51
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Zhang R, Duong NT, Nishiyama Y, Ramamoorthy A. 3D Double-Quantum/Double-Quantum Exchange Spectroscopy of Protons under 100 kHz Magic Angle Spinning. J Phys Chem B 2017; 121:5944-5952. [DOI: 10.1021/acs.jpcb.7b03480] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Rongchun Zhang
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Nghia Tuan Duong
- RIKEN
CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Yusuke Nishiyama
- RIKEN
CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
- JEOL Resonance Inc., Musashino, Akishima, Tokyo 196-8558, Japan
| | - Ayyalusamy Ramamoorthy
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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52
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Wang T, Hong M. Structure and Dynamics of Polysaccharides in Plant Cell Walls from Solid-State NMR. NMR IN GLYCOSCIENCE AND GLYCOTECHNOLOGY 2017. [DOI: 10.1039/9781782623946-00290] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Multidimensional high-resolution magic-angle-spinning solid-state NMR (SSNMR) spectroscopy has recently been shown to have the unique capability of revealing the molecular structure and dynamics of insoluble macromolecules in intact plant cell walls. This chapter summarizes the 2D and 3D SSNMR techniques used so far to study cell walls and key findings about cellulose interactions with matrix polysaccharides, cellulose microfibril structure, polysaccharide–protein interactions that are responsible for wall loosening, and polysaccharide–water interactions in the hydrated primary walls. These results provide detailed molecular insights into the structure of near-native plant cell walls, and revise the conventional tethered-network model by suggesting a single-network model for the primary cell wall, which has found increasing support from recent biochemical and biomechanical data.
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Affiliation(s)
- Tuo Wang
- Department of Chemistry, Massachusetts Institute of Technology 170 Albany Street Cambridge MA 02139 USA
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology 170 Albany Street Cambridge MA 02139 USA
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53
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Gopinath T, Nelson SED, Soller KJ, Veglia G. Probing the Conformationally Excited States of Membrane Proteins via 1H-Detected MAS Solid-State NMR Spectroscopy. J Phys Chem B 2017; 121:4456-4465. [DOI: 10.1021/acs.jpcb.7b03268] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- T. Gopinath
- Department of Chemistry and ‡Department of Biochemistry, Molecular Biology, and
Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Sarah E. D. Nelson
- Department of Chemistry and ‡Department of Biochemistry, Molecular Biology, and
Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Kailey J. Soller
- Department of Chemistry and ‡Department of Biochemistry, Molecular Biology, and
Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Gianluigi Veglia
- Department of Chemistry and ‡Department of Biochemistry, Molecular Biology, and
Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
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54
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Jaipuria G, Leonov A, Giller K, Vasa SK, Jaremko Ł, Jaremko M, Linser R, Becker S, Zweckstetter M. Cholesterol-mediated allosteric regulation of the mitochondrial translocator protein structure. Nat Commun 2017; 8:14893. [PMID: 28358007 PMCID: PMC5379104 DOI: 10.1038/ncomms14893] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 02/08/2017] [Indexed: 12/02/2022] Open
Abstract
Cholesterol is an important regulator of membrane protein function. However, the exact mechanisms involved in this process are still not fully understood. Here we study how the tertiary and quaternary structure of the mitochondrial translocator protein TSPO, which binds cholesterol with nanomolar affinity, is affected by this sterol. Residue-specific analysis of TSPO by solid-state NMR spectroscopy reveals a dynamic monomer–dimer equilibrium of TSPO in the membrane. Binding of cholesterol to TSPO's cholesterol-recognition motif leads to structural changes across the protein that shifts the dynamic equilibrium towards the translocator monomer. Consistent with an allosteric mechanism, a mutation within the oligomerization interface perturbs transmembrane regions located up to 35 Å away from the interface, reaching TSPO's cholesterol-binding motif. The lower structural stability of the intervening transmembrane regions provides a mechanistic basis for signal transmission. Our study thus reveals an allosteric signal pathway that connects membrane protein tertiary and quaternary structure with cholesterol binding. The outer mitochondrial membrane translocator protein (TSPO) mediates several mitochondrial functions and binds cholesterol with a high affinity. Here the authors use solid-state NMR to show that cholesterol binding to TSPO results in allosteric changes that modulate TSPO oligomerization.
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Affiliation(s)
- Garima Jaipuria
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Von-Siebold-Strasse 3a, 37075 Göttingen, Germany
| | - Andrei Leonov
- Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany
| | - Karin Giller
- Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany
| | - Suresh Kumar Vasa
- Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany
| | - Łukasz Jaremko
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Von-Siebold-Strasse 3a, 37075 Göttingen, Germany
| | - Mariusz Jaremko
- Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany
| | - Rasmus Linser
- Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany
| | - Stefan Becker
- Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany
| | - Markus Zweckstetter
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Von-Siebold-Strasse 3a, 37075 Göttingen, Germany.,Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany.,Department of Neurology, University Medical Center Göttingen, University of Göttingen, Waldweg 33, 37073 Göttingen, Germany
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55
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Abstract
Computational modeling of proteins using evolutionary or de novo approaches offers rapid structural characterization, but often suffers from low success rates in generating high quality models comparable to the accuracy of structures observed in X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. A computational/experimental hybrid approach incorporating sparse experimental restraints in computational modeling algorithms drastically improves reliability and accuracy of 3D models. This chapter discusses the use of structural information obtained from various paramagnetic NMR measurements and demonstrates computational algorithms implementing pseudocontact shifts as restraints to determine the structure of proteins at atomic resolution.
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56
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Fillion M, Goudreault M, Voyer N, Bechinger B, Auger M. Amphiphilicity Is a Key Determinant in the Membrane Interactions of Synthetic 14-mer Cationic Peptide Analogues. Biochemistry 2016; 55:6919-6930. [DOI: 10.1021/acs.biochem.6b00961] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
| | | | | | - Burkhard Bechinger
- Université de Strasbourg, CNRS, UMR7177, Institut de
Chimie, 4, Rue Blaise
Pascal, 67070 Strasbourg, France
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57
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Kaplan M, Narasimhan S, de Heus C, Mance D, van Doorn S, Houben K, Popov-Čeleketić D, Damman R, Katrukha EA, Jain P, Geerts WJC, Heck AJR, Folkers GE, Kapitein LC, Lemeer S, van Bergen En Henegouwen PMP, Baldus M. EGFR Dynamics Change during Activation in Native Membranes as Revealed by NMR. Cell 2016; 167:1241-1251.e11. [PMID: 27839865 DOI: 10.1016/j.cell.2016.10.038] [Citation(s) in RCA: 126] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 08/08/2016] [Accepted: 10/20/2016] [Indexed: 10/20/2022]
Abstract
The epidermal growth factor receptor (EGFR) represents one of the most common target proteins in anti-cancer therapy. To directly examine the structural and dynamical properties of EGFR activation by the epidermal growth factor (EGF) in native membranes, we have developed a solid-state nuclear magnetic resonance (ssNMR)-based approach supported by dynamic nuclear polarization (DNP). In contrast to previous crystallographic results, our experiments show that the ligand-free state of the extracellular domain (ECD) is highly dynamic, while the intracellular kinase domain (KD) is rigid. Ligand binding restricts the overall and local motion of EGFR domains, including the ECD and the C-terminal region. We propose that the reduction in conformational entropy of the ECD by ligand binding favors the cooperative binding required for receptor dimerization, causing allosteric activation of the intracellular tyrosine kinase.
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Affiliation(s)
- Mohammed Kaplan
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Siddarth Narasimhan
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Cecilia de Heus
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Deni Mance
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Sander van Doorn
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Klaartje Houben
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Dušan Popov-Čeleketić
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Reinier Damman
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Eugene A Katrukha
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Purvi Jain
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Willie J C Geerts
- Biomolecular Imaging, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Gert E Folkers
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Lukas C Kapitein
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Simone Lemeer
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, 3584 CH Utrecht, the Netherlands
| | | | - Marc Baldus
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands.
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58
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Affiliation(s)
- Benjamin J. Wylie
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
| | - Hoa Q. Do
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
| | - Collin G. Borcik
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
| | - Emily P. Hardy
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
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59
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Abstract
Replication of positive-strand RNA viruses occurs in tight association with reorganized host cell membranes. In a concerted fashion, viral and cellular factors generate distinct organelle-like structures, designated viral replication factories. These virus-induced compartments promote highly efficient genome replication, allow spatiotemporal coordination of the different steps of the viral replication cycle, and protect viral RNA from the hostile cytoplasmic environment. The combined use of ultrastructural and functional studies has greatly increased our understanding of the architecture and biogenesis of viral replication factories. Here, we review common concepts and distinct differences in replication organelle morphology and biogenesis within the Flaviviridae family, exemplified by dengue virus and hepatitis C virus. We discuss recent progress made in our understanding of the complex interplay between viral determinants and subverted cellular membrane homeostasis in biogenesis and maintenance of replication factories of this virus family.
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Affiliation(s)
- David Paul
- Department of Infectious Diseases, Molecular Virology, University of Heidelberg, 69120 Heidelberg, Germany; ,
| | - Ralf Bartenschlager
- Department of Infectious Diseases, Molecular Virology, University of Heidelberg, 69120 Heidelberg, Germany; , .,Division of Virus-Associated Carcinogenesis, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
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60
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Oxidative footprinting in the study of structure and function of membrane proteins: current state and perspectives. Biochem Soc Trans 2016; 43:983-94. [PMID: 26517913 DOI: 10.1042/bst20150130] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Membrane proteins, such as receptors, transporters and ion channels, control the vast majority of cellular signalling and metabolite exchange processes and thus are becoming key pharmacological targets. Obtaining structural information by usage of traditional structural biology techniques is limited by the requirements for the protein samples to be highly pure and stable when handled in high concentrations and in non-native buffer systems, which is often difficult to achieve for membrane targets. Hence, there is a growing requirement for the use of hybrid, integrative approaches to study the dynamic and functional aspects of membrane proteins in physiologically relevant conditions. In recent years, significant progress has been made in the field of oxidative labelling techniques and in particular the X-ray radiolytic footprinting in combination with mass spectrometry (MS) (XF-MS), which provide residue-specific information on the solvent accessibility of proteins. In combination with both low- and high-resolution data from other structural biology approaches, it is capable of providing valuable insights into dynamics of membrane proteins, which have been difficult to obtain by other structural techniques, proving a highly complementary technique to address structure and function of membrane targets. XF-MS has demonstrated a unique capability for identification of structural waters and conformational changes in proteins at both a high degree of spatial and a high degree of temporal resolution. Here, we provide a perspective on the place of XF-MS among other structural biology methods and showcase some of the latest developments in its usage for studying water-mediated transmembrane (TM) signalling, ion transport and ligand-induced allosteric conformational changes in membrane proteins.
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61
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Structural Changes and Proapoptotic Peroxidase Activity of Cardiolipin-Bound Mitochondrial Cytochrome c. Biophys J 2016; 109:1873-84. [PMID: 26536264 DOI: 10.1016/j.bpj.2015.09.016] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 08/11/2015] [Accepted: 09/18/2015] [Indexed: 01/19/2023] Open
Abstract
The cellular process of intrinsic apoptosis relies on the peroxidation of mitochondrial lipids as a critical molecular signal. Lipid peroxidation is connected to increases in mitochondrial reactive oxygen species, but there is also a required role for mitochondrial cytochrome c (cyt-c). In apoptotic mitochondria, cyt-c gains a new function as a lipid peroxidase that catalyzes the reactive oxygen species-mediated chemical modification of the mitochondrial lipid cardiolipin (CL). This peroxidase activity is caused by a conformational change in the protein, resulting from interactions between cyt-c and CL. The nature of the conformational change and how it causes this gain-of-function remain uncertain. Via a combination of functional, structural, and biophysical experiments we investigate the structure and peroxidase activity of cyt-c in its membrane-bound state. We reconstituted cyt-c with CL-containing lipid vesicles, and determined the increase in peroxidase activity resulting from membrane binding. We combined these assays of CL-induced proapoptotic activity with structural and dynamic studies of the membrane-bound protein via solid-state NMR and optical spectroscopy. Multidimensional magic angle spinning (MAS) solid-state NMR of uniformly (13)C,(15)N-labeled protein was used to detect site-specific conformational changes in oxidized and reduced horse heart cyt-c bound to CL-containing lipid bilayers. MAS NMR and Fourier transform infrared measurements show that the peripherally membrane-bound cyt-c experiences significant dynamics, but also retains most or all of its secondary structure. Moreover, in two-dimensional and three-dimensional MAS NMR spectra the CL-bound cyt-c displays a spectral resolution, and thus structural homogeneity, that is inconsistent with extensive membrane-induced unfolding. Cyt-c is found to interact primarily with the membrane interface, without significantly disrupting the lipid bilayer. Thus, membrane binding results in cyt-c gaining the increased peroxidase activity that represents its pivotal proapoptotic function, but we do not observe evidence for large-scale unfolding or penetration into the membrane core.
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62
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Abstract
AbstractIncreasing evidence suggests that most proteins occur and function in complexes rather than as isolated entities when embedded in cellular membranes. Nuclear magnetic resonance (NMR) provides increasing possibilities to study structure, dynamics and assembly of such systems. In our review, we discuss recent methodological progress to study membrane–protein complexes (MPCs) by NMR, starting with expression, isotope-labeling and reconstitution protocols. We review approaches to deal with spectral complexity and limited spectral spectroscopic sensitivity that are usually encountered in NMR-based studies of MPCs. We highlight NMR applications in various classes of MPCs, including G-protein-coupled receptors, ion channels and retinal proteins and extend our discussion to protein–protein complexes that span entire cellular compartments or orchestrate processes such as protein transport across or within membranes. These examples demonstrate the growing potential of NMR-based studies of MPCs to provide critical insight into the energetics of protein–ligand and protein–protein interactions that underlie essential biological functions in cellular membranes.
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63
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Artificial membranes for membrane protein purification, functionality and structure studies. Biochem Soc Trans 2016; 44:877-82. [DOI: 10.1042/bst20160054] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Indexed: 11/17/2022]
Abstract
Membrane proteins represent one of the most important targets for pharmaceutical companies. Unfortunately, technical limitations have long been a major hindrance in our understanding of the function and structure of such proteins. Recent years have seen the refinement of classical approaches and the emergence of new technologies that have resulted in a significant step forward in the field of membrane protein research. This review summarizes some of the current techniques used for studying membrane proteins, with overall advantages and drawbacks for each method.
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64
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Gopinath T, Veglia G. Orphan spin polarization: A catalyst for high-throughput solid-state NMR spectroscopy of proteins. ANNUAL REPORTS ON NMR SPECTROSCOPY 2016; 89:103-121. [PMID: 31631914 PMCID: PMC6800253 DOI: 10.1016/bs.arnmr.2016.04.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Magic angle spinning solid-state NMR (MAS ssNMR) spectroscopy is a powerful method for structure determination of biomacromolecules that are recalcitrant to crystallization (membrane proteins and fibrils). Conventional multidimensional ssNMR methods acquire one experiment at a time. This approach is time consuming and discards orphan (unused) spin operators. Relatively low sensitivity and poor resolution of protein samples require long acquisition times for multidimensional ssNMR experiments. Here, we describe our recent progress in the development of multiple acquisition solid-state NMR methods for protein structure determination. A family of experiments called Polarization Optimized Experiments (POE) were designed, in which we utilized the orphan spin operators that are discarded in classical multidimensional NMR experiments, recovering them to allow simultaneous acquisition of multiple 2D and 3D experiments, all while using conventional probes with spectrometers equipped with one receiver. Three strategies namely, DUMAS, MEIOSIS, and MAeSTOSO were used for the concatenation of various 2D and 3D experiments. These methods open up new avenues for reducing the acquisition times of multidimensional experiments for biomolecular ssNMR spectroscopy.
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Affiliation(s)
- T. Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics- University of Minnesota, Minneapolis, MN 55455
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics- University of Minnesota, Minneapolis, MN 55455
- Department of Chemistry– University of Minnesota, Minneapolis, MN 55455
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65
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Gopinath T, Veglia G. Multiple acquisitions via sequential transfer of orphan spin polarization (MAeSTOSO): How far can we push residual spin polarization in solid-state NMR? JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 267:1-8. [PMID: 27039168 PMCID: PMC4862926 DOI: 10.1016/j.jmr.2016.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 02/22/2016] [Accepted: 03/07/2016] [Indexed: 05/05/2023]
Abstract
Conventional multidimensional magic angle spinning (MAS) solid-state NMR (ssNMR) experiments detect the signal arising from the decay of a single coherence transfer pathway (FID), resulting in one spectrum per acquisition time. Recently, we introduced two new strategies, namely DUMAS (DUal acquisition Magic Angle Spinning) and MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), that enable the simultaneous acquisitions of multidimensional ssNMR experiments using multiple coherence transfer pathways. Here, we combined the main elements of DUMAS and MEIOSIS to harness both orphan spin operators and residual polarization and increase the number of simultaneous acquisitions. We show that it is possible to acquire up to eight two-dimensional experiments using four acquisition periods per each scan. This new suite of pulse sequences, called MAeSTOSO for Multiple Acquisitions via Sequential Transfer of Orphan Spin pOlarization, relies on residual polarization of both (13)C and (15)N pathways and combines low- and high-sensitivity experiments into a single pulse sequence using one receiver and commercial ssNMR probes. The acquisition of multiple experiments does not affect the sensitivity of the main experiment; rather it recovers the lost coherences that are discarded, resulting in a significant gain in experimental time. Both merits and limitations of this approach are discussed.
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Affiliation(s)
- T Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States; Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, United States.
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66
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Zhang R, Mroue KH, Ramamoorthy A. Hybridizing cross-polarization with NOE or refocused-INEPT enhances the sensitivity of MAS NMR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 266:59-66. [PMID: 27040936 PMCID: PMC4851575 DOI: 10.1016/j.jmr.2016.03.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 03/13/2016] [Accepted: 03/24/2016] [Indexed: 05/05/2023]
Abstract
Heteronuclear cross polarization (CP) has been commonly used to enhance the sensitivity of dilute low-γ nuclei in almost all solid-state NMR experiments. However, CP relies on heteronuclear dipolar couplings, and therefore the magnetization transfer efficiency becomes inefficient when the dipolar couplings are weak, as is often the case for mobile components in solids. Here, we demonstrate methods that combine CP with heteronuclear Overhauser effect (referred to as CP-NOE) or with refocused-INEPT (referred to as CP-RINEPT) to overcome the efficiency limitation of CP and enhance the signal-to-noise ratio (S/N) for mobile components. Our experimental results reveal that, compared to the conventional CP, significant S/N ratio enhancement can be achieved for resonances originating from mobile components, whereas the resonance signals associated with rigid groups are not significantly affected due to their long spin-lattice relaxation times. In fact, the S/N enhancement factor is also dependent on the temperature, CP contact time as well as on the system under investigation. Furthermore, we also demonstrate that CP-RINEPT experiment can be successfully employed to independently detect mobile and rigid signals in a single experiment without affecting the data collection time. However, the resolution of CP spectrum obtained from the CP-RINEPT experiment could be slightly compromised by the mandatory use of continuous wave (CW) decoupling during the acquisition of signals from rigid components. In addition, CP-RINEPT experiment can be used for spectral editing utilizing the difference in dynamics of different regions of a molecule and/or different components present in the sample, and could also be useful for the assignment of resonances from mobile components in poorly resolved spectra. Therefore, we believe that the proposed approaches are beneficial for the structural characterization of multiphase and heterogeneous systems, and could be used as a building block in multidimensional solid-state NMR experiments.
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Affiliation(s)
- Rongchun Zhang
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Kamal H Mroue
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
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67
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De Poli M, Zawodny W, Quinonero O, Lorch M, Webb SJ, Clayden J. Conformational photoswitching of a synthetic peptide foldamer bound within a phospholipid bilayer. Science 2016; 352:575-80. [PMID: 27033546 DOI: 10.1126/science.aad8352] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/24/2016] [Indexed: 12/17/2022]
Abstract
The dynamic properties of foldamers, synthetic molecules that mimic folded biomolecules, have mainly been explored in free solution. We report on the design, synthesis, and conformational behavior of photoresponsive foldamers bound in a phospholipid bilayer akin to a biological membrane phase. These molecules contain a chromophore, which can be switched between two configurations by different wavelengths of light, attached to a helical synthetic peptide that both promotes membrane insertion and communicates conformational change along its length. Light-induced structural changes in the chromophore are translated into global conformational changes, which are detected by monitoring the solid-state (19)F nuclear magnetic resonance signals of a remote fluorine-containing residue located 1 to 2 nanometers away. The behavior of the foldamers in the membrane phase is similar to that of analogous compounds in organic solvents.
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Affiliation(s)
- Matteo De Poli
- School of Chemistry, University of Manchester, Manchester M13 9PL, UK
| | - Wojciech Zawodny
- School of Chemistry, University of Manchester, Manchester M13 9PL, UK
| | - Ophélie Quinonero
- School of Chemistry, University of Manchester, Manchester M13 9PL, UK
| | - Mark Lorch
- Department of Chemistry, University of Hull, Hull HU6 7RX, UK
| | - Simon J Webb
- School of Chemistry, University of Manchester, Manchester M13 9PL, UK. Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7DN, UK
| | - Jonathan Clayden
- School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
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68
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Zheng JS, He Y, Zuo C, Cai XY, Tang S, Wang ZA, Zhang LH, Tian CL, Liu L. Robust Chemical Synthesis of Membrane Proteins through a General Method of Removable Backbone Modification. J Am Chem Soc 2016; 138:3553-61. [PMID: 26943264 DOI: 10.1021/jacs.6b00515] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Chemical protein synthesis can provide access to proteins with post-translational modifications or site-specific labelings. Although this technology is finding increasing applications in the studies of water-soluble globular proteins, chemical synthesis of membrane proteins remains elusive. In this report, a general and robust removable backbone modification (RBM) method is developed for the chemical synthesis of membrane proteins. This method uses an activated O-to-N acyl transfer auxiliary to install in the Fmoc solid-phase peptide synthesis process a RBM group with switchable reactivity toward trifluoroacetic acid. The method can be applied to versatile membrane proteins because the RBM group can be placed at any primary amino acid. With RBM, the membrane proteins and their segments behave almost as if they were water-soluble peptides and can be easily handled in the process of ligation, purification, and mass characterizations. After the full-length protein is assembled, the RBM group can be readily removed by trifluoroacetic acid. The efficiency and usefulness of the new method has been demonstrated by the successful synthesis of a two-transmembrane-domain protein (HCV p7 ion channel) with site-specific isotopic labeling and a four-transmembrane-domain protein (multidrug resistance transporter EmrE). This method enables practical synthesis of small- to medium-sized membrane proteins or membrane protein domains for biochemical and biophysical studies.
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Affiliation(s)
- Ji-Shen Zheng
- High Magnetic Field Laboratory, Chinese Academy of Sciences, and School of Life Sciences, University of Science and Technology of China , Hefei 230031, China
| | - Yao He
- High Magnetic Field Laboratory, Chinese Academy of Sciences, and School of Life Sciences, University of Science and Technology of China , Hefei 230031, China
| | - Chao Zuo
- Tsinghua-Peking Center for Life Sciences, Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, China
| | - Xiao-Ying Cai
- High Magnetic Field Laboratory, Chinese Academy of Sciences, and School of Life Sciences, University of Science and Technology of China , Hefei 230031, China
| | - Shan Tang
- Tsinghua-Peking Center for Life Sciences, Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, China
| | - Zhipeng A Wang
- Tsinghua-Peking Center for Life Sciences, Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, China
| | - Long-Hua Zhang
- High Magnetic Field Laboratory, Chinese Academy of Sciences, and School of Life Sciences, University of Science and Technology of China , Hefei 230031, China
| | - Chang-Lin Tian
- High Magnetic Field Laboratory, Chinese Academy of Sciences, and School of Life Sciences, University of Science and Technology of China , Hefei 230031, China
| | - Lei Liu
- Tsinghua-Peking Center for Life Sciences, Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, China
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69
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Habenstein B, Loquet A. Solid-state NMR: An emerging technique in structural biology of self-assemblies. Biophys Chem 2016; 210:14-26. [DOI: 10.1016/j.bpc.2015.07.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Accepted: 07/08/2015] [Indexed: 12/13/2022]
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70
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Vostrikov VV, Gustavsson M, Gopinath T, Mullen D, Dicke AA, Truong V, Veglia G. Ca(2+) ATPase Conformational Transitions in Lipid Bilayers Mapped by Site-directed Ethylation and Solid-State NMR. ACS Chem Biol 2016; 11:329-34. [PMID: 26650884 DOI: 10.1021/acschembio.5b00953] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
To transmit signals across cellular compartments, many membrane-embedded enzymes undergo extensive conformational rearrangements. Monitoring these events in lipid bilayers by NMR at atomic resolution has been challenging due to the large size of these systems. It is further exacerbated for large mammalian proteins that are difficult to express and label with NMR-active isotopes. Here, we synthesized and engineered (13)C ethyl groups on native cysteines to map the structural transitions of the sarcoplasmic reticulum Ca(2+)-ATPase, a 110 kDa transmembrane enzyme that transports Ca(2+) into the sarcoplasmic reticulum. Using magic angle spinning NMR, we monitored the chemical shifts of the methylene and methyl groups of the derivatized cysteine residues along the major steps of the enzymatic cycle. The methylene chemical shifts are sensitive to the ATPase conformational changes induced upon nucleotide and Ca(2+) ion binding and are ideal probes for active and inactive states of the enzyme. This new approach is extendable to large mammalian enzymes and signaling proteins with native or engineered cysteine residues in their amino acid sequence.
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Affiliation(s)
- Vitaly V. Vostrikov
- Department of Biochemistry, Biophysics & Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Martin Gustavsson
- Department of Biochemistry, Biophysics & Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Tata Gopinath
- Department of Biochemistry, Biophysics & Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Dan Mullen
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Alysha A. Dicke
- Department of Biochemistry, Biophysics & Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Vincent Truong
- Department of Biochemistry, Biophysics & Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Gianluigi Veglia
- Department of Biochemistry, Biophysics & Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, United States
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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71
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Joseph B, Sikora A, Cafiso DS. Ligand Induced Conformational Changes of a Membrane Transporter in E. coli Cells Observed with DEER/PELDOR. J Am Chem Soc 2016; 138:1844-7. [PMID: 26795032 PMCID: PMC4837646 DOI: 10.1021/jacs.5b13382] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An unrealized goal in structural biology is the determination of structure and conformational change at high resolution for membrane proteins within the cellular environment. Pulsed electron-electron double resonance (PELDOR) is a well-established technique to follow conformational changes in purified membrane protein complexes. Here we demonstrate the first proof of concept for the use of PELDOR to observe conformational changes in a membrane protein in intact cells. We exploit the fact that outer membrane proteins usually lack reactive cysteines and that paramagnetic spin labels entering the periplasm are selectively reduced to achieve specific labeling of the cobalamin transporter BtuB in Escherichia coli. We characterize conformational changes in the second extracellular loop of BtuB upon ligand binding and compare the PELDOR data with high-resolution crystal structures. Our approach avoids detergent extraction, purification, and reconstitution usually required for these systems. With this approach, structure, function, conformational changes, and molecular interactions of outer membrane proteins can be studied at high resolution in the cellular environment.
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Affiliation(s)
- Benesh Joseph
- Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, University of Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Arthur Sikora
- Department of Chemistry and Center for Membrane Biology, University of Virginia, McCormick Road, Charlottesville VA22904-4319, USA
| | - David S. Cafiso
- Department of Chemistry and Center for Membrane Biology, University of Virginia, McCormick Road, Charlottesville VA22904-4319, USA
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72
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73
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Abstract
The majority of therapeutics target membrane proteins, accessible on the surface of cells, to alter cellular signaling. Cells use membrane proteins to transduce signals into cells, transport ions and molecules, bind cells to a surface or substrate, and catalyze reactions. Newly devised technologies allow us to drug conventionally "undruggable" regions of membrane proteins, enabling modulation of protein-protein, protein-lipid, and protein-nucleic acid interactions. In this review, we survey the state of the art of high-throughput screening and rational design in drug discovery, and we evaluate the advances in biological understanding and technological capacity that will drive pharmacotherapy forward against unorthodox membrane protein targets.
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Affiliation(s)
- Hang Yin
- Department of Chemistry and Biochemistry.,BioFrontiers Institute, and.,Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100082, China
| | - Aaron D Flynn
- BioFrontiers Institute, and.,Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309; ,
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74
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Zhang H, Huang Q, Bei Z, Wei Y, Floudas CA. COMSAT: Residue contact prediction of transmembrane proteins based on support vector machines and mixed integer linear programming. Proteins 2016; 84:332-48. [PMID: 26756402 DOI: 10.1002/prot.24979] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 11/19/2015] [Accepted: 12/10/2015] [Indexed: 12/28/2022]
Abstract
In this article, we present COMSAT, a hybrid framework for residue contact prediction of transmembrane (TM) proteins, integrating a support vector machine (SVM) method and a mixed integer linear programming (MILP) method. COMSAT consists of two modules: COMSAT_SVM which is trained mainly on position-specific scoring matrix features, and COMSAT_MILP which is an ab initio method based on optimization models. Contacts predicted by the SVM model are ranked by SVM confidence scores, and a threshold is trained to improve the reliability of the predicted contacts. For TM proteins with no contacts above the threshold, COMSAT_MILP is used. The proposed hybrid contact prediction scheme was tested on two independent TM protein sets based on the contact definition of 14 Å between Cα-Cα atoms. First, using a rigorous leave-one-protein-out cross validation on the training set of 90 TM proteins, an accuracy of 66.8%, a coverage of 12.3%, a specificity of 99.3% and a Matthews' correlation coefficient (MCC) of 0.184 were obtained for residue pairs that are at least six amino acids apart. Second, when tested on a test set of 87 TM proteins, the proposed method showed a prediction accuracy of 64.5%, a coverage of 5.3%, a specificity of 99.4% and a MCC of 0.106. COMSAT shows satisfactory results when compared with 12 other state-of-the-art predictors, and is more robust in terms of prediction accuracy as the length and complexity of TM protein increase. COMSAT is freely accessible at http://hpcc.siat.ac.cn/COMSAT/.
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Affiliation(s)
- Huiling Zhang
- Centre for High Performance Computing, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Qingsheng Huang
- Centre for High Performance Computing, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Zhendong Bei
- Center for Cloud Computing, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Yanjie Wei
- Centre for High Performance Computing, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Christodoulos A Floudas
- Department of Chemical Engineering, Texas A&M University, College Station, Texas, 77843.,Texas A&M Energy Institute, Texas A&M University, College Station, Texas, 77843
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75
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Pandey MK, Zhang R, Hashi K, Ohki S, Nishijima G, Matsumoto S, Noguchi T, Deguchi K, Goto A, Shimizu T, Maeda H, Takahashi M, Yanagisawa Y, Yamazaki T, Iguchi S, Tanaka R, Nemoto T, Miyamoto T, Suematsu H, Saito K, Miki T, Ramamoorthy A, Nishiyama Y. 1020MHz single-channel proton fast magic angle spinning solid-state NMR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 261:1-5. [PMID: 26524647 PMCID: PMC4688097 DOI: 10.1016/j.jmr.2015.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 10/09/2015] [Accepted: 10/11/2015] [Indexed: 05/05/2023]
Abstract
This study reports a first successful demonstration of a single channel proton 3D and 2D high-throughput ultrafast magic angle spinning (MAS) solid-state NMR techniques in an ultra-high magnetic field (1020MHz) NMR spectrometer comprised of HTS/LTS magnet. High spectral resolution is well demonstrated.
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Affiliation(s)
- Manoj Kumar Pandey
- RIKEN CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Rongchun Zhang
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Kenjiro Hashi
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Shinobu Ohki
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Gen Nishijima
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Shinji Matsumoto
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Takashi Noguchi
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Kenzo Deguchi
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Atsushi Goto
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Tadashi Shimizu
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Hideaki Maeda
- Center for Life Science Technologies, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Masato Takahashi
- Center for Life Science Technologies, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | | | - Toshio Yamazaki
- Center for Life Science Technologies, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Seiya Iguchi
- Center for Life Science Technologies, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Ryoji Tanaka
- JEOL RESONANCE Inc., Akishima, Tokyo 196-8558, Japan
| | | | | | | | | | | | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, MI 48109-1055, USA.
| | - Yusuke Nishiyama
- RIKEN CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan; JEOL RESONANCE Inc., Akishima, Tokyo 196-8558, Japan.
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76
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Zhang R, Nishiyama Y, Ramamoorthy A. Proton-detected 3D (1)H/(13)C/(1)H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz. J Chem Phys 2015; 143:164201. [PMID: 26520504 PMCID: PMC4617735 DOI: 10.1063/1.4933373] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 10/06/2015] [Indexed: 02/06/2023] Open
Abstract
A proton-detected 3D (1)H/(13)C/(1)H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of (13)C-(1)H connectivities, and proximities of (13)C-(1)H and (1)H-(1)H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including (1)H-(1)H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) (1)H/(1)H and 2D (13)C/(1)H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of (1)H-(1)H proximity and (13)C-(1)H connectivity. In addition, the 2D (F1/F2) (1)H/(13)C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of (1)H-(1)H dipolar couplings, enables the measurement of proximities between (13)C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of (1)H-(1)H-(13)C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H2O ⋅ HCl demonstrate the efficiency of the 3D experiment.
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Affiliation(s)
- Rongchun Zhang
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | | | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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77
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Hellmich UA, Mönkemeyer L, Velamakanni S, van Veen HW, Glaubitz C. Effects of nucleotide binding to LmrA: A combined MAS-NMR and solution NMR study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3158-65. [PMID: 26449340 DOI: 10.1016/j.bbamem.2015.10.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/25/2015] [Accepted: 10/01/2015] [Indexed: 11/26/2022]
Abstract
ABC transporters are fascinating examples of fine-tuned molecular machines that use the energy from ATP hydrolysis to translocate a multitude of substrates across biological membranes. While structural details have emerged on many members of this large protein superfamily, a number of functional details are still under debate. High resolution structures yield valuable insights into protein function, but it is the combination of structural, functional and dynamic insights that facilitates a complete understanding of the workings of their complex molecular mechanisms. NMR is a technique well-suited to investigate proteins in atomic resolution while taking their dynamic properties into account. It thus nicely complements other structural techniques, such as X-ray crystallography, that have contributed high-resolution data to the architectural understanding of ABC transporters. Here, we describe the heterologous expression of LmrA, an ABC exporter from Lactococcus lactis, in Escherichia coli. This allows for more flexible isotope labeling for nuclear magnetic resonance (NMR) studies and the easy study of LmrA's multidrug resistance phenotype. We use a combination of solid-state magic angle spinning (MAS) on the reconstituted transporter and solution NMR on its isolated nucleotide binding domain to investigate consequences of nucleotide binding to LmrA. We find that nucleotide binding affects the protein globally, but that NMR is also able to pinpoint local dynamic effects to specific residues, such as the Walker A motif's conserved lysine residue.
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Affiliation(s)
- Ute A Hellmich
- Department of Pharmacy and Biochemistry, Johannes Gutenberg-University Mainz, Germany; Centre for Biomolecular Magnetic Resonance (BMRZ), J.W. Goethe University, Frankfurt, Germany.
| | - Leonie Mönkemeyer
- Centre for Biomolecular Magnetic Resonance (BMRZ), J.W. Goethe University, Frankfurt, Germany; Department of Biophysical Chemistry, J.W. Goethe University, Frankfurt, Germany
| | | | | | - Clemens Glaubitz
- Centre for Biomolecular Magnetic Resonance (BMRZ), J.W. Goethe University, Frankfurt, Germany; Department of Biophysical Chemistry, J.W. Goethe University, Frankfurt, Germany; Cluster of Excellence Macromolecular Complexes Frankfurt, Germany.
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78
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Fillion M, Auger M. Oriented samples: a tool for determining the membrane topology and the mechanism of action of cationic antimicrobial peptides by solid-state NMR. Biophys Rev 2015; 7:311-320. [PMID: 28510228 PMCID: PMC5425733 DOI: 10.1007/s12551-015-0167-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 02/05/2015] [Indexed: 01/12/2023] Open
Abstract
Overuse and misuse of antibiotics have led bacteria to acquire several mechanisms of resistance. In response to this, researchers have identified natural antimicrobial peptides as promising candidates to fight against multiresistant bacteria. However, their mode of action is still unclear, and a better understanding of the mode of action of these peptides is of primary importance to develop new peptides displaying high antibacterial activity and low hemolytic activity. One of the main features that defines the mechanism of action is the membrane topology of the peptide. Among the spectroscopic techniques, solid-state NMR is the technique of choice for determining the location of the peptide within the membrane. It can be achieved by performing experiments with oriented samples. In the literature, the two most common types of oriented samples are bicelles and phospholipids mechanically oriented between glass plates. The mode of perturbation of the membrane-active peptide can be studied by phosphorus-31 and deuterium NMR. On the other hand, several experiments such as nitrogen-15 and fluorine solid-state NMR, that require labeled peptides, can give valuable information on the membrane topology of the peptide. The combination of the latter techniques allows the determination of a precise topology, thus a better knowledge of the molecular determinants involved in the membrane interactions of antimicrobial peptides.
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Affiliation(s)
- Matthieu Fillion
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Centre québécois sur les matériaux fonctionnels (CQMF), Université Laval, Québec, QC, G1V 0A6, Canada
| | - Michèle Auger
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Centre québécois sur les matériaux fonctionnels (CQMF), Université Laval, Québec, QC, G1V 0A6, Canada.
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79
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Leftin A, Molugu TR, Job C, Beyer K, Brown MF. Area per lipid and cholesterol interactions in membranes from separated local-field (13)C NMR spectroscopy. Biophys J 2015; 107:2274-86. [PMID: 25418296 DOI: 10.1016/j.bpj.2014.07.044] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 06/24/2014] [Accepted: 07/15/2014] [Indexed: 10/24/2022] Open
Abstract
Investigations of lipid membranes using NMR spectroscopy generally require isotopic labeling, often precluding structural studies of complex lipid systems. Solid-state (13)C magic-angle spinning NMR spectroscopy at natural isotopic abundance gives site-specific structural information that can aid in the characterization of complex biomembranes. Using the separated local-field experiment DROSS, we resolved (13)C-(1)H residual dipolar couplings that were interpreted with a statistical mean-torque model. Liquid-disordered and liquid-ordered phases were characterized according to membrane thickness and average cross-sectional area per lipid. Knowledge of such structural parameters is vital for molecular dynamics simulations, and provides information about the balance of forces in membrane lipid bilayers. Experiments were conducted with both phosphatidylcholine (dimyristoylphosphatidylcholine (DMPC) and palmitoyloleoylphosphatidylcholine (POPC)) and egg-yolk sphingomyelin (EYSM) lipids, and allowed us to extract segmental order parameters from the (13)C-(1)H residual dipolar couplings. Order parameters were used to calculate membrane structural quantities, including the area per lipid and bilayer thickness. Relative to POPC, EYSM is more ordered in the ld phase and experiences less structural perturbation upon adding 50% cholesterol to form the lo phase. The loss of configurational entropy is smaller for EYSM than for POPC, thus favoring its interaction with cholesterol in raftlike lipid systems. Our studies show that solid-state (13)C NMR spectroscopy is applicable to investigations of complex lipids and makes it possible to obtain structural parameters for biomembrane systems where isotope labeling may be prohibitive.
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Affiliation(s)
- Avigdor Leftin
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona
| | - Trivikram R Molugu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona
| | - Constantin Job
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona
| | - Klaus Beyer
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona; Department of Physics, University of Arizona, Tucson, Arizona.
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80
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Kwon B, Tietze D, White PB, Liao SY, Hong M. Chemical ligation of the influenza M2 protein for solid-state NMR characterization of the cytoplasmic domain. Protein Sci 2015; 24:1087-99. [PMID: 25966817 PMCID: PMC4500309 DOI: 10.1002/pro.2690] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Revised: 04/13/2015] [Accepted: 04/24/2015] [Indexed: 12/17/2022]
Abstract
Solid-state NMR-based structure determination of membrane proteins and large protein complexes faces the challenge of limited spectral resolution when the proteins are uniformly (13)C-labeled. A strategy to meet this challenge is chemical ligation combined with site-specific or segmental labeling. While chemical ligation has been adopted in NMR studies of water-soluble proteins, it has not been demonstrated for membrane proteins. Here we show chemical ligation of the influenza M2 protein, which contains a transmembrane (TM) domain and two extra-membrane domains. The cytoplasmic domain, which contains an amphipathic helix (AH) and a cytoplasmic tail, is important for regulating virus assembly, virus budding, and the proton channel activity. A recent study of uniformly (13)C-labeled full-length M2 by spectral simulation suggested that the cytoplasmic tail is unstructured. To further test this hypothesis, we conducted native chemical ligation of the TM segment and part of the cytoplasmic domain. Solid-phase peptide synthesis of the two segments allowed several residues to be labeled in each segment. The post-AH cytoplasmic residues exhibit random-coil chemical shifts, low bond order parameters, and a surface-bound location, thus indicating that this domain is a dynamic random coil on the membrane surface. Interestingly, the protein spectra are similar between a model membrane and a virus-mimetic membrane, indicating that the structure and dynamics of the post-AH segment is insensitive to the lipid composition. This chemical ligation approach is generally applicable to medium-sized membrane proteins to provide site-specific structural constraints, which complement the information obtained from uniformly (13)C, (15)N-labeled proteins.
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Affiliation(s)
- Byungsu Kwon
- Department of Chemistry, Massachusetts Institute of TechnologyCambridge, Massachusetts, 02139
| | - Daniel Tietze
- Department of Chemistry, Massachusetts Institute of TechnologyCambridge, Massachusetts, 02139
| | - Paul B White
- Department of Chemistry, Massachusetts Institute of TechnologyCambridge, Massachusetts, 02139
| | - Shu Y Liao
- Department of Chemistry, Massachusetts Institute of TechnologyCambridge, Massachusetts, 02139
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of TechnologyCambridge, Massachusetts, 02139
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81
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Zhang R, Ramamoorthy A. Dynamics-based selective 2D (1)H/(1)H chemical shift correlation spectroscopy under ultrafast MAS conditions. J Chem Phys 2015; 142:204201. [PMID: 26026440 PMCID: PMC4449354 DOI: 10.1063/1.4921381] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 05/08/2015] [Indexed: 01/30/2023] Open
Abstract
Dynamics plays important roles in determining the physical, chemical, and functional properties of a variety of chemical and biological materials. However, a material (such as a polymer) generally has mobile and rigid regions in order to have high strength and toughness at the same time. Therefore, it is difficult to measure the role of mobile phase without being affected by the rigid components. Herein, we propose a highly sensitive solid-state NMR approach that utilizes a dipolar-coupling based filter (composed of 12 equally spaced 90° RF pulses) to selectively measure the correlation of (1)H chemical shifts from the mobile regions of a material. It is interesting to find that the rotor-synchronized dipolar filter strength decreases with increasing inter-pulse delay between the 90° pulses, whereas the dipolar filter strength increases with increasing inter-pulse delay under static conditions. In this study, we also demonstrate the unique advantages of proton-detection under ultrafast magic-angle-spinning conditions to enhance the spectral resolution and sensitivity for studies on small molecules as well as multi-phase polymers. Our results further demonstrate the use of finite-pulse radio-frequency driven recoupling pulse sequence to efficiently recouple weak proton-proton dipolar couplings in the dynamic regions of a molecule and to facilitate the fast acquisition of (1)H/(1)H correlation spectrum compared to the traditional 2D NOESY (Nuclear Overhauser effect spectroscopy) experiment. We believe that the proposed approach is beneficial to study mobile components in multi-phase systems, such as block copolymers, polymer blends, nanocomposites, heterogeneous amyloid mixture of oligomers and fibers, and other materials.
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Affiliation(s)
- Rongchun Zhang
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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82
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Sinnige T, Weingarth M, Daniëls M, Boelens R, Bonvin AMJJ, Houben K, Baldus M. Conformational Plasticity of the POTRA 5 Domain in the Outer Membrane Protein Assembly Factor BamA. Structure 2015; 23:1317-24. [PMID: 26027731 DOI: 10.1016/j.str.2015.04.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 04/03/2015] [Accepted: 04/09/2015] [Indexed: 12/22/2022]
Abstract
BamA is the main component of the β-barrel assembly machinery (BAM) that folds and inserts outer membrane proteins in Gram-negative bacteria. Crystal structures have suggested that this process involves conformational changes in the transmembrane β-barrel of BamA that allow for lateral opening, as well as large overall rearrangements of its periplasmic POTRA domains. Here, we identify local dynamics of the BamA POTRA 5 domain by solution and solid-state nuclear magnetic resonance. The protein region undergoing conformational exchange is highly conserved and contains residues critical for interaction with BamD and correct β-barrel assembly in vivo. We show that mutations known to affect the latter processes influence the conformational equilibrium, suggesting that the plasticity of POTRA 5 is related to its interaction with BamD and possibly to substrate binding. Taken together, a view emerges in which local protein plasticity may be critically involved in the different stages of outer membrane protein folding and insertion.
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Affiliation(s)
- Tessa Sinnige
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Markus Weingarth
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Mark Daniëls
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Rolf Boelens
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Alexandre M J J Bonvin
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Klaartje Houben
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands.
| | - Marc Baldus
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands.
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83
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Setzler J, Seith C, Brieg M, Wenzel W. SLIM: an improved generalized Born implicit membrane model. J Comput Chem 2015; 35:2027-39. [PMID: 25243932 DOI: 10.1002/jcc.23717] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 07/02/2014] [Accepted: 07/28/2014] [Indexed: 12/24/2022]
Abstract
In most implicit continuum models, membranes are represented as heterogeneous dielectric environments, but their treatment within computationally efficient generalized Born (GB) models is challenging. Despite several previous attempts, an adequate description of multiple dielectric regions in implicit GB-based membrane models that reproduce the qualitative and quantitative features of Poisson-Boltzmann (PB) electrostatics remains an unmet prerequisite of qualitatively correct implicit membrane models. A novel scheme (SLIM) to decompose one environment consisting of multiple dielectric regions into a sum of multiple environments consisting only of two dielectric regions each is proposed to solve this issue. These simpler environments can be treated with established GB methods. This approach captures qualitative features of PB electrostatic that are not present in previous models. Simulations of three membrane proteins demonstrate that this model correctly reproduces known properties of these proteins in agreement with experimental or other computational studies.
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Affiliation(s)
- Julia Setzler
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021, Karlsruhe, Germany
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84
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Langosch D, Scharnagl C, Steiner H, Lemberg MK. Understanding intramembrane proteolysis: from protein dynamics to reaction kinetics. Trends Biochem Sci 2015; 40:318-27. [PMID: 25941170 DOI: 10.1016/j.tibs.2015.04.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 03/31/2015] [Accepted: 04/01/2015] [Indexed: 12/12/2022]
Abstract
Intramembrane proteolysis - cleavage of proteins within the plane of a membrane - is a widespread phenomenon that can contribute to the functional activation of substrates and is involved in several diseases. Although different families of intramembrane proteases have been discovered and characterized, we currently do not know how these enzymes discriminate between substrates and non-substrates, how site-specific cleavage is achieved, or which factors determine the rate of proteolysis. Focusing on γ-secretase and rhomboid proteases, we argue that answers to these questions may emerge from connecting experimental readouts, such as reaction kinetics and the determination of cleavage sites, to the structures and the conformational dynamics of substrates and enzymes.
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Affiliation(s)
- D Langosch
- Technische Universität München, Lehrstuhl Chemie der Biopolymere, Weihenstephaner Berg 3, 85354 Freising, and Munich Center for Integrated Protein Science (CIMPS(M)), Germany.
| | - C Scharnagl
- Fakultät für Physik E14, Technische Universität München, Maximus-von-Imhof-Forum 4, 85354 Freising, Germany
| | - H Steiner
- Ludwig-Maximilians-University Munich, Metabolic Biochemistry and DZNE (German Center for Neurodegenerative Diseases), Munich, Germany
| | - M K Lemberg
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Deutsches Krebsforschungszentrum (DKFZ)-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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85
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Gopinath T, Mote KR, Veglia G. Simultaneous acquisition of 2D and 3D solid-state NMR experiments for sequential assignment of oriented membrane protein samples. JOURNAL OF BIOMOLECULAR NMR 2015; 62:53-61. [PMID: 25749871 PMCID: PMC4981477 DOI: 10.1007/s10858-015-9916-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 03/03/2015] [Indexed: 05/20/2023]
Abstract
We present a new method called DAISY (Dual Acquisition orIented ssNMR spectroScopY) for the simultaneous acquisition of 2D and 3D oriented solid-state NMR experiments for membrane proteins reconstituted in mechanically or magnetically aligned lipid bilayers. DAISY utilizes dual acquisition of sine and cosine dipolar or chemical shift coherences and long living (15)N longitudinal polarization to obtain two multi-dimensional spectra, simultaneously. In these new experiments, the first acquisition gives the polarization inversion spin exchange at the magic angle (PISEMA) or heteronuclear correlation (HETCOR) spectra, the second acquisition gives PISEMA-mixing or HETCOR-mixing spectra, where the mixing element enables inter-residue correlations through (15)N-(15)N homonuclear polarization transfer. The analysis of the two 2D spectra (first and second acquisitions) enables one to distinguish (15)N-(15)N inter-residue correlations for sequential assignment of membrane proteins. DAISY can be implemented in 3D experiments that include the polarization inversion spin exchange at magic angle via I spin coherence (PISEMAI) sequence, as we show for the simultaneous acquisition of 3D PISEMAI-HETCOR and 3D PISEMAI-HETCOR-mixing experiments.
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Affiliation(s)
| | | | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
- Department of Chemistry and University of Minnesota, Minneapolis, MN 55455
- Corresponding Author. Gianluigi Veglia, 6-155 Jackson Hall, 321 Church St SE, Minneapolis, MN 55455, Phone: (612) 625-0758, Fax: (612) 625-2163,
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86
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Ding Y, Fujimoto LM, Yao Y, Marassi FM. Solid-state NMR of the Yersinia pestis outer membrane protein Ail in lipid bilayer nanodiscs sedimented by ultracentrifugation. JOURNAL OF BIOMOLECULAR NMR 2015; 61:275-86. [PMID: 25578899 PMCID: PMC4398618 DOI: 10.1007/s10858-014-9893-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 12/20/2014] [Indexed: 05/22/2023]
Abstract
Solid-state NMR studies of sedimented soluble proteins has been developed recently as an attractive approach for overcoming the size limitations of solution NMR spectroscopy while bypassing the need for sample crystallization or precipitation (Bertini et al. Proc Natl Acad Sci USA 108(26):10396-10399, 2011). Inspired by the potential benefits of this method, we have investigated the ability to sediment lipid bilayer nanodiscs reconstituted with a membrane protein. In this study, we show that nanodiscs containing the outer membrane protein Ail from Yersinia pestis can be sedimented for solid-state NMR structural studies, without the need for precipitation or lyophilization. Optimized preparations of Ail in phospholipid nanodiscs support both the structure and the fibronectin binding activity of the protein. The same sample can be used for solution NMR, solid-state NMR and activity assays, facilitating structure-activity correlation experiments across a wide range of timescales.
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Affiliation(s)
- Yi Ding
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla CA 92037, USA
| | - L. Miya Fujimoto
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla CA 92037, USA
| | - Yong Yao
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla CA 92037, USA
| | - Francesca M. Marassi
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla CA 92037, USA
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla CA 92037, USA. [Tel: 858-795-5282; Mail: ]
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87
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Gopinath T, Veglia G. Multiple acquisition of magic angle spinning solid-state NMR experiments using one receiver: application to microcrystalline and membrane protein preparations. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 253:143-53. [PMID: 25797011 PMCID: PMC4399235 DOI: 10.1016/j.jmr.2015.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 01/02/2015] [Accepted: 01/04/2015] [Indexed: 05/05/2023]
Abstract
Solid-state NMR spectroscopy of proteins is a notoriously low-throughput technique. Relatively low-sensitivity and poor resolution of protein samples require long acquisition times for multidimensional NMR experiments. To speed up data acquisition, we developed a family of experiments called Polarization Optimized Experiments (POE), in which we utilized the orphan spin operators that are discarded in classical multidimensional NMR experiments, recovering them to allow simultaneous acquisition of multiple 2D and 3D experiments, all while using conventional probes with spectrometers equipped with one receiver. POE allow the concatenation of multiple 2D or 3D pulse sequences into a single experiment, thus potentially combining all of the aforementioned advances, boosting the capability of ssNMR spectrometers at least two-fold without the addition of any hardware. In this perspective, we describe the first generation of POE, such as dual acquisition MAS (or DUMAS) methods, and then illustrate the evolution of these experiments into MEIOSIS, a method that enables the simultaneous acquisition of multiple 2D and 3D spectra. Using these new pulse schemes for the solid-state NMR investigation of biopolymers makes it possible to obtain sequential resonance assignments, as well as distance restraints, in about half the experimental time. While designed for acquisition of heteronuclei, these new experiments can be easily implemented for proton detection and coupled with other recent advancements, such as dynamic nuclear polarization (DNP), to improve signal to noise. Finally, we illustrate the application of these methods to microcrystalline protein preparations as well as single and multi-span membrane proteins reconstituted in lipid membranes.
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Affiliation(s)
- T Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States; Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, United States.
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88
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Eddy MT, Su Y, Silvers R, Andreas L, Clark L, Wagner G, Pintacuda G, Emsley L, Griffin RG. Lipid bilayer-bound conformation of an integral membrane beta barrel protein by multidimensional MAS NMR. JOURNAL OF BIOMOLECULAR NMR 2015; 61:299-310. [PMID: 25634301 PMCID: PMC4398622 DOI: 10.1007/s10858-015-9903-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 01/20/2015] [Indexed: 05/09/2023]
Abstract
The human voltage dependent anion channel 1 (VDAC) is a 32 kDa β-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms two-dimensional lipid crystals, showing remarkable spectral resolution (0.5-0.3 ppm for (13)C line widths and <0.5 ppm (15)N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane β-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the reported assignment approach and the great potential for even more complete assignment studies and de novo structure determination via (1)H detected MAS NMR.
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Affiliation(s)
- Matthew T. Eddy
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Yongchao Su
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Robert Silvers
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Loren Andreas
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Lindsay Clark
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA
| | - Guido Pintacuda
- Centre de RMN à Tres̀ Hauts Champs, Institut des Sciences Analytiques (CNRS, ENS Lyon, UCB Lyon 1), Université de Lyon, 69100 Villeurbanne, France
| | - Lyndon Emsley
- Centre de RMN à Tres̀ Hauts Champs, Institut des Sciences Analytiques (CNRS, ENS Lyon, UCB Lyon 1), Université de Lyon, 69100 Villeurbanne, France
| | - Robert G. Griffin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Corresponding Author:
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89
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Jaroniec CP. Structural studies of proteins by paramagnetic solid-state NMR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 253:50-9. [PMID: 25797004 PMCID: PMC4371136 DOI: 10.1016/j.jmr.2014.12.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 12/17/2014] [Indexed: 05/03/2023]
Abstract
Paramagnetism-based nuclear pseudocontact shifts and spin relaxation enhancements contain a wealth of information in solid-state NMR spectra about electron-nucleus distances on the ∼20 Å length scale, far beyond that normally probed through measurements of nuclear dipolar couplings. Such data are especially vital in the context of structural studies of proteins and other biological molecules that suffer from a sparse number of experimentally-accessible atomic distances constraining their three-dimensional fold or intermolecular interactions. This perspective provides a brief overview of the recent developments and applications of paramagnetic magic-angle spinning NMR to biological systems, with primary focus on the investigations of metalloproteins and natively diamagnetic proteins modified with covalent paramagnetic tags.
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Affiliation(s)
- Christopher P Jaroniec
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA.
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90
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Wylie BJ, Dzikovski BG, Pawsey S, Caporini M, Rosay M, Freed JH, McDermott AE. Dynamic nuclear polarization of membrane proteins: covalently bound spin-labels at protein-protein interfaces. JOURNAL OF BIOMOLECULAR NMR 2015; 61:361-7. [PMID: 25828256 PMCID: PMC4819240 DOI: 10.1007/s10858-015-9919-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Accepted: 03/05/2015] [Indexed: 05/07/2023]
Abstract
We demonstrate that dynamic nuclear polarization of membrane proteins in lipid bilayers may be achieved using a novel polarizing agent: pairs of spin labels covalently bound to a protein of interest interacting at an intermolecular interaction surface. For gramicidin A, nitroxide tags attached to the N-terminal intermolecular interface region become proximal only when bimolecular channels forms in the membrane. We obtained signal enhancements of sixfold for the dimeric protein. The enhancement effect was comparable to that of a doubly tagged sample of gramicidin C, with intramolecular spin pairs. This approach could be a powerful and selective means for signal enhancement in membrane proteins, and for recognizing intermolecular interfaces.
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Affiliation(s)
- Benjamin J Wylie
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
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91
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Thomas L, Kahr J, Schmidt P, Krug U, Scheidt HA, Huster D. The dynamics of the G protein-coupled neuropeptide Y2 receptor in monounsaturated membranes investigated by solid-state NMR spectroscopy. JOURNAL OF BIOMOLECULAR NMR 2015; 61:347-59. [PMID: 25556885 DOI: 10.1007/s10858-014-9892-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 12/20/2014] [Indexed: 05/14/2023]
Abstract
In contrast to the static snapshots provided by protein crystallography, G protein-coupled receptors constitute a group of proteins with highly dynamic properties, which are required in the receptors' function as signaling molecule. Here, the human neuropeptide Y2 receptor was reconstituted into a model membrane composed of monounsaturated phospholipids and solid-state NMR was used to characterize its dynamics. Qualitative static (15)N NMR spectra and quantitative determination of (1)H-(13)C order parameters through measurement of the (1)H-(13)C dipolar couplings of the CH, CH2 and CH3 groups revealed axially symmetric motions of the whole molecule in the membrane and molecular fluctuations of varying amplitude from all molecular segments. The molecular order parameters (S(backbone) = 0.59-0.67, S(CH2) = 0.41-0.51 and S(CH3) = 0.22) obtained in directly polarized (13)C NMR experiments demonstrate that the Y2 receptor is highly mobile in the native-like membrane. Interestingly, according to these results the receptor was found to be slightly more rigid in the membranes formed by the monounsaturated phospholipids than by saturated phospholipids as investigated previously. This could be caused by an increased chain length of the monounsaturated lipids, which may result in a higher helical content of the receptor. Furthermore, the incorporation of cholesterol, phosphatidylethanolamine, or negatively charged phosphatidylserine into the membrane did not have a significant influence on the molecular mobility of the Y2 receptor.
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Affiliation(s)
- Lars Thomas
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107, Leipzig, Germany
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92
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Su Y, Andreas L, Griffin RG. Magic angle spinning NMR of proteins: high-frequency dynamic nuclear polarization and (1)H detection. Annu Rev Biochem 2015; 84:465-97. [PMID: 25839340 DOI: 10.1146/annurev-biochem-060614-034206] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Magic angle spinning (MAS) NMR studies of amyloid and membrane proteins and large macromolecular complexes are an important new approach to structural biology. However, the applicability of these experiments, which are based on (13)C- and (15)N-detected spectra, would be enhanced if the sensitivity were improved. Here we discuss two advances that address this problem: high-frequency dynamic nuclear polarization (DNP) and (1)H-detected MAS techniques. DNP is a sensitivity enhancement technique that transfers the high polarization of exogenous unpaired electrons to nuclear spins via microwave irradiation of electron-nuclear transitions. DNP boosts NMR signal intensities by factors of 10(2) to 10(3), thereby overcoming NMR's inherent low sensitivity. Alternatively, it permits structural investigations at the nanomolar scale. In addition, (1)H detection is feasible primarily because of the development of MAS rotors that spin at frequencies of 40 to 60 kHz or higher and the preparation of extensively (2)H-labeled proteins.
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Affiliation(s)
- Yongchao Su
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139;
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93
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Fasshuber HK, Demers JP, Chevelkov V, Giller K, Becker S, Lange A. Specific 13C labeling of leucine, valine and isoleucine methyl groups for unambiguous detection of long-range restraints in protein solid-state NMR studies. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 252:10-9. [PMID: 25625825 DOI: 10.1016/j.jmr.2014.12.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 12/10/2014] [Accepted: 12/17/2014] [Indexed: 05/08/2023]
Abstract
Here we present an isotopic labeling strategy to easily obtain unambiguous long-range distance restraints in protein solid-state NMR studies. The method is based on the inclusion of two biosynthetic precursors in the bacterial growth medium, α-ketoisovalerate and α-ketobutyrate, leading to the production of leucine, valine and isoleucine residues that are exclusively (13)C labeled on methyl groups. The resulting spectral simplification facilitates the collection of distance restraints, the verification of carbon chemical shift assignments and the measurement of methyl group dynamics. This approach is demonstrated on the type-three secretion system needle of Shigella flexneri, where 49 methyl-methyl and methyl-nitrogen distance restraints including 10 unambiguous long-range distance restraints could be collected. By combining this labeling scheme with ultra-fast MAS and proton detection, the assignment of methyl proton chemical shifts was achieved.
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Affiliation(s)
- Hannes Klaus Fasshuber
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany; Department of Molecular Biophysics, Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Jean-Philippe Demers
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany; Department of Molecular Biophysics, Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Veniamin Chevelkov
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany; Department of Molecular Biophysics, Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Karin Giller
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Stefan Becker
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Adam Lange
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany; Department of Molecular Biophysics, Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institut für Biologie, Humboldt-Universität zu Berlin, Invalidenstr. 110, 10115 Berlin, Germany.
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94
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Wang T, Williams JK, Schmidt-Rohr K, Hong M. Relaxation-compensated difference spin diffusion NMR for detecting 13C-13C long-range correlations in proteins and polysaccharides. JOURNAL OF BIOMOLECULAR NMR 2015; 61:97-107. [PMID: 25510834 PMCID: PMC4522165 DOI: 10.1007/s10858-014-9889-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Accepted: 12/03/2014] [Indexed: 05/04/2023]
Abstract
The measurement of long-range distances remains a challenge in solid-state NMR structure determination of biological macromolecules. In 2D and 3D correlation spectra of uniformly (13)C-labeled biomolecules, inter-residue, inter-segmental, and intermolecular (13)C-(13)C cross peaks that provide important long-range distance constraints for three-dimensional structures often overlap with short-range cross peaks that only reflect the covalent structure of the molecule. It is therefore desirable to develop new approaches to obtain spectra containing only long-range cross peaks. Here we show that a relaxation-compensated modification of the commonly used 2D (1)H-driven spin diffusion (PDSD) experiment allows the clean detection of such long-range cross peaks. By adding a z-filter to keep the total z-period of the experiment constant, we compensate for (13)C T1 relaxation. As a result, the difference spectrum between a long- and a scaled short-mixing time spectrum show only long-range correlation signals. We show that one- and two-bond cross peaks equalize within a few tens of milliseconds. Within ~200 ms, the intensity equilibrates within an amino acid residue and a monosaccharide to a value that reflects the number of spins in the local network. With T1 relaxation compensation, at longer mixing times, inter-residue and inter-segmental cross peaks increase in intensity whereas intra-segmental cross-peak intensities remain unchanged relative to each other and can all be subtracted out. Without relaxation compensation, the difference 2D spectra exhibit both negative and positive intensities due to heterogeneous T1 relaxation in most biomolecules, which can cause peak cancellation. We demonstrate this relaxation-compensated difference PDSD approach on amino acids, monosaccharides, a crystalline model peptide, a membrane-bound peptide and a plant cell wall sample. The resulting difference spectra yield clean multi-bond, inter-residue and intermolecular correlation peaks, which are often difficult to resolve in the parent 2D spectra.
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Affiliation(s)
- Tuo Wang
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - Jonathan K. Williams
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - Klaus Schmidt-Rohr
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02453
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
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95
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Isotope Labeling of Eukaryotic Membrane Proteins in Yeast for Solid-State NMR. Methods Enzymol 2015; 565:193-212. [DOI: 10.1016/bs.mie.2015.05.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
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96
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Fukuda Y, Inoue T. High-temperature and high-resolution crystallography of thermostable copper nitrite reductase. Chem Commun (Camb) 2015; 51:6532-5. [DOI: 10.1039/c4cc09553g] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The structure of thermostable copper nitrite reductase in complex with nitrite was determined at 320 K.
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Affiliation(s)
- Yohta Fukuda
- Department of Applied Chemistry
- Graduate School of Engineering
- Osaka University
- Suita
- Japan
| | - Tsuyoshi Inoue
- Department of Applied Chemistry
- Graduate School of Engineering
- Osaka University
- Suita
- Japan
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97
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Zuo C, Tang S, Zheng JS. Chemical synthesis and biophysical applications of membrane proteins. J Pept Sci 2014; 21:540-9. [DOI: 10.1002/psc.2721] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 10/30/2014] [Accepted: 10/31/2014] [Indexed: 12/16/2022]
Affiliation(s)
- Chao Zuo
- High Magnetic Field Laboratory; Chinese Academy of Sciences; Hefei 230031 China
- Department of Chemistry; Tsinghua University; Beijing 100084 China
| | - Shan Tang
- Department of Chemistry; Tsinghua University; Beijing 100084 China
| | - Ji-Shen Zheng
- High Magnetic Field Laboratory; Chinese Academy of Sciences; Hefei 230031 China
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98
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Yao X, Dürr UHN, Gattin Z, Laukat Y, Narayanan RL, Brückner AK, Meisinger C, Lange A, Becker S, Zweckstetter M. NMR-based detection of hydrogen/deuterium exchange in liposome-embedded membrane proteins. PLoS One 2014; 9:e112374. [PMID: 25375235 PMCID: PMC4223039 DOI: 10.1371/journal.pone.0112374] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 10/05/2014] [Indexed: 11/17/2022] Open
Abstract
Membrane proteins play key roles in biology. Determination of their structure in a membrane environment, however, is highly challenging. To address this challenge, we developed an approach that couples hydrogen/deuterium exchange of membrane proteins to rapid unfolding and detection by solution-state NMR spectroscopy. We show that the method allows analysis of the solvent protection of single residues in liposome-embedded proteins such as the 349-residue Tom40, the major protein translocation pore in the outer mitochondrial membrane, which has resisted structural analysis for many years.
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Affiliation(s)
- Xuejun Yao
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Ulrich H N Dürr
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Zrinka Gattin
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Yvonne Laukat
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | | | | | - Chris Meisinger
- Institut für Biochemie und Molekularbiologie, ZBMZ and BIOSS Centre for Biological Signalling Studies, Universität Freiburg, Freiburg, Germany
| | - Adam Lange
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Stefan Becker
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Markus Zweckstetter
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany; German Center for Neurodegenerative Diseases (DZNE), Goöttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University Medical Center, Göttingen, Germany
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99
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Wang S, Ladizhansky V. Recent advances in magic angle spinning solid state NMR of membrane proteins. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2014; 82:1-26. [PMID: 25444696 DOI: 10.1016/j.pnmrs.2014.07.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Revised: 07/16/2014] [Accepted: 07/20/2014] [Indexed: 05/14/2023]
Abstract
Membrane proteins mediate many critical functions in cells. Determining their three-dimensional structures in the native lipid environment has been one of the main objectives in structural biology. There are two major NMR methodologies that allow this objective to be accomplished. Oriented sample NMR, which can be applied to membrane proteins that are uniformly aligned in the magnetic field, has been successful in determining the backbone structures of a handful of membrane proteins. Owing to methodological and technological developments, Magic Angle Spinning (MAS) solid-state NMR (ssNMR) spectroscopy has emerged as another major technique for the complete characterization of the structure and dynamics of membrane proteins. First developed on peptides and small microcrystalline proteins, MAS ssNMR has recently been successfully applied to large membrane proteins. In this review we describe recent progress in MAS ssNMR methodologies, which are now available for studies of membrane protein structure determination, and outline a few examples, which highlight the broad capability of ssNMR spectroscopy.
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Affiliation(s)
- Shenlin Wang
- Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing 100871, China; College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
| | - Vladimir Ladizhansky
- Department of Physics, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada; Biophysics Interdepartmental Group, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
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100
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Zhou M, Robinson CV. Flexible membrane proteins: functional dynamics captured by mass spectrometry. Curr Opin Struct Biol 2014; 28:122-30. [DOI: 10.1016/j.sbi.2014.08.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 07/23/2014] [Accepted: 08/13/2014] [Indexed: 10/24/2022]
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