51
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Wu Z, Feintuch A, Collauto A, Adams LA, Aurelio L, Graham B, Otting G, Goldfarb D. Selective Distance Measurements Using Triple Spin Labeling with Gd 3+, Mn 2+, and a Nitroxide. J Phys Chem Lett 2017; 8:5277-5282. [PMID: 28990781 DOI: 10.1021/acs.jpclett.7b01739] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Distance measurements by pulse electron paramagnetic resonance techniques, such as double electron-electron resonance (DEER, also called PELDOR), have become an established tool to explore structural properties of biomacromolecules and their assemblies. In such measurements a pair of spin labels provides a single distance constraint. Here we show that by employing three different types of spin labels that differ in their spectroscopic and spin dynamics properties it is possible to extract three independent distances from a single sample. We demonstrate this using the Antennapedia homeodomain orthogonally labeled with Gd3+ and Mn2+ tags in complex with its cognate DNA binding site labeled with a nitroxide.
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52
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Nitsche C, Otting G. NMR studies of ligand binding. Curr Opin Struct Biol 2017; 48:16-22. [PMID: 29017071 DOI: 10.1016/j.sbi.2017.09.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/15/2017] [Accepted: 09/18/2017] [Indexed: 12/17/2022]
Abstract
NMR spectroscopy is an established tool in drug discovery, but its strength is commonly regarded to be largely confined to the early stages of hit discovery and fragment based drug design, where NMR offers unique capabilities of characterizing the binding modes of ligand molecules that bind sufficiently weakly to be in rapid exchange between bound and free state. Here we, first, provide a meta-review of recent reviews on NMR studies of ligand binding and, second, review recent progress towards NMR characterization of the ligand binding mode in stable protein-ligand complexes, with particular emphasis on the global positioning system (GPS) approach enabled by paramagnetic lanthanide tags.
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53
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Jabar S, Adams LA, Wang Y, Aurelio L, Graham B, Otting G. Chemical Tagging with tert-Butyl and Trimethylsilyl Groups for Measuring Intermolecular Nuclear Overhauser Effects in a Large Protein-Ligand Complex. Chemistry 2017; 23:13033-13036. [PMID: 28763128 DOI: 10.1002/chem.201703531] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Indexed: 11/07/2022]
Abstract
Intermolecular 1 H-1 H nuclear Overhauser effects (NOE) present a powerful tool to assess contacts between proteins and binding partners, but are difficult to identify for complexes of high molecular weight. This report shows that intermolecular NOEs can readily be observed following chemical labeling with tert-butyl or trimethylsilyl (TMS) groups. Proteins can be furnished with tert-butyl or TMS groups site-specifically using genetically encoded unnatural amino acids or by chemical modification of single cysteine residues. No isotope labeling is required. The approach is demonstrated with the 95 kDa complex between tetrameric E. coli single-stranded DNA binding protein (SSB) and single-stranded DNA.
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54
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Welegedara AP, Yang Y, Lee MD, Swarbrick JD, Huber T, Graham B, Goldfarb D, Otting G. Double‐Arm Lanthanide Tags Deliver Narrow Gd
3+
–Gd
3+
Distance Distributions in Double Electron–Electron Resonance (DEER) Measurements. Chemistry 2017; 23:11694-11702. [DOI: 10.1002/chem.201702521] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Indexed: 11/10/2022]
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55
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Mahawaththa MC, Pearce BJ, Szabo M, Graham B, Klein CD, Nitsche C, Otting G. Solution conformations of a linked construct of the Zika virus NS2B-NS3 protease. Antiviral Res 2017; 142:141-147. [DOI: 10.1016/j.antiviral.2017.03.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 03/14/2017] [Accepted: 03/18/2017] [Indexed: 01/28/2023]
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56
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Wu Z, Lee MD, Carruthers TJ, Szabo M, Dennis ML, Swarbrick JD, Graham B, Otting G. New Lanthanide Tag for the Generation of Pseudocontact Shifts in DNA by Site-Specific Ligation to a Phosphorothioate Group. Bioconjug Chem 2017; 28:1741-1748. [PMID: 28485576 DOI: 10.1021/acs.bioconjchem.7b00202] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pseudocontact shifts (PCS) generated by paramagnetic lanthanides provide a rich source of long-range structural restraints that can readily be measured by nuclear magnetic resonance (NMR) spectroscopy. Many different lanthanide-binding tags have been designed for site-specific tagging of proteins, but established routes for tagging DNA with a single metal ion rely on difficult chemical synthesis. Here we present a simple and practical strategy for site-specific tagging of inexpensive phosphorothioate (PT) oligonucleotides. Commercially available PT oligonucleotides are diastereomers with S and R stereoconfiguration at the backbone PT site. The respective SP and RP diastereomers can readily be separated by HPLC. A new alkylating lanthanide-binding tag, C10, was synthesized that delivered quantitative tagging yields with both diastereomers. PCSs were observed following ligation with the complementary DNA strand to form double-stranded DNA duplexes. The PCSs were larger for the SP than the RP oligonucleotide and good correlation between back-calculated and experimental PCSs was observed. The C10 tag can also be attached to cysteine residues in proteins, where it generates a stable thioether bond. Ligated to the A28C mutant of ubiquitin, the tag produced excellent fits of magnetic susceptibility anisotropy (Δχ) tensors, with larger tensors than for the tagged PT oligonucleotides, indicating that the tag is not completely immobilized after ligation with a PT group.
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57
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Pearce BJG, Jabar S, Loh CT, Szabo M, Graham B, Otting G. Structure restraints from heteronuclear pseudocontact shifts generated by lanthanide tags at two different sites. JOURNAL OF BIOMOLECULAR NMR 2017; 68:19-32. [PMID: 28434103 DOI: 10.1007/s10858-017-0111-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 04/11/2017] [Indexed: 05/14/2023]
Abstract
Pseudocontact shifts (PCS) encode long-range information on 3D structures of protein backbones and side-chains. The level of structural detail that can be obtained increases with the number of different sites tagged with a paramagnetic metal ion to generate PCSs. Here we show that PCSs from two different sites can suffice to determine the structure of polypeptide chains and their location and orientation relative to the magnetic susceptibility tensor χ, provided that PCSs are available for 1H as well as heteronuclear spins. In addition, PCSs from two different sites are shown to provide detailed structural information on the conformation of methyl group-bearing amino-acid side-chains. A previously published ensemble structure of ubiquitin is shown to explain the magnetic susceptibility and alignment tensors slightly better than structures that try to explain the experimental data by a single conformation, illustrating the potential of PCSs as a tool to investigate small conformational changes.
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58
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Pilla KB, Otting G, Huber T. Protein Structure Determination by Assembling Super-Secondary Structure Motifs Using Pseudocontact Shifts. Structure 2017; 25:559-568. [DOI: 10.1016/j.str.2017.01.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 01/17/2017] [Accepted: 01/29/2017] [Indexed: 11/26/2022]
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59
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Nitsche C, Otting G. Pseudocontact shifts in biomolecular NMR using paramagnetic metal tags. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2017; 98-99:20-49. [PMID: 28283085 DOI: 10.1016/j.pnmrs.2016.11.001] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 11/11/2016] [Accepted: 11/12/2016] [Indexed: 05/14/2023]
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60
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Nitsche C, Mahawaththa MC, Becker W, Huber T, Otting G. Site-selective tagging of proteins by pnictogen-mediated self-assembly. Chem Commun (Camb) 2017; 53:10894-10897. [DOI: 10.1039/c7cc06155b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Trivalent pnictogens (Pn) enable the selective self-assembly between an engineered di-cysteine motif in a protein and a thiol-containing lanthanide (Ln) probe.
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61
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Orton HW, Kuprov I, Loh CT, Otting G. Using Paramagnetism to Slow Down Nuclear Relaxation in Protein NMR. J Phys Chem Lett 2016; 7:4815-4818. [PMID: 27934036 DOI: 10.1021/acs.jpclett.6b02417] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Paramagnetic metal ions accelerate nuclear spin relaxation; this effect is widely used for distance measurement and called paramagnetic relaxation enhancement (PRE). Theoretical predictions established that, under special circumstances, it is also possible to achieve a reduction in nuclear relaxation rates (negative PRE). This situation would occur if the mechanism of nuclear relaxation in the diamagnetic state is counterbalanced by a paramagnetic relaxation mechanism caused by the metal ion. Here we report the first experimental evidence for such a cross-correlation effect. Using a uniformly 15N-labeled mutant of calbindin D9k loaded with either Tm3+ or Tb3+, reduced R1 and R2 relaxation rates of backbone 15N spins were observed compared with the diamagnetic reference (the same protein loaded with Y3+). The effect arises from the compensation of the chemical shift anisotropy tensor by the anisotropic dipolar shielding generated by the unpaired electron spin.
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62
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Chen JL, Wang X, Yang F, Cao C, Otting G, Su XC. 3D Structure Determination of an Unstable Transient Enzyme Intermediate by Paramagnetic NMR Spectroscopy. Angew Chem Int Ed Engl 2016; 55:13744-13748. [DOI: 10.1002/anie.201606223] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 08/15/2016] [Indexed: 12/24/2022]
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63
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Chen JL, Wang X, Yang F, Cao C, Otting G, Su XC. 3D Structure Determination of an Unstable Transient Enzyme Intermediate by Paramagnetic NMR Spectroscopy. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201606223] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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64
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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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65
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O'Malley WI, Abdelkader EH, Aulsebrook ML, Rubbiani R, Loh CT, Grace MR, Spiccia L, Gasser G, Otting G, Tuck KL, Graham B. Luminescent Alkyne-Bearing Terbium(III) Complexes and Their Application to Bioorthogonal Protein Labeling. Inorg Chem 2016; 55:1674-82. [PMID: 26821062 DOI: 10.1021/acs.inorgchem.5b02605] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Two new bifunctional macrocyclic chelate ligands that form luminescent terbium(III) complexes featuring an alkyne group for conjugation to (bio)molecules via the Cu(I)-catalyzed "click" reaction were synthesized. Upon ligation, the complexes exhibit a significant luminescent enhancement when excited at the λ(max) of the "clicked" products. To demonstrate the utility of the complexes for luminescent labeling, they were conjugated in vitro to E. coli aspartate/glutamate-binding protein incorporating a genetically encoded p-azido-L-phenylalanine or p-(azidomethyl)-L-phenylalanine residue. The complexes may prove useful for time-gated assay applications.
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66
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Collauto A, Frydman V, Lee MD, Abdelkader EH, Feintuch A, Swarbrick JD, Graham B, Otting G, Goldfarb D. RIDME distance measurements using Gd(iii) tags with a narrow central transition. Phys Chem Chem Phys 2016; 18:19037-49. [DOI: 10.1039/c6cp03299k] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Methods based on pulse electron paramagnetic resonance allow measurement of the electron–electron dipolar coupling between two high-spin labels.
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67
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Cohen MR, Frydman V, Milko P, Iron MA, Abdelkader EH, Lee MD, Swarbrick JD, Raitsimring A, Otting G, Graham B, Feintuch A, Goldfarb D. Overcoming artificial broadening in Gd3+–Gd3+ distance distributions arising from dipolar pseudo-secular terms in DEER experiments. Phys Chem Chem Phys 2016; 18:12847-59. [DOI: 10.1039/c6cp00829a] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Double electron–electron resonance (DEER) is used to probe structure of Gd3+-tagged biomolecules by determining Gd3+–Gd3+ distances.
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68
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Chen JL, Yang Y, Zhang LL, Liang H, Huber T, Su XC, Otting G. Analysis of the solution conformations of T4 lysozyme by paramagnetic NMR spectroscopy. Phys Chem Chem Phys 2016; 18:5850-9. [DOI: 10.1039/c5cp07196h] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Paramagnetic data show that the average structure of T4-lysozyme in solution is more open than its crystal structure.
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69
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Abdelkader EH, Yao X, Feintuch A, Adams LA, Aurelio L, Graham B, Goldfarb D, Otting G. Pulse EPR-enabled interpretation of scarce pseudocontact shifts induced by lanthanide binding tags. JOURNAL OF BIOMOLECULAR NMR 2016; 64:39-51. [PMID: 26597990 DOI: 10.1007/s10858-015-0003-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 11/17/2015] [Indexed: 06/05/2023]
Abstract
Pseudocontact shifts (PCS) induced by tags loaded with paramagnetic lanthanide ions provide powerful long-range structure information, provided the location of the metal ion relative to the target protein is known. Usually, the metal position is determined by fitting the magnetic susceptibility anisotropy (Δχ) tensor to the 3D structure of the protein in an 8-parameter fit, which requires a large set of PCSs to be reliable. In an alternative approach, we used multiple Gd(3+)-Gd(3+) distances measured by double electron-electron resonance (DEER) experiments to define the metal position, allowing Δχ-tensor determinations from more robust 5-parameter fits that can be performed with a relatively sparse set of PCSs. Using this approach with the 32 kDa E. coli aspartate/glutamate binding protein (DEBP), we demonstrate a structural transition between substrate-bound and substrate-free DEBP, supported by PCSs generated by C3-Tm(3+) and C3-Tb(3+) tags attached to a genetically encoded p-azidophenylalanine residue. The significance of small PCSs was magnified by considering the difference between the chemical shifts measured with Tb(3+) and Tm(3+) rather than involving a diamagnetic reference. The integrative sparse data approach developed in this work makes poorly soluble proteins of limited stability amenable to structural studies in solution, without having to rely on cysteine mutations for tag attachment.
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70
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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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71
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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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72
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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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73
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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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74
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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: 26] [Impact Index Per Article: 2.9] [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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75
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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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