacy, Monash University, Victoria, Australia
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