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Tkach I, Diederichsen U, Bennati M. Studies of transmembrane peptides by pulse dipolar spectroscopy with semi-rigid TOPP spin labels. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2021; 50:143-157. [PMID: 33640998 PMCID: PMC8071797 DOI: 10.1007/s00249-021-01508-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 01/25/2021] [Accepted: 01/29/2021] [Indexed: 12/01/2022]
Abstract
Electron paramagnetic resonance (EPR)-based pulsed dipolar spectroscopy measures the dipolar interaction between paramagnetic centers that are separated by distances in the range of about 1.5-10 nm. Its application to transmembrane (TM) peptides in combination with modern spin labelling techniques provides a valuable tool to study peptide-to-lipid interactions at a molecular level, which permits access to key parameters characterizing the structural adaptation of model peptides incorporated in natural membranes. In this mini-review, we summarize our approach for distance and orientation measurements in lipid environment using novel semi-rigid TOPP [4-(3,3,5,5-tetramethyl-2,6-dioxo-4-oxylpiperazin-1-yl)-L-phenylglycine] labels specifically designed for incorporation in TM peptides. TOPP labels can report single peak distance distributions with sub-angstrom resolution, thus offering new capabilities for a variety of TM peptide investigations, such as monitoring of various helix conformations or measuring of tilt angles in membranes.
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Affiliation(s)
- Igor Tkach
- Max Planck Institute for Biophysical Chemistry, RG Electron-Spin Resonance Spectroscopy, 37077, Göttingen, Germany.
| | - Ulf Diederichsen
- Department of Organic and Biomolecular Chemistry, University of Göttingen, 37077, Göttingen, Germany
| | - Marina Bennati
- Max Planck Institute for Biophysical Chemistry, RG Electron-Spin Resonance Spectroscopy, 37077, Göttingen, Germany
- Department of Organic and Biomolecular Chemistry, University of Göttingen, 37077, Göttingen, Germany
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2
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PELDOR/DEER: An Electron Paramagnetic Resonance Method to Study Membrane Proteins in Lipid Bilayers. Methods Mol Biol 2021. [PMID: 33582999 DOI: 10.1007/978-1-0716-0724-4_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2023]
Abstract
Every membrane protein is involved in close interactions with the lipid environment of cellular membranes. The annular lipids, that are in direct contact with the polypeptide, can in principle be seen as an integral part of its structure, akin to the first hydration shell of soluble proteins. It is therefore desirable to investigate the structure of membrane proteins and especially their conformational flexibility under conditions that are as close as possible to their native state. This can be achieved by reconstituting the protein into proteoliposomes, nanodiscs, or bicelles. In recent years, PELDOR/DEER spectroscopy has proved to be a very useful method to study the structure and function of membrane proteins in such artificial membrane environments. The technique complements both X-ray crystallography and cryo-EM and can be used in combination with virtually any artificial membrane environment and under certain circumstances even in native membranes. Of the above-mentioned membrane mimics, bicelles are currently the least often used for PELDOR studies, although they offer some advantages, especially their ease of use. Here, we provide a step-by-step protocol for studying a bicelle reconstituted membrane protein with PELDOR/DEER spectroscopy.
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Caldwell TA, Baoukina S, Brock AT, Oliver RC, Root KT, Krueger JK, Glover KJ, Tieleman DP, Columbus L. Low- q Bicelles Are Mixed Micelles. J Phys Chem Lett 2018; 9:4469-4473. [PMID: 30024762 PMCID: PMC6353637 DOI: 10.1021/acs.jpclett.8b02079] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Bicelles are used in many membrane protein studies because they are thought to be more bilayer-like than micelles. We investigated the properties of "isotropic" bicelles by small-angle neutron scattering, small-angle X-ray scattering, fluorescence anisotropy, and molecular dynamics. All data suggest that bicelles with a q value below 1 deviate from the classic bicelle that contains lipids in the core and detergent in the rim. Thus not all isotropic bicelles are bilayer-like.
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Affiliation(s)
- Tracy A. Caldwell
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Svetlana Baoukina
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Ashton T. Brock
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Ryan C. Oliver
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Kyle T. Root
- Department of Chemistry, Lock Haven University, Lock Haven, Pennsylvania 17745, United States
| | - Joanna K. Krueger
- Department of Chemistry, The University of North Carolina at Charlotte, Charlotte, North Carolina 28223, United States
| | - Kerney Jebrell Glover
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - D. Peter Tieleman
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Linda Columbus
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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Pan J, Sahoo PK, Dalzini A, Hayati Z, Aryal CM, Teng P, Cai J, Gutierrez HR, Song L. Membrane Disruption Mechanism of a Prion Peptide (106-126) Investigated by Atomic Force Microscopy, Raman and Electron Paramagnetic Resonance Spectroscopy. J Phys Chem B 2017; 121:5058-5071. [PMID: 28459565 PMCID: PMC5770145 DOI: 10.1021/acs.jpcb.7b02772] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A fragment of the human prion protein spanning residues 106-126 (PrP106-126) recapitulates many essential properties of the disease-causing protein such as amyloidogenicity and cytotoxicity. PrP106-126 has an amphipathic characteristic that resembles many antimicrobial peptides (AMPs). Therefore, the toxic effect of PrP106-126 could arise from a direct association of monomeric peptides with the membrane matrix. Several experimental approaches are employed to scrutinize the impacts of monomeric PrP106-126 on model lipid membranes. Porous defects in planar bilayers are observed by using solution atomic force microscopy. Adding cholesterol does not impede defect formation. A force spectroscopy experiment shows that PrP106-126 reduces Young's modulus of planar lipid bilayers. We use Raman microspectroscopy to study the effect of PrP106-126 on lipid atomic vibrational dynamics. For phosphatidylcholine lipids, PrP106-126 disorders the intrachain conformation, while the interchain interaction is not altered; for phosphatidylethanolamine lipids, PrP106-126 increases the interchain interaction, while the intrachain conformational order remains similar. We explain the observed differences by considering different modes of peptide insertion. Finally, electron paramagnetic resonance spectroscopy shows that PrP106-126 progressively decreases the orientational order of lipid acyl chains in magnetically aligned bicelles. Together, our experimental data support the proposition that monomeric PrP106-126 can disrupt lipid membranes by using similar mechanisms found in AMPs.
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Affiliation(s)
- Jianjun Pan
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Prasana K. Sahoo
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Annalisa Dalzini
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
| | - Zahra Hayati
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
| | - Chinta M. Aryal
- Department of Physics, University of South Florida, Tampa, Florida 33620, United States
| | - Peng Teng
- Department of Chemistry, University of South Florida, Tampa, Florida 33620, United States
| | - Jianfeng Cai
- Department of Chemistry, University of South Florida, Tampa, Florida 33620, United States
| | | | - Likai Song
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
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Lin L, Wang X, Li X, Yang Y, Yue X, Zhang Q, Dai Z. Modulating Drug Release Rate from Partially Silica-Coated Bicellar Nanodisc by Incorporating PEGylated Phospholipid. Bioconjug Chem 2016; 28:53-63. [PMID: 27718555 DOI: 10.1021/acs.bioconjchem.6b00508] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This article reports an effective method to regulate hydrophobic drug release rate from partially silica-coated bicellar nanodisc generated from proamphiphilic organoalkoxysilane and dihexanoylphosphatidylcholine by introducing different molar percentages of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-PEG2000 (DSPE-PEG2000) into planar bilayers of hybrid bicelles. It was found that the drug release rate increased with increasing the molar percentages of DSPE-PEG2000, and 57.38%, 69.21%, 78.69%, 81.64%, and 82.23% of hydrophobic doxorubicin was released within 120 h from the nanodics incorporating with 0%, 2.5%, 5%, 10%, and 20% DSPE-PEG2000, respectively. Compared with the non-PEGylated nanodisc and free doxorubicin, the PEGylated nanodiscs showed good biocompatibility, high cellular uptake, and adhesion, as well as high local drug accumulation. In addition, both in vitro and in vivo results demonstrated significantly improved antitumor efficacy of the PEGylated nanodisc than its control groups. Thus, the PEGylated nanodisc with partial silica coating offers a facile and efficient strategy of drug delivery for chemotherapy with improved patient acceptance and compliance.
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Affiliation(s)
| | - Xiaoyou Wang
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery System, College of Engineering, School of Pharmaceutical Sciences, Peking University , Beijing 100871, China
| | | | | | | | - Qiang Zhang
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery System, College of Engineering, School of Pharmaceutical Sciences, Peking University , Beijing 100871, China
| | - Zhifei Dai
- Beijing Key Laboratory of Molecular Pharmaceutics and New Drug Delivery System, College of Engineering, School of Pharmaceutical Sciences, Peking University , Beijing 100871, China
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McCaffrey JE, James ZM, Svensson B, Binder BP, Thomas DD. A bifunctional spin label reports the structural topology of phospholamban in magnetically-aligned bicelles. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 262:50-56. [PMID: 26720587 PMCID: PMC4716873 DOI: 10.1016/j.jmr.2015.12.005] [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: 09/17/2015] [Revised: 11/25/2015] [Accepted: 12/02/2015] [Indexed: 06/05/2023]
Abstract
We have applied a bifunctional spin label and EPR spectroscopy to determine membrane protein structural topology in magnetically-aligned bicelles, using monomeric phospholamban (PLB) as a model system. Bicelles are a powerful tool for studying membrane proteins by NMR and EPR spectroscopies, where magnetic alignment yields topological constraints by resolving the anisotropic spectral properties of nuclear and electron spins. However, EPR bicelle studies are often hindered by the rotational mobility of monofunctional Cys-linked spin labels, which obscures their orientation relative to the protein backbone. The rigid and stereospecific TOAC label provides high orientational sensitivity but must be introduced via solid-phase peptide synthesis, precluding its use in large proteins. Here we show that a bifunctional methanethiosulfonate spin label attaches rigidly and stereospecifically to Cys residues at i and i+4 positions along PLB's transmembrane helix, thus providing orientational resolution similar to that of TOAC, while being applicable to larger membrane proteins for which synthesis is impractical. Computational modeling and comparison with NMR data shows that these EPR experiments provide accurate information about helix tilt relative to the membrane normal, thus establishing a robust method for determining structural topology in large membrane proteins with a substantial advantage in sensitivity over NMR.
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Affiliation(s)
- Jesse E McCaffrey
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Zachary M James
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Bengt Svensson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Benjamin P Binder
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
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Bifunctional Spin Labeling of Muscle Proteins: Accurate Rotational Dynamics, Orientation, and Distance by EPR. Methods Enzymol 2015; 564:101-23. [PMID: 26477249 DOI: 10.1016/bs.mie.2015.06.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2023]
Abstract
While EPR allows for the characterization of protein structure and function due to its exquisite sensitivity to spin label dynamics, orientation, and distance, these measurements are often limited in sensitivity due to the use of labels that are attached via flexible monofunctional bonds, incurring additional disorder and nanosecond dynamics. In this chapter, we present methods for using a bifunctional spin label (BSL) to measure muscle protein structure and dynamics. We demonstrate that bifunctional attachment eliminates nanosecond internal rotation of the spin label, thereby allowing the accurate measurement of protein backbone rotational dynamics, including microsecond-to-millisecond motions by saturation transfer EPR. BSL also allows for accurate determination of helix orientation and disorder in mechanically and magnetically aligned systems, due to the label's stereospecific attachment. Similarly, labeling with a pair of BSL greatly enhances the resolution and accuracy of distance measurements measured by double electron-electron resonance (DEER). Finally, when BSL is applied to a protein with high helical content in an assembly with high orientational order (e.g., muscle fiber or membrane), two-probe DEER experiments can be combined with single-probe EPR experiments on an oriented sample in a process we call BEER, which has the potential for ab initio high-resolution structure determination.
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