51
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Strickland M, Schwieters CD, Göbl C, Opina ACL, Strub MP, Swenson RE, Vasalatiy O, Tjandra N. Characterizing the magnetic susceptibility tensor of lanthanide-containing polymethylated-DOTA complexes. JOURNAL OF BIOMOLECULAR NMR 2016; 66:125-139. [PMID: 27659040 PMCID: PMC6628275 DOI: 10.1007/s10858-016-0061-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 09/13/2016] [Indexed: 05/16/2023]
Abstract
Lanthanide complexes based on the DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) cage are commonly used as phase contrast agents in magnetic resonance imaging, but can also be utilized in structural NMR applications due to their ability to induce either paramagnetic relaxation enhancement or a pseudocontact shift (PCS) depending on the choice of the lanthanide. The size and sign of the PCS for any given atom is determined by its coordinates relative to the metal center, and the characteristics of the lanthanide's magnetic susceptibility tensor. Using a polymethylated DOTA tag (Ln-M8-SPy) conjugated to ubiquitin, we calculated the position of the metal center and characterized the susceptibility tensor for a number of lanthanides (dysprosium, thulium, and ytterbium) under a range of pH and temperature conditions. We found that there was a difference in temperature sensitivity for each of the complexes studied, which depended on the size of the lanthanide ion as well as the isomeric state of the cage. Using 17O-NMR, we confirmed that the temperature sensitivity of the compounds was enhanced by the presence of an apically bound water molecule. Since amide-containing lanthanide complexes are known to be pH sensitive and can be used as probes of physiological pH, we also investigated the effect of pH on the Ln-M8-SPy susceptibility tensor, but we found that the changes in this pH range (5.0-7.4) were not significant.
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Affiliation(s)
- Madeleine Strickland
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Charles D Schwieters
- Office of Intramural Research, Center for Information Technology, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Christoph Göbl
- Department of Chemistry, Technische Universität München, Lichtenbergstraße 4, 85748, Garching, Germany
| | - Ana C L Opina
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Rockville, MD, 20850, USA
| | - Marie-Paule Strub
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Rolf E Swenson
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Rockville, MD, 20850, USA
| | - Olga Vasalatiy
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Rockville, MD, 20850, USA
| | - Nico Tjandra
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
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52
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Chen WN, Nitsche C, Pilla KB, Graham B, Huber T, Klein CD, Otting G. Sensitive NMR Approach for Determining the Binding Mode of Tightly Binding Ligand Molecules to Protein Targets. J Am Chem Soc 2016; 138:4539-46. [PMID: 26974502 DOI: 10.1021/jacs.6b00416] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Structure-guided drug design relies on detailed structural knowledge of protein-ligand complexes, but crystallization of cocomplexes is not always possible. Here we present a sensitive nuclear magnetic resonance (NMR) approach to determine the binding mode of tightly binding lead compounds in complex with difficult target proteins. In contrast to established NMR methods, it does not depend on rapid exchange between bound and free ligand or on stable isotope labeling, relying instead on a tert-butyl group as a chemical label. tert-Butyl groups are found in numerous protein ligands and deliver an exceptionally narrow and tall (1)H NMR signal. We show that a tert-butyl group also produces outstandingly intense intra- and intermolecular NOESY cross-peaks. These enable measurements of pseudocontact shifts generated by lanthanide tags attached to the protein, which in turn allows positioning of the ligand on the protein. Once the ligand has been located, assignments of intermolecular NOEs become possible even without prior resonance assignments of protein side chains. The approach is demonstrated with the dengue virus NS2B-NS3 protease in complex with a high-affinity ligand containing a tert-butyl group.
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Affiliation(s)
- Wan-Na Chen
- Australian National University , Research School of Chemistry, Canberra, ACT 2601, Australia
| | - Christoph Nitsche
- Australian National University , Research School of Chemistry, Canberra, ACT 2601, Australia.,Medicinal Chemistry, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University , Im Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Kala Bharath Pilla
- Australian National University , Research School of Chemistry, Canberra, ACT 2601, Australia
| | - Bim Graham
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, VIC 3052, Australia
| | - Thomas Huber
- Australian National University , Research School of Chemistry, Canberra, ACT 2601, Australia
| | - Christian D Klein
- Medicinal Chemistry, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University , Im Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Gottfried Otting
- Australian National University , Research School of Chemistry, Canberra, ACT 2601, Australia
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53
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Yang F, Wang X, Pan BB, Su XC. Single-armed phenylsulfonated pyridine derivative of DOTA is rigid and stable paramagnetic tag in protein analysis. Chem Commun (Camb) 2016; 52:11535-11538. [DOI: 10.1039/c6cc06114a] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Single-armed DOTA-like phenylsulfonated pyridine derivatives are rigid and stable paramagnetic tags for site-specific labelling of proteins. The respective protein conjugates yield valuable long-range structural restraints for proteins.
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Affiliation(s)
- Feng Yang
- State Key Laboratory of Elemento-Organic Chemistry
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin)
- Nankai University
- Tianjin 300071
- China
| | - Xiao Wang
- State Key Laboratory of Elemento-Organic Chemistry
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin)
- Nankai University
- Tianjin 300071
- China
| | - Bin-Bin Pan
- State Key Laboratory of Elemento-Organic Chemistry
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin)
- Nankai University
- Tianjin 300071
- China
| | - Xun-Cheng Su
- State Key Laboratory of Elemento-Organic Chemistry
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin)
- Nankai University
- Tianjin 300071
- China
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54
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Pseudocontact Shift-Driven Iterative Resampling for 3D Structure Determinations of Large Proteins. J Mol Biol 2016; 428:522-32. [DOI: 10.1016/j.jmb.2016.01.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 01/08/2016] [Accepted: 01/08/2016] [Indexed: 01/23/2023]
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55
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Abdelkader EH, Lee MD, Feintuch A, Cohen MR, Swarbrick JD, Otting G, Graham B, Goldfarb D. A New Gd(3+) Spin Label for Gd(3+)-Gd(3+) Distance Measurements in Proteins Produces Narrow Distance Distributions. J Phys Chem Lett 2015; 6:5016-5021. [PMID: 26623480 DOI: 10.1021/acs.jpclett.5b02451] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Gd(3+) tags have been shown to be useful for performing distance measurements in biomolecules via the double electron-electron resonance (DEER) technique at Q- and W-band frequencies. We introduce a new cyclen-based Gd(3+) tag that exhibits a relatively narrow electron paramagnetic resonance (EPR) spectrum, affording high sensitivity, and which yields exceptionally narrow Gd(3+)-Gd(3+) distance distributions in doubly tagged proteins owing to a very short tether. Both the maxima and widths of distance distributions measured for tagged mutants of the proteins ERp29 and T4 lysozyme, featuring Gd(3+)-Gd(3+) distances of ca. 6 and 4 nm, respectively, were well reproduced by simulated distance distributions based on available crystal structures and sterically allowed rotamers of the tag. The precision of the position of the Gd(3+) ion is comparable to that of the nitroxide radical in an MTSL-tagged protein and thus the new tag represents an attractive tool for performing accurate distance measurements and potentially probing protein conformational equilibria.
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Affiliation(s)
- Elwy H Abdelkader
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Michael D Lee
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Akiva Feintuch
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
| | - Marie Ramirez Cohen
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
| | - James D Swarbrick
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Gottfried Otting
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville VIC 3052, Australia
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel
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56
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Brath U, Swamy SI, Veiga AX, Tung CC, Van Petegem F, Erdélyi M. Paramagnetic Ligand Tagging To Identify Protein Binding Sites. J Am Chem Soc 2015; 137:11391-8. [PMID: 26289584 PMCID: PMC4583072 DOI: 10.1021/jacs.5b06220] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
Transient
biomolecular interactions are the cornerstones of the
cellular machinery. The identification of the binding sites for low
affinity molecular encounters is essential for the development of
high affinity pharmaceuticals from weakly binding leads but is hindered
by the lack of robust methodologies for characterization of weakly
binding complexes. We introduce a paramagnetic ligand tagging approach
that enables localization of low affinity protein–ligand binding
clefts by detection and analysis of intermolecular protein NMR pseudocontact
shifts, which are invoked by the covalent attachment of a paramagnetic
lanthanoid chelating tag to the ligand of interest. The methodology
is corroborated by identification of the low millimolar volatile anesthetic
interaction site of the calcium sensor protein calmodulin. It presents
an efficient route to binding site localization for low affinity complexes
and is applicable to rapid screening of protein–ligand systems
with varying binding affinity.
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Affiliation(s)
- Ulrika Brath
- Department of Chemistry and Molecular Biology and the Swedish NMR Centre, University of Gothenburg , SE-412 96 Gothenburg, Sweden
| | - Shashikala I Swamy
- Department of Chemistry and Molecular Biology and the Swedish NMR Centre, University of Gothenburg , SE-412 96 Gothenburg, Sweden
| | - Alberte X Veiga
- Department of Chemistry and Molecular Biology and the Swedish NMR Centre, University of Gothenburg , SE-412 96 Gothenburg, Sweden
| | - Ching-Chieh Tung
- Department of Biochemistry and Molecular Biology, University of British Columbia , Vancouver, BC V6T 1Z3, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, University of British Columbia , Vancouver, BC V6T 1Z3, Canada
| | - Máté Erdélyi
- Department of Chemistry and Molecular Biology and the Swedish NMR Centre, University of Gothenburg , SE-412 96 Gothenburg, Sweden
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57
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Dynamic binding mode of a Synaptotagmin-1-SNARE complex in solution. Nat Struct Mol Biol 2015; 22:555-64. [PMID: 26030874 PMCID: PMC4496268 DOI: 10.1038/nsmb.3035] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 04/27/2015] [Indexed: 12/21/2022]
Abstract
Rapid neurotransmitter release depends on the Ca2+-sensor Synaptotagmin-1 and the SNARE complex formed by synaptobrevin, syntaxin-1 and SNAP-25. How Synaptotagmin-1 triggers release remains unclear, in part because elucidating high-resolution structures of Synaptotagmin-1-SNARE complexes has been challenging. An NMR approach based on lanthanide-induced pseudocontact shifts now reveals a dynamic binding mode where basic residues in the concave side of the Synaptotagmin-1 C2B domain β-sandwich interact with a polyacidic region of the SNARE complex formed by syntaxin-1 and SNAP-25. The physiological relevance of this dynamic structural model is supported by mutations in basic residues of Synaptotagmin-1 that markedly impair SNARE-complex binding in vitro and Synaptotagmin-1 function in neurons. Mutations with milder effects on binding have correspondingly milder effects on Synaptotagmin-1 function. Our results support a model whereby their dynamic interaction facilitates cooperation between synaptotagmin-1 and the SNAREs in inducing membrane fusion.
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58
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Pilla KB, Leman JK, Otting G, Huber T. Capturing conformational States in proteins using sparse paramagnetic NMR data. PLoS One 2015; 10:e0127053. [PMID: 25992808 PMCID: PMC4436263 DOI: 10.1371/journal.pone.0127053] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Accepted: 04/10/2015] [Indexed: 12/20/2022] Open
Abstract
Capturing conformational changes in proteins or protein-protein complexes is a challenge for both experimentalists and computational biologists. Solution nuclear magnetic resonance (NMR) is unique in that it permits structural studies of proteins under greatly varying conditions, and thus allows us to monitor induced structural changes. Paramagnetic effects are increasingly used to study protein structures as they give ready access to rich structural information of orientation and long-range distance restraints from the NMR signals of backbone amides, and reliable methods have become available to tag proteins with paramagnetic metal ions site-specifically and at multiple sites. In this study, we show how sparse pseudocontact shift (PCS) data can be used to computationally model conformational states in a protein system, by first identifying core structural elements that are not affected by the environmental change, and then computationally completing the remaining structure based on experimental restraints from PCS. The approach is demonstrated on a 27 kDa two-domain NS2B-NS3 protease system of the dengue virus serotype 2, for which distinct closed and open conformational states have been observed in crystal structures. By changing the input PCS data, the observed conformational states in the dengue virus protease are reproduced without modifying the computational procedure. This data driven Rosetta protocol enables identification of conformational states of a protein system, which are otherwise difficult to obtain either experimentally or computationally.
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Affiliation(s)
- Kala Bharath Pilla
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Julia Koehler Leman
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, 21218, United States of America
| | - Gottfried Otting
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Thomas Huber
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
- * E-mail:
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59
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Crick DJ, Wang JX, Graham B, Swarbrick JD, Mott HR, Nietlispach D. Integral membrane protein structure determination using pseudocontact shifts. JOURNAL OF BIOMOLECULAR NMR 2015; 61:197-207. [PMID: 25604936 PMCID: PMC4412549 DOI: 10.1007/s10858-015-9899-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/13/2015] [Indexed: 05/16/2023]
Abstract
Obtaining enough experimental restraints can be a limiting factor in the NMR structure determination of larger proteins. This is particularly the case for large assemblies such as membrane proteins that have been solubilized in a membrane-mimicking environment. Whilst in such cases extensive deuteration strategies are regularly utilised with the aim to improve the spectral quality, these schemes often limit the number of NOEs obtainable, making complementary strategies highly beneficial for successful structure elucidation. Recently, lanthanide-induced pseudocontact shifts (PCSs) have been established as a structural tool for globular proteins. Here, we demonstrate that a PCS-based approach can be successfully applied for the structure determination of integral membrane proteins. Using the 7TM α-helical microbial receptor pSRII, we show that PCS-derived restraints from lanthanide binding tags attached to four different positions of the protein facilitate the backbone structure determination when combined with a limited set of NOEs. In contrast, the same set of NOEs fails to determine the correct 3D fold. The latter situation is frequently encountered in polytopical α-helical membrane proteins and a PCS approach is thus suitable even for this particularly challenging class of membrane proteins. The ease of measuring PCSs makes this an attractive route for structure determination of large membrane proteins in general.
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Affiliation(s)
- Duncan J. Crick
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Jue X. Wang
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Australia
| | - James D. Swarbrick
- Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Australia
| | - Helen R. Mott
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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60
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Chen WN, Kuppan KV, Lee MD, Jaudzems K, Huber T, Otting G. O-tert-Butyltyrosine, an NMR tag for high-molecular-weight systems and measurements of submicromolar ligand binding affinities. J Am Chem Soc 2015; 137:4581-6. [PMID: 25789794 DOI: 10.1021/jacs.5b01918] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
O-tert-Butyltyrosine (Tby) is an unnatural amino acid that can be site-specifically incorporated into proteins using established orthogonal aminoacyl-tRNA synthetase/tRNA systems. Here we show that the tert-butyl group presents an outstanding NMR tag that can readily be observed in one-dimensional (1)H NMR spectra without any isotope labeling. Owing to rapid bond rotations and the chemical equivalence of the protons of a solvent-exposed tert-butyl group from Tby, the singlet resonance from the tert-butyl group generates an easily detectable narrow signal in a spectral region with limited overlap with other methyl resonances. The potential of the tert-butyl (1)H NMR signal in protein research is illustrated by the observation and assignment of two resonances in the Bacillus stearothermophilus DnaB hexamer (320 kDa), demonstrating that this protein preferentially assumes a 3-fold rather than 6-fold symmetry in solution, and by the quantitative measurement of the submicromolar dissociation constant Kd (0.2 μM) of the complex between glutamate and the Escherichia coli aspartate/glutamate binding protein (DEBP, 32 kDa). The outstanding signal height of the (1)H NMR signal of the Tby tert-butyl group allows Kd measurements using less concentrated protein solutions than usual, providing access to Kd values 1 order of magnitude lower than established NMR methods that employ direct protein detection for Kd measurements.
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Affiliation(s)
- Wan-Na Chen
- †Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Kekini Vahini Kuppan
- †Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Michael David Lee
- ‡Monash Institute of Pharmaceutical Sciences, Parkville, VIC 3052, Australia
| | | | - Thomas Huber
- †Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Gottfried Otting
- †Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
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61
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Lee MD, Loh CT, Shin J, Chhabra S, Dennis ML, Otting G, Swarbrick JD, Graham B. Compact, hydrophilic, lanthanide-binding tags for paramagnetic NMR spectroscopy. Chem Sci 2015; 6:2614-2624. [PMID: 29560247 PMCID: PMC5812434 DOI: 10.1039/c4sc03892d] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 02/25/2015] [Indexed: 01/18/2023] Open
Abstract
The design, synthesis and evaluation of four novel lanthanide-binding tags for paramagnetic NMR spectroscopy are reported.
The design, synthesis and evaluation of four novel lanthanide-binding tags for paramagnetic NMR spectroscopy are reported. Each tag is based on the ((2S,2′S,2′′S,2′′′S)-1,1′,1′′,1′′′-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetrakis(propan-2-ol)) scaffold, featuring small chiral alcohol coordinating pendants to minimise the size and hydrophobic character of each tag. The tags feature different linkers of variable length for conjugation to protein via a single cysteine residue. Each tag's ability to induce pseudocontact shifts (PCS) was assessed on a ubiquitin A28C mutant. Two enantiomeric tags of particular note, C7 and C8, produced significantly larger Δχ-tensors compared to a previously developed tag, C1, attributed to the extremely short linker utilised, limiting the mobility of the bound lanthanide ion. The C7 and C8 tags' capacity to induce PCSs was further demonstrated on GB1 Q32C and 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) S112C/C80A mutants. Whilst factors such as the choice of lanthanide ion, pH and site of conjugation influence the size of the PCSs obtained, the tags represent a significant advance in the field.
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Affiliation(s)
- M D Lee
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - C-T Loh
- Research School of Chemistry , Australian National University , Canberra , ACT 0200 , Australia
| | - J Shin
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - S Chhabra
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - M L Dennis
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - G Otting
- Research School of Chemistry , Australian National University , Canberra , ACT 0200 , Australia
| | - J D Swarbrick
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - B Graham
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
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62
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Loh CT, Graham B, Abdelkader EH, Tuck KL, Otting G. Generation of pseudocontact shifts in proteins with lanthanides using small "clickable" nitrilotriacetic acid and iminodiacetic acid tags. Chemistry 2015; 21:5084-92. [PMID: 25676727 DOI: 10.1002/chem.201406274] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Indexed: 01/07/2023]
Abstract
Pseudocontact shifts (PCS) induced by paramagnetic lanthanide ions provide unique long-range structural information in nuclear magnetic resonance (NMR) spectra, but the site-specific attachment of lanthanide tags to proteins remains a challenge. Here we incorporated p-azido-phenylalanine (AzF) site-specifically into the proteins ubiquitin and GB1, and ligated the AzF residue with alkyne derivatives of small nitrilotriacetic acid and iminodiacetic acid tags using the Cu(I) -catalysed "click" reaction. These tags form lanthanide complexes with no or only a small net charge and produced sizeable PCSs with paramagnetic lanthanide ions in all mutants tested. The PCSs were readily fitted by single magnetic susceptibility anisotropy tensors. Protein precipitation during the click reaction was greatly alleviated by the presence of 150 mM NaCl.
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Affiliation(s)
- Choy-Theng Loh
- Research School of Chemistry, Australian National University, Canberra ACT 2601 (Australia)
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63
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Feintuch A, Otting G, Goldfarb D. Gd3+ Spin Labeling for Measuring Distances in Biomacromolecules. Methods Enzymol 2015; 563:415-57. [DOI: 10.1016/bs.mie.2015.07.006] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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64
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Yang Y, Wang JT, Pei YY, Su XC. Site-specific tagging proteins via a rigid, stable and short thiolether tether for paramagnetic spectroscopic analysis. Chem Commun (Camb) 2015; 51:2824-7. [DOI: 10.1039/c4cc08493d] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction of phenylsulfonated pyridine derivatives and protein thiols is suitable for high-resolution spectroscopic analysis by generation of a rigid, stable and short thiolether tether.
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Affiliation(s)
- Yin Yang
- State-Key Laboratory of Elemento-organic Chemistry
- Innovation Center of Chemical Science and Engineering (Tianjin)
- Nankai University
- Tianjin
- China
| | - Jin-Tao Wang
- State-Key Laboratory of Elemento-organic Chemistry
- Innovation Center of Chemical Science and Engineering (Tianjin)
- Nankai University
- Tianjin
- China
| | - Ying-Ying Pei
- State-Key Laboratory of Elemento-organic Chemistry
- Innovation Center of Chemical Science and Engineering (Tianjin)
- Nankai University
- Tianjin
- China
| | - Xun-Cheng Su
- State-Key Laboratory of Elemento-organic Chemistry
- Innovation Center of Chemical Science and Engineering (Tianjin)
- Nankai University
- Tianjin
- China
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65
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Sengupta I, Gao M, Arachchige RJ, Nadaud PS, Cunningham TF, Saxena S, Schwieters CD, Jaroniec CP. Protein structural studies by paramagnetic solid-state NMR spectroscopy aided by a compact cyclen-type Cu(II) binding tag. JOURNAL OF BIOMOLECULAR NMR 2015; 61:1-6. [PMID: 25432438 PMCID: PMC4304965 DOI: 10.1007/s10858-014-9880-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 11/18/2014] [Indexed: 05/07/2023]
Abstract
Paramagnetic relaxation enhancements (PREs) are a rich source of structural information in protein solid-state NMR spectroscopy. Here we demonstrate that PRE measurements in natively diamagnetic proteins are facilitated by a thiol-reactive compact, cyclen-based, high-affinity Cu(2+) binding tag, 1-[2-(pyridin-2-yldisulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (TETAC), that overcomes the key shortcomings associated with the use of larger, more flexible metal-binding tags. Using the TETAC-Cu(2+) K28C mutant of B1 immunoglobulin-binding domain of protein G as a model, we find that amino acid residues located within ~10 Å of the Cu(2+) center experience considerable transverse PREs leading to severely attenuated resonances in 2D (15)N-(13)C correlation spectra. For more distant residues, electron-nucleus distances are accessible via quantitative measurements of longitudinal PREs, and we demonstrate such measurements for (15)N-Cu(2+) distances up to ~20 Å.
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Affiliation(s)
- Ishita Sengupta
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Min Gao
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Rajith J. Arachchige
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Philippe S. Nadaud
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Timothy F. Cunningham
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Charles D. Schwieters
- Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Christopher P. Jaroniec
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
- Corresponding author: Christopher P. Jaroniec,
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66
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New developments in spin labels for pulsed dipolar EPR. Molecules 2014; 19:16998-7025. [PMID: 25342554 PMCID: PMC6271499 DOI: 10.3390/molecules191016998] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 10/07/2014] [Accepted: 10/13/2014] [Indexed: 11/17/2022] Open
Abstract
Spin labelling is a chemical technique that enables the integration of a molecule containing an unpaired electron into another framework for study. Given the need to understand the structure, dynamics, and conformational changes of biomacromolecules, spin labelling provides a relatively non-intrusive technique and has certain advantages over X-ray crystallography; which requires high quality crystals. The technique relies on the design of binding probes that target a functional group, for example, the thiol group of a cysteine residue within a protein. The unpaired electron is typically supplied through a nitroxide radical and sterically shielded to preserve stability. Pulsed electron paramagnetic resonance (EPR) techniques allow small magnetic couplings to be measured (e.g., <50 MHz) providing information on single label probes or the dipolar coupling between multiple labels. In particular, distances between spin labels pairs can be derived which has led to many protein/enzymes and nucleotides being studied. Here, we summarise recent examples of spin labels used for pulse EPR that serve to illustrate the contribution of chemistry to advancing discoveries in this field.
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Helmling C, Bessi I, Wacker A, Schnorr KA, Jonker HRA, Richter C, Wagner D, Kreibich M, Schwalbe H. Noncovalent spin labeling of riboswitch RNAs to obtain long-range structural NMR restraints. ACS Chem Biol 2014; 9:1330-9. [PMID: 24673892 DOI: 10.1021/cb500050t] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Paramagnetic relaxation enhancement (PRE) NMR is a powerful method to study structure, dynamics and function of proteins. Up to now, the application of PRE NMR on RNAs is a significant challenge due to the limited size of chemically synthesized RNA. Here, we present a noncovalent spin labeling strategy to spin label RNAs in high yields required for NMR studies. The approach requires the presence of a helix segment composed of about 10 nucleotides (nt) but is not restricted by the size of the RNA. We show successful application of this strategy on the 2'dG sensing aptamer domain of Mesoplasma florum (78 nt). The aptamer domain was prepared in two fragments. A larger fragment was obtained by biochemical means, while a short spin labeled fragment was prepared by chemical solid-phase synthesis. The two fragments were annealed noncovalently by hybridization. We performed NMR, cw-EPR experiments and gel shift assays to investigate the stability of the two-fragment complex. NMR analysis in (15)N-TROSY and (1)H,(1)H-NOESY spectra of both unmodified and spin labeled aptamer domain show that the fragmented system forms a stable hybridization product, is in structural agreement with the full length aptamer domain and maintains its function. Together with structure modeling, experimentally determined (1)H-Γ2 rates are in agreement with reported crystal structure data and show that distance restraints up to 25 Å can be obtained from NMR PRE data of RNA.
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Affiliation(s)
- Christina Helmling
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Irene Bessi
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Anna Wacker
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Kai A. Schnorr
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Hendrik R. A. Jonker
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Christian Richter
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Dominic Wagner
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Michael Kreibich
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
| | - Harald Schwalbe
- Institute of Organic Chemistry
and Chemical Biology, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany
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69
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Chen WN, Loscha KV, Nitsche C, Graham B, Otting G. The dengue virus NS2B-NS3 protease retains the closed conformation in the complex with BPTI. FEBS Lett 2014; 588:2206-11. [PMID: 24859037 DOI: 10.1016/j.febslet.2014.05.018] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 04/16/2014] [Accepted: 05/07/2014] [Indexed: 12/19/2022]
Abstract
The C-terminal β-hairpin of NS2B (NS2Bc) in the dengue virus NS2B-NS3 protease is required for full enzymatic activity. In crystal structures without inhibitor and in the complex with bovine pancreatic trypsin inhibitor (BPTI), NS2Bc is displaced from the active site. In contrast, nuclear magnetic resonance (NMR) studies in solution only ever showed NS2Bc in the enzymatically active closed conformation. Here we demonstrate by pseudocontact shifts from a lanthanide tag that NS2Bc remains in the closed conformation also in the complex with BPTI. Therefore, the closed conformation is the best template for drug discovery.
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Affiliation(s)
- Wan-Na Chen
- Australian National University, Research School of Chemistry, Canberra, ACT 0200, Australia
| | - Karin V Loscha
- Australian National University, Research School of Chemistry, Canberra, ACT 0200, Australia
| | - Christoph Nitsche
- Medicinal Chemistry, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Bim Graham
- Medicinal Chemistry and Drug Action, Monash Institute of Pharmaceutical Sciences, Parkville, VIC 3052, Australia
| | - Gottfried Otting
- Australian National University, Research School of Chemistry, Canberra, ACT 0200, Australia.
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70
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de la Cruz L, Chen WN, Graham B, Otting G. Binding mode of the activity-modulating C-terminal segment of NS2B to NS3 in the dengue virus NS2B-NS3 protease. FEBS J 2014; 281:1517-33. [PMID: 24472363 DOI: 10.1111/febs.12729] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 01/21/2014] [Accepted: 01/24/2014] [Indexed: 12/16/2022]
Abstract
The two-component dengue virus NS2B-NS3 protease (NS2B-NS3pro) is an established drug target but inhibitor design is hampered by uncertainties about its 3D structure in solution. Crystal structures reported very different conformations for the functionally important C-terminal segment of the NS2B cofactor (NS2Bc), indicating open and closed conformations in the absence and presence of inhibitors, respectively. An earlier NMR study in solution indicated that a closed state is the preferred conformation in the absence of an artificial linker engineered between NS2B and NS3pro. To obtain direct structural information on the fold of unlinked NS2B-NS3pro in solution, we tagged NS3pro with paramagnetic tags and measured pseudocontact shifts by NMR to position NS2Bc relative to NS3pro. NS2Bc was found to bind to NS3pro in the same way as reported in a previously published model and crystal structure of the closed state. The structure is destabilized, however, by high ionic strength and basic pH, showing the importance of electrostatic forces to tie NS2Bc to NS3pro. Narrow NMR signals previously thought to represent the open state are associated with protein degradation. In conclusion, the closed conformation of the NS2B-NS3 protease is the best model for structure-guided drug design.
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Affiliation(s)
- Laura de la Cruz
- Research School of Chemistry, Australian National University, Canberra, Australia
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71
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Hass MAS, Ubbink M. Structure determination of protein–protein complexes with long-range anisotropic paramagnetic NMR restraints. Curr Opin Struct Biol 2014; 24:45-53. [DOI: 10.1016/j.sbi.2013.11.010] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 11/22/2013] [Accepted: 11/22/2013] [Indexed: 10/25/2022]
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72
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Goldfarb D. Gd3+ spin labeling for distance measurements by pulse EPR spectroscopy. Phys Chem Chem Phys 2014; 16:9685-99. [DOI: 10.1039/c3cp53822b] [Citation(s) in RCA: 145] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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73
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Zhang Y, Yamaguchi T, Kato K. New NMR Tools for Characterizing the Dynamic Conformations and Interactions of Oligosaccharides. CHEM LETT 2013. [DOI: 10.1246/cl.130789] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Ying Zhang
- Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences
- Department of Functional Molecular Science, The Graduate University for Advanced Studies
- Graduate School of Pharmaceutical Sciences, Nagoya City University
| | - Takumi Yamaguchi
- Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences
- Department of Functional Molecular Science, The Graduate University for Advanced Studies
- Graduate School of Pharmaceutical Sciences, Nagoya City University
| | - Koichi Kato
- Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences
- Department of Functional Molecular Science, The Graduate University for Advanced Studies
- Graduate School of Pharmaceutical Sciences, Nagoya City University
- The Glycoscience Institute, Ochanomizu University
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74
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Slack JR, Woods M. The effect of regioisomerism on the coordination chemistry and CEST properties of lanthanide(III) NB-DOTA-tetraamide chelates. J Biol Inorg Chem 2013; 19:173-89. [PMID: 24287873 DOI: 10.1007/s00775-013-1060-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 10/24/2013] [Indexed: 01/31/2023]
Abstract
Chemical exchange saturation transfer (CEST) offers many advantages as a method of generating contrast in magnetic resonance images. However, many of the exogenous agents currently under investigation suffer from detection limits that are still somewhat short of what can be achieved with more traditional Gd(3+) agents. To remedy this limitation we have undertaken an investigation of Ln(3+) DOTA-tetraamide chelates (where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) that have unusually rigid ligand structures: the nitrobenzyl derivatives of DOTA-tetraamides with (2-phenylethyl)amide substituents. In this report we examine the effect of incorporating hydrophobic amide substituents on water exchange and CEST. The ligand systems chosen afforded a total of three CEST-active isomeric square antiprismatic chelates; each of these chelates was found to have different water exchange and CEST characteristics. The position of a nitrobenzyl substituent on the macrocyclic ring strongly influenced the way in which the chelate and Ln(3+) coordination cage distorted. These differential distortions were found to affect the rate of water proton exchange in the chelates. But, by far the greatest effect arose from altering the position of the hydrophobic amide substituent, which, when forced upwards around the water binding site, caused a substantial reduction in the rate of water proton exchange. Such slow water proton exchange afforded a chelate that was 4.5 times more effective as a CEST agent than its isomeric counterparts in dry acetonitrile and at low temperatures and very low presaturation powers.
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Affiliation(s)
- Jacqueline R Slack
- Department of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, OR, 97201, USA
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75
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Shishmarev D, Wang Y, Mason CE, Su XC, Oakley AJ, Graham B, Huber T, Dixon NE, Otting G. Intramolecular binding mode of the C-terminus of Escherichia coli single-stranded DNA binding protein determined by nuclear magnetic resonance spectroscopy. Nucleic Acids Res 2013; 42:2750-7. [PMID: 24288378 PMCID: PMC3936761 DOI: 10.1093/nar/gkt1238] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Single-stranded DNA (ssDNA) binding protein (SSB) is an essential protein to protect ssDNA and recruit specific ssDNA-processing proteins. Escherichia coli SSB forms a tetramer at neutral pH, comprising a structurally well-defined ssDNA binding domain (OB-domain) and a disordered C-terminal domain (C-domain) of ∼64 amino acid residues. The C-terminal eight-residue segment of SSB (C-peptide) has been shown to interact with the OB-domain, but crystal structures failed to reveal any electron density of the C-peptide. Here we show that SSB forms a monomer at pH 3.4, which is suitable for studies by high-resolution nuclear magnetic resonance (NMR) spectroscopy. The OB-domain retains its 3D structure in the monomer, and the C-peptide is shown by nuclear Overhauser effects and lanthanide-induced pseudocontact shifts to bind to the OB-domain at a site that harbors ssDNA in the crystal structure of the SSB–ssDNA complex. 15N relaxation data demonstrate high flexibility of the polypeptide segment linking the C-peptide to the OB-domain and somewhat increased flexibility of the C-peptide compared with the OB-domain, suggesting that the C-peptide either retains high mobility in the bound state or is in a fast equilibrium with an unbound state.
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Affiliation(s)
- Dmitry Shishmarev
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 0200, Australia, Centre for Medical and Molecular Bioscience and School of Chemistry, University of Wollongong, New South Wales 2522, Australia and Medicinal Chemistry and Drug Action, Monash Institute of Pharmaceutical Sciences, Parkville Victoria 3052, Australia
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76
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Huang F, Pei YY, Zuo HH, Chen JL, Yang Y, Su XC. Bioconjugation of proteins with a paramagnetic NMR and fluorescent tag. Chemistry 2013; 19:17141-9. [PMID: 24307370 DOI: 10.1002/chem.201302273] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Indexed: 11/05/2022]
Abstract
Site-specific labeling of proteins with lanthanide ions offers great opportunities for investigating the structure, function, and dynamics of proteins by virtue of the unique properties of lanthanides. Lanthanide-tagged proteins can be studied by NMR, X-ray, fluorescence, and EPR spectroscopy. However, the rigidity of a lanthanide tag in labeling of proteins plays a key role in the determination of protein structures and interactions. Pseudocontact shift (PCS) and paramagnetic relaxation enhancement (PRE) are valuable long-range structure restraints in structural-biology NMR spectroscopy. Generation of these paramagnetic restraints generally relies on site-specific tagging of the target proteins with paramagnetic species. To avoid nonspecific interaction between the target protein and paramagnetic tag and achieve reliable paramagnetic effects, the rigidity, stability, and size of lanthanide tag is highly important in paramagnetic labeling of proteins. Here 4'-mercapto-2,2':6',2''-terpyridine-6,6''-dicarboxylic acid (4MTDA) is introduced as a a rigid paramagnetic and fluorescent tag which can be site-specifically attached to a protein by formation of a disulfide bond. 4MTDA can be readily immobilized by coordination of the protein side chain to the lanthanide ion. Large PCSs and RDCs were observed for 4MTDA-tagged proteins in complexes with paramagnetic lanthanide ions. At an excitation wavelength of 340 nm, the complex formed by protein-4MTDA and Tb(3+) produces high fluorescence with the main emission at 545 nm. These interesting features of 4MTDA make it a very promising tag that can be exploited in NMR, fluorescence, and EPR spectroscopic studies on protein structure, interaction, and dynamics.
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Affiliation(s)
- Feng Huang
- State Key Laboratory of Elemento-organic Chemistry and College of Chemistry, Nankai University, Weijin Road 94, Tianjin 300071 (P. R. China), Fax: (+86) 22-23500623
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77
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Russo L, Maestre-Martinez M, Wolff S, Becker S, Griesinger C. Interdomain dynamics explored by paramagnetic NMR. J Am Chem Soc 2013; 135:17111-20. [PMID: 24111622 DOI: 10.1021/ja408143f] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
An ensemble-based approach is presented to explore the conformational space sampled by a multidomain protein showing moderate interdomain dynamics in terms of translational and rotational motions. The strategy was applied on a complex of calmodulin (CaM) with the IQ-recognition motif from the voltage-gated calcium channel Ca(v)1.2 (IQ), which adopts three different interdomain orientations in the crystal. The N60D mutant of calmodulin was used to collect pseudocontact shifts and paramagnetically induced residual dipolar couplings for six different lanthanide ions. Then, starting from the crystal structure, pools of conformations were generated by free MD. We found the three crystal conformations in solution, but four additional MD-derived conformations had to be included into the ensemble to fulfill all the paramagnetic data and cross-validate optimally against unused paramagnetic data. Alternative approaches led to similar ensembles. Our "ensemble" approach is a simple and efficient tool to probe and describe the interdomain dynamics and represents a general method that can be used to provide a proper ensemble description of multidomain proteins.
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Affiliation(s)
- Luigi Russo
- NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry , Am Fassberg 11 37077 Göttingen, Germany
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78
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Matalon E, Huber T, Hagelueken G, Graham B, Frydman V, Feintuch A, Otting G, Goldfarb D. Gadolinium(III) Spin Labels for High-Sensitivity Distance Measurements in Transmembrane Helices. Angew Chem Int Ed Engl 2013; 52:11831-4. [DOI: 10.1002/anie.201305574] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 08/14/2013] [Indexed: 12/28/2022]
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79
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Matalon E, Huber T, Hagelueken G, Graham B, Frydman V, Feintuch A, Otting G, Goldfarb D. Gadolinium(III) Spin Labels for High-Sensitivity Distance Measurements in Transmembrane Helices. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201305574] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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80
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Edwards DT, Ma Z, Meade TJ, Goldfarb D, Han S, Sherwin MS. Extending the distance range accessed with continuous wave EPR with Gd3+ spin probes at high magnetic fields. Phys Chem Chem Phys 2013; 15:11313-26. [PMID: 23732863 PMCID: PMC4142211 DOI: 10.1039/c3cp43787f] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Interspin distances between 0.8 nm and 2.0 nm can be measured through the dipolar broadening of the continuous wave (cw) EPR spectrum of nitroxide spin labels at X-band (9.4 GHz, 0.35 T). We introduce Gd(3+) as a promising alternative spin label for distance measurements by cw EPR above 7 Tesla, where the |-1/2〉 to |1/2〉 transition narrows below 1 mT and becomes extremely sensitive to dipolar broadening. To estimate the distance limits of cw EPR with Gd(3+), we have measured spectra of frozen solutions of GdCl3 at 8.6 T (240 GHz) and 10 K at concentrations ranging from 50 mM to 0.1 mM, covering a range of average interspin distances. These experiments show substantial dipolar broadening at distances where line broadening cannot be observed with nitroxides at X-band. This data, and its agreement with calculated dipolar-broadened lineshapes, show Gd(3+) to be sensitive to distances as long as ∼3.8 nm. Further, the linewidth of a bis-Gd(3+) complex with a flexible ∼1.6 nm bridge is strongly broadened as compared to the mono-Gd(3+) complex, demonstrating the potential for application to pairwise distances. Gd-DOTA-based chelates that can be functionalized to protein surfaces display linewidths narrower than aqueous GdCl3, implying they should be even more sensitive to dipolar broadening. Therefore, we suggest that the combination of tailored Gd(3+) labels and high magnetic fields can extend the longest interspin distances measurable by cw EPR from 2.0 nm to 3.8 nm. cw EPR data at 260 K demonstrate that the line broadening remains clear out to similar average interspin distances, offering Gd(3+) probes as promising distance rulers at temperatures higher than possible with conventional pulsed EPR distance measurements.
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Affiliation(s)
- Devin T. Edwards
- Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, USA
| | - Zhidong Ma
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
| | - Thomas J. Meade
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
- Department of Molecular Biosciences, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
- Department of Neurobiology & Physiology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
- Department of Radiology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
| | - Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, USA
- Institute for Terahertz Science and Technology, Santa Barbara, California 93106, USA
| | - Mark S. Sherwin
- Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, USA
- Institute for Terahertz Science and Technology, Santa Barbara, California 93106, USA
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81
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Shishmarev D, Otting G. How reliable are pseudocontact shifts induced in proteins and ligands by mobile paramagnetic metal tags? A modelling study. JOURNAL OF BIOMOLECULAR NMR 2013; 56:203-16. [PMID: 23652856 DOI: 10.1007/s10858-013-9738-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 04/27/2013] [Indexed: 05/20/2023]
Abstract
The anisotropic component of the magnetic susceptibility tensor (Δχ tensor) associated with various paramagnetic metal ions can induce pseudocontact shifts (PCSs) and residual dipolar couplings (RDCs) in proteins, yielding valuable restraints in structural studies. In particular, PCSs have successfully been used to study ligands that bind to proteins tagged with a paramagnetic metal ion, which is of great interest in fragment-based drug design. To create easy-to-interpret PCSs, the metal ion must be attached to the protein in a rigid manner. Most of the existing methods for site-specific attachment of a metal tag, however, result in tethers with residual flexibility. Here we present model calculations to quantify the extent, to which mobility of the metal-binding tag can compromise the quality of the Δχ tensor that can be determined from the PCSs observed in the protein. Assuming that the protein can be approximated by a sphere and the tag is attached by a single tether, the results show that a single effective ∆χ tensor can describe the PCSs and RDCs of the protein spins very well even in the presence of substantial tag mobility, implying that PCSs of ligands in binding pockets of the protein can be predicted with similar accuracy. In contrast, the quality of the PCS prediction for nuclear spins positioned above the surface of the protein is significantly poorer, with implications for studies of protein-protein complexes. The simulations probed the sensitivity of the effective Δχ tensor to different parameters, including length of the tether between protein and metal ion, protein size, type and amplitude of tag motion, tensor orientation relative to the protein and direction of tag motion. Tether length and amplitude of motion were identified as two key parameters. It is shown that the amplitude of tag motions cannot be quantified by simple comparisons of the effective Δχ tensor with the alignment tensor determined from RDCs.
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Affiliation(s)
- Dmitry Shishmarev
- Research School of Chemistry, Australian National University, Canberra, ACT, 0200, Australia
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82
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Yagi H, Pilla KB, Maleckis A, Graham B, Huber T, Otting G. Three-dimensional protein fold determination from backbone amide pseudocontact shifts generated by lanthanide tags at multiple sites. Structure 2013; 21:883-90. [PMID: 23643949 DOI: 10.1016/j.str.2013.04.001] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 03/28/2013] [Accepted: 04/01/2013] [Indexed: 01/15/2023]
Abstract
Site-specific attachment of paramagnetic lanthanide ions to a protein generates pseudocontact shifts (PCS) in the nuclear magnetic resonance (NMR) spectra of the protein that are easily measured as changes in chemical shifts. By labeling the protein with lanthanide tags at four different sites, PCSs are observed for most amide protons and accurate information is obtained about their coordinates in three-dimensional space. The approach is demonstrated with the chaperone ERp29, for which large differences have been reported between X-ray and NMR structures of the C-terminal domain, ERp29-C. The results unambiguously show that the structure of rat ERp29-C in solution is similar to the crystal structure of human ERp29-C. PCSs of backbone amides were the only structural restraints required. Because these can be measured for more dilute protein solutions than other NMR restraints, the approach greatly widens the range of proteins amenable to structural studies in solution.
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Affiliation(s)
- Hiromasa Yagi
- Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
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83
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Kaminker I, Tkach I, Manukovsky N, Huber T, Yagi H, Otting G, Bennati M, Goldfarb D. W-band orientation selective DEER measurements on a Gd3+/nitroxide mixed-labeled protein dimer with a dual mode cavity. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 227:66-71. [PMID: 23314001 DOI: 10.1016/j.jmr.2012.11.028] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 11/29/2012] [Accepted: 11/29/2012] [Indexed: 06/01/2023]
Abstract
Double electron-electron resonance (DEER) at W-band (95 GHz) was applied to measure the distance between a pair of nitroxide and Gd(3+) chelate spin labels, about 6 nm apart, in a homodimer of the protein ERp29. While high-field DEER measurements on systems with such mixed labels can be highly attractive in terms of sensitivity and the potential to access long distances, a major difficulty arises from the large frequency spacing (about 700 MHz) between the narrow, intense signal of the Gd(3+) central transition and the nitroxide signal. This is particularly problematic when using standard single-mode cavities. Here we show that a novel dual-mode cavity that matches this large frequency separation dramatically increases the sensitivity of DEER measurements, allowing evolution times as long as 12 μs in a protein. This opens the possibility of accessing distances of 8 nm and longer. In addition, orientation selection can be resolved and analyzed, thus providing additional structural information. In the case of W-band DEER on a Gd(3+)-nitroxide pair, only two angles and their distributions have to be determined, which is a much simpler problem to solve than the five angles and their distributions associated with two nitroxide spin labels.
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Affiliation(s)
- Ilia Kaminker
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
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84
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Yagi H, Maleckis A, Otting G. A systematic study of labelling an α-helix in a protein with a lanthanide using IDA-SH or NTA-SH tags. JOURNAL OF BIOMOLECULAR NMR 2013; 55:157-166. [PMID: 23263916 DOI: 10.1007/s10858-012-9697-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 12/15/2012] [Indexed: 06/01/2023]
Abstract
The previously published IDA-SH and NTA-SH tags are small synthetic lanthanide-binding tags derived from cysteine, which afford site-specific lanthanide labelling by disulfide-bond formation with a cysteine residue of the target protein. Following attachment to a single cysteine in an α-helix, sizeable pseudocontact shifts (PCS) can be observed, if the lanthanide is immobilized by additional coordination to a negatively charged amino-acid side chain that is located in a neighboring turn of the helix. To identify the best labelling strategy for PCS measurements, we performed a systematic study, where IDA-SH or NTA-SH tags were ligated to a cysteine residue in position i of an α-helix, and aspartate or glutamate residues were placed in the positions i - 4 or i + 4. The largest anisotropy components of the magnetic susceptibility tensor were observed for an NTA-SH tag in position i with a glutamate residue in position i - 4. While the NTA-SH tag produced sizeable PCSs regardless of the presence of nearby carboxyl groups of the protein, the IDA-SH tag generated a good lanthanide binding site only if an aspartate was placed in position i + 4. The findings provide a firm basis for the design of site-directed mutants that are suitable for the reliable generation of PCSs in proteins with paramagnetic lanthanides.
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Affiliation(s)
- Hiromasa Yagi
- Research School of Chemistry, Australian National University, Canberra, ACT, 0200, Australia
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85
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Loh CT, Ozawa K, Tuck KL, Barlow N, Huber T, Otting G, Graham B. Lanthanide Tags for Site-Specific Ligation to an Unnatural Amino Acid and Generation of Pseudocontact Shifts in Proteins. Bioconjug Chem 2013; 24:260-8. [DOI: 10.1021/bc300631z] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Choy Theng Loh
- Research School of Chemistry, Australian National University, Canberra, ACT 0200,
Australia
| | - Kiyoshi Ozawa
- School of Chemistry, University of Wollongong, NSW 2522, Australia
| | - Kellie L. Tuck
- School of Chemistry, Monash University, Clayton, VIC 3800, Australia
| | - Nicholas Barlow
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Parkville,
VIC 3052, Australia
| | - Thomas Huber
- Research School of Chemistry, Australian National University, Canberra, ACT 0200,
Australia
| | - Gottfried Otting
- Research School of Chemistry, Australian National University, Canberra, ACT 0200,
Australia
| | - Bim Graham
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Parkville,
VIC 3052, Australia
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86
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Dumont E, Pompidor G, D'Aléo A, Vicat J, Toupet L, Kahn R, Girard E, Maury O, Giraud N. Exploration of the supramolecular interactions involving tris-dipicolinate lanthanide complexes in protein crystals by a combined biostructural, computational and NMR study. Phys Chem Chem Phys 2013; 15:18235-42. [DOI: 10.1039/c3cp53671h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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87
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Yang Y, Li QF, Cao C, Huang F, Su XC. Site-specific labeling of proteins with a chemically stable, high-affinity tag for protein study. Chemistry 2012; 19:1097-103. [PMID: 23154941 DOI: 10.1002/chem.201202495] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 09/20/2012] [Indexed: 01/04/2023]
Abstract
Site-specific labeling of proteins with paramagnetic lanthanides offers unique opportunities by virtue of NMR spectroscopy in structural biology. In particular, these paramagnetic data, generated by the anisotropic paramagnetism including pseudocontact shifts (PCS), residual dipolar couplings (RDC), and paramagnetic relaxation enhancement (PRE), are highly valuable in structure determination and mobility studies of proteins and protein-ligand complexes. Herein, we present a new way to label proteins in a site-specific manner with a high-affinity and chemically stable tag, 4-vinyl(pyridine-2,6-diyl)bismethylenenitrilo tetrakis(acetic acid) (4VPyMTA), through thiol alkylation. Its performance has been demonstrated in G47C and E64C mutants of human ubiquitin both in vitro and in a crowded environment. In comparison with the published tags, 4VPyMTA has several interesting features: 1) it has a very high binding affinity for lanthanides (higher than EDTA), 2) there is no heterogeneity in complexes with lanthanides, 3) the derivatized protein is stable and potentially applicable to the in situ analysis of proteins.
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Affiliation(s)
- Yin Yang
- State Key Laboratory of Elemento-organic Chemistry, Nankai University, Weijin Road 94, Tianjin 300071, PR China
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88
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Jaudzems K, Jia X, Yagi H, Zhulenkovs D, Graham B, Otting G, Liepinsh E. Structural basis for 5'-end-specific recognition of single-stranded DNA by the R3H domain from human Sμbp-2. J Mol Biol 2012; 424:42-53. [PMID: 22999958 DOI: 10.1016/j.jmb.2012.09.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Revised: 09/07/2012] [Accepted: 09/12/2012] [Indexed: 10/27/2022]
Abstract
The R3H domain is a conserved sequence motif in nucleic acid binding proteins. Previously, we reported the solution structure of the R3H domain and identified a putative nucleic acid binding site composed of three conserved basic residues [Liepinsh, E., Leonchiks, A., Sharipo, A., Guignard, L. & Otting, G. (2003). Solution structure of the R3H domain from human Sμbp-2. J. Mol. Biol.326, 217-223]. Here, we determine the binding affinities of mononucleotides and dinucleotides for the R3H domain from human Sμbp-2 (Sμbp2-R3H) and map their binding sites on the protein's surface. Although the binding affinities show up to 260-fold selectivity between different nucleotides, their binding sites and conformations seem very similar. Further, we report the NMR structure of the Sμbp2-R3H in complex with deoxyguanosine 5'-monophosphate (dGMP) mimicking the 5'-end of single-stranded DNA. Pseudocontact shifts from a paramagnetic lanthanide tag attached to residue 731 in the mutant A731C confirmed that binding of dGMP brings a loop of the protein into closer proximity. The structure provides the first structural insight into single-stranded nucleic acid recognition by the R3H domain and shows that the R3H domain specifically binds the phosphorylated 5'-end through electrostatic interactions with the two conserved arginines and stacking interactions with the highly conserved histidine.
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Affiliation(s)
- Kristaps Jaudzems
- Department of Physical Organic Chemistry, Latvian Institute of Organic Synthesis, Latvia.
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89
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Kobashigawa Y, Saio T, Ushio M, Sekiguchi M, Yokochi M, Ogura K, Inagaki F. Convenient method for resolving degeneracies due to symmetry of the magnetic susceptibility tensor and its application to pseudo contact shift-based protein-protein complex structure determination. JOURNAL OF BIOMOLECULAR NMR 2012; 53:53-63. [PMID: 22487935 PMCID: PMC3351616 DOI: 10.1007/s10858-012-9623-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 03/27/2012] [Indexed: 05/14/2023]
Abstract
Pseudo contact shifts (PCSs) induced by paramagnetic lanthanide ions fixed in a protein frame provide long-range distance and angular information, and are valuable for the structure determination of protein-protein and protein-ligand complexes. We have been developing a lanthanide-binding peptide tag (hereafter LBT) anchored at two points via a peptide bond and a disulfide bond to the target proteins. However, the magnetic susceptibility tensor displays symmetry, which can cause multiple degenerated solutions in a structure calculation based solely on PCSs. Here we show a convenient method for resolving this degeneracy by changing the spacer length between the LBT and target protein. We applied this approach to PCS-based rigid body docking between the FKBP12-rapamycin complex and the mTOR FRB domain, and demonstrated that degeneracy could be resolved using the PCS restraints obtained from two-point anchored LBT with two different spacer lengths. The present strategy will markedly increase the usefulness of two-point anchored LBT for protein complex structure determination.
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Affiliation(s)
- Yoshihiro Kobashigawa
- Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, N-21, W-11, Kita-ku, Sapporo, 001-0021 Japan
| | - Tomohide Saio
- Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, N-21, W-11, Kita-ku, Sapporo, 001-0021 Japan
| | - Masahiro Ushio
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
| | - Mitsuhiro Sekiguchi
- Analysis and Pharmacokinetics Research Labs, Department of Drug Discovery, Astellas Pharma Inc., Tokyo, Japan
| | - Masashi Yokochi
- Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, N-21, W-11, Kita-ku, Sapporo, 001-0021 Japan
| | - Kenji Ogura
- Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, N-21, W-11, Kita-ku, Sapporo, 001-0021 Japan
| | - Fuyuhiko Inagaki
- Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, N-21, W-11, Kita-ku, Sapporo, 001-0021 Japan
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90
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Schmitz C, Vernon R, Otting G, Baker D, Huber T. Protein structure determination from pseudocontact shifts using ROSETTA. J Mol Biol 2012; 416:668-77. [PMID: 22285518 DOI: 10.1016/j.jmb.2011.12.056] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 12/16/2011] [Accepted: 12/27/2011] [Indexed: 11/25/2022]
Abstract
Paramagnetic metal ions generate pseudocontact shifts (PCSs) in nuclear magnetic resonance spectra that are manifested as easily measurable changes in chemical shifts. Metals can be incorporated into proteins through metal binding tags, and PCS data constitute powerful long-range restraints on the positions of nuclear spins relative to the coordinate system of the magnetic susceptibility anisotropy tensor (Δχ-tensor) of the metal ion. We show that three-dimensional structures of proteins can reliably be determined using PCS data from a single metal binding site combined with backbone chemical shifts. The program PCS-ROSETTA automatically determines the Δχ-tensor and metal position from the PCS data during the structure calculations, without any prior knowledge of the protein structure. The program can determine structures accurately for proteins of up to 150 residues, offering a powerful new approach to protein structure determination that relies exclusively on readily measurable backbone chemical shifts and easily discriminates between correctly and incorrectly folded conformations.
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Affiliation(s)
- Christophe Schmitz
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia
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91
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Metal-Based Spin Labeling for Distance Determination. STRUCTURAL INFORMATION FROM SPIN-LABELS AND INTRINSIC PARAMAGNETIC CENTRES IN THE BIOSCIENCES 2012. [DOI: 10.1007/430_2011_63] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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92
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Kaminker I, Yagi H, Huber T, Feintuch A, Otting G, Goldfarb D. Spectroscopic selection of distance measurements in a protein dimer with mixed nitroxide and Gd3+ spin labels. Phys Chem Chem Phys 2012; 14:4355-8. [DOI: 10.1039/c2cp40219j] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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93
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de la Cruz L, Nguyen THD, Ozawa K, Shin J, Graham B, Huber T, Otting G. Binding of low molecular weight inhibitors promotes large conformational changes in the dengue virus NS2B-NS3 protease: fold analysis by pseudocontact shifts. J Am Chem Soc 2011; 133:19205-15. [PMID: 22007671 DOI: 10.1021/ja208435s] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The two-component dengue virus NS2B-NS3 protease (DEN NS2B-NS3pro) is an established drug target, but inhibitor design is hampered by the lack of a crystal structure of the protease in its fully active form. In solution and without inhibitors, the functionally important C-terminal segment of the NS2B cofactor is dissociated from DEN NS3pro ("open state"), necessitating a large structural change to produce the "closed state" thought to underpin activity. We analyzed the fold of DEN NS2B-NS3pro in solution with and without bound inhibitor by nuclear magnetic resonance (NMR) spectroscopy. Multiple paramagnetic lanthanide tags were attached to different sites to generate pseudocontact shifts (PCS). In the face of severe spectral overlap and broadening of many signals by conformational exchange, methods for assignment of (15)N-HSQC cross-peaks included selective mutation, combinatorial isotope labeling, and comparison of experimental PCSs and PCSs back-calculated for a structural model of the closed conformation built by using the structure of the related West Nile virus (WNV) protease as a template. The PCSs show that, in the presence of a positively charged low-molecular weight inhibitor, the enzyme assumes a closed state that is very similar to the closed state previously observed for the WNV protease. Therefore, a model of the protease built on the closed conformation of the WNV protease is a better template for rational drug design than available crystal structures, at least for positively charged inhibitors. To assess the open state, we created a binding site for a Gd(3+) complex and measured paramagnetic relaxation enhancements. The results show that the specific open conformation displayed in the crystal of DEN NS2B-NS3pro is barely populated in solution. The techniques used open an avenue to the fold analysis of proteins that yield poor NMR spectra, as PCSs from multiple sites in combination with model building generate powerful information even from incompletely assigned (15)N-HSQC spectra.
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Affiliation(s)
- Laura de la Cruz
- Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
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