701
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Liu YJ, Hansen GPR, Venancio-Marques A, Baigl D. Cell-free preparation of functional and triggerable giant proteoliposomes. Chembiochem 2013; 14:2243-7. [PMID: 24115581 DOI: 10.1002/cbic.201300501] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Indexed: 01/15/2023]
Abstract
Heat, we leak: We express a membrane protein outside well-defined giant liposomes obtained by gravity-transferred sucrose-in-oil droplets into a cell-free, reconstituted expression system. We show that the presence of the liposome is necessary during expression for efficient protein insertion into the membrane and that temperature can trigger the resulting membrane function.
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Affiliation(s)
- Yan-Jun Liu
- Department of Chemistry, Ecole Normale Superieure, 24 rue Lhomond, 75005 Paris (France) http://www.baigllab.com/; Université Pierre et Marie Curie Paris 6, 4 place Jussieu, 75005 Paris (France); UMR 8640, CNRS, 3 rue Michel-Ange, 75016 Paris (France)
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702
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Wang X, Huang G, Yu D, Ge B, Wang J, Xu F, Huang F, Xu H, Lu JR. Solubilization and stabilization of isolated photosystem I complex with lipopeptide detergents. PLoS One 2013; 8:e76256. [PMID: 24098786 PMCID: PMC3787008 DOI: 10.1371/journal.pone.0076256] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 08/22/2013] [Indexed: 11/20/2022] Open
Abstract
It is difficult to maintain a target membrane protein in a soluble and functional form in aqueous solution without biological membranes. Use of surfactants can improve solubility, but it remains challenging to identify adequate surfactants that can improve solubility without damaging their native structures and biological functions. Here we report the use of a new class of lipopeptides to solubilize photosystem I (PS-I), a well known membrane protein complex. Changes in the molecular structure of these surfactants affected their amphiphilicity and the goal of this work was to exploit a delicate balance between detergency and biomimetic performance in PS-I solubilization via their binding capacity. Meanwhile, the effects of these surfactants on the thermal and structural stability and functionality of PS-I in aqueous solution were investigated by circular dichroism, fluorescence spectroscopy, SDS-PAGE analysis and O2 uptake measurements, respectively. Our studies showed that the solubility of PS-I depended on both the polarity and charge in the hydrophilic head of the lipopeptides and the length of its hydrophobic tail. The best performing lipopeptides in favour of PS-I solubility turned out to be C14DK and C16DK, which were comparable to the optimal amphiphilicity of the conventional chemical surfactants tested. Lipopeptides showed obvious advantages in enhancing PS-I thermostability over sugar surfactant DDM and some full peptide amphiphiles reported previously. Fluorescence spectroscopy along with SDS-PAGE analysis demonstrated that lipopeptides did not undermine the polypeptide composition and conformation of PS-I after solubilization; instead they showed better performance in improving the structural stability and integrity of this multi-subunit membrane protein than conventional detergents. Furthermore, O2 uptake measurements indicated that PS-I solubilized with lipopeptides maintained its functionality. The underlying mechanism for the favorable actions of lipopeptide in PS-I solubilization and stabilization is discussed.
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Affiliation(s)
- Xiaoqiang Wang
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong, P. R. China
| | - Guihong Huang
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong, P. R. China
| | - Daoyong Yu
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong, P. R. China
| | - Baosheng Ge
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong, P. R. China
| | - Jiqian Wang
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong, P. R. China
| | - Fengxi Xu
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong, P. R. China
| | - Fang Huang
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong, P. R. China
- * E-mail: (FH); (HX)
| | - Hai Xu
- State Key Laboratory of Heavy Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong, P. R. China
- * E-mail: (FH); (HX)
| | - Jian R. Lu
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
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703
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Khelashvili G, LeVine MV, Shi L, Quick M, Javitch JA, Weinstein H. The membrane protein LeuT in micellar systems: aggregation dynamics and detergent binding to the S2 site. J Am Chem Soc 2013; 135:14266-75. [PMID: 23980525 PMCID: PMC3788620 DOI: 10.1021/ja405984v] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Structural and functional properties of integral membrane proteins are often studied in detergent micellar environments (proteomicelles), but how such proteomicelles form and organize is not well understood. This makes it difficult to evaluate the relationship between the properties of the proteins measured in such a detergent-solubilized form and under native conditions. To obtain mechanistic information about this relationship for the leucine transporter (LeuT), a prokaryotic homologue of the mammalian neurotransmitter/sodium symporters (NSSs), we studied the properties of proteomicelles formed by n-dodecyl-β,D-maltopyranoside (DDM) detergent. Extensive atomistic molecular dynamics simulations of different protein/detergent/water number ratios revealed the formation of a proteomicelle characterized by a constant-sized shell of detergents surrounding LeuT protecting its transmembrane segments from unfavorable hydrophobic/hydrophilic exposure. Regardless of the DDM content in the simulated system, this shell consisted of a constant number of DDM molecules (∼120 measured at a 4 Å cutoff distance from LeuT). In contrast, the overall number of DDMs in the proteomicelle (aggregation number) was found to depend on the detergent concentration, reaching a saturation value of 226±17 DDMs in the highest concentration regime simulated. Remarkably, we found that at high detergent-to-protein ratios we observed two independent ways of DDM penetration into LeuT, both leading to a positioning of the DDM molecule in the second substrate (S2) binding site of LeuT. Consonant with several recent experimental studies demonstrating changes in functional properties of membrane proteins due to detergent, our findings highlight how the environment in which the membrane proteins are examined may affect the outcome and interpretation of their mechanistic features.
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Affiliation(s)
- George Khelashvili
- Department of Physiology and Biophysics, Weill Cornell Medical College of Cornell University (WCMC) , New York, New York 10065, United States
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704
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Jafurulla M, Rao BD, Sreedevi S, Ruysschaert JM, Covey DF, Chattopadhyay A. Stereospecific requirement of cholesterol in the function of the serotonin1A receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:158-63. [PMID: 24008092 DOI: 10.1016/j.bbamem.2013.08.015] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 08/16/2013] [Accepted: 08/23/2013] [Indexed: 01/04/2023]
Abstract
The serotonin1A receptor is an important member of the G protein-coupled receptor (GPCR) family. It is involved in the generation and modulation of a variety of cognitive and behavioral functions and serves as a drug target. Previous work from our laboratory has established the sensitivity of the function of the serotonin1A receptor to membrane cholesterol. Solubilization of the hippocampal serotonin1A receptor utilizing the zwitterionic detergent CHAPS is accompanied by loss of cholesterol and results in reduction in specific ligand binding. Replenishment of cholesterol to solubilized membranes restores specific ligand binding to the receptor. We utilized this strategy of sterol replenishment of solubilized membranes to explore the stereospecific stringency of cholesterol for receptor function. We used two stereoisomers of cholesterol, ent-cholesterol (enantiomer of cholesterol) and epi-cholesterol (a diastereomer of cholesterol), for this purpose. Importantly, we show here that while ent-cholesterol could replace cholesterol in supporting receptor function, epi-cholesterol could not. These results imply that the requirement of membrane cholesterol for the serotonin1A receptor function is diastereospecific, yet not enantiospecific. Our results extend and help define specificity of the interaction of membrane cholesterol with the serotonin1A receptor, and represent the first report utilizing ent-cholesterol to examine stereospecificity of GPCR-cholesterol interaction.
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Affiliation(s)
- Md Jafurulla
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
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705
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Xia Y, Peng L. Photoactivatable Lipid Probes for Studying Biomembranes by Photoaffinity Labeling. Chem Rev 2013; 113:7880-929. [DOI: 10.1021/cr300419p] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Yi Xia
- Aix-Marseille Université, Centre Interdisciplinaire de Nanoscience de Marseille, CNRS UMR 7325, Campus de Luminy, 13288 Marseille, France
| | - Ling Peng
- Aix-Marseille Université, Centre Interdisciplinaire de Nanoscience de Marseille, CNRS UMR 7325, Campus de Luminy, 13288 Marseille, France
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706
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Purushothaman S, Gauthé BLLE, Brooks NJ, Templer RH, Ces O. Automated laboratory based X-ray beamline with multi-capillary sample chamber. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:085104. [PMID: 24007104 DOI: 10.1063/1.4816825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
An automated laboratory based X-ray beamline with a multi-capillary sample chamber capable of undertaking small angle X-ray scattering measurements on a maximum of 104 samples at a time as a function of temperature between 5 and 85 °C has been developed. The modular format of the system enables the user to simultaneously equilibrate samples at eight different temperatures with an accuracy of ±0.005 °C. This system couples a rotating anode generator and 2D optoelectronic detector with Franks X-ray optics, leading to typical exposure times of less than 5 min for lyotropic liquid crystalline samples. Beamline control including sample exchange and data acquisition has been fully automated via a custom designed LabVIEW framework.
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Affiliation(s)
- S Purushothaman
- Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
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707
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Hocking HG, Zangger K, Madl T. Studying the structure and dynamics of biomolecules by using soluble paramagnetic probes. Chemphyschem 2013; 14:3082-94. [PMID: 23836693 PMCID: PMC4171756 DOI: 10.1002/cphc.201300219] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Indexed: 12/20/2022]
Abstract
Characterisation of the structure and dynamics of large biomolecules and biomolecular complexes by NMR spectroscopy is hampered by increasing overlap and severe broadening of NMR signals. As a consequence, the number of available NMR spectroscopy data is often sparse and new approaches to provide complementary NMR spectroscopy data are needed. Paramagnetic relaxation enhancements (PREs) obtained from inert and soluble paramagnetic probes (solvent PREs) provide detailed quantitative information about the solvent accessibility of NMR-active nuclei. Solvent PREs can be easily measured without modification of the biomolecule; are sensitive to molecular structure and dynamics; and are therefore becoming increasingly powerful for the study of biomolecules, such as proteins, nucleic acids, ligands and their complexes in solution. In this Minireview, we give an overview of the available solvent PRE probes and discuss their applications for structural and dynamic characterisation of biomolecules and biomolecular complexes.
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Affiliation(s)
- Henry G Hocking
- Chair of Biomolecular NMR, Department Chemie, Technische Universität München, 85747 Garching (Germany); Institute of Structural Biology, Helmholtz Zentrum München, 85764 Neuherberg (Germany)
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708
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A detergent-free strategy for the reconstitution of active enzyme complexes from native biological membranes into nanoscale discs. BMC Biotechnol 2013; 13:41. [PMID: 23663692 PMCID: PMC3702409 DOI: 10.1186/1472-6750-13-41] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 05/07/2013] [Indexed: 01/15/2023] Open
Abstract
Background The reconstitution of membrane proteins and complexes into nanoscale lipid bilayer structures has contributed significantly to biochemical and biophysical analyses. Current methods for performing such reconstitutions entail an initial detergent-mediated step to solubilize and isolate membrane proteins. Exposure to detergents, however, can destabilize many membrane proteins and result in a loss of function. Amphipathic copolymers have recently been used to stabilize membrane proteins and complexes following suitable detergent extraction. However, the ability of these copolymers to extract proteins directly from native lipid bilayers for subsequent reconstitution and characterization has not been explored. Results The styrene-maleic acid (SMA) copolymer effectively solubilized membranes of isolated mitochondria and extracted protein complexes. Membrane complexes were reconstituted into polymer-bound nanoscale discs along with endogenous lipids. Using respiratory Complex IV as a model, these particles were shown to maintain the enzymatic activity of multicomponent electron transporting complexes. Conclusions We report a novel process for reconstituting fully operational protein complexes directly from cellular membranes into nanoscale lipid bilayers using the SMA copolymer. This facile, single-step strategy obviates the requirement for detergents and yields membrane complexes suitable for structural and functional studies.
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709
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Oliver RC, Lipfert J, Fox DA, Lo RH, Doniach S, Columbus L. Dependence of micelle size and shape on detergent alkyl chain length and head group. PLoS One 2013; 8:e62488. [PMID: 23667481 PMCID: PMC3648574 DOI: 10.1371/journal.pone.0062488] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 03/20/2013] [Indexed: 11/19/2022] Open
Abstract
Micelle-forming detergents provide an amphipathic environment that can mimic lipid bilayers and are important tools for solubilizing membrane proteins for functional and structural investigations in vitro. However, the formation of a soluble protein-detergent complex (PDC) currently relies on empirical screening of detergents, and a stable and functional PDC is often not obtained. To provide a foundation for systematic comparisons between the properties of the detergent micelle and the resulting PDC, a comprehensive set of detergents commonly used for membrane protein studies are systematically investigated. Using small-angle X-ray scattering (SAXS), micelle shapes and sizes are determined for phosphocholines with 10, 12, and 14 alkyl carbons, glucosides with 8, 9, and 10 alkyl carbons, maltosides with 8, 10, and 12 alkyl carbons, and lysophosphatidyl glycerols with 14 and 16 alkyl carbons. The SAXS profiles are well described by two-component ellipsoid models, with an electron rich outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core composed of the alkyl chains. The minor axis of the elliptical micelle core from these models is constrained by the length of the alkyl chain, and increases by 1.2-1.5 Å per carbon addition to the alkyl chain. The major elliptical axis also increases with chain length; however, the ellipticity remains approximately constant for each detergent series. In addition, the aggregation number of these detergents increases by ∼16 monomers per micelle for each alkyl carbon added. The data provide a comprehensive view of the determinants of micelle shape and size and provide a baseline for correlating micelle properties with protein-detergent interactions.
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Affiliation(s)
- Ryan C. Oliver
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Jan Lipfert
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Daniel A. Fox
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Ryan H. Lo
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
| | - Sebastian Doniach
- Departments of Physics and Applied Physics, Biophysics Program, Stanford, California, United States of America
- Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California, United States of America
| | - Linda Columbus
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, United States of America
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710
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Santos FM, Pedro AQ, Soares RF, Martins R, Bonifácio MJ, Queiroz JA, Passarinha LA. Performance of hydrophobic interaction ligands for human membrane-bound catechol-O
-methyltransferase purification. J Sep Sci 2013; 36:1693-702. [DOI: 10.1002/jssc.201300010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 02/21/2013] [Accepted: 02/28/2013] [Indexed: 12/17/2022]
Affiliation(s)
- Fátima Milhano Santos
- CICS-UBI- Centro de Investigação em Ciências da Saúde; Universidade da Beira Interior; Covilhã Portugal
| | - Augusto Quaresma Pedro
- CICS-UBI- Centro de Investigação em Ciências da Saúde; Universidade da Beira Interior; Covilhã Portugal
| | - Rui Filipe Soares
- CICS-UBI- Centro de Investigação em Ciências da Saúde; Universidade da Beira Interior; Covilhã Portugal
| | - Rita Martins
- CICS-UBI- Centro de Investigação em Ciências da Saúde; Universidade da Beira Interior; Covilhã Portugal
| | - Maria João Bonifácio
- Departamento de Investigação e Desenvolvimento; BIAL; S. Mamede do Coronado Portugal
| | - João António Queiroz
- CICS-UBI- Centro de Investigação em Ciências da Saúde; Universidade da Beira Interior; Covilhã Portugal
| | - Luís António Passarinha
- CICS-UBI- Centro de Investigação em Ciências da Saúde; Universidade da Beira Interior; Covilhã Portugal
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711
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Marty MT, Wilcox KC, Klein WL, Sligar SG. Nanodisc-solubilized membrane protein library reflects the membrane proteome. Anal Bioanal Chem 2013; 405:4009-16. [PMID: 23400332 PMCID: PMC3628400 DOI: 10.1007/s00216-013-6790-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 01/18/2013] [Accepted: 01/24/2013] [Indexed: 11/28/2022]
Abstract
The isolation and identification of unknown membrane proteins offers the prospect of discovering new pharmaceutical targets and identifying key biochemical receptors. However, interactions between membrane protein targets and soluble ligands are difficult to study in vitro due to the insolubility of membrane proteins in non-detergent systems. Nanodiscs, nanoscale discoidal lipid bilayers encircled by a membrane scaffold protein belt, have proven to be an effective platform to solubilize membrane proteins and have been used to study a wide variety of purified membrane proteins. This report details the incorporation of an unbiased population of membrane proteins from Escherichia coli membranes into Nanodiscs. This solubilized membrane protein library (SMPL) forms a soluble in vitro model of the membrane proteome. Since Nanodiscs contain isolated proteins or small complexes, the SMPL is an ideal platform for interactomics studies and pull-down assays of membrane proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the protein population before and after formation of the Nanodisc library indicates that a large percentage of the proteins are incorporated into the library. Proteomic identification of several prominent bands demonstrates the successful incorporation of outer and inner membrane proteins into the Nanodisc library.
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Affiliation(s)
- Michael T. Marty
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Kyle C. Wilcox
- Department of Neurobiology, Northwestern University, Evanston, IL 60208; USA
| | - William L. Klein
- Department of Neurobiology, Northwestern University, Evanston, IL 60208; USA
| | - Stephen G. Sligar
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
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712
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Yuzlenko O, Lazaridis T. Membrane protein native state discrimination by implicit membrane models. J Comput Chem 2013; 34:731-8. [PMID: 23224861 PMCID: PMC3584241 DOI: 10.1002/jcc.23189] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 10/16/2012] [Accepted: 10/28/2012] [Indexed: 02/01/2023]
Abstract
Four implicit membrane models [IMM1, generalized Born (GB)-surface area-implicit membrane (GBSAIM), GB with a simple switching (GBSW), and heterogeneous dielectric GB (HDGB)] were tested for their ability to discriminate the native conformation of five membrane proteins from 450 decoys generated by the Rosetta-Membrane program. The energy ranking of the native state and Z-scores were used to assess the performance of the models. The effect of membrane thickness was examined and was found to be substantial. Quite satisfactory discrimination was achieved with the all-atom IMM1 and GBSW models at 25.4 Å thickness and with the HDGB model at 28.5 Å thickness. The energy components by themselves were not discriminative. Both van der Waals and electrostatic interactions contributed to native state discrimination, to a different extent in each model. Computational efficiency of the models decreased in the order: extended-atom IMM1 > all-atom IMM1 > GBSAIM > GBSW > HDGB. These results encourage the further development and use of implicit membrane models for membrane protein structure prediction.
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Affiliation(s)
- Olga Yuzlenko
- Department of Chemistry, City College of the City University of New York, 160 Convent Avenue, New York, New York 10031, USA
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713
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Abstract
Mass spectrometry (MS) of intact soluble protein complexes has emerged as a powerful technique to study the stoichiometry, structure-function and dynamics of protein assemblies. Recent developments have extended this technique to the study of membrane protein complexes, where it has already revealed subunit stoichiometries and specific phospholipid interactions. Here we describe a protocol for MS of membrane protein complexes. The protocol begins with the preparation of the membrane protein complex, enabling not only the direct assessment of stoichiometry, delipidation and quality of the target complex but also the evaluation of the purification strategy. A detailed list of compatible nonionic detergents is included, along with a protocol for screening detergents to find an optimal one for MS, biochemical and structural studies. This protocol also covers the preparation of lipids for protein-lipid binding studies and includes detailed settings for a quadrupole time-of-flight (Q-TOF) mass spectrometer after the introduction of complexes from gold-coated nanoflow capillaries.
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Affiliation(s)
- Arthur Laganowsky
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 5QY, UK
| | - Eamonn Reading
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 5QY, UK
| | - Jonathan T.S. Hopper
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 5QY, UK
| | - Carol V. Robinson
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 5QY, UK
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714
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Transmembrane signaling and assembly of the cytochrome b6f-lipidic charge transfer complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:1295-308. [PMID: 23507619 DOI: 10.1016/j.bbabio.2013.03.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 02/27/2013] [Accepted: 03/06/2013] [Indexed: 12/30/2022]
Abstract
Structure-function properties of the cytochrome b6f complex are sufficiently unique compared to those of the cytochrome bc1 complex that b6f should not be considered a trivially modified bc1 complex. A unique property of the dimeric b6f complex is its involvement in transmembrane signaling associated with the p-side oxidation of plastoquinol. Structure analysis of lipid binding sites in the cyanobacterial b6f complex prepared by hydrophobic chromatography shows that the space occupied by the H transmembrane helix in the cytochrome b subunit of the bc1 complex is mostly filled by a lipid in the b6f crystal structure. It is suggested that this space can be filled by the domain of a transmembrane signaling protein. The identification of lipid sites and likely function defines the intra-membrane conserved central core of the b6f complex, consisting of the seven trans-membrane helices of the cytochrome b and subunit IV polypeptides. The other six TM helices, contributed by cytochrome f, the iron-sulfur protein, and the four peripheral single span subunits, define a peripheral less conserved domain of the complex. The distribution of conserved and non-conserved domains of each monomer of the complex, and the position and inferred function of a number of the lipids, suggests a model for the sequential assembly in the membrane of the eight subunits of the b6f complex, in which the assembly is initiated by formation of the cytochrome b6-subunit IV core sub-complex in a monomer unit. Two conformations of the unique lipidic chlorophyll a, defined in crystal structures, are described, and functions of the outlying β-carotene, a possible 'latch' in supercomplex formation, are discussed. This article is part of a Special Issue entitled: Respiratory complex III and related bc complexes.
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715
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Abstract
Liposome structures have a wide range of applications in biology, biochemistry, and biophysics. As a result, several methods for forming liposomes have been developed. This review provides a critical comparison of existing microfluidic technologies for forming liposomes and, when applicable, a comparison with their analogous macroscale counterparts. The properties of the generated liposomes, including size, size distribution, lamellarity, membrane composition, and encapsulation efficiency, form the basis for comparison. We hope that this critique will allow the reader to make an informed decision as to which method should be used for a given biological application.
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Affiliation(s)
- Dirk van Swaay
- Institute for Chemical and Bioengineering, ETH Zurich, Zurich, Switzerland
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716
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Yuan M, Yeung CW, Li YY, Diao H, Cheung KMC, Chan D, Cheah K, Chan PB. Effects of nucleus pulposus cell-derived acellular matrix on the differentiation of mesenchymal stem cells. Biomaterials 2013; 34:3948-3961. [PMID: 23465833 DOI: 10.1016/j.biomaterials.2013.02.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Accepted: 02/01/2013] [Indexed: 12/18/2022]
Abstract
Recent attempts to treat disc degeneration with mesenchymal stem cells (MSCs) showed encouraging results. Differentiating MSCs towards nucleus pulposus cell (NPC)-like lineages represents a speculative mechanism. Niche factors including hypoxia, growth factors and cell-cell interactions have been suggested but the matrix niche factor has not been studied. Our collagen microencapsulation provides a 3D model to study matrix niche as it enables the encapsulated cells to remodel the template matrix. We previously demonstrated the chondro-inductive role of of chondrocytes-derived matrix in MSCs and showed that NPCs maintained their phenotype and remodeled the template matrix of collagen microspheres into a glycosaminoglycan (GAG)-rich one. Here we aim to study the effects of NPC-derived matrix on MSC differentiation towards NPC-like lineages by firstly producing an NPC-derived matrix in collagen microspheres, secondly optimizing a decellularization protocol to discard NPCs yet retaining the matrix, thirdly repopulating the acellular NPC-derived matrix with MSCs and fourthly evaluating their phenotype. Finally, we injected these microspheres in a pilot rabbit disc degeneration model. Results showed that NPCs survived, maintained their phenotypic markers and produced GAGs. A decellularization protocol with maximal removal of the NPCs, minimal loss in major matrix components and partial retention of NPC-specific markers was identified. The resulting acellular matrix supported MSC survival and matrix production, and up-regulated the gene expression of NPC markers including type II collagen and glypican 3. Finally, injection of MSC in these microspheres in rabbit degenerative disc better maintained hydration level with more pronounced staining of GAGs and type II collagen than controls.
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Affiliation(s)
- Minting Yuan
- Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region
| | - Chiu Wai Yeung
- Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region
| | - Yuk Yin Li
- Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region
| | - Huajia Diao
- Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region
| | - K M C Cheung
- Department of Biochemistry, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region
| | - D Chan
- Department of Orthopaedics & Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region
| | - K Cheah
- Department of Orthopaedics & Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region
| | - Pui Barbara Chan
- Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region.
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717
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Kuhnline Sloan CD, Marty MT, Sligar SG, Bailey RC. Interfacing lipid bilayer nanodiscs and silicon photonic sensor arrays for multiplexed protein-lipid and protein-membrane protein interaction screening. Anal Chem 2013; 85:2970-6. [PMID: 23425255 PMCID: PMC3600637 DOI: 10.1021/ac3037359] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Soluble proteins are key mediators of many biochemical signaling pathways via direct interaction with the lipid bilayer and via membrane-bound receptors. Components of the cell membrane are involved in many important biological processes, including viral infection, blood clotting, and signal transduction, and as such, they are common targets of therapeutic agents. Therefore, the development of analytical approaches to study interactions at the cell membrane is of critical importance. Herein, we integrate two key technologies, silicon photonic microring resonator arrays and phospholipid bilayer nanodiscs, which together allow multiplexed screening of soluble protein interactions with lipid and membrane-embedded targets. Microring resonator arrays are an intrinsically multiplexable, label-free analysis platform that has previously been applied to studying protein-protein, protein-nucleic acid, and nucleic acid-nucleic acid interactions. Nanodiscs are protein-stabilized lipid assemblies that represent a convenient construct to mimic the native phospholipid bilayer, investigate the effects of membrane composition, and solubilize membrane-embedded targets. Exploiting the natural affinity of nanodisc-supported lipid bilayers for oxide-passivated silicon, we assembled single and multiplex sensor arrays via direct physisorption, characterizing electrostatic effects on the nanodisc attachment. Using model systems, we demonstrate the applicability of this platform for the parallel screening of protein interactions with nanodisc-embedded lipids, glycolipids, and membrane proteins.
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Affiliation(s)
| | - Michael T. Marty
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL, 61801
| | - Stephen G. Sligar
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL, 61801
- Department of Biochemistry, University of Illinois Urbana-Champaign, Urbana, IL, 61801
| | - Ryan C. Bailey
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL, 61801
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718
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Manzo G, Carboni M, Rinaldi AC, Casu M, Scorciapino MA. Characterization of sodium dodecylsulphate and dodecylphosphocholine mixed micelles through NMR and dynamic light scattering. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2013; 51:176-183. [PMID: 23364831 DOI: 10.1002/mrc.3930] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 12/26/2012] [Accepted: 01/04/2012] [Indexed: 06/01/2023]
Abstract
The complexity of biological membranes leads to the use of extremely simplified models in biophysical investigations of membrane-bound proteins and peptides. Liposomes are probably the most widely used membrane models due, especially, to their versatility in terms of electric charge and size. However, liquid-state NMR suffers the lack of such a model, because even the smallest liposomes slowly tumble in solution, resulting in a dramatic signals broadening. Micelles are typically used as good substitutes, with sodium dodecylsulphate (SDS) and dodecylphosphocholine (DPC) being the most widely employed surfactants. However, they are always used separately to mimic prokaryotic and eukaryotic membranes, respectively, and accurate investigations as a function of surface charge cannot be performed. In this work, the critical micelle concentration (CMC) of binary mixtures with different SDS/DPC ratios has been determined by following the chemical shift variation of selected (1)H and (31)P NMR signals as a function of total surfactant concentration. The regular solution theory and the Motomura's formalism have been applied to characterize the micellization both in water and in phosphate buffer saline, and results were compared with those obtained directly from the experimental NMR chemical shift. The ζ-potential and size distribution of the mixed micelles have been estimated with dynamic light scattering measurements. Results showed that SDS and DPC are synergic and can be used together to prepare mixed micelles with different negative/zwitterionic surfactants molar ratio.
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Affiliation(s)
- Giorgia Manzo
- Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria di Monserrato, I-09042, Monserrato, CA, Italy
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719
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Inagaki S, Ghirlando R, Grisshammer R. Biophysical characterization of membrane proteins in nanodiscs. Methods 2013; 59:287-300. [PMID: 23219517 PMCID: PMC3608844 DOI: 10.1016/j.ymeth.2012.11.006] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 11/20/2012] [Accepted: 11/23/2012] [Indexed: 12/25/2022] Open
Abstract
Nanodiscs are self-assembled discoidal phospholipid bilayers surrounded and stabilized by membrane scaffold proteins (MSPs), that have become a powerful and promising tool for the study of membrane proteins. Even though their reconstitution is highly regulated by the type of MSP and phospholipid input, a biophysical characterization leading to the determination of the stoichiometry of MSP, lipid and membrane protein is essential. This is important for biological studies, as the oligomeric state of membrane proteins often correlates with their functional activity. Typically combinations of several methods are applied using, for example, modified samples that incorporate fluorescent labels, along with procedures that result in nanodisc disassembly and lipid dissolution. To obtain a comprehensive understanding of the native properties of nanodiscs, modification-free analysis methods are required. In this work we provide a strategy, using a combination of dynamic light scattering and analytical ultracentrifugation, for the biophysical characterization of unmodified nanodiscs. In this manner we characterize the nanodisc preparation in terms of its overall polydispersity and characterize the hydrodynamically resolved nanodisc of interest in terms of its sedimentation coefficient, Stokes' radius and overall protein and lipid stoichiometry. Functional and biological applications are also discussed for the study of the membrane protein embedded in nanodiscs under defined experimental conditions.
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Affiliation(s)
- Sayaka Inagaki
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, 5625 Fishers Lane, Room 4S12, Rockville, Maryland 20852, USA
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Building 5, Room 208, 5 Memorial Drive, Bethesda, Maryland, 20814, USA
| | - Reinhard Grisshammer
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, 5625 Fishers Lane, Room 4S12, Rockville, Maryland 20852, USA
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720
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Su PC, Si W, Baker DL, Berger BW. High-yield membrane protein expression from E. coli using an engineered outer membrane protein F fusion. Protein Sci 2013; 22:434-43. [PMID: 23345122 DOI: 10.1002/pro.2224] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 11/12/2012] [Accepted: 01/15/2013] [Indexed: 11/12/2022]
Abstract
Obtaining high yields of membrane proteins necessary to perform detailed structural study is difficult due to poor solubility and variability in yields from heterologous expression systems. To address this issue, an Escherichia coli-based membrane protein overexpression system utilizing an engineered bacterial outer membrane protein F (pOmpF) fusion has been developed. Full-length human receptor activity-modifying protein 1 (RAMP1) was expressed using pOmpF, solubilized in FC15 and purified to homogeneity. Using circular dichroism and fluorescence spectroscopy, purified full-length RAMP1 is composed of approximately 90% α-helix, and retains its solubility and structure in FC15 over a wide range of temperatures (20-60°C). Thus, our approach provides a useful, complementary approach to achieve high-yield, full-length membrane protein overexpression for biophysical studies.
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Affiliation(s)
- Pin-Chuan Su
- Department of Chemical Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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721
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Rubio L, Alonso C, Rodríguez G, Cócera M, López-Iglesias C, Coderch L, De la Maza A, Parra J, López O. Bicellar systems as new delivery strategy for topical application of flufenamic acid. Int J Pharm 2013; 444:60-9. [DOI: 10.1016/j.ijpharm.2013.01.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 01/14/2013] [Accepted: 01/17/2013] [Indexed: 11/25/2022]
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722
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Dürr UH, Soong R, Ramamoorthy A. When detergent meets bilayer: birth and coming of age of lipid bicelles. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2013; 69:1-22. [PMID: 23465641 PMCID: PMC3741677 DOI: 10.1016/j.pnmrs.2013.01.001] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 08/30/2012] [Indexed: 05/12/2023]
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723
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Visualizing a multidrug resistance protein, EmrE, with major bacterial lipids using Brewster angle microscopy. Chem Phys Lipids 2013; 167-168:33-42. [DOI: 10.1016/j.chemphyslip.2013.01.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 12/22/2012] [Accepted: 01/18/2013] [Indexed: 11/17/2022]
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724
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Addition of subunit γ, K+ ions, and lipid restores the thermal stability of solubilized Na,K-ATPase. Arch Biochem Biophys 2013; 530:93-100. [DOI: 10.1016/j.abb.2012.12.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 12/21/2012] [Accepted: 12/23/2012] [Indexed: 11/19/2022]
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725
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Lichtenberg D, Ahyayauch H, Alonso A, Goñi FM. Detergent solubilization of lipid bilayers: a balance of driving forces. Trends Biochem Sci 2013; 38:85-93. [DOI: 10.1016/j.tibs.2012.11.005] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 11/15/2012] [Accepted: 11/20/2012] [Indexed: 11/25/2022]
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726
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Hagn F, Etzkorn M, Raschle T, Wagner G. Optimized phospholipid bilayer nanodiscs facilitate high-resolution structure determination of membrane proteins. J Am Chem Soc 2013; 135:1919-25. [PMID: 23294159 DOI: 10.1021/ja310901f] [Citation(s) in RCA: 391] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Structural studies of membrane proteins are still hampered by difficulties of finding appropriate membrane-mimicking media that maintain protein structure and function. Phospholipid nanodiscs seem promising to overcome the intrinsic problems of detergent-containing environments. While nanodiscs can offer a near-native environment, the large particle size complicates their routine use in the structural analysis of membrane proteins by solution NMR. Here, we introduce nanodiscs assembled from shorter ApoA-I protein variants that are of markedly smaller diameter and show that the resulting discs provide critical improvements for the structure determination of membrane proteins by NMR. Using the bacterial outer-membrane protein OmpX as an example, we demonstrate that the combination of small nanodisc size, high deuteration levels of protein and lipids, and the use of advanced non-uniform NMR sampling methods enable the NMR resonance assignment as well as the high-resolution structure determination of polytopic membrane proteins in a detergent-free, near-native lipid bilayer setting. By applying this method to bacteriorhodopsin, we show that our smaller nanodiscs can also be beneficial for the structural characterization of the important class of seven-transmembrane helical proteins. Our set of engineered nanodiscs of subsequently smaller diameters can be used to screen for optimal NMR spectral quality for small to medium-sized membrane proteins while still providing a functional environment. In addition to their key improvements for de novo structure determination, due to their smaller size these nanodiscs enable the investigation of interactions between membrane proteins and their (soluble) partner proteins, unbiased by the presence of detergents that might disrupt biologically relevant interactions.
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Affiliation(s)
- Franz Hagn
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, United States
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727
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How to investigate interactions between membrane proteins and ligands by solid-state NMR. Methods Mol Biol 2013; 914:65-86. [PMID: 22976023 DOI: 10.1007/978-1-62703-023-6_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
Solid-state NMR is an established method for biophysical studies of membrane proteins within the lipid bilayers and an emerging technique for structural biology in general. In particular magic angle sample spinning has been found to be very useful for the investigation of large membrane proteins and their interaction with small molecules within the lipid bilayer. Using a number of examples, we illustrate and discuss in this chapter, which information can be gained and which experimental parameters need to be considered when planning such experiments. We focus especially on the interaction of diffusive ligands with membrane proteins.
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728
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Noguchi H. Structure formation in binary mixtures of lipids and detergents: Self-assembly and vesicle division. J Chem Phys 2013; 138:024907. [DOI: 10.1063/1.4774324] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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729
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Tauran Y, Brioude A, Shahgaldian P, Cumbo A, Kim B, Perret F, Coleman AW, Montasser I. Calix-arene silver nanoparticles interactions with surfactants are charge, size and critical micellar concentration dependent. Chem Commun (Camb) 2013; 48:9483-5. [PMID: 22899213 DOI: 10.1039/c2cc34670b] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The interactions of silver nanoparticles capped by various calix[n]arenes bearing sulphonate groups at the para and/or phenolic faces with cationic, neutral and anionic surfactants have been studied. Changes in the plasmonic absorption show that only the calix[4]arene derivatives sulphonated at the para-position interact and then only with cationic surfactants. The interactions follow the CMC values of the surfactants either as simple molecules or mixed micelles.
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Affiliation(s)
- Yannick Tauran
- LMI CNRS UMR 5615, Univ. Lyon 1, Villeurbanne, F69622, France
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730
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Skieterska K, Duchou J, Lintermans B, Van Craenenbroeck K. Detection of G Protein-Coupled Receptor (GPCR) Dimerization by Coimmunoprecipitation. Methods Cell Biol 2013; 117:323-40. [DOI: 10.1016/b978-0-12-408143-7.00017-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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731
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Bartsch P, Harsman A, Wagner R. Single channel analysis of membrane proteins in artificial bilayer membranes. Methods Mol Biol 2013; 1033:345-61. [PMID: 23996188 DOI: 10.1007/978-1-62703-487-6_22] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The planar lipid bilayer technique is a powerful experimental approach for electrical single channel recordings of pore-forming membrane proteins in a chemically well-defined and easily modifiable environment. Here we provide a general survey of the basic materials and procedures required to set up a robust bilayer system and perform electrophysiological single channel recordings of reconstituted proteins suitable for the in-depth characterization of their functional properties.
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Affiliation(s)
- Philipp Bartsch
- Biophysics, Department of Biology/Chemistry, University of Osnabrueck, Osnabrueck, Germany
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732
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Recent Developments in the Production, Analysis, and Applications of Cubic Phases Formed by Lipids. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/b978-0-12-411515-6.00006-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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733
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Directed evolution of G-protein-coupled receptors for high functional expression and detergent stability. Methods Enzymol 2013; 520:67-97. [PMID: 23332696 DOI: 10.1016/b978-0-12-391861-1.00004-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
G-protein-coupled receptors (GPCRs) are cell-surface receptors exhibiting a key role in cellular signal transduction processes, thus making them pharmacologically highly relevant target proteins. However, the molecular mechanisms driving receptor activation by ligand binding and signal transduction are poorly understood, since as integral membrane proteins, most GPCRs are very challenging for functional and structural studies. The biophysical properties of natural GPCRs, usually required by the cell in only low amounts, support their functionality in the lipid bilayer but are insufficient for high-level recombinant overexpression and stability in detergent solution. Current structural information about GPCRs is thus limited to a subset of GPCRs with either intrinsically favorable or properly improved biophysical behavior. Recently, directed protein evolution techniques for functional expression and detergent stability have been developed to increase the accessibility of GPCRs for functional and structural studies. Directed evolution does not rely on any preconceived notion of what might be limiting biophysical properties. By random mutagenesis combined with a high-throughput screening and selection system, directed protein evolution has the power to efficiently isolate rare phenotypes and thus contribute to the elucidation of the stability-determining factors, in addition to solving the practical problem of creating stable GPCRs. In the current chapter, protocols for generation of genetic diversity within GPCRs and selection are provided and discussed.
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734
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Abstract
Differential scanning calorimetry (DSC) is a highly sensitive non-perturbing technique for measuring the thermodynamic properties of thermally induced transitions. This technique is particularly useful for the characterization of lipid/protein interactions. This chapter presents an introduction to DSC instrumentation, basic theory, and methods and describes DSC applications for characterizing protein effects on model lipid membranes. Examples of the use of DSC for the evaluation of protein effects on modulation of membrane domains and membrane stability are given.
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Affiliation(s)
- Olga Cañadas
- Department of Biochemistry and Molecular Biology I, Faculty of Biology, CIBER de Enfermedades Respiratorias, Madrid, Spain
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735
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Lynch AP, Ahearne M. Strategies for developing decellularized corneal scaffolds. Exp Eye Res 2012; 108:42-7. [PMID: 23287438 DOI: 10.1016/j.exer.2012.12.012] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 12/17/2012] [Accepted: 12/18/2012] [Indexed: 12/01/2022]
Abstract
The main obstacle to successfully engineering corneal tissue has been the replication of the structural and biochemical composition of native cornea in a scaffold. In recent years decellularized corneas have been under investigation as an alternative scaffold source for use in engineering cornea. Several strategies for lysing cells and removing cellular material from corneas are discussed. The removal of such cellular components and antigen molecules whilst maintaining the corneal extracellular matrix components and architecture is required to generate scaffolds capable of generating functional tissue grafts suitable for transplantation. Different techniques to ascertain the degree of decellularization and the change in structural, mechanical and biological characteristics of the corneas after treatment are examined. In addition several in vitro and in vivo studies have been performed to ascertain the suitability of decellularized corneas as a scaffold for restoring vision.
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Affiliation(s)
- Amy P Lynch
- Trinity Centre for Bioengineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
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736
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Dong J, Li Y, Mo X. The study of a new detergent (octyl-glucopyranoside) for decellularizing porcine pericardium as tissue engineering scaffold. J Surg Res 2012; 183:56-67. [PMID: 23267763 DOI: 10.1016/j.jss.2012.11.047] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 10/18/2012] [Accepted: 11/28/2012] [Indexed: 01/12/2023]
Abstract
BACKGROUND The use of extracellular matrix (ECM) derived from decellularized tissue is increasingly frequent in regenerative medicine and tissue engineering. However, it is recognized that currently used decellularization procedures have negative effects on ECM integrity. The objective of this study was to investigate the impact of a decellularization protocol with a new detergent on the ECM integrity of porcine pericardium (PP) compared with other traditional detergents. MATERIALS AND METHODS Fresh PP were decellularized by sodium deoxycholate in combination with Triton X-100 (SDT), sodium dodecyl sulfate (SDS), and octyl-glucopyranoside (OGP), respectively. Histologic analysis and scanning electron microscopy were performed to confirm the removal of cells and to examine the structure of ECM. DNA content was examined by the method of DNA extraction. Mechanical properties and biochemical compositions of ECM were also studied. RESULTS Histologic analysis and DNA determination demonstrated that SDS and OGP completely removed the cells, and the major ECM structure was preserved well for PP treated with 1% (wt/vol) OGP but disrupted for PP treated with SDS; whereas treatment with SDT was insufficient to remove cells from PP. Uniaxial tensile tests showed that PP decellularized by OGP had similar mechanical properties to native PP, whereas the mechanical properties of PP decellularized by SDS and SDT decreased. The biochemical compositions of PP decellularized by OGP were also well conserved, except that glycosaminoglycans markedly decreased. Moreover, the results obtained in the MTT study further indicated that the cytotoxicity of PP decellularized by OGP was significantly lower than that decellularized by SDS and SDT. CONCLUSION It is suggested that the environmentally friendly and nontoxic OGP can be used as a decellularizing agent. The OGP method could achieve both complete removal of cells from native PP and preservation of the matrix structure; thus, it might be a suitable approach to preparation of tissue engineering heart valve scaffold.
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Affiliation(s)
- Jiaoming Dong
- College of Chemistry, Chemical Engineering and Biotechnology, Dong hua University, Shanghai, China
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737
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Leney A, McMorran LM, Radford SE, Ashcroft AE. Amphipathic polymers enable the study of functional membrane proteins in the gas phase. Anal Chem 2012; 84:9841-7. [PMID: 23072351 PMCID: PMC3977578 DOI: 10.1021/ac302223s] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 10/16/2012] [Indexed: 01/11/2023]
Abstract
Membrane proteins are notoriously challenging to analyze using mass spectrometry (MS) because of their insolubility in aqueous solution. Current MS methods for studying intact membrane proteins involve solubilization in detergent. However, detergents can destabilize proteins, leading to protein unfolding and aggregation, or resulting in inactive entities. Amphipathic polymers, termed amphipols, can be used as a substitute for detergents and have been shown to enhance the stability of membrane proteins. Here, we show the utility of amphipols for investigating the structural and functional properties of membrane proteins using electrospray ionization mass spectrometry (ESI-MS). The functional properties of two bacterial outer-membrane β-barrel proteins, OmpT and PagP, in complex with the amphipol A8-35 are demonstrated, and their structural integrities are confirmed in the gas phase using ESI-MS coupled with ion mobility spectrometry (IMS). The data illustrate the power of ESI-IMS-MS in separating distinct populations of amphipathic polymers from the amphipol-membrane complex while maintaining a conformationally "nativelike" membrane protein structure in the gas phase. Together, the data indicate the potential importance and utility of amphipols for the analysis of membrane proteins using MS.
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Affiliation(s)
- Aneika
C. Leney
- Astbury Centre
for Structural Molecular Biology, School
of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Lindsay M. McMorran
- Astbury Centre
for Structural Molecular Biology, School
of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Sheena E. Radford
- Astbury Centre
for Structural Molecular Biology, School
of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Alison E. Ashcroft
- Astbury Centre
for Structural Molecular Biology, School
of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
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738
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Dürr UN, Gildenberg M, Ramamoorthy A. The magic of bicelles lights up membrane protein structure. Chem Rev 2012; 112:6054-74. [PMID: 22920148 PMCID: PMC3497859 DOI: 10.1021/cr300061w] [Citation(s) in RCA: 266] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Indexed: 12/12/2022]
Affiliation(s)
| | - Melissa Gildenberg
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055,
United States
| | - Ayyalusamy Ramamoorthy
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055,
United States
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739
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Karhemo PR, Hyvönen M, Laakkonen P. Metastasis-associated cell surface oncoproteomics. Front Pharmacol 2012; 3:192. [PMID: 23162466 PMCID: PMC3491318 DOI: 10.3389/fphar.2012.00192] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 10/16/2012] [Indexed: 12/18/2022] Open
Abstract
Oncoproteomics aims to the discovery of molecular markers, drug targets, and pathways by studying cancer specific protein expression, localization, modification, and interaction. Cell surface proteins play a central role in several pathological conditions, including cancer and its metastatic spread. However, cell surface proteins are underrepresented in proteomics analyses performed from the whole cell extracts due to their hydrophobicity and low abundance. Different methods have been developed to enrich and isolate the cell surface proteins to reduce sample complexity. Despite the method selected, the primary difficulty encountered is the solubilization of the hydrophobic transmembrane proteins from the lipid bilayer. This review focuses on proteomic analyses of metastasis-associated proteins identified using the cell surface biotinylation method. Interestingly, also certain intracellular proteins were identified from the cell surface samples. The function of these proteins at the cell surface might well differ from their function inside the cell.
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Affiliation(s)
- Piia-Riitta Karhemo
- Research Programs Unit, Molecular Cancer Biology and Institute of Biomedicine, Biomedicum Helsinki, University of Helsinki Helsinki, Finland
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740
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Abstract
Lipid bilayers are natural barriers of biological cells and cellular compartments. Membrane proteins integrated in biological membranes enable vital cell functions such as signal transduction and the transport of ions or small molecules. In order to determine the activity of a protein of interest at defined conditions, the membrane protein has to be integrated into artificial lipid bilayers immobilized on a surface. For the fabrication of such biosensors expertise is required in material science, surface and analytical chemistry, molecular biology and biotechnology. Specifically, techniques are needed for structuring surfaces in the micro- and nanometer scale, chemical modification and analysis, lipid bilayer formation, protein expression, purification and solubilization, and most importantly, protein integration into engineered lipid bilayers. Electrochemical and optical methods are suitable to detect membrane activity-related signals. The importance of structural knowledge to understand membrane protein function is obvious. Presently only a few structures of membrane proteins are solved at atomic resolution. Functional assays together with known structures of individual membrane proteins will contribute to a better understanding of vital biological processes occurring at biological membranes. Such assays will be utilized in the discovery of drugs, since membrane proteins are major drug targets.
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741
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Kumar M, Habel JEO, Shen YX, Meier WP, Walz T. High-density reconstitution of functional water channels into vesicular and planar block copolymer membranes. J Am Chem Soc 2012; 134:18631-7. [PMID: 23082933 PMCID: PMC3497857 DOI: 10.1021/ja304721r] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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The exquisite selectivity and unique transport properties
of membrane
proteins can be harnessed for a variety of engineering and biomedical
applications if suitable membranes can be produced. Amphiphilic block
copolymers (BCPs), developed as stable lipid analogs, form membranes
that functionally incorporate membrane proteins and are ideal for
such applications. While high protein density and planar membrane
morphology are most desirable, BCP–membrane protein aggregates
have so far been limited to low protein densities in either vesicular
or bilayer morphologies. Here, we used dialysis to reproducibly form
planar and vesicular BCP membranes with a high density of reconstituted
aquaporin-0 (AQP0) water channels. We show that AQP0 retains its biological
activity when incorporated at high density in BCP membranes, and that
the morphology of the BCP–protein aggregates can be controlled
by adjusting the amount of incorporated AQP0. We also show that BCPs
can be used to form two-dimensional crystals of AQP0.
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Affiliation(s)
- Manish Kumar
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, United States.
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742
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Lluis MW, Godfroy JI, Yin H. Protein engineering methods applied to membrane protein targets. Protein Eng Des Sel 2012; 26:91-100. [DOI: 10.1093/protein/gzs079] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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743
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Morgner N, Montenegro F, Barrera NP, Robinson CV. Mass spectrometry--from peripheral proteins to membrane motors. J Mol Biol 2012; 423:1-13. [PMID: 22750574 PMCID: PMC4058634 DOI: 10.1016/j.jmb.2012.06.033] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 06/18/2012] [Accepted: 06/20/2012] [Indexed: 10/28/2022]
Abstract
That membrane protein complexes could survive in the gas phase had always seemed impossible. The lack of chargeable residues, high hydrophobicity, and poor solubility and the vast excess of detergent contributed to the view that it would not be possible to obtain mass spectra of intact membrane complexes. With the recent success in recording mass spectra of these complexes, first from recombinant sources and later from the cellular environment, many surprising properties of these gas phase membrane complexes have been revealed. The first of these was that the interactions between membrane and soluble subunits could survive in vacuum, without detergent molecules adhering to the complex. The second unexpected feature was that their hydrophobicity and, consequently, lower charge state did not preclude ionization. The final surprising finding was that these gas phase membrane complexes carry with them lipids, bound specifically in subunit interfaces. This provides us with an opportunity to distinguish annular lipids that surround the membrane complexes, from structural lipids that have a role in maintaining structure and subunit interactions. In this perspective, we track these developments and suggest explanations for the various discoveries made during this research.
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Affiliation(s)
- Nina Morgner
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 5QY, UK
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744
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Sherratt AR, Blais DR, Ghasriani H, Pezacki JP, Goto NK. Activity-Based Protein Profiling of the Escherichia coli GlpG Rhomboid Protein Delineates the Catalytic Core. Biochemistry 2012; 51:7794-803. [DOI: 10.1021/bi301087c] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Allison R. Sherratt
- Department of Biochemistry,
Microbiology and Immunology, University of Ottawa, Health Sciences Campus, 451 Smyth Road, Ottawa, Canada K1H 8M5
| | - David R. Blais
- Steacie Institute for Molecular
Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Canada K1A 0R6
| | - Houman Ghasriani
- Department of Chemistry, University of Ottawa, 10 Marie-Curie, Ottawa, Canada
K1N 6N5
| | - John Paul Pezacki
- Department of Biochemistry,
Microbiology and Immunology, University of Ottawa, Health Sciences Campus, 451 Smyth Road, Ottawa, Canada K1H 8M5
- Steacie Institute for Molecular
Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Canada K1A 0R6
- Department of Chemistry, University of Ottawa, 10 Marie-Curie, Ottawa, Canada
K1N 6N5
| | - Natalie K. Goto
- Department of Biochemistry,
Microbiology and Immunology, University of Ottawa, Health Sciences Campus, 451 Smyth Road, Ottawa, Canada K1H 8M5
- Department of Chemistry, University of Ottawa, 10 Marie-Curie, Ottawa, Canada
K1N 6N5
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745
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Roussel G, Perpète EA, Matagne A, Tinti E, Michaux C. Towards a universal method for protein refolding: The trimeric beta barrel membrane Omp2a as a test case. Biotechnol Bioeng 2012; 110:417-23. [DOI: 10.1002/bit.24722] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 08/09/2012] [Accepted: 08/20/2012] [Indexed: 12/31/2022]
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746
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Orwick-Rydmark M, Lovett JE, Graziadei A, Lindholm L, Hicks MR, Watts A. Detergent-free incorporation of a seven-transmembrane receptor protein into nanosized bilayer Lipodisq particles for functional and biophysical studies. NANO LETTERS 2012; 12:4687-92. [PMID: 22827450 DOI: 10.1021/nl3020395] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
SMA-Lipodisq nanoparticles, with one bacteriorhodopsin (bR) per 12 nm particle on average (protein/lipid molar ratio, 1:172), were prepared without the use of detergents. Using pulsed and continuous wave nitroxide spin label electron paramagnetic resonance, the structural and dynamic integrity of bR was retained when compared with data for bR obtained in the native membrane and in detergents and then with crystal data. This indicates the potential of Lipodisq nanoparticles as a useful membrane mimetic.
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Affiliation(s)
- Marcella Orwick-Rydmark
- Department of Biochemistry, Biomembrane Structure Unit, University of Oxford, Oxford, OX1 3QU, United Kingdom
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747
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Haferkamp I, Linka N. Functional expression and characterisation of membrane transport proteins. PLANT BIOLOGY (STUTTGART, GERMANY) 2012; 14:675-90. [PMID: 22639981 DOI: 10.1111/j.1438-8677.2012.00591.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Membrane transporters set the framework organising the complexity of plant metabolism in cells, tissues and organisms. Their substrate specificity and controlled activity in different cells is a crucial part for plant metabolism to run pathways in concert. Transport proteins catalyse the uptake and exchange of ions, substrates, intermediates, products and cofactors across membranes. Given the large number of metabolites, a wide spectrum of transporters is required. The vast majority of in silico annotated membrane transporters in plant genomes, however, has not yet been functionally characterised. Hence, to understand the metabolic network as a whole, it is important to understand how transporters connect and control the metabolic pathways of plant cells. Heterologous expression and in vitro activity studies of recombinant transport proteins have highly improved their functional analysis in the last two decades. This review provides a comprehensive overview of the recent advances in membrane protein expression and functional characterisation using various host systems and transport assays.
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Affiliation(s)
- I Haferkamp
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - N Linka
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
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748
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Harder D, Fotiadis D. Measuring substrate binding and affinity of purified membrane transport proteins using the scintillation proximity assay. Nat Protoc 2012; 7:1569-78. [PMID: 22864198 DOI: 10.1038/nprot.2012.090] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The scintillation proximity assay (SPA) is a rapid radioligand binding assay. Upon binding of radioactively labeled ligands (here L-[(3)H]arginine or D-[(3)H]glucose) to acceptor proteins immobilized on fluoromicrospheres (containing the scintillant), a light signal is stimulated and measured. The application of SPA to purified, detergent-solubilized membrane transport proteins allows substrate-binding properties to be assessed (e.g., substrate specificity and affinity), usually within 1 d. Notably, the SPA makes it possible to study specific transporters without interference from other cellular components, such as endogenous transporters. Reconstitution of the target transporter into proteoliposomes is not required. The SPA procedure allows high sample throughput and simple sample handling without the need for washing or separation steps: components are mixed in one well and the signal is measured directly after incubation. Therefore, the SPA is an excellent tool for high-throughput screening experiments, e.g., to search for substrates and inhibitors, and it has also recently become an attractive tool for drug discovery.
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Affiliation(s)
- Daniel Harder
- Institute of Biochemistry and Molecular Medicine, and Swiss National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland
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749
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Lu H, Hoshiba T, Kawazoe N, Chen G. Comparison of decellularization techniques for preparation of extracellular matrix scaffolds derived from three-dimensional cell culture. J Biomed Mater Res A 2012; 100:2507-16. [PMID: 22623317 DOI: 10.1002/jbm.a.34150] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 02/16/2012] [Indexed: 11/09/2022]
Abstract
Extracellular matrix (ECM) scaffolds derived from cultured cells have drawn increasing attention for use in tissue engineering. We have developed a method to prepare cultured cell-derived ECM scaffolds by combining three-dimensional cell culture, decellularization, and selective template removal. Cell-ECM-template complexes were first formed by culture of cells in a poly(lactic-co-glycolic acid) (PLGA) mesh template to deposit their own ECM. The complexes were subsequently decellularized to remove cellular components. Finally, the PLGA template was selectively removed to obtain the ECM scaffolds. Seven decellularization methods were compared for their decellularization effects during scaffold preparation. They were: freeze-thaw cycling (-80°C, six times) with ammonia water (25 mM); 0.1% Triton™ X-100 (TX100) with 1.5M KCl aqueous solution; freeze-thaw cycling alone; ammonia water alone; TX100 extraction; osmotic shock with 1.5M KCl; and freeze-thaw cycling with 3M NaCl. Among these methods, the methods of freeze-thaw cycling with NH(4) OH and TX100 with 1.5M KCl showed the best effect on the removal of cellular components from the complexes, while the other five methods could only partially remove cellular components. The ECM scaffolds prepared by these two methods had similar gross appearances and microstructures. In vivo implantation of the ECM scaffolds prepared by these two methods induced mild host responses. The two decellularization methods were demonstrated to be effective for preparation of cultured cell-derived ECM scaffolds.
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Affiliation(s)
- Hongxu Lu
- Tissue Regeneration Materials Unit, International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba, Ibaraki, Japan
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750
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Kopera E, Belczyk-Ciesielska A, Bal W. Application of Ni(II)-assisted peptide bond hydrolysis to non-enzymatic affinity tag removal. PLoS One 2012; 7:e36350. [PMID: 22574150 PMCID: PMC3344860 DOI: 10.1371/journal.pone.0036350] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 04/02/2012] [Indexed: 11/18/2022] Open
Abstract
In this study, we demonstrate a non-enzymatic method for hydrolytic peptide bond cleavage, applied to the removal of an affinity tag from a recombinant fusion protein, SPI2-SRHWAP-His(6). This method is based on a highly specific Ni(II) reaction with (S/T)XHZ peptide sequences. It can be applied for the protein attached to an affinity column or to the unbound protein in solution. We studied the effect of pH, temperature and Ni(II) concentration on the efficacy of cleavage and developed an analytical protocol, which provides active protein with a 90% yield and ∼100% purity. The method works well in the presence of non-ionic detergents, DTT and GuHCl, therefore providing a viable alternative for currently used techniques.
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Affiliation(s)
- Edyta Kopera
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | | | - Wojciech Bal
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
- * E-mail:
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