1
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Burden DL, Meyer JJ, Michael RD, Anderson SC, Burden HM, Peña SM, Leong-Fern KJ, Van Ye LA, Meyer EC, Keranen-Burden LM. Confirming Silent Translocation through Nanopores with Simultaneous Single-Molecule Fluorescence and Single-Channel Electrical Recordings. Anal Chem 2023; 95:18020-18028. [PMID: 37991877 PMCID: PMC10719886 DOI: 10.1021/acs.analchem.3c02329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 11/07/2023] [Accepted: 11/08/2023] [Indexed: 11/24/2023]
Abstract
Most of what is known concerning the luminal passage of materials through nanopores arises from electrical measurements. Whether nanopores are biological, solid-state, synthetic, hybrid, glass-capillary-based, or protein ion channels in cells and tissues, characteristic signatures embedded in the flow of ionic current are foundational to understanding functional behavior. In contrast, this work describes passage through a nanopore that occurs without producing an electrical signature. We refer to the phenomenon as "silent translocation." By definition, silent translocations are invisible to the standard tools of electrophysiology and fundamentally require a simultaneous ancillary measurement technique for positive identification. As a result, this phenomenon has been largely unexplored in the literature. Here, we report on a derivative of Cyanine 5 (sCy5a) that passes through the α-hemolysin (αHL) nanopore silently. Simultaneously acquired single-molecule fluorescence and single-channel electrical recordings from bilayers formed over a closed microcavity demonstrate that translocation does indeed take place, albeit infrequently. We report observations of silent translocation as a function of time, dye concentration, and nanopore population in the bilayer. Lastly, measurement of the translocation rate as a function of applied potential permits estimation of an effective energy barrier for transport through the pore as well as the effective charge on the dye, all in the absence of an information-containing electrical signature.
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Affiliation(s)
- Daniel L. Burden
- Chemistry Department, Wheaton College, Wheaton, Illinois 60187, United States
| | - Joshua J. Meyer
- Chemistry Department, Wheaton College, Wheaton, Illinois 60187, United States
| | - Richard D. Michael
- Chemistry Department, Wheaton College, Wheaton, Illinois 60187, United States
| | - Sophie C. Anderson
- Chemistry Department, Wheaton College, Wheaton, Illinois 60187, United States
| | - Hannah M. Burden
- Chemistry Department, Wheaton College, Wheaton, Illinois 60187, United States
| | - Sophia M. Peña
- Chemistry Department, Wheaton College, Wheaton, Illinois 60187, United States
| | | | - Lily Anne Van Ye
- Chemistry Department, Wheaton College, Wheaton, Illinois 60187, United States
| | - Elizabeth C. Meyer
- Chemistry Department, Wheaton College, Wheaton, Illinois 60187, United States
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2
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Margheritis E, Kappelhoff S, Cosentino K. Pore-Forming Proteins: From Pore Assembly to Structure by Quantitative Single-Molecule Imaging. Int J Mol Sci 2023; 24:ijms24054528. [PMID: 36901959 PMCID: PMC10003378 DOI: 10.3390/ijms24054528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 02/11/2023] [Accepted: 02/21/2023] [Indexed: 03/03/2023] Open
Abstract
Pore-forming proteins (PFPs) play a central role in many biological processes related to infection, immunity, cancer, and neurodegeneration. A common feature of PFPs is their ability to form pores that disrupt the membrane permeability barrier and ion homeostasis and generally induce cell death. Some PFPs are part of the genetically encoded machinery of eukaryotic cells that are activated against infection by pathogens or in physiological programs to carry out regulated cell death. PFPs organize into supramolecular transmembrane complexes that perforate membranes through a multistep process involving membrane insertion, protein oligomerization, and finally pore formation. However, the exact mechanism of pore formation varies from PFP to PFP, resulting in different pore structures with different functionalities. Here, we review recent insights into the molecular mechanisms by which PFPs permeabilize membranes and recent methodological advances in their characterization in artificial and cellular membranes. In particular, we focus on single-molecule imaging techniques as powerful tools to unravel the molecular mechanistic details of pore assembly that are often obscured by ensemble measurements, and to determine pore structure and functionality. Uncovering the mechanistic elements of pore formation is critical for understanding the physiological role of PFPs and developing therapeutic approaches.
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3
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Blum D, Reuter M, Schliebs W, Tomaschewski J, Erdmann R, Wagner R. Membrane binding and pore forming insertion of PEX5 into horizontal lipid bilayer. Biol Chem 2023; 404:157-167. [PMID: 36260915 DOI: 10.1515/hsz-2022-0183] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 08/29/2022] [Indexed: 11/15/2022]
Abstract
The assembly of the peroxisomal translocon involves the transition of a soluble form of the peroxisomal targeting receptor PEX5 into a membrane-bound form, which becomes an integral membrane component of the import pore for peroxisomal matrix proteins. How this transition occurs is still a mystery. We addressed this question using a artificial horizontal bilayer in combination with fluorescence time-correlated single photon counting (TCSPC) and electrophysiological channel recording. Purified human isoform PEX5L and truncated PEX5L(1-335) lacking the cargo binding domain were selectively labeled with thiol-reactive Atto-dyes. Diffusion coefficients of labeled protein in solution show that PEX5L is monomeric with a rather compact spherical conformation, while the truncated protein appeared in a more extended conformation. Labeled PEX5L and the truncated PEX5L(1-335) bind stably to horizontal bilayer thereby accumulating around 100-fold. The diffusion coefficients of the membrane-bound PEX5L forms are 3-4 times lower than in solution, indicating the formation of larger complexes. Electrophysiological single channel recording shows that membrane-bound labeled and non-labeled PEX5L, but not the truncated PEX5L(1-335), can form ion conducting membrane channels. The data suggest that PEX5L is the pore-forming component of the oligomeric peroxisomal translocon and that spontaneous PEX5L membrane surface binding might be an important step in its assembly.
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Affiliation(s)
- Daniel Blum
- MOLIFE Research Center, Jacobs, University Bremen, D-28759 Bremen, Germany
| | - Maren Reuter
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Medizinische Fakultät, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Wolfgang Schliebs
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Medizinische Fakultät, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Jana Tomaschewski
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Medizinische Fakultät, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Ralf Erdmann
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Medizinische Fakultät, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Richard Wagner
- MOLIFE Research Center, Jacobs, University Bremen, D-28759 Bremen, Germany
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4
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Ensslen T, Behrends JC. A chip-based array for high-resolution fluorescence characterization of free-standing horizontal lipid membranes under voltage clamp. LAB ON A CHIP 2022; 22:2902-2910. [PMID: 35839072 DOI: 10.1039/d2lc00357k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Optical techniques, such as fluorescence microscopy, are of great value in characterizing the structural dynamics of membranes and membrane proteins. A particular challenge is to combine high-resolution optical measurements with high-resolution voltage clamp electrical recordings providing direct information on e.g. single ion channel gating and/or membrane capacitance. Here, we report on a novel chip-based array device which facilitates optical access with water or oil-immersion objectives of high numerical aperture to horizontal free-standing lipid membranes while controlling membrane voltage and recording currents using individual micropatterned Ag/AgCl-electrodes. Wide-field and confocal imaging, as well as time-resolved single photon counting on free-standing membranes spanning sub-nanoliter cavities are demonstrated while electrical signals, including single channel activity, are simultaneously acquired. This optically addressable microelectrode cavity array will allow combined electrical-optical studies of membranes and membrane proteins to be performed as a routine experiment.
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Affiliation(s)
- Tobias Ensslen
- Laboratory for Membrane Physiology and Technology, Department of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany.
| | - Jan C Behrends
- Laboratory for Membrane Physiology and Technology, Department of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany.
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5
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SUPER-RESOLUTION MICROSCOPY FOR THE STUDY OF STORE-OPERATED CALCIUM ENTRY. Cell Calcium 2022; 104:102595. [DOI: 10.1016/j.ceca.2022.102595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 05/03/2022] [Accepted: 05/05/2022] [Indexed: 11/19/2022]
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6
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Davis MM, Lamichhane R, Bruce BD. Elucidating Protein Translocon Dynamics with Single-Molecule Precision. Trends Cell Biol 2021; 31:569-583. [PMID: 33865650 DOI: 10.1016/j.tcb.2021.03.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 01/28/2023]
Abstract
Translocons are protein assemblies that facilitate the targeting and transport of proteins into and across biological membranes. Our understanding of these systems has been advanced using genetics, biochemistry, and structural biology. Despite these classic advances, until recently we have still largely lacked a detailed understanding of how translocons recognize and facilitate protein translocation. With the advent and improvements of cryogenic electron microscopy (cryo-EM) single-particle analysis and single-molecule fluorescence microscopy, the details of how translocons function are finally emerging. Here, we introduce these methods and evaluate their importance in understanding translocon structure, function, and dynamics.
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Affiliation(s)
- Madeline M Davis
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA
| | - Rajan Lamichhane
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA
| | - Barry D Bruce
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA; Department of Microbiology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA; Graduate Program in Genome Science and Technology, University of Tennessee at Knoxville, Knoxville, TN 37996, USA; Chemical and Biomolecular Engineering, University of Tennessee at Knoxville, Knoxville, TN 37996, USA.
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7
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Ros U, Pedrera L, Garcia-Saez AJ. Techniques for studying membrane pores. Curr Opin Struct Biol 2021; 69:108-116. [PMID: 33945958 DOI: 10.1016/j.sbi.2021.03.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 03/23/2021] [Accepted: 03/27/2021] [Indexed: 01/30/2023]
Abstract
Pore-forming proteins (PFPs) are of special interest because of the association of their activity with the disruption of the membrane impermeability barrier and cell death. They generally convert from a monomeric, soluble form into transmembrane oligomers that induce the opening of membrane pores. The study of pore formation in membranes with molecular detail remains a challenging endeavor because of its highly dynamic and complex nature, usually involving diverse oligomeric structures with different functionalities. Here we discuss current methods applied for the structural and functional characterization of PFPs at the individual vesicle and cell level. We highlight how the development of high-resolution and single-molecule imaging techniques allows the analysis of the structural organization of protein oligomers and pore entities in lipid membranes.
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Affiliation(s)
- Uris Ros
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Joseph-Stelzmann-Strasse 26, Cologne, Germany
| | - Lohans Pedrera
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Joseph-Stelzmann-Strasse 26, Cologne, Germany
| | - Ana J Garcia-Saez
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Joseph-Stelzmann-Strasse 26, Cologne, Germany.
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8
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Parperis C, Wallace MI. Single-molecule imaging of pore-forming toxin dynamics in droplet interface bilayers. Methods Enzymol 2021; 649:431-459. [PMID: 33712195 DOI: 10.1016/bs.mie.2021.01.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Single-channel recording from pore-forming toxins (PFTs) provides a clear and direct molecular readout of toxin action. However to complete any mechanistic understanding of PFT behavior, this functional kinetic readout must be linked to the underlying changes in toxin structure, binding, conformation, or stoichiometry. Here we review how single-molecule imaging methods might be used to further our understanding of PFTs, and provide detailed practical guidance on the use of droplet interface bilayers as a method capable of examining both single-molecule fluorescence and single-channel electrical signals from PFTs.
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Affiliation(s)
- Christopher Parperis
- Department of Chemistry, Britannia House, King's College London, London, United Kingdom
| | - Mark I Wallace
- Department of Chemistry, Britannia House, King's College London, London, United Kingdom.
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9
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Ciftci D, Huysmans GHM, Wang X, He C, Terry D, Zhou Z, Fitzgerald G, Blanchard SC, Boudker O. Single-molecule transport kinetics of a glutamate transporter homolog shows static disorder. SCIENCE ADVANCES 2020; 6:eaaz1949. [PMID: 32523985 PMCID: PMC7259943 DOI: 10.1126/sciadv.aaz1949] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 03/26/2020] [Indexed: 06/11/2023]
Abstract
Kinetic properties of membrane transporters are typically poorly defined because high-resolution functional assays analogous to single-channel recordings are lacking. Here, we measure single-molecule transport kinetics of a glutamate transporter homolog from Pyrococcus horikoshii, GltPh, using fluorescently labeled periplasmic amino acid binding protein as a fluorescence resonance energy transfer-based sensor. We show that individual transporters can function at rates varying by at least two orders of magnitude that persist for multiple turnovers. A gain-of-function mutant shows increased population of the fast-acting transporters, leading to a 10-fold increase in the mean transport rate. These findings, which are broadly consistent with earlier single-molecule measurements of GltPh conformational dynamics, suggest that GltPh transport is defined by kinetically distinct populations that exhibit long-lasting "molecular memory."
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Affiliation(s)
- Didar Ciftci
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
- Tri-Institutional Training Program in Chemical Biology, New York, NY 10065, USA
| | - Gerard H. M. Huysmans
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Xiaoyu Wang
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Changhao He
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Daniel Terry
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Zhou Zhou
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Gabriel Fitzgerald
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Scott C. Blanchard
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
- Tri-Institutional Training Program in Chemical Biology, New York, NY 10065, USA
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
- Tri-Institutional Training Program in Chemical Biology, New York, NY 10065, USA
- Howard Hughes Medical Institute, Weill Cornell Medicine, New York, NY, 10065, USA
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10
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Cowgill J, Chanda B. The contribution of voltage clamp fluorometry to the understanding of channel and transporter mechanisms. J Gen Physiol 2019; 151:1163-1172. [PMID: 31431491 PMCID: PMC6785729 DOI: 10.1085/jgp.201912372] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Cowgill and Chanda discuss the importance of voltage clamp fluorometry to the functional interpretation of ion channel and transporter structures. Key advances in single particle cryo-EM methods in the past decade have ushered in a resolution revolution in modern biology. The structures of many ion channels and transporters that were previously recalcitrant to crystallography have now been solved. Yet, despite having atomistic models of many complexes, some in multiple conformations, it has been challenging to glean mechanistic insight from these structures. To some extent this reflects our inability to unambiguously assign a given structure to a particular physiological state. One approach that may allow us to bridge this gap between structure and function is voltage clamp fluorometry (VCF). Using this technique, dynamic conformational changes can be measured while simultaneously monitoring the functional state of the channel or transporter. Many of the important papers that have used VCF to probe the gating mechanisms of channels and transporters have been published in the Journal of General Physiology. In this review, we provide an overview of the development of VCF and discuss some of the key problems that have been addressed using this approach. We end with a brief discussion of the outlook for this technique in the era of high-resolution structures.
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Affiliation(s)
- John Cowgill
- Graduate Program in Biophysics, University of Wisconsin, Madison, WI.,Department of Neuroscience, University of Wisconsin, Madison, WI
| | - Baron Chanda
- Department of Neuroscience, University of Wisconsin, Madison, WI .,Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI
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11
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Tsemperouli M, Amstad E, Sakai N, Matile S, Sugihara K. Black Lipid Membranes: Challenges in Simultaneous Quantitative Characterization by Electrophysiology and Fluorescence Microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:8748-8757. [PMID: 31244250 DOI: 10.1021/acs.langmuir.9b00673] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Horizontal black lipid membranes (BLMs) enable optical microscopy to be combined with the electrophysiological measurements for studying ion channels, peptide pores, and ionophores. However, a careful literature review reveals that simultaneous fluorescence and electrical recordings in horizontal BLMs have been rarely reported for an unclear reason, whereas many works employ bright-field microscopy instead of fluorescence microscopy or perform fluorescence imaging and electrical measurements one after another separately without truly exploiting the advantage of the combined setup. In this work, the major causes related to the simultaneous electrical and fluorescence recordings in horizontal BLMs are identified, and several solutions to counteract the issue are also proposed.
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Affiliation(s)
- Maria Tsemperouli
- School of Chemistry and Biochemistry , University of Geneva , CH-1211 Geneva , Switzerland
| | - Esther Amstad
- Institute of Materials , Ecole Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
| | - Naomi Sakai
- School of Chemistry and Biochemistry , University of Geneva , CH-1211 Geneva , Switzerland
| | - Stefan Matile
- School of Chemistry and Biochemistry , University of Geneva , CH-1211 Geneva , Switzerland
| | - Kaori Sugihara
- School of Chemistry and Biochemistry , University of Geneva , CH-1211 Geneva , Switzerland
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12
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Allen-Benton M, Findlay HE, Booth PJ. Probing membrane protein properties using droplet interface bilayers. Exp Biol Med (Maywood) 2019; 244:709-720. [PMID: 31053046 PMCID: PMC6552395 DOI: 10.1177/1535370219847939] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
IMPACT STATEMENT The paper presents a comprehensive review of integral membrane protein studies utilizing droplet interface bilayers. Droplet interface bilayers are a novel method of constructing artificial lipid bilayers with enhanced stability and physicochemical complexity compared to existing methods. Their unique morphology also suggests applications in the construction of synthetic biological systems and protocells. As well as serving as a guide to in vitro membrane protein functional studies using droplet interface bilayers in the literature to date, a novel in vitro study of a flippase protein in a droplet interface bilayer is presented.
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Affiliation(s)
| | | | - Paula J Booth
- Department of Chemistry, King’s College London,
London SE1 1DB, UK
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13
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Ando T, Bhamidimarri SP, Brending N, Colin-York H, Collinson L, De Jonge N, de Pablo PJ, Debroye E, Eggeling C, Franck C, Fritzsche M, Gerritsen H, Giepmans BNG, Grunewald K, Hofkens J, Hoogenboom JP, Janssen KPF, Kaufman R, Klumpermann J, Kurniawan N, Kusch J, Liv N, Parekh V, Peckys DB, Rehfeldt F, Reutens DC, Roeffaers MBJ, Salditt T, Schaap IAT, Schwarz US, Verkade P, Vogel MW, Wagner R, Winterhalter M, Yuan H, Zifarelli G. The 2018 correlative microscopy techniques roadmap. JOURNAL OF PHYSICS D: APPLIED PHYSICS 2018; 51:443001. [PMID: 30799880 PMCID: PMC6372154 DOI: 10.1088/1361-6463/aad055] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/14/2018] [Accepted: 07/01/2018] [Indexed: 05/19/2023]
Abstract
Developments in microscopy have been instrumental to progress in the life sciences, and many new techniques have been introduced and led to new discoveries throughout the last century. A wide and diverse range of methodologies is now available, including electron microscopy, atomic force microscopy, magnetic resonance imaging, small-angle x-ray scattering and multiple super-resolution fluorescence techniques, and each of these methods provides valuable read-outs to meet the demands set by the samples under study. Yet, the investigation of cell development requires a multi-parametric approach to address both the structure and spatio-temporal organization of organelles, and also the transduction of chemical signals and forces involved in cell-cell interactions. Although the microscopy technologies for observing each of these characteristics are well developed, none of them can offer read-out of all characteristics simultaneously, which limits the information content of a measurement. For example, while electron microscopy is able to disclose the structural layout of cells and the macromolecular arrangement of proteins, it cannot directly follow dynamics in living cells. The latter can be achieved with fluorescence microscopy which, however, requires labelling and lacks spatial resolution. A remedy is to combine and correlate different readouts from the same specimen, which opens new avenues to understand structure-function relations in biomedical research. At the same time, such correlative approaches pose new challenges concerning sample preparation, instrument stability, region of interest retrieval, and data analysis. Because the field of correlative microscopy is relatively young, the capabilities of the various approaches have yet to be fully explored, and uncertainties remain when considering the best choice of strategy and workflow for the correlative experiment. With this in mind, the Journal of Physics D: Applied Physics presents a special roadmap on the correlative microscopy techniques, giving a comprehensive overview from various leading scientists in this field, via a collection of multiple short viewpoints.
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Affiliation(s)
- Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan
| | | | | | - H Colin-York
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
| | | | - Niels De Jonge
- INM-Leibniz Institute for New Materials, 66123 Saarbrücken, Germany
- Saarland University, 66123 Saarbrücken, Germany
| | - P J de Pablo
- Dpto. Física de la Materia Condensada Universidad Autónoma de Madrid 28049, Madrid, Spain
- Instituto de Física de la Materia Condensada IFIMAC, Universidad Autónoma de Madrid 28049, Madrid, Spain
| | - Elke Debroye
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | - Christian Eggeling
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
- Institute of Applied Optics, Friedrich-Schiller University, Jena, Germany
- Leibniz Institute of Photonic Technology (IPHT), Jena, Germany
| | - Christian Franck
- Department of Mechanical Engineering, University of Wisconsin-Madison, 1513 University Ave, Madison, WI 53706, United States of America
| | - Marco Fritzsche
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Hans Gerritsen
- Debye Institute, Utrecht University, Utrecht, Netherlands
| | - Ben N G Giepmans
- Department of Cell Biology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Kay Grunewald
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- Centre of Structural Systems Biology Hamburg and University of Hamburg, Hamburg, Germany
- Heinrich-Pette-Institute, Leibniz Institute of Virology, Hamburg, Germany
| | - Johan Hofkens
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | | | | | - Rainer Kaufman
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- Centre of Structural Systems Biology Hamburg and University of Hamburg, Hamburg, Germany
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Judith Klumpermann
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584CX Utrecht, Netherlands
| | - Nyoman Kurniawan
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584CX Utrecht, Netherlands
| | - Viha Parekh
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Diana B Peckys
- Faculty of Medicine, Saarland University, 66421 Homburg, Germany
| | - Florian Rehfeldt
- University of Göttingen, Third Institute of Physics-Biophysics, 37077 Göttingen, Germany
| | - David C Reutens
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Tim Salditt
- University of Göttingen, Institute for X-Ray Physics, 37077 Göttingen, Germany
| | - Iwan A T Schaap
- SmarAct GmbH, Schütte-Lanz-Str. 9, D-26135 Oldenburg, Germany
| | - Ulrich S Schwarz
- Institute for Theoretical Physics and BioQuant, Heidelberg University, Heidelberg, Germany
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Michael W Vogel
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Richard Wagner
- Department of Life Sciences & Chemistry, Jacobs University, Bremen, Germany
| | | | - Haifeng Yuan
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | - Giovanni Zifarelli
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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14
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Booth MJ, Restrepo Schild V, Downs FG, Bayley H. Functional aqueous droplet networks. MOLECULAR BIOSYSTEMS 2018; 13:1658-1691. [PMID: 28766622 DOI: 10.1039/c7mb00192d] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Droplet interface bilayers (DIBs), comprising individual lipid bilayers between pairs of aqueous droplets in an oil, are proving to be a useful tool for studying membrane proteins. Recently, attention has turned to the elaboration of networks of aqueous droplets, connected through functionalized interface bilayers, with collective properties unachievable in droplet pairs. Small 2D collections of droplets have been formed into soft biodevices, which can act as electronic components, light-sensors and batteries. A substantial breakthrough has been the development of a droplet printer, which can create patterned 3D droplet networks of hundreds to thousands of connected droplets. The 3D networks can change shape, or carry electrical signals through defined pathways, or express proteins in response to patterned illumination. We envisage using functional 3D droplet networks as autonomous synthetic tissues or coupling them with cells to repair or enhance the properties of living tissues.
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Affiliation(s)
- Michael J Booth
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
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15
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Sadler EE, Kapanidis AN, Tucker SJ. Solution-Based Single-Molecule FRET Studies of K(+) Channel Gating in a Lipid Bilayer. Biophys J 2017; 110:2663-2670. [PMID: 27332124 PMCID: PMC4919593 DOI: 10.1016/j.bpj.2016.05.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 04/26/2016] [Accepted: 05/09/2016] [Indexed: 01/30/2023] Open
Abstract
Ion channels are dynamic multimeric proteins that often undergo multiple unsynchronized structural movements as they switch between their open and closed states. Such structural changes are difficult to measure within the context of a native lipid bilayer and have often been monitored via macroscopic changes in Förster resonance energy transfer (FRET) between probes attached to different parts of the protein. However, the resolution of this approach is limited by ensemble averaging of structurally heterogeneous subpopulations. These problems can be overcome by measurement of FRET in single molecules, but this presents many challenges, in particular the ability to control labeling of subunits within a multimeric protein with acceptor and donor fluorophores, as well as the requirement to image large numbers of individual molecules in a membrane environment. To address these challenges, we randomly labeled tetrameric KirBac1.1 potassium channels, reconstituted them into lipid nanodiscs, and performed single-molecule FRET confocal microscopy with alternating-laser excitation as the channels diffused in solution. These solution-based single-molecule FRET measurements of a multimeric ion channel in a lipid bilayer have allowed us to probe the structural changes that occur upon channel activation and inhibition. Our results provide direct evidence of the twist-to-shrink movement of the helix bundle crossing during channel gating and demonstrate how this method might be applied to real-time structural studies of ion channel gating.
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Affiliation(s)
- Emma E Sadler
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
| | - Achillefs N Kapanidis
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, United Kingdom.
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16
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Sasmal DK, Pulido LE, Kasal S, Huang J. Single-molecule fluorescence resonance energy transfer in molecular biology. NANOSCALE 2016; 8:19928-19944. [PMID: 27883140 PMCID: PMC5145784 DOI: 10.1039/c6nr06794h] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Single-molecule fluorescence resonance energy transfer (smFRET) is a powerful technique for studying the conformation dynamics and interactions of individual biomolecules. In this review, we describe the concept and principle of smFRET, illustrate general instrumentation and microscopy settings for experiments, and discuss the methods and algorithms for data analysis. Subsequently, we review applications of smFRET in protein conformational changes, ion channel open-close properties, receptor-ligand interactions, nucleic acid structure regulation, vesicle fusion, and force induced conformational dynamics. Finally, we discuss the main limitations of smFRET in molecular biology.
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Affiliation(s)
- Dibyendu K Sasmal
- The Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
| | - Laura E Pulido
- The Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
| | - Shan Kasal
- The Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
| | - Jun Huang
- The Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
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17
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Marin V, Kieffer R, Padmos R, Aubin-Tam ME. Stable Free-Standing Lipid Bilayer Membranes in Norland Optical Adhesive 81 Microchannels. Anal Chem 2016; 88:7466-70. [DOI: 10.1021/acs.analchem.6b00926] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Victor Marin
- Department of Bionanoscience,
Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ, Delft, The Netherlands
| | - Roland Kieffer
- Department of Bionanoscience,
Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ, Delft, The Netherlands
| | - Raymond Padmos
- Department of Bionanoscience,
Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ, Delft, The Netherlands
| | - Marie-Eve Aubin-Tam
- Department of Bionanoscience,
Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ, Delft, The Netherlands
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18
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Sasmal DK, Yadav R, Lu HP. Single-Molecule Patch-Clamp FRET Anisotropy Microscopy Studies of NMDA Receptor Ion Channel Activation and Deactivation under Agonist Ligand Binding in Living Cells. J Am Chem Soc 2016; 138:8789-801. [DOI: 10.1021/jacs.6b03496] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Dibyendu Kumar Sasmal
- Center for Photochemical
Sciences, Department of Chemistry, Bowling Green State University, Bowling
Green, Ohio 43403, United States
| | - Rajeev Yadav
- Center for Photochemical
Sciences, Department of Chemistry, Bowling Green State University, Bowling
Green, Ohio 43403, United States
| | - H. Peter Lu
- Center for Photochemical
Sciences, Department of Chemistry, Bowling Green State University, Bowling
Green, Ohio 43403, United States
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19
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van Oijen AM, Dixon NE. Probing molecular choreography through single-molecule biochemistry. Nat Struct Mol Biol 2015; 22:948-52. [DOI: 10.1038/nsmb.3119] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 10/06/2015] [Indexed: 01/09/2023]
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20
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Cosentino K, Ros U, García-Sáez AJ. Assembling the puzzle: Oligomerization of α-pore forming proteins in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:457-466. [PMID: 26375417 DOI: 10.1016/j.bbamem.2015.09.013] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/26/2015] [Accepted: 09/09/2015] [Indexed: 12/21/2022]
Abstract
Pore forming proteins (PFPs) share the ability of creating pores that allow the passage of ions, proteins or other constituents through a wide variety of target membranes, ranging from bacteria to humans. They often cause cell death, as pore formation disrupts the membrane permeability barrier required for maintaining cell homeostasis. The organization into supramolecular complexes or oligomers that pierce the membrane is a common feature of PFPs. However, the molecular pathway of self-assembly and pore opening remains unclear. Here, we review the most recent discoveries in the mechanism of membrane oligomerization and pore formation of a subset of PFPs, the α-PFPs, whose pore-forming domains are formed by helical segments. Only now we are starting to grasp the molecular details of their function, mainly thanks to the introduction of single molecule microscopy and nanoscopy techniques. This article is part of a Special Issue entitled: Pore-forming toxins edited by Mauro Dalla Serra and Franco Gambale.
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Affiliation(s)
- Katia Cosentino
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Uris Ros
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany.,Center for Protein Studies, Havana University, Havana, Cuba
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.,Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
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21
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Insights into the molecular foundations of electrical excitation. J Mol Biol 2015; 427:1-2. [PMID: 25542854 DOI: 10.1016/j.jmb.2014.12.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/22/2014] [Accepted: 10/12/2014] [Indexed: 01/04/2023]
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