1
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The Structural and Functional Diversity of Intrinsically Disordered Regions in Transmembrane Proteins. J Membr Biol 2019; 252:273-292. [DOI: 10.1007/s00232-019-00069-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 05/17/2019] [Indexed: 10/26/2022]
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2
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Le Bon C, Marconnet A, Masscheleyn S, Popot JL, Zoonens M. Folding and stabilizing membrane proteins in amphipol A8-35. Methods 2018; 147:95-105. [PMID: 29678587 DOI: 10.1016/j.ymeth.2018.04.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 04/06/2018] [Accepted: 04/13/2018] [Indexed: 01/07/2023] Open
Abstract
Membrane proteins (MPs) are important pharmacological targets because of their involvement in many essential cellular processes whose dysfunction can lead to a large variety of diseases. A detailed knowledge of the structure of MPs and the molecular mechanisms of their activity is essential to the design of new therapeutic agents. However, studying MPs in vitro is challenging, because it generally implies their overexpression under a functional form, followed by their extraction from membranes and purification. Targeting an overexpressed MP to a membrane is often toxic and expression yields tend to be limited. One alternative is the formation of inclusion bodies (IBs) in the cytosol of the cell, from which MPs need then to be folded to their native conformation before structural and functional analysis can be contemplated. Folding MPs targeted to IBs is a difficult task. Specially designed amphipathic polymers called 'amphipols' (APols), which have been initially developed with the view of improving the stability of MPs in aqueous solutions compared to detergents, can be used to fold both α-helical and β-barrel MPs. APols represent an interesting novel amphipathic medium, in which high folding yields can be achieved. In this review, the properties of APol A8-35 and of the complexes they form with MPs are summarized. An overview of the most important studies reported so far using A8-35 to fold MPs is presented. Finally, from a practical point of view, a detailed description of the folding and trapping methods is given.
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Affiliation(s)
- Christel Le Bon
- CNRS/Université Paris-7 UMR 7099, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France
| | - Anaïs Marconnet
- CNRS/Université Paris-7 UMR 7099, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France
| | - Sandrine Masscheleyn
- CNRS/Université Paris-7 UMR 7099, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France
| | - Jean-Luc Popot
- CNRS/Université Paris-7 UMR 7099, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France
| | - Manuela Zoonens
- CNRS/Université Paris-7 UMR 7099, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France.
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3
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Affiliation(s)
- M. J. Greenall
- Institute of Mathematics,
Physics and Computer Science, Physical Sciences Building, Aberystwyth University, Aberystwyth SY23 3BZ, United Kingdom
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4
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Analysing DHPC/DMPC bicelles by diffusion NMR and multivariate decomposition. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2910-7. [DOI: 10.1016/j.bbamem.2015.09.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 08/06/2015] [Accepted: 09/01/2015] [Indexed: 12/16/2022]
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5
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Folding and stability of integral membrane proteins in amphipols. Arch Biochem Biophys 2014; 564:327-43. [PMID: 25449655 DOI: 10.1016/j.abb.2014.10.013] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 10/11/2014] [Accepted: 10/22/2014] [Indexed: 11/23/2022]
Abstract
Amphipols (APols) are a family of amphipathic polymers designed to keep transmembrane proteins (TMPs) soluble in aqueous solutions in the absence of detergent. APols have proven remarkably efficient at (i) stabilizing TMPs, as compared to detergent solutions, and (ii) folding them from a denatured state to a native, functional one. The underlying physical-chemical mechanisms are discussed.
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6
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Le Bon C, Popot JL, Giusti F. Labeling and functionalizing amphipols for biological applications. J Membr Biol 2014; 247:797-814. [PMID: 24696186 PMCID: PMC4185061 DOI: 10.1007/s00232-014-9655-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 03/07/2014] [Indexed: 12/19/2022]
Abstract
Amphipols (APols) are short amphipathic polymers developed as an alternative to detergents for handling membrane proteins (MPs) in aqueous solution. MPs are, as a rule, much more stable following trapping with APols than they are in detergent solutions. The best-characterized APol to date, called A8-35, is a mixture of short-chain sodium polyacrylates randomly derivatized with octylamine and isopropylamine. Its solution properties have been studied in detail, and it has been used extensively for biochemical and biophysical studies of MPs. One of the attractive characteristics of APols is that it is relatively easy to label them, isotopically or otherwise, without affecting their physical-chemical properties. Furthermore, several variously modified APols can be mixed, achieving multiple functionalization of MP/APol complexes in the easiest possible manner. Labeled or tagged APols are being used to study the solution properties of APols, their miscibility, their biodistribution upon injection into living organisms, their association with MPs and the composition, structure and dynamics of MP/APol complexes, examining the exchange of surfactants at the surface of MPs, labeling MPs to follow their distribution in fractionation experiments or to immobilize them, increasing the contrast between APols and solvent or MPs in biophysical experiments, improving NMR spectra, etc. Labeling or functionalization of APols can take various courses, each of which has its specific constraints and advantages regarding both synthesis and purification. The present review offers an overview of the various derivatives of A8-35 and its congeners that have been developed in our laboratory and discusses the pros and cons of various synthetic routes.
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Affiliation(s)
- Christel Le Bon
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, UMR 7099, Institut de Biologie Physico-Chimique (FRC 550), CNRS/Université Paris 7, 13 rue Pierre et Marie Curie, 75005, Paris, France
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7
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Abstract
Amphipols (APols) are short amphipathic polymers that can substitute for detergents at the transmembrane surface of membrane proteins (MPs) and, thereby, keep them soluble in detergent free aqueous solutions. APol-trapped MPs are, as a rule, more stable biochemically than their detergent-solubilized counterparts. APols have proven useful to produce MPs, most noticeably by assisting their folding from the denatured state obtained after solubilizing MP inclusion bodies in either SDS or urea. They facilitate the handling in aqueous solution of fragile MPs for the purpose of proteomics, structural and functional studies, and therapeutics. Because APols can be chemically labeled or functionalized, and they form very stable complexes with MPs, they can also be used to functionalize those indirectly, which opens onto many novel applications. Following a brief recall of the properties of APols and MP/APol complexes, an update is provided of recent progress in these various fields.
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Affiliation(s)
- Manuela Zoonens
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, Institut de Biologie Physico-Chimique (FRC 550), Centre National de la Recherche Scientifique/Université Paris-7, 13, rue Pierre-et-Marie-Curie, 75005 Paris, France
| | - Jean-Luc Popot
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, Institut de Biologie Physico-Chimique (FRC 550), Centre National de la Recherche Scientifique/Université Paris-7, 13, rue Pierre-et-Marie-Curie, 75005 Paris, France
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8
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Li M, Morales HH, Katsaras J, Kučerka N, Yang Y, Macdonald PM, Nieh MP. Morphological characterization of DMPC/CHAPSO bicellar mixtures: a combined SANS and NMR study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:15943-15957. [PMID: 24059815 DOI: 10.1021/la402799b] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Spontaneously forming structures of a system composed of dimyristoyl phosphatidylcholine (DMPC) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) were studied by small-angle neutron scattering (SANS), (31)P NMR, and stimulated echo (STE) pulsed field gradient (PFG) (1)H NMR diffusion measurements. Charged lipid dimyristoyl phosphatidylglycerol (DMPG) was used to induce different surface charge densities. The structures adopted were investigated as a function of temperature and lipid concentration for samples with a constant molar ratio of long-chain to short-chain lipids (= 3). In the absence of DMPG, zwitterionic bicellar mixtures exhibited a phase transition from discoidal bicelles, or ribbons, to multilamellar vesicles either upon dilution or with increased temperature. CHAPSO-containing mixtures showed a higher thermal stability in morphology than DHPC-containing mixtures at the corresponding lipid concentrations. In the presence of DMPG, discoidal bicelles (or ribbons) were also found at low temperature and lower lipid concentration mixtures. At high temperature, perforated lamellae were observed in high-concentration mixtures (≥7.5 wt %) whereas uniform unilamellar vesicles and bicelles formed in low-concentration mixtures (≤2.5 wt %), respectively, when the mixtures were moderately and highly charged. From the results, spontaneous structural diagrams of the zwitterionic and charged systems were constructed.
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Affiliation(s)
- Ming Li
- Polymer Program, Institute of Materials Science, University of Connecticut , Storrs, Connecticut 06269, United States
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9
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Detergent quantification in membrane protein samples and its application to crystallization experiments. Amino Acids 2013; 45:1293-302. [PMID: 24105076 DOI: 10.1007/s00726-013-1600-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 09/19/2013] [Indexed: 10/26/2022]
Abstract
The structural characterization of membrane proteins remains a challenging field, largely because the use of stabilizing detergents is required. Researchers must first select a suitable detergent for the solubility and stability of their protein during in vitro studies. In addition, an appropriate concentration of detergent in membrane protein samples can be essential for protein solubility, stability, and experimental success. For example, in membrane protein crystallography, detergent concentration in the crystallization drop can be a critical parameter influencing crystal growth. Over the past decade, multiple techniques have been developed for the measurement of detergent concentration using a wide variety of strategies. These methods include colorimetric reactions, which target specific detergent classes, and analytical techniques applicable to a wide variety of detergents. This review will summarize and discuss the available options. It will be a useful resource to those selecting a strategy that best fits their experimental requirements and available instruments.
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10
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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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11
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Pocanschi CL, Popot JL, Kleinschmidt JH. Folding and stability of outer membrane protein A (OmpA) from Escherichia coli in an amphipathic polymer, amphipol A8-35. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2013; 42:103-18. [DOI: 10.1007/s00249-013-0887-z] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 01/02/2013] [Indexed: 11/29/2022]
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12
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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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13
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NMR methods for measuring lateral diffusion in membranes. Chem Phys Lipids 2013; 166:31-44. [DOI: 10.1016/j.chemphyslip.2012.12.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 12/11/2012] [Accepted: 12/12/2012] [Indexed: 02/07/2023]
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14
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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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15
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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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16
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Kyrychenko A, Rodnin MV, Vargas-Uribe M, Sharma SK, Durand G, Pucci B, Popot JL, Ladokhin AS. Folding of diphtheria toxin T-domain in the presence of amphipols and fluorinated surfactants: Toward thermodynamic measurements of membrane protein folding. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1818:1006-12. [PMID: 21945883 PMCID: PMC3261334 DOI: 10.1016/j.bbamem.2011.09.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 08/18/2011] [Accepted: 09/12/2011] [Indexed: 11/22/2022]
Abstract
Solubilizing membrane proteins for functional, structural and thermodynamic studies is usually achieved with the help of detergents, which, however, tend to destabilize them. Several classes of non-detergent surfactants have been designed as milder substitutes for detergents, most prominently amphipathic polymers called 'amphipols' and fluorinated surfactants. Here we test the potential usefulness of these compounds for thermodynamic studies by examining their effect on conformational transitions of the diphtheria toxin T-domain. The advantage of the T-domain as a model system is that it exists as a soluble globular protein at neutral pH yet is converted into a membrane-competent form by acidification and inserts into the lipid bilayer as part of its physiological action. We have examined the effects of various surfactants on two conformational transitions of the T-domain, thermal unfolding and pH-induced transition to a membrane-competent form. All tested detergent and non-detergent surfactants lowered the cooperativity of the thermal unfolding of the T-domain. The dependence of enthalpy of unfolding on surfactant concentration was found to be least for fluorinated surfactants, thus making them useful candidates for thermodynamic studies. Circular dichroism measurements demonstrate that non-ionic homopolymeric amphipols (NAhPols), unlike any other surfactants, can actively cause a conformational change of the T-domain. NAhPol-induced structural rearrangements are different from those observed during thermal denaturation and are suggested to be related to the formation of the membrane-competent form of the T-domain. Measurements of leakage of vesicle content indicate that interaction with NAhPols not only does not prevent the T-domain from inserting into the bilayer, but it can make bilayer permeabilization even more efficient, whereas the pH-dependence of membrane permeabilization becomes more cooperative. This article is part of a Special Issue entitled: Protein Folding in Membranes.
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Affiliation(s)
- Alexander Kyrychenko
- Department of Biochemistry and Molecular Biology, Kansas University Medical Center, Kansas City, KS 66160-7421, U.S.A
| | - Mykola V. Rodnin
- Department of Biochemistry and Molecular Biology, Kansas University Medical Center, Kansas City, KS 66160-7421, U.S.A
| | - Mauricio Vargas-Uribe
- Department of Biochemistry and Molecular Biology, Kansas University Medical Center, Kansas City, KS 66160-7421, U.S.A
| | - Shivaji K. Sharma
- Université d’Avignon et des Pays de Vaucluse, Equipe Chimie Bioorganique et Systèmes Amphiphiles, 33 rue Louis Pasteur, F-84000 Avignon, France
| | - Grégory Durand
- Université d’Avignon et des Pays de Vaucluse, Equipe Chimie Bioorganique et Systèmes Amphiphiles, 33 rue Louis Pasteur, F-84000 Avignon, France
- Institut des Biomolécules Max Mousseron (UMR 5247), 15 avenue Charles Flahault, F-34093 Montpellier Cedex 05, France
| | - Bernard Pucci
- Université d’Avignon et des Pays de Vaucluse, Equipe Chimie Bioorganique et Systèmes Amphiphiles, 33 rue Louis Pasteur, F-84000 Avignon, France
- Institut des Biomolécules Max Mousseron (UMR 5247), 15 avenue Charles Flahault, F-34093 Montpellier Cedex 05, France
| | - Jean-Luc Popot
- Institut de Biologie Physico-Chimique, UMR 7099, CNRS and Université Paris-7 F-75005, Paris, France
| | - Alexey S. Ladokhin
- Department of Biochemistry and Molecular Biology, Kansas University Medical Center, Kansas City, KS 66160-7421, U.S.A
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17
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O'Malley MA, Helgeson ME, Wagner NJ, Robinson AS. Toward rational design of protein detergent complexes: determinants of mixed micelles that are critical for the in vitro stabilization of a G-protein coupled receptor. Biophys J 2012; 101:1938-48. [PMID: 22004748 DOI: 10.1016/j.bpj.2011.09.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 09/06/2011] [Accepted: 09/12/2011] [Indexed: 01/02/2023] Open
Abstract
Although reconstitution of membrane proteins within protein detergent complexes is often used to enable their structural or biophysical characterization, it is unclear how one should rationally choose the appropriate micellar environment to preserve native protein folding. Here, we investigated model mixed micelles consisting of a nonionic glucosylated alkane surfactant from the maltoside and thiomaltoside families, bile salt surfactant, and the steryl derivative cholesteryl hemisuccinate. We correlated several key attributes of these micelles with the in vitro ligand-binding activity of hA(2)aR in these systems. Through small-angle neutron scattering and radioligand-binding analysis, we found several key aspects of mixed micellar systems that preserve the activity of hA(2)aR, including a critical amount of cholesteryl hemisuccinate per micelle, and an optimal hydrophobic thickness of the micelle that is analogous to the thickness of native mammalian bilayers. These features are closely linked to the headgroup chemistry of the surfactant and the hydrocarbon chain length, which influence both the morphology and composition of resulting micelles. This study should serve as a general guide for selecting the appropriate mixed surfactant systems to stabilize membrane proteins for biophysical analysis.
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Affiliation(s)
- Michelle A O'Malley
- Department of Chemical Engineering, University of Delaware, Newark, Delaware, USA
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18
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Abla M, Durand G, Breyton C, Raynal S, Ebel C, Pucci B. A diglucosylated fluorinated surfactant to handle integral membrane proteins in aqueous solution. J Fluor Chem 2012. [DOI: 10.1016/j.jfluchem.2011.05.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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19
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Popot JL, Althoff T, Bagnard D, Banères JL, Bazzacco P, Billon-Denis E, Catoire LJ, Champeil P, Charvolin D, Cocco MJ, Crémel G, Dahmane T, de la Maza LM, Ebel C, Gabel F, Giusti F, Gohon Y, Goormaghtigh E, Guittet E, Kleinschmidt JH, Kühlbrandt W, Le Bon C, Martinez KL, Picard M, Pucci B, Sachs JN, Tribet C, van Heijenoort C, Wien F, Zito F, Zoonens M. Amphipols from A to Z. Annu Rev Biophys 2011; 40:379-408. [PMID: 21545287 DOI: 10.1146/annurev-biophys-042910-155219] [Citation(s) in RCA: 207] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Amphipols (APols) are short amphipathic polymers that can substitute for detergents to keep integral membrane proteins (MPs) water soluble. In this review, we discuss their structure and solution behavior; the way they associate with MPs; and the structure, dynamics, and solution properties of the resulting complexes. All MPs tested to date form water-soluble complexes with APols, and their biochemical stability is in general greatly improved compared with MPs in detergent solutions. The functionality and ligand-binding properties of APol-trapped MPs are reviewed, and the mechanisms by which APols stabilize MPs are discussed. Applications of APols include MP folding and cell-free synthesis, structural studies by NMR, electron microscopy and X-ray diffraction, APol-mediated immobilization of MPs onto solid supports, proteomics, delivery of MPs to preexisting membranes, and vaccine formulation.
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Affiliation(s)
- J-L Popot
- Institut de Biologie Physico-Chimique, CNRS/Université Paris-7 UMR 7099, Paris, France.
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20
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Perlmutter JD, Drasler WJ, Xie W, Gao J, Popot JL, Sachs JN. All-atom and coarse-grained molecular dynamics simulations of a membrane protein stabilizing polymer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:10523-10537. [PMID: 21806035 PMCID: PMC3214636 DOI: 10.1021/la202103v] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Amphipathic polymers called amphipols (APols) have been developed as an alternative to detergents for stabilizing membrane proteins (MPs) in aqueous solutions. APols provide MPs with a particularly mild environment and, as a rule, keep them in a native functional state for longer periods than do detergents. Amphipol A8-35, a derivative of polyacrylate, is widely used and has been particularly well studied experimentally. In aqueous solutions, A8-35 molecules self-assemble into well-defined globular particles with a mass of ∼40 kDa and a R(g) of ∼2.4 nm. As a first step towards describing MP/A8-35 complexes by molecular dynamics (MD), we present three sets of simulations of the pure APol particle. First, we performed a series of all-atom MD (AAMD) simulations of the particle in solution, starting from an arbitrary initial configuration. Although AAMD simulations result in stable cohesive particles over a 45 ns simulation, the equilibration of the particle organization is limited. This motivated the use of coarse-grained MD (CGMD), allowing us to investigate processes on the microsecond time scale, including de novo particle assembly. We present a detailed description of the parametrization of the CGMD model from the AAMD simulations and a characterization of the resulting CGMD particles. Our third set of simulations utilizes reverse coarse-graining (rCG), through which we obtain all-atom coordinates from a CGMD simulation. This allows a higher-resolution characterization of a configuration determined by a long-timescale simulation. Excellent agreement is observed between MD models and experimental, small-angle neutron scattering data. The MD data provides new insight into the structure and dynamics of A8-35 particles, which is possibly relevant to the stabilizing effects of APols on MPs, as well as a starting point for modeling MP/A8-35 complexes.
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Affiliation(s)
- Jason D Perlmutter
- Department of Biomedical Engineering, 312 Church Street SE, University of Minnesota, Minneapolis, Minnesota 55455, USA
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21
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Abstract
This minireview focuses on diffusion NMR studies in bicelles. Following a discourse on diffusion fundamentals, and a comparative overview of fluorescence and NMR-based techniques for measuring diffusion, the pulsed field gradient (PFG) NMR diffusion method is introduced, emphasizing its specific advantages and limitations when applied to diffusion measurements in macroscopically oriented lamellar systems such as magnetically aligned bicelles. The utility of PFG NMR diffusion measurements in bicellar model membrane systems for examining lateral diffusion of membrane-bound molecular species is demonstrated, along with certain features of lateral diffusion that such studies illuminate. Further, those aspects of bicelle morphology that have been resolved using PFG NMR diffusion studies of various molecular weight soluble polymeric species are reviewed. The discussion concludes with an outline of future prospects for diffusion NMR studies in bicelles.
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Affiliation(s)
- Peter M. Macdonald
- Department of Chemistry, University of Toronto, Toronto, ON, Canada
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3359 Mississauga Road North, Mississauga, ON L5L 1C6, Canada
| | - Ronald Soong
- Department of Chemistry, University of Toronto, Toronto, ON, Canada
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3359 Mississauga Road North, Mississauga, ON L5L 1C6, Canada
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22
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Dahmane T, Giusti F, Catoire LJ, Popot JL. Sulfonated amphipols: synthesis, properties, and applications. Biopolymers 2011; 95:811-23. [PMID: 21638274 DOI: 10.1002/bip.21683] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 05/19/2011] [Accepted: 05/23/2011] [Indexed: 01/20/2023]
Abstract
Amphipols (APols) are amphiphatic polymers that keep membrane proteins (MPs) water-soluble. The best characterized and most widely used APol to date, A8-35, comprises a polyacrylate backbone grafted with octyl- and isopropylamine side chains. The nature of its hydrophilic moieties prevents its use at the slightly acidic pH that is desirable to slow down the rate of amide proton exchange in solution NMR studies. We describe here the synthesis and properties of pH-insensitive APols obtained by replacing isopropyles with taurine. Sulfonated APols (SAPols) can be used to trap MPs in the form of small complexes, to stabilize them, and to keep them water-soluble even at low pH. [(15) N,(1) H]-transverse relaxation-optimized spectroscopy NMR spectra obtained at pH 6.8 of a bacterial outer MP folded in SAPols show that the protein is correctly folded. The spectra have a resolution similar to that achieved with A8-35 and reveal water-exposed amide and indole protons whose resonance peaks are absent at pH 8.0.
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Affiliation(s)
- Tassadite Dahmane
- Laboratoire de Physico-Chimie Moléculaire des Membranes Biologiques, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, CNRS IFR 550, 13 rue Pierre et Marie Curie, F-75005 Paris, France
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23
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Howell SC, Mittal R, Huang L, Travis B, Breyer RM, Sanders CR. CHOBIMALT: a cholesterol-based detergent. Biochemistry 2011; 49:9572-83. [PMID: 20919740 DOI: 10.1021/bi101334j] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cholesterol and its hemisuccinate and sulfate derivatives are widely used in studies of purified membrane proteins but are difficult to solubilize in aqueous solution, even in the presence of detergent micelles. Other cholesterol derivatives do not form conventional micelles and lead to viscous solutions. To address these problems, a cholesterol-based detergent, CHOBIMALT, has been synthesized and characterized. At concentrations above 3−4 μM, CHOBIMALT forms micelles without the need for elevated temperatures or sonic disruption. Diffusion and fluorescence measurements indicated that CHOBIMALT micelles are large (210±30 kDa). The ability to solubilize a functional membrane protein was explored using a G-protein coupled receptor, the human kappa opioid receptor type 1 (hKOR1). While CHOBIMALT alone was not found to be effective as a surfactant for membrane extraction, when added to classical detergent micelles CHOBIMALT was observed to dramatically enhance the thermal stability of solubilized hKOR1.
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Affiliation(s)
- Stanley C Howell
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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24
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Ebel C. Sedimentation velocity to characterize surfactants and solubilized membrane proteins. Methods 2011; 54:56-66. [DOI: 10.1016/j.ymeth.2010.11.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 11/18/2010] [Accepted: 11/19/2010] [Indexed: 02/07/2023] Open
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25
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O'Malley MA, Helgeson ME, Wagner NJ, Robinson AS. The morphology and composition of cholesterol-rich micellar nanostructures determine transmembrane protein (GPCR) activity. Biophys J 2011; 100:L11-3. [PMID: 21244820 DOI: 10.1016/j.bpj.2010.12.3698] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Revised: 11/22/2010] [Accepted: 12/10/2010] [Indexed: 12/01/2022] Open
Abstract
We examined model mixed micelles consisting of the nonionic surfactant n-dodecyl-β-D-maltoside, 3-(3-cholamidopropyl)-dimethylammoniopropane sulfonate, and the cholesterol derivative cholesteryl hemisuccinate (CHS) to identify micellar properties that are correlated with the in vitro conformational stability and activity of the human adenosine A₂a receptor, a G-protein coupled receptor. Small-angle neutron scattering was used to determine micellar structure and composition as a function of concentration of the various components, and radioligand binding was used as a sensitive probe for receptor activity. Micelles adopted an oblate ellipsoidal morphology and exhibited a reduction in size and change in curvature upon addition of CHS. Our results show a strong correlation between the number of CHS monomers per micelle and the activity of the receptor reconstituted in those micelles. Micelles that yield optimal human adenosine A₂a receptor stability closely mimic the cholesterol composition and thickness of mammalian membranes. Thus, successful reconstitution of the receptor is dependent on both specific lipid-protein interactions and the geometry of the micelle environment.
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26
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Nieh MP, Raghunathan VA, Pabst G, Harroun T, Nagashima K, Morales H, Katsaras J, Macdonald P. Temperature driven annealing of perforations in bicellar model membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:4838-4847. [PMID: 21438512 DOI: 10.1021/la104750x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Bicellar model membranes composed of 1,2-dimyristoylphosphatidylcholine (DMPC) and 1,2-dihexanoylphosphatidylcholine (DHPC), with a DMPC/DHPC molar ratio of 5, and doped with the negatively charged lipid 1,2-dimyristoylphosphatidylglycerol (DMPG), at DMPG/DMPC molar ratios of 0.02 or 0.1, were examined using small angle neutron scattering (SANS), (31)P NMR, and (1)H pulsed field gradient (PFG) diffusion NMR with the goal of understanding temperature effects on the DHPC-dependent perforations in these self-assembled membrane mimetics. Over the temperature range studied via SANS (300-330 K), these bicellar lipid mixtures exhibited a well-ordered lamellar phase. The interlamellar spacing d increased with increasing temperature, in direct contrast to the decrease in d observed upon increasing temperature with otherwise identical lipid mixtures lacking DHPC. (31)P NMR measurements on magnetically aligned bicellar mixtures of identical composition indicated a progressive migration of DHPC from regions of high curvature into planar regions with increasing temperature, and in accord with the "mixed bicelle model" (Triba, M. N.; Warschawski, D. E.; Devaux, P. E. Biophys. J.2005, 88, 1887-1901). Parallel PFG diffusion NMR measurements of transbilayer water diffusion, where the observed diffusion is dependent on the fractional surface area of lamellar perforations, showed that transbilayer water diffusion decreased with increasing temperature. A model is proposed consistent with the SANS, (31)P NMR, and PFG diffusion NMR data, wherein increasing temperature drives the progressive migration of DHPC out of high-curvature regions, consequently decreasing the fractional volume of lamellar perforations, so that water occupying these perforations redistributes into the interlamellar volume, thereby increasing the interlamellar spacing.
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Affiliation(s)
- Mu-Ping Nieh
- Chemical, Materials and Biomolecular Engineering Department, Institute of Material Sciences, University of Connecticut, 97 North Eagleville Road, Storrs, Connecticut 06269-3136, USA
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27
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Banères JL, Popot JL, Mouillac B. New advances in production and functional folding of G-protein-coupled receptors. Trends Biotechnol 2011; 29:314-22. [PMID: 21497924 DOI: 10.1016/j.tibtech.2011.03.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 02/25/2011] [Accepted: 03/02/2011] [Indexed: 12/17/2022]
Abstract
G-protein-coupled receptors (GPCRs), the largest family of integral membrane proteins, participate in the regulation of many physiological functions and are the targets of approximately 30% of currently marketed drugs. However, knowledge of the structural and molecular bases of GPCR functions remains limited owing to difficulties related to their overexpression, purification and stabilization. The development of new strategies aimed at obtaining large amounts of functional GPCRs is therefore crucial. Here, we review the most recent advances in the production and functional folding of GPCRs from Escherichia coli inclusion bodies. Major breakthroughs open exciting perspectives for structural and dynamic investigations of GPCRs. In particular, combining targeting to bacterial inclusion bodies with amphipol-assisted folding is emerging as a highly powerful strategy.
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Affiliation(s)
- Jean-Louis Banères
- CNRS, UMR-5247, Institut des Biomolécules Max Mousseron, Faculté de Pharmacie, 15 avenue Charles Flahault, F-34000 Montpellier, France
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28
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Production of membrane proteins without cells or detergents. N Biotechnol 2011; 28:250-4. [DOI: 10.1016/j.nbt.2010.07.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 07/05/2010] [Accepted: 07/08/2010] [Indexed: 12/14/2022]
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29
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Kaya AI, Thaker TM, Preininger AM, Iverson TM, Hamm HE. Coupling efficiency of rhodopsin and transducin in bicelles. Biochemistry 2011; 50:3193-203. [PMID: 21375271 DOI: 10.1021/bi200037j] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
G protein coupled receptors (GPCRs) can be activated by various extracellular stimuli, including hormones, peptides, odorants, neurotransmitters, nucleotides, or light. After activation, receptors interact with heterotrimeric G proteins and catalyze GDP release from the Gα subunit, the rate limiting step in G protein activation, to form a high affinity nucleotide-free GPCR-G protein complex. In vivo, subsequent GTP binding reduces affinity of the Gα protein for the activated receptor. In this study, we investigated the biochemical and structural characteristics of the prototypical GPCR, rhodopsin, and its signaling partner, transducin (G(t)), in bicelles to better understand the effects of membrane composition on high affinity complex formation, stability, and receptor mediated nucleotide release. Our results demonstrate that the high-affinity complex (rhodopsin-G(t)(empty)) forms more readily and has dramatically increased stability when rhodopsin is integrated into bicelles of a defined composition. We increased the half-life of functional complex to 1 week in the presence of negatively charged phospholipids. These data suggest that a membrane-like structure is an important contributor to the formation and stability of functional receptor-G protein complexes and can extend the range of studies that investigate properties of these complexes.
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Affiliation(s)
- Ali I Kaya
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600, United States
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30
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Qureshi T, Goto NK. Contemporary methods in structure determination of membrane proteins by solution NMR. Top Curr Chem (Cham) 2011; 326:123-85. [PMID: 22160391 DOI: 10.1007/128_2011_306] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Integral membrane proteins are vital to life, being responsible for information and material exchange between a cell and its environment. Although high-resolution structural information is needed to understand how these functions are achieved, membrane proteins remain an under-represented subset of the protein structure databank. Solution NMR is increasingly demonstrating its ability to help address this knowledge shortfall, with the development of a diverse array of techniques to counter the challenges presented by membrane proteins. Here we document the advances that are helping to define solution NMR as an effective tool for membrane protein structure determination. Developments introduced over the last decade in the production of isotope-labeled samples, reconstitution of these samples into the growing selection of NMR-compatible membrane-mimetic systems, and the approaches used for the acquisition and application of structural restraints from these complexes are reviewed.
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Affiliation(s)
- Tabussom Qureshi
- Department of Chemistry, University of Ottawa, Ottawa, ON, Canada
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31
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Koehler J, Sulistijo ES, Sakakura M, Kim HJ, Ellis CD, Sanders CR. Lysophospholipid micelles sustain the stability and catalytic activity of diacylglycerol kinase in the absence of lipids. Biochemistry 2010; 49:7089-99. [PMID: 20666483 DOI: 10.1021/bi100575s] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
There has been a renewal of interest in interactions of membrane proteins with detergents and lipids, sparked both by recent results that illuminate the structural details of these interactions and also by the realization that some experimental membrane protein structures are distorted by detergent-protein interactions. The integral membrane enzyme diacylglycerol kinase (DAGK) has long been thought to require the presence of lipid as an obligate "cofactor" in order to be catalytically viable in micelles. Here, we report that near-optimal catalytic properties are observed for DAGK in micelles composed of lysomyristoylphosphatidylcholine (LMPC), with significant activity also being observed in micelles composed of lysomyristoylphosphatidylglycerol and tetradecylphosphocholine. All three of these detergents were also sustained high stability of the enzyme. NMR measurements revealed significant differences in DAGK-detergent interactions involving LMPC micelles versus micelles composed of dodecylphosphocholine. These results highlight the fact that some integral membrane proteins can maintain native-like properties in lipid-free detergent micelles and also suggest that C(14)-based detergents may be worthy of more widespread use in studies of membrane proteins.
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Affiliation(s)
- Julia Koehler
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8725, USA
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32
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Park KH, Billon-Denis E, Dahmane T, Lebaupain F, Pucci B, Breyton C, Zito F. In the cauldron of cell-free synthesis of membrane proteins: playing with new surfactants. N Biotechnol 2010; 28:255-61. [PMID: 20800706 DOI: 10.1016/j.nbt.2010.08.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 07/22/2010] [Accepted: 08/18/2010] [Indexed: 02/06/2023]
Abstract
Cell-free protein synthesis is a well-known technique for the roles it has played in deciphering the genetic code and in the beginnings of signal sequence studies. Since then, many efforts have been made to optimise this technique and, recently, to adapt it to membrane protein production with yields compatible with structural investigations. The versatility of the method allows membrane proteins to be obtained directly stabilised in surfactant micelles or inserted in a lipidic environment (proteoliposome, bicelle, and nanodisc) at the end of synthesis. Among the surfactants used, non-detergent ones such as fluorinated surfactants proved to be a good alternative in terms of colloidal stability and preservation of the integrity of membrane proteins, as shown for Escherichia coli homo-pentameric channel, MscL (Park et al., Biochem. J., 403: 183-187). Here we report cell-free expression of Escherichia coli leader peptidase (a transmembrane protease), Halobacterium salinarium bacteriorhodopsin (a transmembrane protein binding a hydrophobic cofactor) and E. coli MscL in the presence of non-detergent surfactants, amphipols and fluorinated surfactants in comparison to their expression in classical detergents. The results confirm the potentialities of fluorinated surfactants and, although pointing to limitations in using the first generations amphipols, results are discussed in the light of membrane protein refolding, especially in the case of bacteriorhodopsin. Preliminary experiments using new generations of amphipols supports choices made in developing new molecules.
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Affiliation(s)
- Kyu-Ho Park
- Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, CNRS FRC 550, F-75005 Paris, France
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33
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Debnath DK, Otzen DE. Cell-free synthesis and folding of transmembrane OmpA reveals higher order structures and premature truncations. Biophys Chem 2010; 152:80-8. [PMID: 20813447 DOI: 10.1016/j.bpc.2010.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 08/04/2010] [Accepted: 08/08/2010] [Indexed: 01/23/2023]
Abstract
We use a cell-free transcription-translation system to monitor the effect of different lipids on the synthesis and folding of the transmembrane domain of the outer membrane protein OmpA from E. coli under physiological conditions. Folding is consistent with previous observations made in vitro at high pH. Synthesis and folding yields are optimal in phosphocholine lipids, particularly in short chain lipids and small vesicles, while lipid rafts do not promote folding compared to the folding in the absence of lipids. Truncated species are observed during translation in the presence of the periplasmic chaperone Skp, which likely binds to the newly synthesized polypeptide chain during cell-free translation and thus prematurely terminate polypeptide chain synthesis. In contrast, folded and unfolded dimers of OmpA correlate negatively with folding yields. This suggests that dimer formation competes with folding and insertion of monomeric OmpA, though folded dimers slowly appear to convert to folded monomers.
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Affiliation(s)
- Dilip K Debnath
- Center for insoluble protein structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C., Denmark
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34
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Popot JL. Amphipols, Nanodiscs, and Fluorinated Surfactants: Three Nonconventional Approaches to Studying Membrane Proteins in Aqueous Solutions. Annu Rev Biochem 2010; 79:737-75. [DOI: 10.1146/annurev.biochem.052208.114057] [Citation(s) in RCA: 241] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jean-Luc Popot
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, Unité Mixte de Recherche 7099, Centre National de la Recherche Scientifique and Université Paris-7 Denis Diderot, Institut de Biologie Physico-Chimique, F-75005 Paris, France; e-mail:
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35
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Kang C, Vanoye CG, Welch RC, Van Horn WD, Sanders CR. Functional delivery of a membrane protein into oocyte membranes using bicelles. Biochemistry 2010; 49:653-5. [PMID: 20044833 DOI: 10.1021/bi902155t] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Voltage-gated potassium channel modulatory membrane protein KCNE3 was overexpressed and purified into both micelles and bicelles. Remarkably, microinjection of KCNE3 in bicelles into Xenopus oocytes resulted in functional co-assembly with the human KCNQ1 channel expressed therein. Microinjection of LMPC micelles containing KCNE3 did not result in channel modulation, indicating that bicelles sometimes succeed at delivering a membrane protein into a cellular membrane when classical micelles fail. Backbone NMR resonance assignments were completed for KCNE3 in both bicelles and LMPC, indicating that the secondary structure distribution in KCNE3's N-terminus and transmembrane domains exhibits only modest differences from that of KCNE1, even though these KCNE family members have very different effects on KCNQ1 channel function.
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Affiliation(s)
- Congbao Kang
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8725, USA
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36
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Chae PS, Guzei IA, Gellman SH. Crystallographic characterization of N-oxide tripod amphiphiles. J Am Chem Soc 2010; 132:1953-9. [PMID: 20095541 PMCID: PMC3090072 DOI: 10.1021/ja9085148] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tripod amphiphiles are designed to promote the solubilization and stabilization of intrinsic membrane proteins in aqueous solution; facilitation of crystallization is a long-range goal. Membrane proteins are subjects of extensive interest because of their critical biological roles, but proteins of this type can be difficult to study because of their low solubility in water. The nonionic detergents that are typically used to achieve solubility can have the unintended effect of causing protein denaturation. Tripod amphiphiles differ from conventional detergents in that the lipophilic segment contains a branchpoint, and previous work has shown that this unusual amphiphilic architecture can be advantageous relative to traditional detergent structures. Here, we report the crystal structures of several tripod amphiphiles that contain an N-oxide hydrophilic group. The data suggest that tripods can adapt themselves to a nonpolar surface by altering the hydrophobic appendage that projects toward that surface and their overall orientation relative to that surface. Although it is not possible to draw firm conclusions regarding amphiphile association in solution from crystallographic data, trends observed among the packing patterns reported here suggest design strategies to be implemented in future studies.
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Affiliation(s)
- Pil Seok Chae
- Department of Chemistry, University of Wisconsin, Madison, WI 53706
| | - Ilia A. Guzei
- Department of Chemistry, University of Wisconsin, Madison, WI 53706
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37
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Helbig AO, Heck AJR, Slijper M. Exploring the membrane proteome--challenges and analytical strategies. J Proteomics 2010; 73:868-78. [PMID: 20096812 DOI: 10.1016/j.jprot.2010.01.005] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 01/08/2010] [Accepted: 01/08/2010] [Indexed: 12/22/2022]
Abstract
The analysis of proteins in biological membranes forms a major challenge in proteomics. Despite continuous improvements and the development of more sensitive analytical methods, the analysis of membrane proteins has always been hampered by their hydrophobic properties and relatively low abundance. In this review, we describe recent successful strategies that have led to in-depth analyses of the membrane proteome. To facilitate membrane proteome analysis, it is essential that biochemical enrichment procedures are combined with special analytical workflows that are all optimized to cope with hydrophobic polypeptides. These include techniques for protein solubilization, and also well-matched developments in protein separation and protein digestion procedures. Finally, we discuss approaches to target membrane-protein complexes and lipid-protein interactions, as such approaches offer unique insights into function and architecture of cellular membranes.
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Affiliation(s)
- Andreas O Helbig
- Biomolecular Mass Spectrometry and Proteomics Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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38
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Amphipols and fluorinated surfactants: Two alternatives to detergents for studying membrane proteins in vitro. Methods Mol Biol 2010; 601:219-45. [PMID: 20099149 DOI: 10.1007/978-1-60761-344-2_14] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
Handling integral membrane proteins in aqueous solutions traditionally relies on the use of detergents, which are surfactants capable of dispersing the components of biological membranes into mixed micelles. The dissociating character of detergents, however, most often causes solubilized membrane proteins to be unstable. This has prompted the development of alternative, less-aggressive surfactants designed to keep membrane proteins soluble, after they have been solubilized, under milder conditions. A short overview is presented of the structure, properties, and uses of two families of such surfactants: amphiphilic polymers ("amphipols") and fluorinated surfactants.
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39
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Bazzacco P, Sharma KS, Durand G, Giusti F, Ebel C, Popot JL, Pucci B. Trapping and Stabilization of Integral Membrane Proteins by Hydrophobically Grafted Glucose-Based Telomers. Biomacromolecules 2009; 10:3317-26. [DOI: 10.1021/bm900938w] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Paola Bazzacco
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France, Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d’Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, F-84000 Avignon, France, CEA, IBS, Laboratoire de Biophysique Moléculaire, F-38054 Grenoble, France, CNRS, UMR5075, F-38027 Grenoble, France,
| | - K. Shivaji Sharma
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France, Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d’Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, F-84000 Avignon, France, CEA, IBS, Laboratoire de Biophysique Moléculaire, F-38054 Grenoble, France, CNRS, UMR5075, F-38027 Grenoble, France,
| | - Grégory Durand
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France, Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d’Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, F-84000 Avignon, France, CEA, IBS, Laboratoire de Biophysique Moléculaire, F-38054 Grenoble, France, CNRS, UMR5075, F-38027 Grenoble, France,
| | - Fabrice Giusti
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France, Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d’Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, F-84000 Avignon, France, CEA, IBS, Laboratoire de Biophysique Moléculaire, F-38054 Grenoble, France, CNRS, UMR5075, F-38027 Grenoble, France,
| | - Christine Ebel
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France, Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d’Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, F-84000 Avignon, France, CEA, IBS, Laboratoire de Biophysique Moléculaire, F-38054 Grenoble, France, CNRS, UMR5075, F-38027 Grenoble, France,
| | - Jean-Luc Popot
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France, Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d’Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, F-84000 Avignon, France, CEA, IBS, Laboratoire de Biophysique Moléculaire, F-38054 Grenoble, France, CNRS, UMR5075, F-38027 Grenoble, France,
| | - Bernard Pucci
- Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France, Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d’Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, F-84000 Avignon, France, CEA, IBS, Laboratoire de Biophysique Moléculaire, F-38054 Grenoble, France, CNRS, UMR5075, F-38027 Grenoble, France,
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40
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Tribet C, Diab C, Dahmane T, Zoonens M, Popot JL, Winnik FM. Thermodynamic characterization of the exchange of detergents and amphipols at the surfaces of integral membrane proteins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:12623-34. [PMID: 19594168 DOI: 10.1021/la9018772] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The aggregation of integral membrane proteins (IMPs) in aqueous media is a significant concern for mechanistic investigations and pharmaceutical applications of this important class of proteins. Complexation of IMPs with amphiphiles, either detergents or short amphiphilic polymers known as amphipols (APols), renders IMPs water-soluble. It is common knowledge that IMP-detergent complexes are labile, while IMP-APol complexes are exceptionally stable and do not dissociate even under conditions of extreme dilution. To understand the thermodynamic origin of this difference in stability and to guide the design of new APols, we have studied by isothermal titration calorimetry (ITC) the heat exchanges during two reciprocal processes, the "trapping" of detergent-solubilized IMPs in APols and the "stripping" of IMP-APol complexes by detergents, using two IMPs (the transmembrane domain of porin OmpA from Escherichia coli and bacteriorhodopsin from Halobium salinarium), two APols [an anionic polymer derived from acrylic acid (A8-35) and a cationic phosphorylcholine-based polymer (C22-43)], and two neutral detergents [n-octyl thioglucoside (OTG) and n-octyltetraethylene glycol (C(8)E(4))]. In the presence of detergent, free APols and IMP-APol complexes form mixed particles, APol-detergent and IMP-APol-detergent, respectively, according to the regular mixing model. Diluting IMP-APol-detergent complexes below the critical micellar concentration (CMC) of the detergent triggers the dispersion of detergent molecules as monomers, a process characterized by an enthalpy of demicellization. The enthalpy of APol <--> detergent exchange on the hydrophobic surface of IMPs is negligibly small, an indication of the similarity of the molecular interactions of IMPs with the two types of amphiphiles. The enhanced stability against dilution of IMP-APol complexes, compared to IMP-detergent ones, originates from the difference in entropy gain achieved upon release in water of a few APol molecules (in the case of IMP-APol complexes) or several hundred detergent molecules (in the case of IMP-detergent complexes). The data account both for the stability of IMP-APols complexes in the absence of detergent and for the ease with which detergents displace APols from the surface of proteins.
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Affiliation(s)
- C Tribet
- Physico-chimie des Polymères et Milieux Dispersés, UMR 7615, CNRS and Université Paris 6, ESPCI, 10 rue Vauquelin, F-75231 Paris, France
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41
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Kim HJ, Howell SC, Van Horn WD, Jeon YH, Sanders CR. Recent Advances in the Application of Solution NMR Spectroscopy to Multi-Span Integral Membrane Proteins. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2009; 55:335-360. [PMID: 20161395 PMCID: PMC2782866 DOI: 10.1016/j.pnmrs.2009.07.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Affiliation(s)
- Hak Jun Kim
- Korea Polar Research Institute, Korea Ocean Research and Development Institute, Incheon, 406-840, Korea
| | - Stanley C. Howell
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
| | - Wade D. Van Horn
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
| | - Young Ho Jeon
- Center for Magnetic Resonance, Korea Basic Research Institute, Daejon, 305-333, Korea
| | - Charles R. Sanders
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
- Corresponding Author: ; phone: 615-936-3756; fax: 615-936-2211
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42
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Wittlich M, Thiagarajan P, Koenig BW, Hartmann R, Willbold D. NMR structure of the transmembrane and cytoplasmic domains of human CD4 in micelles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:122-7. [PMID: 19781520 DOI: 10.1016/j.bbamem.2009.09.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 08/31/2009] [Accepted: 09/15/2009] [Indexed: 10/20/2022]
Abstract
The human cluster determinant 4 (CD4) is a type I transmembrane glycoprotein involved in T-cell signalling. It is expressed primarily on the surface of T helper cells but also on subsets of memory and regulatory T lymphocytes (CD4(+) cells). It serves as a coreceptor in T-cell receptor recognition of MHC II antigen complexes. Besides its cellular functions, CD4 serves as the main receptor for human immunodeficiency virus type I (HIV-1). During T-cell infection, the CD4 extracellular domain is bound by HIV-1 gp120, the viral surface glycoprotein, which triggers a number of conformational changes ultimately resulting in virion entry of the cell. Subsequently, CD4 is downregulated in infected cells by multiple strategies that involve direct interactions of the HIV-1 proteins VpU and Nef with the cytoplasmic part of CD4. In the present work, we describe the NOE-based solution structure of the transmembrane and cytoplasmic domains of the cystein-free variant of CD4 (CD4mut) in dodecylphosphocholine (DPC) micelles. Furthermore, we have characterized micelle-inserted CD4mut by paramagentic relaxation enhancement (PRE) agents and (1)H-(15)N heteronuclear NOE data. CD4mut features a stable and well-defined transmembrane helix from M372 to V395 buried in the micellar core and a cytoplasmic helix ranging from A404 to L413. Experimental data suggest the amphipathic cytoplasmic helix to be in close contact with the micellar surface. The role of the amphipathic helix and its interaction with the micellar surface is discussed with respect to the biological function of the full-length CD4 protein.
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Affiliation(s)
- Marc Wittlich
- Forschungszentrum Jülich, Institut für Strukturbiochemie (ISB-3), 52425 Jülich, Germany
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43
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Glück JM, Wittlich M, Feuerstein S, Hoffmann S, Willbold D, Koenig BW. Integral Membrane Proteins in Nanodiscs Can Be Studied by Solution NMR Spectroscopy. J Am Chem Soc 2009; 131:12060-1. [DOI: 10.1021/ja904897p] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Julian M. Glück
- Institute of Structural Biology and Biophysics (ISB-3), Research Centre Jülich, D-52425 Jülich, Germany, and Institute of Physical Biology and BMFZ, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Marc Wittlich
- Institute of Structural Biology and Biophysics (ISB-3), Research Centre Jülich, D-52425 Jülich, Germany, and Institute of Physical Biology and BMFZ, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Sophie Feuerstein
- Institute of Structural Biology and Biophysics (ISB-3), Research Centre Jülich, D-52425 Jülich, Germany, and Institute of Physical Biology and BMFZ, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Silke Hoffmann
- Institute of Structural Biology and Biophysics (ISB-3), Research Centre Jülich, D-52425 Jülich, Germany, and Institute of Physical Biology and BMFZ, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Dieter Willbold
- Institute of Structural Biology and Biophysics (ISB-3), Research Centre Jülich, D-52425 Jülich, Germany, and Institute of Physical Biology and BMFZ, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Bernd W. Koenig
- Institute of Structural Biology and Biophysics (ISB-3), Research Centre Jülich, D-52425 Jülich, Germany, and Institute of Physical Biology and BMFZ, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
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44
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Katzen F, Peterson TC, Kudlicki W. Membrane protein expression: no cells required. Trends Biotechnol 2009; 27:455-60. [PMID: 19616329 DOI: 10.1016/j.tibtech.2009.05.005] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Revised: 05/02/2009] [Accepted: 05/06/2009] [Indexed: 01/10/2023]
Abstract
Structural and functional studies of membrane proteins have been severely hampered by difficulties in producing sufficient quantities of properly folded protein products. It is well established that cell-based expression of membrane proteins is generally problematic and frequently results in low yield, cell toxicity, protein aggregation and misfolding. Owing to its inherent open nature, cell-free protein expression has become a highly promising tool for the fast and efficient production of these difficult-to-express proteins. Here we review the most recent advances in this field, underscoring the potentials and weaknesses of the newly developed approaches and place specific emphasis on the use of nanolipoprotein particles (NLPs or nanodiscs).
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Affiliation(s)
- Federico Katzen
- Life Technologies, 5791 Van Allen Way, Carlsbad, CA 92008, USA
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45
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Magnan CN, Randall A, Baldi P. SOLpro: accurate sequence-based prediction of protein solubility. ACTA ACUST UNITED AC 2009; 25:2200-7. [PMID: 19549632 DOI: 10.1093/bioinformatics/btp386] [Citation(s) in RCA: 343] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
MOTIVATION Protein insolubility is a major obstacle for many experimental studies. A sequence-based prediction method able to accurately predict the propensity of a protein to be soluble on overexpression could be used, for instance, to prioritize targets in large-scale proteomics projects and to identify mutations likely to increase the solubility of insoluble proteins. RESULTS Here, we first curate a large, non-redundant and balanced training set of more than 17 000 proteins. Next, we extract and study 23 groups of features computed directly or predicted (e.g. secondary structure) from the primary sequence. The data and the features are used to train a two-stage support vector machine (SVM) architecture. The resulting predictor, SOLpro, is compared directly with existing methods and shows significant improvement according to standard evaluation metrics, with an overall accuracy of over 74% estimated using multiple runs of 10-fold cross-validation.
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Affiliation(s)
- Christophe N Magnan
- Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California, Irvine, CA, USA
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46
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Smith A, Nie S. Nanocrystal Synthesis in an Amphibious Bath: Spontaneous Generation of Hydrophilic and Hydrophobic Surface Coatings. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200804179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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47
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Sharma KS, Durand G, Giusti F, Olivier B, Fabiano AS, Bazzacco P, Dahmane T, Ebel C, Popot JL, Pucci B. Glucose-based amphiphilic telomers designed to keep membrane proteins soluble in aqueous solutions: synthesis and physicochemical characterization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:13581-13590. [PMID: 18980351 DOI: 10.1021/la8023056] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A novel class of nonionic amphipols (NAPols) designed to handle membrane proteins in aqueous solutions has been synthesized, and its solution properties have been examined. These were synthesized through free radical cotelomerization of glucose-based hydrophilic and amphiphilic monomers derived from tris(hydroxymethyl)acrylamidomethane using azobisisobutyronitrile as the initiator and thiol as the transfer agent. The molecular weight and the hydrophilic/lipophilic balance of the cotelomers were modulated by varying the thiol/monomers and the hydrophilic monomer/amphiphilic monomer ratios, respectively, and were characterized by 'H NMR, UV, gel permeation chromatography, and Fourier transform infrared spectroscopy. Their physicochemical properties in aqueous solution were studied by dynamic light scattering, aqueous size-exclusion chromatography, analytical ultracentrifugation, and surface-tension measurements. NAPols are highly soluble in water and form, within a large concentration range, well-defined supramolecular assemblies with a diameter of approximately 6-7 nm, a narrow particle size distribution, and an average molecular weight close to 50 x 10(3) g x mol(-1). Varying the hydrophilic/amphiphilic monomer ratio of NAPols in the range of 3.0-4.9, the degree of polymerization in the range of 51-78, and the resulting average molar mass in the range of 20-29 x 10(3) g x mol(-1) has little incidence on their solution properties. Glucose-based NAPols efficiently kept soluble in aqueous solutions two test membrane proteins: bacteriorhodopsin and the transmembrane domain of Escherichia coli's outer membrane protein A.
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Affiliation(s)
- K Shivaji Sharma
- Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d'Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, F-84000 Avignon, France
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48
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Thauvin C, Rickling S, Schultz P, Célia H, Meunier S, Mioskowski C. Carbon nanotubes as templates for polymerized lipid assemblies. NATURE NANOTECHNOLOGY 2008; 3:743-8. [PMID: 19057595 DOI: 10.1038/nnano.2008.318] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 09/29/2008] [Indexed: 05/21/2023]
Abstract
Amphiphilic molecules-molecules that have both hydrophobic and hydrophilic properties-can self-assemble in water to form diverse structures such as micelles, vesicles and tubes, and these nanostructures can be used for delivering drugs, stabilizing membrane proteins or as nanoreactors. We have previously shown that lipids can self-organize on the surface of single-walled carbon nanotubes into regular ring-shaped assemblies. Here we show that these lipid assemblies can be polymerized and isolated from the nanotube template by application of an electric field. We also demonstrate that these assemblies are monodispersed, water-soluble, and can dissolve various hydrophobic rylene dyes, fullerenes and membrane proteins. The stability of these constructs and their diverse applications will be useful in the fields of cosmetics, medicine and material sciences.
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Affiliation(s)
- Cédric Thauvin
- Laboratoire de Synthèse Bio-Organique, CNRS-ULP UMR7175/LC1, Faculté de Pharmacie, Université Louis Pasteur, 74 Route du Rhin, BP 24, 67401 Illkirch, France
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49
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Zou C, Naider F, Zerbe O. Biosynthesis and NMR-studies of a double transmembrane domain from the Y4 receptor, a human GPCR. JOURNAL OF BIOMOLECULAR NMR 2008; 42:257-269. [PMID: 18937032 DOI: 10.1007/s10858-008-9281-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Revised: 09/24/2008] [Accepted: 09/26/2008] [Indexed: 05/26/2023]
Abstract
The human Y4 receptor, a class A G-protein coupled receptor (GPCR) primarily targeted by the pancreatic polypeptide (PP), is involved in a large number of physiologically important functions. This paper investigates a Y4 receptor fragment (N-TM1-TM2) comprising the N-terminal domain, the first two transmembrane (TM) helices and the first extracellular loop followed by a (His)(6) tag, and addresses synthetic problems encountered when recombinantly producing such fragments from GPCRs in Escherichia coli. Rigorous purification and usage of the optimized detergent mixture 28 mM dodecylphosphocholine (DPC)/118 mM% 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] (LPPG) resulted in high quality TROSY spectra indicating protein conformational homogeneity. Almost complete assignment of the backbone, including all TM residue resonances was obtained. Data on internal backbone dynamics revealed a high secondary structure content for N-TM1-TM2. Secondary chemical shifts and sequential amide proton nuclear Overhauser effects defined the TM helices. Interestingly, the properties of the N-terminal domain of this large fragment are highly similar to those determined on the isolated N-terminal domain in the presence of DPC micelles.
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Affiliation(s)
- Chao Zou
- Institute of Organic Chemistry, University of Zurich, Switzerland
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50
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Reisinger V, Eichacker LA. Solubilization of membrane protein complexes for blue native PAGE. J Proteomics 2008; 71:277-83. [PMID: 18573355 DOI: 10.1016/j.jprot.2008.05.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 05/28/2008] [Accepted: 05/29/2008] [Indexed: 12/27/2022]
Abstract
Blue native PAGE is an electrophoretic technique for high-resolution separation of membrane proteins. The method has been proven especially useful for investigation of native protein complexes enabling a characterization of potential protein-protein interactions in the context of functional proteomics. Blue native PAGE is easy to realise, results are reproducible and a high number of protocols are available. However, care should be taken during solubilization of protein complexes to achieve significant results in BN-PAGE analysis. Solubilization of membranes and proteins is not only influenced by detergent-lipid and detergent-protein interactions but also by lipid-lipid, lipid-protein and protein-protein interactions. Interactions have been investigated experimentally and theoretically. But, in practice, the experimental results do not always mirror the theoretical basis and therefore optimal solubilization conditions for each membrane and membrane protein complex should be investigated individually to tap the full potential of BN-PAGE analysis.
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Affiliation(s)
- Veronika Reisinger
- Department Biology I, Ludwig-Maximilians-Universität München, Menzingerstrasse 67, Munich, Germany
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