1
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van Aalst EJ, Jang J, Halligan TC, Wylie BJ. Strategies for acquisition of resonance assignment spectra of highly dynamic membrane proteins: a GPCR case study. JOURNAL OF BIOMOLECULAR NMR 2023; 77:191-202. [PMID: 37493866 PMCID: PMC10838152 DOI: 10.1007/s10858-023-00421-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Accepted: 07/11/2023] [Indexed: 07/27/2023]
Abstract
In protein nuclear magnetic resonance (NMR), chemical shift assignment provides a wealth of information. However, acquisition of high-quality solid-state NMR spectra depends on protein-specific dynamics. For membrane proteins, bilayer heterogeneity further complicates this observation. Since the efficiency of cross-polarization transfer is strongly entwined with protein dynamics, optimal temperatures for spectral sensitivity and resolution will depend not only on inherent protein dynamics, but temperature-dependent phase properties of the bilayer environment. We acquired 1-, 2-, and 3D homo- and heteronuclear experiments of the chemokine receptor CCR3 in a 7:3 phosphatidylcholine:cholesterol lipid environment. 1D direct polarization, cross polarization (CP), and T2' experiments indicate sample temperatures below - 25 °C facilitate higher CP enhancement and longer-lived transverse relaxation times. T1rho experiments indicate intermediate timescales are minimized below a sample temperature of - 20 °C. 2D DCP NCA experiments indicated optimal CP efficiency and resolution at a sample temperature of - 30 °C, corroborated by linewidth analysis in 3D NCACX at - 30 °C compared to - 5 °C. This optimal temperature is concluded to be directly related the lipid phase transition, measured to be between - 20 and 15 °C based on rINEPT signal of all-trans and trans-gauche lipid acyl conformations. Our results have critical implications in acquisition of SSNMR membrane protein assignment spectra, as we hypothesize that different lipid compositions with different phase transition properties influence protein dynamics and therefore the optimal acquisition temperature.
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Affiliation(s)
- Evan J van Aalst
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79415, USA
| | - Jun Jang
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79415, USA
| | - Ty C Halligan
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79415, USA
| | - Benjamin J Wylie
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79415, USA.
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2
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van Aalst EJ, Borcik CG, Wylie BJ. Spectroscopic signatures of bilayer ordering in native biological membranes. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183891. [PMID: 35217001 PMCID: PMC10793244 DOI: 10.1016/j.bbamem.2022.183891] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
Membrane proteins and polycyclic lipids like cholesterol and hopanoids coordinate phospholipid bilayer ordering. This phenomenon manifests as partitioning of the liquid crystalline phase into liquid-ordered (Lo) and liquid-disordered (Ld) regions. In Eukaryotes, microdomains are rich in cholesterol and sphingolipids and serve as signal transduction scaffolds. In Prokaryotes, Lo microdomains increase pathogenicity and antimicrobial resistance. Previously, we identified spectroscopically distinct chemical shift signatures for all-trans (AT) and trans-gauche (TG) acyl chain conformations, cyclopropyl ring lipids (CPR), and hopanoids in prokaryotic lipid extracts and used Polarization Transfer (PT) SSNMR to investigate bilayer ordering. To investigate how these findings relate to native bilayer organization, we interrogate whole cell and whole membrane extract samples of Burkholderia thailendensis to investigate bilayer ordering in situ. In 13C-13C 2D SSNMR spectra, we assigned chemical shifts for lipid species in both samples, showing conservation of lipids of interest in our native membrane sample. A one-dimensional temperature series of PT SSNMR and transverse relaxation measurements of AT versus TG acyl conformations in the membrane sample confirm bilayer ordering and a broadened phase transition centered at a lower-than-expected temperature. Bulk protein backbone Cα dynamics and correlations consistent with lipid-protein contacts within are further indicative of microdomain formation and lipid ordering. In aggregate, these findings provide evidence for microdomain formation in vivo and provide insight into phase separation and transition mechanics in biological membranes.
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Affiliation(s)
- Evan J van Aalst
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79415, USA
| | - Collin G Borcik
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79415, USA
| | - Benjamin J Wylie
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79415, USA.
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3
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Tan H, Zhao Y, Zhao W, Xie H, Chen Y, Tong Q, Yang J. Dynamics properties of membrane proteins in native cell membranes revealed by solid-state NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2022; 1864:183791. [PMID: 34624277 DOI: 10.1016/j.bbamem.2021.183791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/17/2021] [Accepted: 09/20/2021] [Indexed: 11/17/2022]
Abstract
Cell membranes provide an environment that is essential to the functions of membrane proteins. Cell membranes are mainly composed of proteins and highly diverse phospholipids. The influence of diverse lipid compositions of native cell membranes on the dynamics of the embedded membrane proteins has not been examined. Here we employ solid-state NMR to investigate the dynamics of E. coli Aquaporin Z (AqpZ) in its native inner cell membranes, and reveal the influence of diverse lipid compositions on the dynamics of AqpZ by comparing it in native cell membranes to that in POPC/POPG bilayers. We demonstrate that the dynamic rigidity of AqpZ generally conserves in both native cell membranes and POPC/POPG bilayers, due to its tightly packed tetrameric structure. In the gel and the liquid crystal phases of lipids, our experimental results show that AqpZ is more dynamic in native cell membranes than that in POPC/POPG bilayers. In addition, we observe that phase transitions of lipids in native membranes are less sensitive to temperature variations compared with that in POPC/POPG bilayers, which results in that the dynamics of AqpZ is less affected by the phase transitions of lipids in native cell membranes than that in POPC/POPG bilayers. This study provides new insights into the dynamics of membrane proteins in native cell membranes.
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Affiliation(s)
- 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, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR 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, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Weijing 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, PR 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, PR 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, PR China
| | - 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, PR China; Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, PR 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, PR China; Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, PR China.
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4
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Borcik CG, Versteeg DB, Wylie BJ. An Inward-Rectifier Potassium Channel Coordinates the Properties of Biologically Derived Membranes. Biophys J 2019; 116:1701-1718. [PMID: 31010661 DOI: 10.1016/j.bpj.2019.03.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 03/20/2019] [Accepted: 03/25/2019] [Indexed: 12/13/2022] Open
Abstract
KirBac1.1 is a prokaryotic inward-rectifier K+ channel from Burkholderia pseudomallei. It shares the common inward-rectifier K+ channel fold with eukaryotic channels, including conserved lipid-binding pockets. Here, we show that KirBac1.1 changes the phase properties and dynamics of the surrounding bilayer. KirBac1.1 was reconstituted into vesicles composed of 13C-enriched biological lipids. Two-dimensional liquid-state and solid-state NMR experiments were used to assign lipid 1H and 13C chemical shifts as a function of lipid identity and conformational degrees of freedom. A solid-state NMR temperature series reveals that KirBac1.1 lowers the primary thermotropic phase transition of Escherichia coli lipid membranes while introducing both fluidity and internal lipid order into the fluid phases. In B. thailandensis liposomes, the bacteriohopanetetrol hopanoid, and potentially ornithine lipids, introduce a similar primary lipid-phase transition and liquid-ordered properties. Adding KirBac1.1 to B. thailandensis lipids increases B. thailandensis lipid fluidity while preserving internal lipid order. This synergistic effect of KirBac1.1 in bacteriohopanetetrol-rich membranes has implications for bilayer dynamic structure. If membrane proteins can anneal lipid translational degrees of freedom while preserving internal order, it could offer an explanation to the nature of liquid-ordered protein-lipid organization in vivo.
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Affiliation(s)
- Collin G Borcik
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas
| | - Derek B Versteeg
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas
| | - Benjamin J Wylie
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas.
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5
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Li M, Mandal A, Tyurin VA, DeLucia M, Ahn J, Kagan VE, van der Wel PCA. Surface-Binding to Cardiolipin Nanodomains Triggers Cytochrome c Pro-apoptotic Peroxidase Activity via Localized Dynamics. Structure 2019; 27:806-815.e4. [PMID: 30879887 DOI: 10.1016/j.str.2019.02.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 01/16/2019] [Accepted: 02/15/2019] [Indexed: 02/06/2023]
Abstract
The peroxidation of cardiolipins by reactive oxygen species, which is regulated and enhanced by cytochrome c (cyt c), is a critical signaling event in mitochondrial apoptosis. We probe the molecular underpinnings of this mitochondrial death signal through structural and functional studies of horse heart cyt c binding to mixed-lipid membranes containing cardiolipin with mono- and polyunsaturated acyl chains. Lipidomics reveal the selective oxidation of polyunsaturated fatty acid (PUFA) cardiolipin (CL), while multidimensional solid-state NMR probes the structure and dynamics of the membrane and the peripherally bound protein. The hydrophilic milieu at the membrane interface stabilizes a native-like fold, but also leads to localized flexibility at the membrane-interacting protein face. PUFA CL acts as both a preferred substrate and a dynamic regulator by affecting the dynamics of the cyt c N70-I85 Ω loop, which covers the heme cavity.
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Affiliation(s)
- Mingyue Li
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Abhishek Mandal
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Vladimir A Tyurin
- Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Maria DeLucia
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jinwoo Ahn
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Valerian E Kagan
- Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Radiation Oncology, University of Pittsburgh, Pittsburgh, PA 15213, USA; Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA 15213, USA; Laboratory of Navigational Redox Lipidomics, IM Sechenov Moscow State Medical University, Moscow 119146, Russian Federation
| | - Patrick C A van der Wel
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA; Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands.
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6
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Yari H, Nkepang G, Awasthi V. Surface Modification of Liposomes by a Lipopolymer Targeting Prostate Specific Membrane Antigen for Theranostic Delivery in Prostate Cancer. MATERIALS 2019; 12:ma12050756. [PMID: 30841602 PMCID: PMC6427334 DOI: 10.3390/ma12050756] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 02/25/2019] [Accepted: 02/27/2019] [Indexed: 01/16/2023]
Abstract
Prostate specific membrane antigen (PSMA) is a marker for diagnosis and targeted delivery of therapeutics to advanced/metastasized prostate cancer. We report a liposome-based system for theranostic delivery to PSMA-expressing (PSMA+) LNCaP cells. A lipopolymer (P3) comprising of PSMA ligand (PSMAL), polyethylene glycol (PEG2000), and palmitate was synthesized and post-inserted into the surface of preformed liposomes. These P3-liposomes were loaded with doxorubicin and radiolabeled with 99mTc radionuclide to study their theranostic characteristics. Differential expression of PSMA on LNCaP and PC3 cells was confirmed by immunoblotting as well as by uptake of PSMAL labeled with 18F radionuclide. We found that the uptake of 99mTc-labeled P3-liposomes by LNCaP cells was >3-fold higher than 99mTc-labeled Plain-liposomes; the amount of doxorubicin delivered to LNCaP cells was also found to be >3-fold higher by P3-liposomes. Cell-based cytotoxicity assay results showed that doxorubicin-loaded P3-liposomes were significantly more toxic to LNCaP cells (p < 0.05), but not to PSMA-negative PC3 cells. Compared to doxorubicin-loaded Plain-liposomes, the IC50 value of doxorubicin-loaded P3-liposomes was reduced by ~5-fold in LNCaP cells. Together, these results suggest that surface functionalization of liposomes with small PSMA-binding motifs, such as PSMAL, can provide a viable platform for specific delivery of theranostics to PSMA+ prostate cancer.
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Affiliation(s)
- Hooman Yari
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, 1110 North Stonewall Avenue, Oklahoma City, OK 73117, USA.
| | - Gregory Nkepang
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, 1110 North Stonewall Avenue, Oklahoma City, OK 73117, USA.
| | - Vibhudutta Awasthi
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, 1110 North Stonewall Avenue, Oklahoma City, OK 73117, USA.
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7
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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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8
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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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9
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Leninger M, Traaseth NJ. NMR Spectroscopy Approach to Study the Structure, Orientation, and Mechanism of the Multidrug Exporter EmrE. Methods Mol Biol 2018; 1700:83-96. [PMID: 29177827 PMCID: PMC5926179 DOI: 10.1007/978-1-4939-7454-2_6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Multidrug exporters are a class of membrane proteins that remove antibiotics from the cytoplasm of bacteria and in the process confer multidrug resistance to the organism. This chapter outlines the sample preparation and optimization of oriented solid-state NMR experiments applied to the study of structure and dynamics for the model transporter EmrE from the small multidrug resistance (SMR) family.
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Affiliation(s)
- Maureen Leninger
- 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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Dingeldein APG, Pokorná Š, Lidman M, Sparrman T, Šachl R, Hof M, Gröbner G. Apoptotic Bax at Oxidatively Stressed Mitochondrial Membranes: Lipid Dynamics and Permeabilization. Biophys J 2017; 112:2147-2158. [PMID: 28538152 DOI: 10.1016/j.bpj.2017.04.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 02/23/2017] [Accepted: 04/05/2017] [Indexed: 12/20/2022] Open
Abstract
Mitochondria are crucial compartments of eukaryotic cells because they function as the cellular power plant and play a central role in the early stages of programmed cell death (apoptosis). To avoid undesired cell death, this apoptotic pathway is tightly regulated by members of the Bcl-2 protein family, which interact on the external surface of the mitochondria, i.e., the mitochondrial outer membrane (MOM), and modulate its permeability to apoptotic factors, controlling their release into the cytosol. A growing body of evidence suggests that the MOM lipids play active roles in this permeabilization process. In particular, oxidized phospholipids (OxPls) formed under intracellular stress seem to directly induce apoptotic activity at the MOM. Here we show that the process of MOM pore formation is sensitive to the type of OxPls species that are generated. We created MOM-mimicking liposome systems, which resemble the cellular situation before apoptosis and upon triggering of oxidative stress conditions. These vesicles were studied using 31P solid-state magic-angle-spinning nuclear magnetic resonance spectroscopy and differential scanning calorimetry, together with dye leakage assays. Direct polarization and cross-polarization nuclear magnetic resonance experiments enabled us to probe the heterogeneity of these membranes and their associated molecular dynamics. The addition of apoptotic Bax protein to OxPls-containing vesicles drastically changed the membranes' dynamic behavior, almost completely negating the previously observed effect of temperature on the lipids' molecular dynamics and inducing an ordering effect that led to more cooperative membrane melting. Our results support the hypothesis that the mitochondrion-specific lipid cardiolipin functions as a first contact site for Bax during its translocation to the MOM in the onset of apoptosis. In addition, dye leakage assays revealed that different OxPls species in the MOM-mimicking vesicles can have opposing effects on Bax pore formation.
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Affiliation(s)
| | - Šárka Pokorná
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Lidman
- Department of Chemistry, Umeå University, Umeå, Sweden
| | | | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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11
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Lakomek NA, Frey L, Bibow S, Böckmann A, Riek R, Meier BH. Proton-Detected NMR Spectroscopy of Nanodisc-Embedded Membrane Proteins: MAS Solid-State vs Solution-State Methods. J Phys Chem B 2017; 121:7671-7680. [PMID: 28737919 DOI: 10.1021/acs.jpcb.7b06944] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The structural and dynamical characterization of membrane proteins in a lipid bilayer at physiological pH and temperature and free of crystal constraints is crucial for the elucidation of a structure/dynamics-activity relationship. Toward this aim, we explore here the properties of the outer-membrane protein OmpX embedded in lipid bilayer nanodiscs using proton-detected magic angle spinning (MAS) solid-state NMR at 60 and 110 kHz. [1H,15N]-correlation spectra overlay well with the corresponding solution-state NMR spectra. Line widths as well as line intensities in solid and solution both depend critically on the sample temperature and, in particular, on the crossing of the lipid phase transition temperature. MAS (110 kHz) experiments yield well-resolved NMR spectra also for fully protonated OmpX and both below and above the lipid phase transition temperature.
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Affiliation(s)
| | - Lukas Frey
- ETH Zürich , Physical Chemistry, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Stefan Bibow
- ETH Zürich , Physical Chemistry, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Anja Böckmann
- Institut de Biologie et Chimie des Protéines, Bases Moléculaires et Structurales des Systèmes Infectieux, Labex Ecofect, UMR 5086 CNRS, Université de Lyon , 7 passage du Vercors, 69367 Lyon, France
| | - Roland Riek
- ETH Zürich , Physical Chemistry, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Beat H Meier
- ETH Zürich , Physical Chemistry, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
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12
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Mandal A, van der Wel PCA. MAS 1H NMR Probes Freezing Point Depression of Water and Liquid-Gel Phase Transitions in Liposomes. Biophys J 2017; 111:1965-1973. [PMID: 27806278 DOI: 10.1016/j.bpj.2016.09.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 09/09/2016] [Accepted: 09/21/2016] [Indexed: 10/20/2022] Open
Abstract
The lipid bilayer typical of hydrated biological membranes is characterized by a liquid-crystalline, highly dynamic state. Upon cooling or dehydration, these membranes undergo a cooperative transition to a rigidified, more-ordered, gel phase. This characteristic phase transition is of significant biological and biophysical interest, for instance in studies of freezing-tolerant organisms. Magic-angle-spinning (MAS) solid-state NMR (ssNMR) spectroscopy allows for the detection and characterization of the phase transitions over a wide temperature range. In this study we employ MAS 1H NMR to probe the phase transitions of both solvent molecules and different hydrated phospholipids, including tetraoleoyl cardiolipin (TOCL) and several phosphatidylcholine lipid species. The employed MAS NMR sample conditions cause a previously noted substantial reduction in the freezing point of the solvent phase. The effect on the solvent is caused by confinement of the aqueous solvent in the small and densely packed MAS NMR samples. In this study we report and examine how the freezing point depression also impacts the lipid phase transition, causing a ssNMR-observed reduction in the lipids' melting temperature (Tm). The molecular underpinnings of this phenomenon are discussed and compared with previous studies of membrane-associated water phases and the impact of membrane-protective cryoprotectants.
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Affiliation(s)
- Abhishek Mandal
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Patrick C A van der Wel
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
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13
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Saurel O, Iordanov I, Nars G, Demange P, Le Marchand T, Andreas LB, Pintacuda G, Milon A. Local and Global Dynamics in Klebsiella pneumoniae Outer Membrane Protein a in Lipid Bilayers Probed at Atomic Resolution. J Am Chem Soc 2017; 139:1590-1597. [DOI: 10.1021/jacs.6b11565] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Olivier Saurel
- Institut de Pharmacologie
et de Biologie Structurale (CNRS/Université Paul Sabatier),
Université de Toulouse, 31077 Toulouse, France
| | - Iordan Iordanov
- Institut de Pharmacologie
et de Biologie Structurale (CNRS/Université Paul Sabatier),
Université de Toulouse, 31077 Toulouse, France
| | - Guillaume Nars
- Institut de Pharmacologie
et de Biologie Structurale (CNRS/Université Paul Sabatier),
Université de Toulouse, 31077 Toulouse, France
| | - Pascal Demange
- Institut de Pharmacologie
et de Biologie Structurale (CNRS/Université Paul Sabatier),
Université de Toulouse, 31077 Toulouse, France
| | - Tanguy Le Marchand
- Institut de Sciences
Analytiques (UMR 5280 CNRS/ENS-Lyon/UCB Lyon 1), Université
de Lyon, 69007 Lyon, France
| | - Loren B. Andreas
- Institut de Sciences
Analytiques (UMR 5280 CNRS/ENS-Lyon/UCB Lyon 1), Université
de Lyon, 69007 Lyon, France
| | - Guido Pintacuda
- Institut de Sciences
Analytiques (UMR 5280 CNRS/ENS-Lyon/UCB Lyon 1), Université
de Lyon, 69007 Lyon, France
| | - Alain Milon
- Institut de Pharmacologie
et de Biologie Structurale (CNRS/Université Paul Sabatier),
Université de Toulouse, 31077 Toulouse, France
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14
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Warnet XL, Laadhari M, Arnold AA, Marcotte I, Warschawski DE. A 2H magic-angle spinning solid-state NMR characterisation of lipid membranes in intact bacteria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:146-52. [DOI: 10.1016/j.bbamem.2015.10.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 10/06/2015] [Accepted: 10/26/2015] [Indexed: 10/22/2022]
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15
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Affiliation(s)
- Charles R Sanders
- Department of Biochemistry and Department of Medicine, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN 37027
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16
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Observing the overall rocking motion of a protein in a crystal. Nat Commun 2015; 6:8361. [PMID: 26436197 PMCID: PMC4600728 DOI: 10.1038/ncomms9361] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 08/13/2015] [Indexed: 12/25/2022] Open
Abstract
The large majority of three-dimensional structures of biological macromolecules have been determined by X-ray diffraction of crystalline samples. High-resolution structure determination crucially depends on the homogeneity of the protein crystal. Overall ‘rocking' motion of molecules in the crystal is expected to influence diffraction quality, and such motion may therefore affect the process of solving crystal structures. Yet, so far overall molecular motion has not directly been observed in protein crystals, and the timescale of such dynamics remains unclear. Here we use solid-state NMR, X-ray diffraction methods and μs-long molecular dynamics simulations to directly characterize the rigid-body motion of a protein in different crystal forms. For ubiquitin crystals investigated in this study we determine the range of possible correlation times of rocking motion, 0.1–100 μs. The amplitude of rocking varies from one crystal form to another and is correlated with the resolution obtainable in X-ray diffraction experiments. Small-amplitude overall motion of molecules in crystals limits the achievable resolution in X-ray diffraction, yet little is known about its exact nature. Here, the authors obtain NMR, XRD and MD data from three different crystal forms of a protein (ubiquitin) to gain insight into amplitude and timescale of such motions.
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17
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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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