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Zhang Z, Su Y, Xiao H, Yang J. Selective Nuclear Magnetic Resonance Method for Enhancing Long-Range Heteronuclear Correlations in Solids. J Phys Chem Lett 2022; 13:6376-6382. [PMID: 35796704 DOI: 10.1021/acs.jpclett.2c01527] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The long-range heteronuclear correlation remains a significant challenge in solid-state nuclear magnetic resonance (NMR), which is critical in the structural elucidation of biomolecular, material, and pharmaceutical solids. We propose a selective NMR method, heteronuclear selective phase-optimized recoupling (hetSPR), to selectively enhance long-range correlations of interest by utilizing characteristic chemical shifts. Compared to conventional methods, hetSPR can selectively enhance desired heteronuclear correlations (e.g., 1H-13C and 1H-19F) by factors up to 5 and largely suppress the unwanted ones. The method proves useful by enhancing the long-range correlation from an intermolecular 1H-19F distance of 4.8 Å by a factor of 2.4 in a fluorinated pharmaceutical drug, bicalutamide, under fast magic-angle spinning. It does not use selective pulses and is thus user-friendly even for nonexperts. The new method is expected to boost solid-state NMR to elucidate the structures of various solids.
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Affiliation(s)
- Zhengfeng Zhang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Yongchao Su
- Division of Molecular Pharmaceutics and Drug Delivery, College of Pharmacy, the University of Texas at Austin, Austin, Texas 78712, United States
- Department of Industrial and Physical Pharmacy, College of Pharmacy, Purdue University, West Lafayette, Indiana 47907, United States
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Hang Xiao
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Jun Yang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
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2
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Xiao H, Zhang Z, Zhao Y, Yang J. Spectral editing of alanine, serine, and threonine in uniformly labeled proteins based on frequency-selective homonuclear recoupling in solid-state NMR. JOURNAL OF BIOMOLECULAR NMR 2021; 75:193-202. [PMID: 33890210 DOI: 10.1007/s10858-021-00367-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 04/02/2021] [Indexed: 06/12/2023]
Abstract
Spectral editing is crucial to simplify the crowded solid-state NMR spectra of proteins. New techniques are introduced to edit 13C-13C correlations of uniformly labeled proteins under moderate magic-angle spinning (MAS), based on our recent frequency-selective homonuclear recoupling sequences [Zhang et al., J. Phys. Chem. Lett. 2020, 11, 8077-8083]. The signals of alanine, serine, or threonine residues are selected out by selective 13Cα-13Cβ double-quantum filtering (DQF). The 13Cα-13Cβ correlations of alanine residues are selectively established with efficiency up to ~ 1.8 times that by dipolar-assisted rotational resonance (DARR). The techniques are shown in 2D/3D NCCX experiments and applied to the uniformly 13C, 15N labeled Aquaporin Z (AqpZ) membrane protein, demonstrating their potential to simplify spectral analyses in biological solid-state NMR.
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Affiliation(s)
- Hang Xiao
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, P. R. China
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Zhengfeng Zhang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.
| | - Yongxiang Zhao
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, P. R. China
| | - Jun Yang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China.
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3
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Li J, Sae Her A, Traaseth NJ. Site-specific resolution of anionic residues in proteins using solid-state NMR spectroscopy. JOURNAL OF BIOMOLECULAR NMR 2020; 74:355-363. [PMID: 32514875 PMCID: PMC7472563 DOI: 10.1007/s10858-020-00323-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 05/29/2020] [Indexed: 06/11/2023]
Abstract
NMR spectroscopy is commonly used to infer site-specific acid dissociation constants (pKa) since the chemical shift is sensitive to the protonation state. Methods that probe atoms nearest to the functional groups involved in acid/base chemistry are the most sensitive for determining the protonation state. In this work, we describe a magic-angle-spinning (MAS) solid-state NMR approach to measure chemical shifts on the side chain of the anionic residues aspartate and glutamate. This method involves a combination of double quantum spectroscopy in the indirect dimension and REDOR dephasing to provide a sensitive and resolved view of these amino acid residues that are commonly involved in enzyme catalysis and membrane protein transport. To demonstrate the applicability of the approach, we carried out measurements using a microcrystalline soluble protein (ubiquitin) and a membrane protein embedded in lipid bilayers (EmrE). Overall, the resolution available from the double quantum dimension and confidence in identification of aspartate and glutamate residues from the REDOR filter make this method the most convenient for characterizing protonation states and deriving pKa values using MAS solid-state NMR.
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Affiliation(s)
- Jianping Li
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY, 10003, USA
| | - Ampon Sae Her
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY, 10003, USA
| | - Nathaniel J Traaseth
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY, 10003, USA.
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4
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Jain MG, Rajalakshmi G, Madhu PK, Agarwal V, Mote KR. Overcoming Prohibitively Large Radiofrequency Demands for the Measurement of Internuclear Distances with Solid-State NMR under Fast Magic-Angle Spinning. J Phys Chem B 2020; 124:1444-1451. [DOI: 10.1021/acs.jpcb.9b11849] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Mukul G. Jain
- Tata Institute of Fundamental Research Hyderabad, Survey No. 36/P Gopanpally, Serilingampally, Ranga Reddy District, Hyderabad, Telangana 500107, India
| | - G. Rajalakshmi
- Tata Institute of Fundamental Research Hyderabad, Survey No. 36/P Gopanpally, Serilingampally, Ranga Reddy District, Hyderabad, Telangana 500107, India
| | - P. K. Madhu
- Tata Institute of Fundamental Research Hyderabad, Survey No. 36/P Gopanpally, Serilingampally, Ranga Reddy District, Hyderabad, Telangana 500107, India
| | - Vipin Agarwal
- Tata Institute of Fundamental Research Hyderabad, Survey No. 36/P Gopanpally, Serilingampally, Ranga Reddy District, Hyderabad, Telangana 500107, India
| | - Kaustubh R. Mote
- Tata Institute of Fundamental Research Hyderabad, Survey No. 36/P Gopanpally, Serilingampally, Ranga Reddy District, Hyderabad, Telangana 500107, India
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Ding X, Fu R, Tian F. De novo resonance assignment of the transmembrane domain of LR11/SorLA in E. coli membranes. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 310:106639. [PMID: 31734618 PMCID: PMC6935515 DOI: 10.1016/j.jmr.2019.106639] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 10/28/2019] [Accepted: 10/30/2019] [Indexed: 05/17/2023]
Abstract
Membrane proteins perform many important cellular functions. Historically, structural studies of these proteins have been conducted in detergent preparations and synthetic lipid bilayers. More recently, magic-angle-spinning (MAS) solid-state NMR has been employed to analyze membrane proteins in native membrane environments, but resonance assignments with this technique remain challenging due to limited spectral resolution and high resonance degeneracy. To tackle this issue, we combine reverse labeling of amino acids, frequency-selective dipolar dephasing, and NMR difference spectroscopy. These methods have resulted in nearly complete resonance assignments of the transmembrane domain of human LR11 (SorLA) protein in E. coli membranes. To reduce background signals from E. coli lipids and proteins and improve spectral sensitivity, we effectively utilize amylose affinity chromatography to prepare membrane vesicles when MBP is included as a fusion partner in the expression construct.
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Affiliation(s)
- Xiaoyan Ding
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Hershey, PA 17033, USA
| | - Riqiang Fu
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., Tallahassee, FL 32310, USA.
| | - Fang Tian
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Hershey, PA 17033, USA.
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6
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Higman VA. Solid-state MAS NMR resonance assignment methods for proteins. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2018; 106-107:37-65. [PMID: 31047601 DOI: 10.1016/j.pnmrs.2018.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 04/19/2018] [Accepted: 04/24/2018] [Indexed: 06/09/2023]
Abstract
The prerequisite to structural or functional studies of proteins by NMR is generally the assignment of resonances. Since the first assignment of proteins by solid-state MAS NMR was conducted almost two decades ago, a wide variety of different pulse sequences and methods have been proposed and continue to be developed. Traditionally, a variety of 2D and 3D 13C-detected experiments have been used for the assignment of backbone and side-chain 13C and 15N resonances. These methods have found widespread use across the field. But as the hardware has changed and higher spinning frequencies and magnetic fields are becoming available, the ability to use direct proton detection is opening up a new set of assignment methods based on triple-resonance experiments. This review describes solid-state MAS NMR assignment methods using carbon detection and proton detection at different deuteration levels. The use of different isotopic labelling schemes as an aid to assignment in difficult cases is discussed as well as the increasing number of software packages that support manual and automated resonance assignment.
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Affiliation(s)
- Victoria A Higman
- Department of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TU, UK.
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7
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Wang S, Matsuda I, Long F, Ishii Y. Spectral editing at ultra-fast magic-angle-spinning in solid-state NMR: facilitating protein sequential signal assignment by HIGHLIGHT approach. JOURNAL OF BIOMOLECULAR NMR 2016; 64:131-141. [PMID: 26781951 DOI: 10.1007/s10858-016-0014-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 01/12/2016] [Indexed: 06/05/2023]
Abstract
This study demonstrates a novel spectral editing technique for protein solid-state NMR (SSNMR) to simplify the spectrum drastically and to reduce the ambiguity for protein main-chain signal assignments in fast magic-angle-spinning (MAS) conditions at a wide frequency range of 40-80 kHz. The approach termed HIGHLIGHT (Wang et al., in Chem Comm 51:15055-15058, 2015) combines the reverse (13)C, (15)N-isotope labeling strategy and selective signal quenching using the frequency-selective REDOR pulse sequence under fast MAS. The scheme allows one to selectively observe the signals of "highlighted" labeled amino-acid residues that precede or follow unlabeled residues through selectively quenching (13)CO or (15)N signals for a pair of consecutively labeled residues by recoupling (13)CO-(15)N dipolar couplings. Our numerical simulation results showed that the scheme yielded only ~15% loss of signals for the highlighted residues while quenching as much as ~90% of signals for non-highlighted residues. For lysine-reverse-labeled micro-crystalline GB1 protein, the 2D (15)N/(13)Cα correlation and 2D (13)Cα/(13)CO correlation SSNMR spectra by the HIGHLIGHT approach yielded signals only for six residues following and preceding the unlabeled lysine residues, respectively. The experimental dephasing curves agreed reasonably well with the corresponding simulation results for highlighted and quenched residues at spinning speeds of 40 and 60 kHz. The compatibility of the HIGHLIGHT approach with fast MAS allows for sensitivity enhancement by paramagnetic assisted data collection (PACC) and (1)H detection. We also discuss how the HIGHLIGHT approach facilitates signal assignments using (13)C-detected 3D SSNMR by demonstrating full sequential assignments of lysine-reverse-labeled micro-crystalline GB1 protein (~300 nmol), for which data collection required only 11 h. The HIGHLIGHT approach offers valuable means of signal assignments especially for larger proteins through reducing the number of resonance and clarifying multiple starting points in sequential assignment with enhanced sensitivity.
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Affiliation(s)
- Songlin Wang
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Isamu Matsuda
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Fei Long
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Yoshitaka Ishii
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607, USA.
- Center for Structural Biology, University of Illinois at Chicago, Chicago, IL, 60607, USA.
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8
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Wang S, Parthasarathy S, Xiao Y, Nishiyama Y, Long F, Matsuda I, Endo Y, Nemoto T, Yamauchi K, Asakura T, Takeda M, Terauchi T, Kainosho M, Ishii Y. Nano-mole scale sequential signal assignment by (1)H-detected protein solid-state NMR. Chem Commun (Camb) 2015; 51:15055-8. [PMID: 26317132 DOI: 10.1039/c5cc04618a] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present a 3D (1)H-detected solid-state NMR (SSNMR) approach for main-chain signal assignments of 10-100 nmol of fully protonated proteins using ultra-fast magic-angle spinning (MAS) at ∼80 kHz by a novel spectral-editing method, which permits drastic spectral simplification. The approach offers ∼110 fold time saving over a traditional 3D (13)C-detected SSNMR approach.
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Affiliation(s)
- Songlin Wang
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
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9
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Banigan JR, Gayen A, Cho MK, Traaseth NJ. A structured loop modulates coupling between the substrate-binding and dimerization domains in the multidrug resistance transporter EmrE. J Biol Chem 2014; 290:805-14. [PMID: 25406320 DOI: 10.1074/jbc.m114.601963] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Secondary active transporters undergo large conformational changes to facilitate the efflux of substrates across the lipid bilayer. Among the smallest known transport proteins are members of the small multidrug resistance (SMR) family that are composed of four transmembrane (TM) domains and assemble into dimers. An unanswered question in the SMR field is how the dimerization domain (TM4) is coupled with the substrate-binding chamber (TM1-3). To provide insight for this essential aspect of ion-coupled transport, we carried out a structure-function study on the SMR protein EmrE using solid-state NMR spectroscopy in lipid bilayers and resistance assays in Escherichia coli. The chemical shifts for EmrE were consistent with β-strand secondary structure for the loop connecting TM3 and TM4. Based on these structural results, EmrE mutants were created to ascertain whether a specific loop length and composition were necessary for function. A linker encompassing six extra Gly residues relative to wild-type EmrE failed to give resistance; however, the number of residues in the loop was not the only criterion for a functional efflux pump. Replacement of the central hydrophobic residue with Gly (L83G) also conferred no ethidium resistance phenotype, which supported the conclusion that the structure and length of the loop were both essential for ion-coupled transport. Taken together with a bioinformatics analysis, a structured linker is likely conserved across the SMR family to play an active role in mediating the conformational switch between inward-open and outward-open states necessary for drug efflux. These findings underscore the important role loops can play in mediating efflux.
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Affiliation(s)
- James R Banigan
- From the Department of Chemistry, New York University, New York, New York 10003
| | - Anindita Gayen
- From the Department of Chemistry, New York University, New York, New York 10003
| | - Min-Kyu Cho
- From the Department of Chemistry, New York University, New York, New York 10003
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Jayanthi S, Akbey Ü, Uluca B, Oschkinat H, Vega S. A Floquet description of phase alternated sequences for efficient homonuclear recoupling in solid perdeuterated systems. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 234:10-20. [PMID: 23831836 DOI: 10.1016/j.jmr.2013.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 05/08/2013] [Accepted: 05/21/2013] [Indexed: 06/02/2023]
Abstract
A Floquet description of a phase alternated homonuclear recoupling scheme for perdeuterated systems is presented. As a result, we demonstrate improvements in the recoupling efficiency of the DOuble Nucleus Enhanced Recoupling [DONER; J. Am. Chem. Soc. 131 (2009) 17054] technique by utilizing Phase Alternated Recoupling Irradiation Schemes [PARIS; Chem. Phys. Lett. 469 (2009) 342]. The effect of proton and deuterium radio frequency irradiation during recoupling has been systematically studied and theoretical observations have been verified experimentally using a deuterated model compound, L-Alanine, at 10 and 20 kHz magic angle spinning frequency. Experimental results are well in agreement with theoretical observations, thereby significantly increasing the recoupling efficiency of conventional DONER in perdeuterated systems.
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Affiliation(s)
- Sundaresan Jayanthi
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
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Miao Y, Cross TA, Fu R. Identifying inter-residue resonances in crowded 2D (13)C- (13)C chemical shift correlation spectra of membrane proteins by solid-state MAS NMR difference spectroscopy. JOURNAL OF BIOMOLECULAR NMR 2013; 56:265-73. [PMID: 23708936 PMCID: PMC3717563 DOI: 10.1007/s10858-013-9745-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 05/14/2013] [Indexed: 05/11/2023]
Abstract
The feasibility of using difference spectroscopy, i.e. subtraction of two correlation spectra at different mixing times, for substantially enhanced resolution in crowded two-dimensional (13)C-(13)C chemical shift correlation spectra is presented. With the analyses of (13)C-(13)C spin diffusion in simple spin systems, difference spectroscopy is proposed to partially separate the spin diffusion resonances of relatively short intra-residue distances from the longer inter-residue distances, leading to a better identification of the inter-residue resonances. Here solid-state magic-angle-spinning NMR spectra of the full length M2 protein embedded in synthetic lipid bilayers have been used to illustrate the resolution enhancement in the difference spectra. The integral membrane M2 protein of Influenza A virus assembles as a tetrameric bundle to form a proton-conducting channel that is activated by low pH and is essential for the viral lifecycle. Based on known amino acid resonance assignments from amino acid specific labeled samples of truncated M2 sequences or from time-consuming 3D experiments of uniformly labeled samples, some inter-residue resonances of the full length M2 protein can be identified in the difference spectra of uniformly (13)C labeled protein that are consistent with the high resolution structure of the M2 (22-62) protein (Sharma et al., Science 330(6003):509-512, 2010).
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Affiliation(s)
- Yimin Miao
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32310, USA
| | - Timothy A. Cross
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32310, USA
- National High Magnet Field Lab, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, USA
| | - Riqiang Fu
- National High Magnet Field Lab, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, USA
- Corresponding author: Riqiang Fu (), 1800 East Paul Dirac Drive, Tallahassee, FL 32310, Tel: +1 850 644 5044, Fax: +1 850 644 1366
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12
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Banigan JR, Gayen A, Traaseth NJ. Combination of ¹⁵N reverse labeling and afterglow spectroscopy for assigning membrane protein spectra by magic-angle-spinning solid-state NMR: application to the multidrug resistance protein EmrE. JOURNAL OF BIOMOLECULAR NMR 2013; 55:391-9. [PMID: 23539118 PMCID: PMC3747971 DOI: 10.1007/s10858-013-9724-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 03/15/2013] [Indexed: 05/20/2023]
Abstract
Magic-angle-spinning (MAS) solid-state NMR spectroscopy has emerged as a viable method to characterize membrane protein structure and dynamics. Nevertheless, the spectral resolution for uniformly labeled samples is often compromised by redundancy of the primary sequence and the presence of helical secondary structure that results in substantial resonance overlap. The ability to simplify the spectrum in order to obtain unambiguous site-specific assignments is a major bottleneck for structure determination. To address this problem, we used a combination of (15)N reverse labeling, afterglow spectroscopic techniques, and frequency-selective dephasing experiments that dramatically improved the ability to resolve peaks in crowded spectra. This was demonstrated using the polytopic membrane protein EmrE, an efflux pump involved in multidrug resistance. Residues preceding the (15)N reverse labeled amino acid were imaged using a 3D NCOCX afterglow experiment and those following were recorded using a frequency-selective dephasing experiment. Our approach reduced the spectral congestion and provided a sensitive way to obtain chemical shift assignments for a membrane protein where no high-resolution structure is available. This MAS methodology is widely applicable to the study of other polytopic membrane proteins in functional lipid bilayer environments.
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Affiliation(s)
| | | | - Nathaniel J. Traaseth
- Author for correspondence: Nathaniel J. Traaseth 100 Washington Square East New York, NY 10003 Phone: (212) 992-9784
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13
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Banigan JR, Traaseth NJ. Utilizing afterglow magnetization from cross-polarization magic-angle-spinning solid-state NMR spectroscopy to obtain simultaneous heteronuclear multidimensional spectra. J Phys Chem B 2012; 116:7138-44. [PMID: 22582831 PMCID: PMC3418334 DOI: 10.1021/jp303269m] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The time required for data acquisition and subsequent spectral assignment are limiting factors for determining biomolecular structure and dynamics using solid-state NMR spectroscopy. While strong magnetic dipolar couplings give rise to relatively broad spectra lines, the couplings also mediate the coherent magnetization transfer via the Hartmann-Hahn cross-polarization (HH-CP) experiment. This mechanism is used in nearly all backbone assignment experiments for carrying out polarization transfer between (1)H, (15)N, and (13)C. In this Article, we describe a general spectroscopic approach to use the residual or "afterglow" magnetization from the (15)N to (13)C selective HH-CP experiment to collect a second multidimensional heteronuclear data set. This approach allowed for the collection of two commonly used sequential assignment experiments (2D NCA and NCO or 3D NCACX and NCOCX) at the same time. Our "afterglow" technique was demonstrated with uniformly [(13)C,(15)N] and [1,3-(13)C] glycerol-labeled ubiquitin using instrumentation available on all standard solid-state NMR spectrometers configured for magic-angle-spinning. This method is compatible with several other sensitivity enhancement experiments and can be used as an isotopic filtering tool to reduce the spectral complexity and decrease the time needed for assignment.
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Affiliation(s)
- James R. Banigan
- Department of Chemistry, New York University, New York, NY 10003
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14
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Verardi R, Traaseth NJ, Masterson LR, Vostrikov VV, Veglia G. Isotope labeling for solution and solid-state NMR spectroscopy of membrane proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 992:35-62. [PMID: 23076578 PMCID: PMC3555569 DOI: 10.1007/978-94-007-4954-2_3] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In this chapter, we summarize the isotopic labeling strategies used to obtain high-quality solution and solid-state NMR spectra of biological samples, with emphasis on integral membrane proteins (IMPs). While solution NMR is used to study IMPs under fast tumbling conditions, such as in the presence of detergent micelles or isotropic bicelles, solid-state NMR is used to study the structure and orientation of IMPs in lipid vesicles and bilayers. In spite of the tremendous progress in biomolecular NMR spectroscopy, the homogeneity and overall quality of the sample is still a substantial obstacle to overcome. Isotopic labeling is a major avenue to simplify overlapped spectra by either diluting the NMR active nuclei or allowing the resonances to be separated in multiple dimensions. In the following we will discuss isotopic labeling approaches that have been successfully used in the study of IMPs by solution and solid-state NMR spectroscopy.
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Affiliation(s)
- Raffaello Verardi
- 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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