1
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Tong Q, Tan H, Li J, Xie H, Zhao Y, Chen Y, Yang J. Extensively sparse 13C labeling to simplify solid-state NMR 13C spectra of membrane proteins. JOURNAL OF BIOMOLECULAR NMR 2021; 75:245-254. [PMID: 34148188 DOI: 10.1007/s10858-021-00372-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Accepted: 06/08/2021] [Indexed: 06/12/2023]
Abstract
Solid-state Nuclear Magnetic Resonance (ssNMR) is an emerging technique to investigate the structures and dynamics of membrane proteins in an artificial or native membrane environment. However, the structural studies of proteins by ssNMR are usually prolonged or impeded by signal assignments, especially the assignments of signals for collection of distance restraints, because of serious overlapping of signals in 2D 13C-13C spectra. Sparse labeling of 13C spins is an effective approach to simplify the 13C spectra and facilitate the extractions of distance restraints. Here, we propose a new reverse labeling combination of six types of amino acid residues (Ile, Leu, Phe, Trp, Tyr and Lys), and show a clean reverse labeling effect on a model membrane protein E. coli aquaporin Z (AqpZ). We further combine this reverse labeling combination and alternate 13C-12C labeling, and demonstrate an enhanced dilution effect in 13C-13C spectra. In addition, the influences of reverse labeling on the labeling of the other types of residues are quantitatively analyzed in the two strategies (1, reverse labeling and 2, reverse labeling combining alternate 13C-12C labeling). The signal intensities of some other types of residues in 2D 13C-13C spectra are observed to be 20-50% weaker because of the unwanted reverse labeling. The extensively sparse 13C labeling proposed in this study is expected to be useful in the collection of distance restraints using 2D 13C-13C spectra of membrane proteins.
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Affiliation(s)
- Qiong Tong
- 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, People's Republic of China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China
| | - Huan Tan
- 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, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Jianping Li
- 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, People's Republic of China
| | - Huayong Xie
- 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, People's Republic of China
| | - Yongxiang Zhao
- 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, People's Republic of China
| | - Yanke Chen
- 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, People's Republic of 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, People's Republic of China.
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.
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2
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Kupče Ē, Mote KR, Webb A, Madhu PK, Claridge TDW. Multiplexing experiments in NMR and multi-nuclear MRI. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2021; 124-125:1-56. [PMID: 34479710 DOI: 10.1016/j.pnmrs.2021.03.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 02/28/2021] [Accepted: 03/02/2021] [Indexed: 05/22/2023]
Abstract
Multiplexing NMR experiments by direct detection of multiple free induction decays (FIDs) in a single experiment offers a dramatic increase in the spectral information content and often yields significant improvement in sensitivity per unit time. Experiments with multi-FID detection have been designed with both homonuclear and multinuclear acquisition, and the advent of multiple receivers on commercial spectrometers opens up new possibilities for recording spectra from different nuclear species in parallel. Here we provide an extensive overview of such techniques, designed for applications in liquid- and solid-state NMR as well as in hyperpolarized samples. A brief overview of multinuclear MRI is also provided, to stimulate cross fertilization of ideas between the two areas of research (NMR and MRI). It is shown how such techniques enable the design of experiments that allow structure elucidation of small molecules from a single measurement. Likewise, in biomolecular NMR experiments multi-FID detection allows complete resonance assignment in proteins. Probes with multiple RF microcoils routed to multiple NMR receivers provide an alternative way of increasing the throughput of modern NMR systems, effectively reducing the cost of NMR analysis and increasing the information content at the same time. Solid-state NMR experiments have also benefited immensely from both parallel and sequential multi-FID detection in a variety of multi-dimensional pulse schemes. We are confident that multi-FID detection will become an essential component of future NMR methodologies, effectively increasing the sensitivity and information content of NMR measurements.
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Affiliation(s)
- Ēriks Kupče
- Bruker UK Ltd., Banner Lane, Coventry CV4 9GH, United Kingdom.
| | - Kaustubh R Mote
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research-Hyderabad, 36/P Gopanpally Village, Ranga Reddy District, Hyderabad 500 046, Telangana, India
| | - Andrew Webb
- Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, Netherlands
| | - Perunthiruthy K Madhu
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research-Hyderabad, 36/P Gopanpally Village, Ranga Reddy District, Hyderabad 500 046, Telangana, India
| | - Tim D W Claridge
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, UK
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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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5
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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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Kupče Ē, Mote KR, Madhu PK. Experiments with direct detection of multiple FIDs. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 304:16-34. [PMID: 31077929 DOI: 10.1016/j.jmr.2019.04.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 03/26/2019] [Accepted: 04/29/2019] [Indexed: 05/04/2023]
Abstract
Pulse schemes with direct observation of multiple free induction decays (FIDs) offer a dramatic increase in the spectral information content of NMR experiments and often yield substantial improvement in measurement sensitivity per unit time. Availability of multiple receivers on the state-of-the-art commercial spectrometers allows spectra from different nuclear species to be recorded in parallel routinely. Experiments with multi-FID detection have been designed with both, homonuclear and multinuclear acquisition. We provide a brief overview of such techniques designed for applications in liquid- and solid- state NMR as well as in hyperpolarized samples. Here we show how these techniques have led to design of experiments that allow structure elucidation of small molecules and resonance assignment in proteins from a single measurement. Probes with multiple RF micro-coils routed to multiple NMR receivers provide an alternative way of increasing the throughput of modern NMR systems. Solid-state NMR experiments have also benefited immensely from both parallel and simultaneous FID acquisition in a variety of multi-dimensional pulse schemes. We believe that multi-FID detection will become an essential component of the future NMR methodologies effectively increasing the information content of NMR experiments and reducing the cost of NMR analysis.
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Affiliation(s)
- Ēriks Kupče
- Bruker UK Ltd., Banner Lane, Coventry CV4 9GH, United Kingdom.
| | - Kaustubh R Mote
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research Hyderabad, 36/P Gopanpally Village, Ranga Reddy District, Hyderabad 500107, India
| | - Perunthiruthy K Madhu
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research Hyderabad, 36/P Gopanpally Village, Ranga Reddy District, Hyderabad 500107, India
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7
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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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8
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Banigan JR, Leninger M, Her AS, Traaseth NJ. Assessing Interactions Between a Polytopic Membrane Protein and Lipid Bilayers Using Differential Scanning Calorimetry and Solid-State NMR. J Phys Chem B 2018; 122:2314-2322. [PMID: 29457729 DOI: 10.1021/acs.jpcb.8b00479] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It is known that the lipid composition within a cellular membrane can influence membrane protein structure and function. In this Article, we investigated how structural changes to a membrane protein upon substrate binding can impact the lipid bilayer. To carry out this study, we reconstituted the secondary active drug transporter EmrE into a variety of phospholipid bilayers varying in headgroup and chain length and carried out differential scanning calorimetry (DSC) and solid-state NMR experiments. The DSC results revealed a difference in cooperativity of the lipid phase transition for drug-free EmrE protonated at glutamic acid 14 (i.e., proton-loaded form) and the tetraphenylphosphonium (TPP+) bound form of the protein (i.e., drug-loaded form). To complement these findings, we acquired magic-angle-spinning (MAS) spectra in the presence and absence of TPP+ by directly probing the phospholipid headgroup using 31P NMR. These spectra showed a reduction in lipid line widths around the main phase transition for samples where EmrE was bound to TPP+ compared to the drug free form. Finally, we collected oriented solid-state NMR spectra on isotopically enriched EmrE that displayed chemical shift perturbations to both transmembrane and loop residues upon TPP+ binding. All of these results prompt us to propose a mechanism whereby substrate-induced changes to the structural dynamics of EmrE alters the surrounding lipids within the bilayer.
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Affiliation(s)
- James R Banigan
- Department of Chemistry, New York University , New York, New York 10003, United States
| | - Maureen Leninger
- Department of Chemistry, New York University , New York, New York 10003, United States
| | - Ampon Sae Her
- Department of Chemistry, New York University , New York, New York 10003, United States
| | - Nathaniel J Traaseth
- Department of Chemistry, New York University , New York, New York 10003, United States
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9
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Abstract
Biomolecular solid-state NMR experiments have traditionally been collected through detection of 13C or 15N nuclei. Since these nuclei have relatively low sensitivity stemming from their smaller gyromagnetic ratios relative to 1H, the time required to collect multi-dimensional datasets serves as a limitation to resonance assignment and structure determination. One improvement in the field has been to employ simultaneous or parallel acquisition techniques with the goal of acquiring more than one dataset at a time and therefore speeding up the overall data collection process. Central to these experiments is the cross-polarization (CP) element, which serves as a way to transfer magnetization between nuclei via magnetic dipolar couplings. In this chapter, we show how residual signal remaining after CP is a polarization source that can be used to acquire additional datasets. The setup of this class of experiments, referred to as Afterglow spectroscopy, is described and demonstrated using a membrane protein transporter involved in multidrug resistance.
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Affiliation(s)
- Gili Abramov
- 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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10
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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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11
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Sharma K, Madhu PK, Mote KR. A suite of pulse sequences based on multiple sequential acquisitions at one and two radiofrequency channels for solid-state magic-angle spinning NMR studies of proteins. JOURNAL OF BIOMOLECULAR NMR 2016; 65:127-141. [PMID: 27364976 DOI: 10.1007/s10858-016-0043-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 06/14/2016] [Indexed: 05/04/2023]
Abstract
One of the fundamental challenges in the application of solid-state NMR is its limited sensitivity, yet a majority of experiments do not make efficient use of the limited polarization available. The loss in polarization in a single acquisition experiment is mandated by the need to select out a single coherence pathway. In contrast, sequential acquisition strategies can encode more than one pathway in the same experiment or recover unused polarization to supplement a standard experiment. In this article, we present pulse sequences that implement sequential acquisition strategies on one and two radiofrequency channels with a combination of proton and carbon detection to record multiple experiments under magic-angle spinning. We show that complementary 2D experiments such as [Formula: see text] and [Formula: see text] or DARR and [Formula: see text], and 3D experiments such as [Formula: see text] and [Formula: see text], or [Formula: see text] and [Formula: see text] can be combined in a single experiment to ensure time savings of at least 40 %. These experiments can be done under fast or slow-moderate magic-angle spinning frequencies aided by windowed [Formula: see text] acquisition and homonulcear decoupling. The pulse sequence suite is further expanded by including pathways that allow the recovery of residual polarization, the so-called 'afterglow' pathways, to encode a number of pulse sequences to aid in assignments and chemical-shift mapping.
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Affiliation(s)
- Kshama Sharma
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad, 21, Brundavan Colony, Narsingi, Hyderabad, 500 075, India
| | - Perunthiruthy K Madhu
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad, 21, Brundavan Colony, Narsingi, Hyderabad, 500 075, India.
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, 400 005, India.
| | - Kaustubh R Mote
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad, 21, Brundavan Colony, Narsingi, Hyderabad, 500 075, India.
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12
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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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14
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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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15
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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
- To whom correspondence should be addressed: Gianluigi Veglia, Department of Biochemistry, Biophysics, and Molecular Biology, University of Minnesota, 6-155 Jackson Hall, MN 55455. Telephone: (612) 625-0758. Fax: (612) 625-2163.
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16
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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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17
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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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18
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Demers JP, Vijayan V, Lange A. Recovery of Bulk Proton Magnetization and Sensitivity Enhancement in Ultrafast Magic-Angle Spinning Solid-State NMR. J Phys Chem B 2015; 119:2908-20. [DOI: 10.1021/jp511987y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Jean-Philippe Demers
- Department of NMR-Based Structural
Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Vinesh Vijayan
- Department of NMR-Based Structural
Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Adam Lange
- Department of NMR-Based Structural
Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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19
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Prasanna C, Dubey A, Atreya HS. Amino Acid Selective Unlabeling in Protein NMR Spectroscopy. Methods Enzymol 2015; 565:167-89. [DOI: 10.1016/bs.mie.2015.05.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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20
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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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21
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Cho MK, Gayen A, Banigan J, Leninger M, Traaseth NJ. Intrinsic conformational plasticity of native EmrE provides a pathway for multidrug resistance. J Am Chem Soc 2014; 136:8072-80. [PMID: 24856154 PMCID: PMC4063181 DOI: 10.1021/ja503145x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Indexed: 12/24/2022]
Abstract
EmrE is a multidrug resistance efflux pump with specificity to a wide range of antibiotics and antiseptics. To obtain atomic-scale insight into the attributes of the native state that encodes the broad specificity, we used a hybrid of solution and solid-state NMR methods in lipid bilayers and bicelles. Our results indicate that the native EmrE dimer oscillates between inward and outward facing structural conformations at an exchange rate (k(ex)) of ~300 s(-1) at 37 °C (millisecond motions), which is ~50-fold faster relative to the tetraphenylphosphonium (TPP(+)) substrate-bound form of the protein. These observables provide quantitative evidence that the rate-limiting step in the TPP(+) transport cycle is not the outward-inward conformational change in the absence of drug. In addition, using differential scanning calorimetry, we found that the width of the gel-to-liquid crystalline phase transition was 2 °C broader in the absence of the TPP(+) substrate versus its presence, which suggested that changes in transporter dynamics can impact the phase properties of the membrane. Interestingly, experiments with cross-linked EmrE showed that the millisecond inward-open to outward-open dynamics was not the culprit of the broadening. Instead, the calorimetry and NMR data supported the conclusion that faster time scale structural dynamics (nanosecond-microsecond) were the source and therefore impart the conformationally plastic character of native EmrE capable of binding structurally diverse substrates. These findings provide a clear example how differences in membrane protein transporter structural dynamics between drug-free and bound states can have a direct impact on the physical properties of the lipid bilayer in an allosteric fashion.
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Affiliation(s)
| | | | - James
R. Banigan
- Department of Chemistry, New York University, New York, New York 10003, United States
| | - Maureen Leninger
- Department of Chemistry, New York University, New York, New York 10003, United States
| | - Nathaniel J. Traaseth
- Department of Chemistry, New York University, New York, New York 10003, United States
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22
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Banigan JR, Gayen A, Traaseth NJ. Correlating lipid bilayer fluidity with sensitivity and resolution of polytopic membrane protein spectra by solid-state NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:334-41. [PMID: 24835018 DOI: 10.1016/j.bbamem.2014.05.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 04/26/2014] [Accepted: 05/04/2014] [Indexed: 11/17/2022]
Abstract
Solid-state NMR spectroscopy has emerged as an excellent tool to study the structure and dynamics of membrane proteins under native-like conditions in lipid bilayers. One of the key considerations in experimental design is the uniaxial rotational diffusion of the protein that can affect the NMR spectral observables. In this regard, temperature plays a fundamental role in modulating the phase properties of the lipids, which directly influences the rotational diffusion rate of the protein in the bilayer. In fact, it is well established that below the main phase transition temperature of the lipid bilayer the protein's motion is significantly slowed while above this critical temperature the rate is increased. In this article, we carried out a systematic comparison of the signal intensity and spectral resolution as a function of temperature using magic-angle-spinning (MAS) solid-state NMR spectroscopy. These observables were directly correlated with the relative fluidity of the lipid bilayer as inferred from differential scanning calorimetry (DSC). We applied our hybrid biophysical approach to two polytopic membrane proteins from the small multidrug resistance family (EmrE and SugE) reconstituted into model membrane lipid bilayers (DMPC-14:0 and DPPC-16:0). From these experiments, we conclude that the rotational diffusion giving optimal spectral resolution occurs at a bilayer fluidity of ~5%, which corresponds to the percentage of lipids in the fluid or liquid-crystalline fraction. At the temperature corresponding to this critical value of fluidity, there is sufficient mobility to reduce inhomogeneous line broadening that occurs at lower temperatures. A greater extent of fluidity leads to faster uniaxial rotational diffusion and a sigmoidal-type reduction in the NMR signal intensity, which stems from intermediate-exchange dynamics where the motion has a similar frequency as the NMR observables (i.e., dipolar couplings and chemical shift anisotropy). These experiments provide insight into the optimal temperature range and corresponding bilayer fluidity to study membrane proteins by solid-state NMR spectroscopy.
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Affiliation(s)
- James R Banigan
- Department of Chemistry, New York University, New York, NY 10003
| | - Anindita Gayen
- Department of Chemistry, New York University, New York, NY 10003
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23
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EmrE dimerization depends on membrane environment. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1817-22. [PMID: 24680655 DOI: 10.1016/j.bbamem.2014.03.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 03/14/2014] [Accepted: 03/18/2014] [Indexed: 11/22/2022]
Abstract
The small multi-drug resistant (SMR) transporter EmrE functions as a homodimer. Although the small size of EmrE would seem to make it an ideal model system, it can also make it challenging to work with. As a result, a great deal of controversy has surrounded even such basic questions as the oligomeric state. Here we show that the purified protein is a homodimer in isotropic bicelles with a monomer-dimer equilibrium constant (KMD(2D)) of 0.002-0.009mol% for both the substrate-free and substrate-bound states. Thus, the dimer is stabilized in bicelles relative to detergent micelles where the KMD(2D) is only 0.8-0.95mol% (Butler et al. 2004). In dilauroylphosphatidylcholine (DLPC) liposomes KMD(2D) is 0.0005-0.0008mol% based on Förster resonance energy transfer (FRET) measurements, slightly tighter than bicelles. These results emphasize the importance of the lipid membrane in influencing dimer affinity.
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24
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Lu GJ, Opella SJ. Resonance assignments of a membrane protein in phospholipid bilayers by combining multiple strategies of oriented sample solid-state NMR. JOURNAL OF BIOMOLECULAR NMR 2014; 58:69-81. [PMID: 24356892 PMCID: PMC3928288 DOI: 10.1007/s10858-013-9806-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 12/12/2013] [Indexed: 06/01/2023]
Abstract
Oriented sample solid-state NMR spectroscopy can be used to determine the three-dimensional structures of membrane proteins in magnetically or mechanically aligned lipid bilayers. The bottleneck for applying this technique to larger and more challenging proteins is making resonance assignments, which is conventionally accomplished through the preparation of multiple selectively isotopically labeled samples and performing an analysis of residues in regular secondary structure based on Polarity Index Slant Angle (PISA) Wheels and Dipolar Waves. Here we report the complete resonance assignment of the full-length mercury transporter, MerF, an 81-residue protein, which is challenging because of overlapping PISA Wheel patterns from its two trans-membrane helices, by using a combination of solid-state NMR techniques that improve the spectral resolution and provide correlations between residues and resonances. These techniques include experiments that take advantage of the improved resolution of the MSHOT4-Pi4/Pi pulse sequence; the transfer of resonance assignments through frequency alignment of heteronuclear dipolar couplings, or through dipolar coupling correlated isotropic chemical shift analysis; (15)N/(15)N dilute spin exchange experiments; and the use of the proton-evolved local field experiment with isotropic shift analysis to assign the irregular terminal and loop regions of the protein, which is the major "blind spot" of the PISA Wheel/Dipolar Wave method.
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25
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Bellstedt P, Seiboth T, Häfner S, Kutscha H, Ramachandran R, Görlach M. Resonance assignment for a particularly challenging protein based on systematic unlabeling of amino acids to complement incomplete NMR data sets. JOURNAL OF BIOMOLECULAR NMR 2013; 57:65-72. [PMID: 23943084 DOI: 10.1007/s10858-013-9768-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 08/03/2013] [Indexed: 06/02/2023]
Abstract
NMR-based structure determination of a protein requires the assignment of resonances as indispensable first step. Even though heteronuclear through-bond correlation methods are available for that purpose, challenging situations arise in cases where the protein in question only yields samples of limited concentration and/or stability. Here we present a strategy based upon specific individual unlabeling of all 20 standard amino acids to complement standard NMR experiments and to achieve unambiguous backbone assignments for the fast precipitating 23 kDa catalytic domain of human aprataxin of which only incomplete standard NMR data sets could be obtained. Together with the validation of this approach utilizing the protein GB1 as a model, a comprehensive insight into metabolic interconversion ("scrambling") of NH and CO groups in a standard Escherichia coli expression host is provided.
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Affiliation(s)
- Peter Bellstedt
- Biomolecular NMR Spectroscopy, Leibniz Institute for Age Research, Fritz Lipmann Institute, Beutenbergstr. 11, 07745, Jena, Germany.
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26
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Gayen A, Banigan JR, Traaseth NJ. Ligand-induced conformational changes of the multidrug resistance transporter EmrE probed by oriented solid-state NMR spectroscopy. Angew Chem Int Ed Engl 2013; 52:10321-4. [PMID: 23939862 DOI: 10.1002/anie.201303091] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 07/12/2013] [Indexed: 11/10/2022]
Affiliation(s)
- Anindita Gayen
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003 (USA) http://www.nyu.edu/fas/dept/chemistry/traasethgroup/
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27
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Gayen A, Banigan JR, Traaseth NJ. Ligand-Induced Conformational Changes of the Multidrug Resistance Transporter EmrE Probed by Oriented Solid-State NMR Spectroscopy. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201303091] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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