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Zabelin AA, Kovalev VB, Shkuropatov AY. On the Mechanism of Selective Chemical Exchange of Bacteriopheophytins in the Reaction Centers of Rhodobacter sphaeroides R-26. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:1119-1129. [PMID: 36273880 DOI: 10.1134/s0006297922100054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/11/2022] [Accepted: 08/10/2022] [Indexed: 06/16/2023]
Abstract
To elucidate the mechanism of site-selective chemical replacement of chromophores in the reaction centers (RCs) of photosynthetic bacteria by external pigments, we investigated how the efficiency of incorporation of plant pheophytin a (Pheo) into the binding sites for bacteriopheophytin a molecules (BPheo) in the isolated Rhodobacter sphaeroides R-26 RCs depended on the incubation medium temperature, Pheo aggregation state, and the presence of organic solvent (acetone). When Pheo was in a form of monomers in free detergent micelles in a water-detergent incubation medium, the degree of selective replacement of photochemically inactive BPheo HB molecules upon incubation of the RC/Pheo mixture at 5°C was ~15%. The exchange efficiency increased to 40% upon incubation at 25°C and reached 100% at the same temperature when 10% acetone was added to the incubation medium. At both 5 and 25°C, the degree of pigment exchange increased approximately twice, when a mixture of Pheo monomers and dimers in the presence of 10% acetone was used as the incubation medium. The removal of acetone from this medium with the preservation of pigment forms led to a significant decrease in the efficiency of Pheo incorporation. The effect of acetone on the pigment exchange was also observed at an elevated incubation temperature (43.5°C), when functionally active BPheo HA molecules were partially replaced. The results are discussed in terms of the mechanism according to which (i) the temperature-dependent internal movements of the RC protein facilitate the release of the BPheo molecule from the binding site with simultaneous insertion of the Pheo molecule into the same site in a coupled process, (ii) the role of temperature largely depends on the steric accessibility of binding pockets in the RC protein, (iii) the incorporation of Pheo occurs from a pool of monomeric molecules included in the RC-detergent micelles, and (iv) the presence of acetone in the incubation medium facilitates the exchange of Pheo monomers between micelles in the solution and the detergent belt of the RC complex.
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Affiliation(s)
- Alexey A Zabelin
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
| | - Vyacheslav B Kovalev
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Anatoly Ya Shkuropatov
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
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2
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Zampieri V, Hilpert C, Garnier M, Gestin Y, Delolme S, Martin J, Falson P, Launay G, Chaptal V. The Det.Belt Server: A Tool to Visualize and Estimate Amphipathic Solvent Belts around Membrane Proteins. MEMBRANES 2021; 11:459. [PMID: 34206634 PMCID: PMC8307592 DOI: 10.3390/membranes11070459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 06/11/2021] [Accepted: 06/17/2021] [Indexed: 11/23/2022]
Abstract
Detergents wrap around membrane proteins to form a belt covering the hydrophobic part of the protein serving for membrane insertion and interaction with lipids. The number of detergent monomers forming this belt is usually unknown to investigators, unless dedicated detergent quantification is undertaken, which for many projects is difficult to setup. Yet, having an approximate knowledge of the amount of detergent forming the belt is extremely useful, to better grasp the protein of interest in interaction with its direct environment rather than picturing the membrane protein "naked". We created the Det.Belt server to dress up membrane proteins and represent in 3D the bulk made by detergent molecules wrapping in a belt. Many detergents are included in a database, allowing investigators to screen in silico the effect of different detergents around their membrane protein. The input number of detergents is changeable with fast recomputation of the belt for interactive usage. Metrics representing the belt are readily available together with scripts to render quality 3D images for publication. The Det.Belt server is a tool for biochemists to better grasp their sample.
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Affiliation(s)
- Veronica Zampieri
- EMBL Grenoble, 71 Avenue des Martyrs, CS 90181, CEDEX 9, 38042 Grenoble, France;
| | - Cécile Hilpert
- Molecular Microbiology and Structural Biochemistry Laboratory (CNRS UMR 5086), University of Lyon, IBCP, 7 Passage du Vercors, 69367 Lyon, France; (C.H.); (M.G.); (Y.G.); (S.D.); (J.M.); (P.F.)
| | - Mélanie Garnier
- Molecular Microbiology and Structural Biochemistry Laboratory (CNRS UMR 5086), University of Lyon, IBCP, 7 Passage du Vercors, 69367 Lyon, France; (C.H.); (M.G.); (Y.G.); (S.D.); (J.M.); (P.F.)
| | - Yannick Gestin
- Molecular Microbiology and Structural Biochemistry Laboratory (CNRS UMR 5086), University of Lyon, IBCP, 7 Passage du Vercors, 69367 Lyon, France; (C.H.); (M.G.); (Y.G.); (S.D.); (J.M.); (P.F.)
| | - Sébastien Delolme
- Molecular Microbiology and Structural Biochemistry Laboratory (CNRS UMR 5086), University of Lyon, IBCP, 7 Passage du Vercors, 69367 Lyon, France; (C.H.); (M.G.); (Y.G.); (S.D.); (J.M.); (P.F.)
| | - Juliette Martin
- Molecular Microbiology and Structural Biochemistry Laboratory (CNRS UMR 5086), University of Lyon, IBCP, 7 Passage du Vercors, 69367 Lyon, France; (C.H.); (M.G.); (Y.G.); (S.D.); (J.M.); (P.F.)
| | - Pierre Falson
- Molecular Microbiology and Structural Biochemistry Laboratory (CNRS UMR 5086), University of Lyon, IBCP, 7 Passage du Vercors, 69367 Lyon, France; (C.H.); (M.G.); (Y.G.); (S.D.); (J.M.); (P.F.)
| | - Guillaume Launay
- Molecular Microbiology and Structural Biochemistry Laboratory (CNRS UMR 5086), University of Lyon, IBCP, 7 Passage du Vercors, 69367 Lyon, France; (C.H.); (M.G.); (Y.G.); (S.D.); (J.M.); (P.F.)
| | - Vincent Chaptal
- Molecular Microbiology and Structural Biochemistry Laboratory (CNRS UMR 5086), University of Lyon, IBCP, 7 Passage du Vercors, 69367 Lyon, France; (C.H.); (M.G.); (Y.G.); (S.D.); (J.M.); (P.F.)
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3
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Modafferi D, Zazubovich V, Kálmán L. Bound detergent molecules in bacterial reaction centers facilitate detection of tetryl explosive. PHOTOSYNTHESIS RESEARCH 2020; 145:145-157. [PMID: 32632533 DOI: 10.1007/s11120-020-00770-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 06/24/2020] [Indexed: 06/11/2023]
Abstract
Bacterial reaction centers (BRC) from Rhodobacter sphaeroides were found to accelerate, about 100-fold, the reaction between tetryl (2,4,6-trinitrophenylmethylnitramine) explosive and n-lauryl-N-N-dimethylamine-N-oxide (LDAO) that results in the formation of picric acid-like product with characteristic UV-VIS absorption spectrum with peaks at 345 and 415 nm. Moreover, this product also affects the spectra of BRC cofactors in the NIR spectral region and stabilizes the conformational changes associated with slow charge recombination. The evolution of the NIR absorption changes correlated with the kinetics of the product formation. Comparison between the wild-type and the R26 carotenoid-less strain indicates that tetryl-LDAO reaction is roughly five times faster for R26, which allows for identifying the carotenoid binding site as the optimal reaction site. Another, less-defined reaction site is located in the BRC's hydrophobic cavity. These effects are highly selective for tetryl and not observed for several other widespread nitric explosives; slowed-down charge recombination allows for distinguishing between tetryl and QB-site herbicides. The current limit of detection is in the ppb range or ~ 100 nM. Details of the molecular mechanisms of the reactions and perspectives of using these effects in bioassays or biosensors for explosives detection are also discussed.
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Affiliation(s)
- Daniel Modafferi
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada
- Department of Chemical Engineering, McGill University, Montreal, QC, Canada
| | - Valter Zazubovich
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada.
| | - László Kálmán
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada.
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4
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Zabelin AA, Shkuropatova VA, Shuvalov VA, Shkuropatov AY. Spectral and Photochemical Properties of Rhodobacter sphaeroides R-26 Reaction Center Films in Vacuum. BIOCHEMISTRY (MOSCOW) 2019; 84:1107-1115. [PMID: 31693470 DOI: 10.1134/s000629791909013x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Using absorption spectroscopy in the visible/near-IR and mid-IR regions, spectral and photochemical properties of isolated reaction centers (RCs) from Rhodobacter sphaeroides R-26 were studied in dried films on the inorganic support surface (quartz or CaF2 plates) under vacuum dehydration conditions (10-2 or 7·10-5 mm Hg). Three detergents, N,N-dimethyldodecylamine N-oxide (LDAO), Triton X-100 (TX100), and n-dodecyl-β-D-maltoside (DM), were tested for their ability to stabilize the RC-detergent complexes in the vacuum-dried state. It was shown that in the presence of LDAO, RC complexes underwent destruction in vacuum. In contrast, DM provided an environment that minimized irreversible disruptive changes in the RCs in vacuum. The effects of vacuum dehydration on the RC-DM films included a small increase in the content of α-helices in the RC protein, a short-wavelength reversible shift in the optical transitions of pigments, and minor changes in the electronic structure of the P+ dimer. The films retained their photochemical activity upon excitation with high-intensity light (200 mW/cm2). TX100 also helped to maintain spectral and functional properties of the RCs in vacuum; however, in this case, the stabilizing effect was less pronounced than in the presence of DM, especially, at high detergent concentrations. The results are discussed within the framework of a model suggesting that the detergent-protein interactions and the properties of detergent micelles play a dominant role in maintaining the structure of the RCs upon vacuum dehydration of the RC complexes. The obtained data can be useful for developing hybrid photoconverting systems based on bacterial RCs.
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Affiliation(s)
- A A Zabelin
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
| | - V A Shkuropatova
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - V A Shuvalov
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - A Ya Shkuropatov
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
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5
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Quantification of Detergents Complexed with Membrane Proteins. Sci Rep 2017; 7:41751. [PMID: 28176812 PMCID: PMC5297245 DOI: 10.1038/srep41751] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 12/23/2016] [Indexed: 01/20/2023] Open
Abstract
Most membrane proteins studies require the use of detergents, but because of the lack of a general, accurate and rapid method to quantify them, many uncertainties remain that hamper proper functional and structural data analyses. To solve this problem, we propose a method based on matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) that allows quantification of pure or mixed detergents in complex with membrane proteins. We validated the method with a wide variety of detergents and membrane proteins. We automated the process, thereby allowing routine quantification for a broad spectrum of usage. As a first illustration, we show how to obtain information of the amount of detergent in complex with a membrane protein, essential for liposome or nanodiscs reconstitutions. Thanks to the method, we also show how to reliably and easily estimate the detergent corona diameter and select the smallest size, critical for favoring protein-protein contacts and triggering/promoting membrane protein crystallization, and to visualize the detergent belt for Cryo-EM studies.
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6
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Nalepa A, Malferrari M, Lubitz W, Venturoli G, Möbius K, Savitsky A. Local water sensing: water exchange in bacterial photosynthetic reaction centers embedded in a trehalose glass studied using multiresonance EPR. Phys Chem Chem Phys 2017; 19:28388-28400. [DOI: 10.1039/c7cp03942e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Pulsed EPR spectroscopies and isotope labeled water are applied to detect and quantify the local water in a bacterial reaction center embedded into a trehalose glass.
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Affiliation(s)
- Anna Nalepa
- Max-Planck-Institut für Chemische Energiekonversion
- D-45470 Mülheim an der Ruhr
- Germany
| | - Marco Malferrari
- Laboratorio di Biochimica e Biofisica
- Dipartimento di Farmacia e Biotecnologie
- FaBiT
- Università di Bologna
- I-40126 Bologna
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion
- D-45470 Mülheim an der Ruhr
- Germany
| | - Giovanni Venturoli
- Laboratorio di Biochimica e Biofisica
- Dipartimento di Farmacia e Biotecnologie
- FaBiT
- Università di Bologna
- I-40126 Bologna
| | - Klaus Möbius
- Max-Planck-Institut für Chemische Energiekonversion
- D-45470 Mülheim an der Ruhr
- Germany
- Department of Physics
- Free University Berlin
| | - Anton Savitsky
- Max-Planck-Institut für Chemische Energiekonversion
- D-45470 Mülheim an der Ruhr
- Germany
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7
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Abstract
X-ray crystallography remains the most robust method to determine protein structure at the atomic level. However, the bottlenecks of protein expression and purification often discourage further study. In this chapter, we address the most common problems encountered at these stages. Based on our experiences in expressing and purifying antimicrobial efflux proteins, we explain how a pure and homogenous protein sample can be successfully crystallized by the vapor diffusion method. We present our current protocols and methodologies for this technique. Case studies show step-by-step how we have overcome problems related to expression and diffraction, eventually producing high-quality membrane protein crystals for structural determinations. It is our hope that a rational approach can be made of the often anecdotal process of membrane protein crystallization.
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8
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Tang KH, Blankenship RE. Neutron and light scattering studies of light-harvesting photosynthetic antenna complexes. PHOTOSYNTHESIS RESEARCH 2012; 111:205-217. [PMID: 21710338 DOI: 10.1007/s11120-011-9665-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 06/02/2011] [Indexed: 05/31/2023]
Abstract
Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been employed in studying the structural information of various biological systems, particularly in systems without high-resolution structural information available. In this report, we briefly present some principles and biological applications of neutron scattering and DLS, compare the differences in information that can be obtained with small-angle X-ray scattering (SAXS), and then report recent studies of SANS and DLS, together with other biophysical approaches, for light-harvesting antenna complexes and reaction centers of purple and green phototrophic bacteria.
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Affiliation(s)
- Kuo-Hsiang Tang
- Department of Biology and Department of Chemistry, Washington University in St. Louis, Campus Box 1137, St. Louis, MO 63130, USA
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9
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Malferrari M, Francia F, Venturoli G. Coupling between Electron Transfer and Protein–Solvent Dynamics: FTIR and Laser-Flash Spectroscopy Studies in Photosynthetic Reaction Center Films at Different Hydration Levels. J Phys Chem B 2011; 115:14732-50. [DOI: 10.1021/jp2057767] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Marco Malferrari
- Laboratorio di Biochimica e Biofisica, Dipartimento di Biologia, Università di Bologna, 40126 Bologna, Italy
| | - Francesco Francia
- Laboratorio di Biochimica e Biofisica, Dipartimento di Biologia, Università di Bologna, 40126 Bologna, Italy
| | - Giovanni Venturoli
- Laboratorio di Biochimica e Biofisica, Dipartimento di Biologia, Università di Bologna, 40126 Bologna, Italy
- Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, c/o Dipartimento di Fisica, Università di Bologna, 40127 Bologna, Italy
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10
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Schulz GE. Validation of the detergent micelle classification for membrane protein crystals and explanation of the Matthews Graph for soluble proteins. Protein Sci 2011; 20:1765-70. [PMID: 21815230 DOI: 10.1002/pro.709] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 06/04/2011] [Accepted: 07/21/2011] [Indexed: 11/10/2022]
Abstract
Protein crystals are of wide-spread interest because many of them allow structure analyses at atomic resolution. For soluble proteins, the packing density of such crystals is distributed according to the Matthews Graph. For integral membrane proteins, the respective graph is similar but at lower density and much broader. By visualizing the relative positions and orientations of membrane proteins in crystals, it has been suggested that the detergent micelles surrounding these proteins form sheets, filaments, or remain isolated in the crystal giving rise to three distinct packing density distributions that superimpose to form the observed broad distribution. This classification was indirect because detergent is not visible in X-ray crystallography. Given the extensive work involved in analyzing detergent structure directly by neutron diffraction, it seems unlikely that a statistically relevant number of them will be established in the near future. Therefore, the proposed classification is here scrutinized by a simulation in which an average detergent-carrying membrane protein was randomly packed to form crystals. The analysis reproduced the three types of detergent structures together with their packing density distributions and relative frequencies, which validates the previous classification. The simulation program was also run for crystals from soluble proteins using ellipsoids as reference shapes and defining a shape factor that quantifies the deviation from the nearest ellipsoid. This series reproduced and thus explained the Matthews Graph.
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Affiliation(s)
- Georg E Schulz
- Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstr 21, D-79104 Freiburg im Breisgau, Germany.
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11
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Mukherjee D, May M, Khomami B. Detergent–protein interactions in aqueous buffer suspensions of Photosystem I (PS I). J Colloid Interface Sci 2011; 358:477-84. [DOI: 10.1016/j.jcis.2011.03.070] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 03/18/2011] [Accepted: 03/18/2011] [Indexed: 11/27/2022]
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12
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Deshmukh SS, Akhavein H, Williams JC, Allen JP, Kálmán L. Light-Induced Conformational Changes in Photosynthetic Reaction Centers: Impact of Detergents and Lipids on the Electronic Structure of the Primary Electron Donor. Biochemistry 2011; 50:5249-62. [DOI: 10.1021/bi200595z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- S. S. Deshmukh
- Department of Physics, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - H. Akhavein
- Department of Physics, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - J. C. Williams
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, 85287-1604, United States
| | - J. P. Allen
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, 85287-1604, United States
| | - L. Kálmán
- Department of Physics, Concordia University, Montreal, Quebec H4B 1R6, Canada
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13
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Schulz GE. A new classification of membrane protein crystals. J Mol Biol 2011; 407:640-6. [PMID: 21315729 DOI: 10.1016/j.jmb.2011.02.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Revised: 02/01/2011] [Accepted: 02/01/2011] [Indexed: 10/18/2022]
Abstract
Although being much smaller than the number of soluble proteins in the Protein Data Bank, the number of membrane proteins therein now approaches 700, and a statistical analysis becomes meaningful. Such an analysis showed that the conventional subdivision into monotopic, β-barrel and α-helical membrane proteins is appropriate but should be amended by a classification according to the detergent micelle structure in the crystal, which can be derived from the packing of the membrane-immersed parts of the proteins. The crystal packing density is specific for the three conventional types of membrane proteins and soluble proteins. It is also specific for three observed detergent arrangements that are micelle pockets, micelle filaments and micelle sheets, demonstrating that the detergent structure affects crystallization. The packing density distribution of crystals from integral membrane proteins has approximately the same shape as that of soluble proteins but is by a factor of two broader and shifted to lower density. It seems unlikely that the differences can be explained by a mere solvent expansion due to the required detergent. The crystallized membrane proteins were further analyzed with respect to protein mass, oligomerization and crystallographic asymmetric unit, space group, crystal ordering and symmetry. The results provide a new view on membrane proteins.
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Affiliation(s)
- Georg E Schulz
- Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstrasse 21,D-79104 Freiburg im Breisgau, Germany.
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14
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Broser M, Gabdulkhakov A, Kern J, Guskov A, Müh F, Saenger W, Zouni A. Crystal structure of monomeric photosystem II from Thermosynechococcus elongatus at 3.6-a resolution. J Biol Chem 2010; 285:26255-62. [PMID: 20558739 DOI: 10.1074/jbc.m110.127589] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The membrane-embedded photosystem II core complex (PSIIcc) uses light energy to oxidize water in photosynthesis. Information about the spatial structure of PSIIcc obtained from x-ray crystallography was so far derived from homodimeric PSIIcc of thermophilic cyanobacteria. Here, we report the first crystallization and structural analysis of the monomeric form of PSIIcc with high oxygen evolution capacity, isolated from Thermosynechococcus elongatus. The crystals belong to the space group C222(1), contain one monomer per asymmetric unit, and diffract to a resolution of 3.6 A. The x-ray diffraction pattern of the PSIIcc-monomer crystals exhibit less anisotropy (dependence of resolution on crystal orientation) compared with crystals of dimeric PSIIcc, and the packing of the molecules within the unit cell is different. In the monomer, 19 protein subunits, 35 chlorophylls, two pheophytins, the non-heme iron, the primary plastoquinone Q(A), two heme groups, 11 beta-carotenes, 22 lipids, seven detergent molecules, and the Mn(4)Ca cluster of the water oxidizing complex could be assigned analogous to the dimer. Based on the new structural information, the roles of lipids and protein subunits in dimer formation of PSIIcc are discussed. Due to the lack of non-crystallographic symmetry and the orientation of the membrane normal of PSIIcc perpendicular ( approximately 87 degrees ) to the crystallographic b-axis, further information about the structure of the Mn(4)Ca cluster is expected to become available from orientation-dependent spectroscopy on this new crystal form.
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Affiliation(s)
- Matthias Broser
- Institute of Chemistry, Max Volmer Laboratory of Biophysical Chemistry, Technische Universität Berlin, Berlin, Germany
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15
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Fiedler S, Broecker J, Keller S. Protein folding in membranes. Cell Mol Life Sci 2010; 67:1779-98. [PMID: 20101433 PMCID: PMC11115603 DOI: 10.1007/s00018-010-0259-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 01/01/2010] [Accepted: 01/06/2010] [Indexed: 10/19/2022]
Abstract
Separation of cells and organelles by bilayer membranes is a fundamental principle of life. Cellular membranes contain a baffling variety of proteins, which fulfil vital functions as receptors and signal transducers, channels and transporters, motors and anchors. The vast majority of membrane-bound proteins contain bundles of alpha-helical transmembrane domains. Understanding how these proteins adopt their native, biologically active structures in the complex milieu of a membrane is therefore a major challenge in today's life sciences. Here, we review recent progress in the folding, unfolding and refolding of alpha-helical membrane proteins and compare the molecular interactions that stabilise proteins in lipid bilayers. We also provide a critical discussion of a detergent denaturation assay that is increasingly used to determine membrane-protein stability but is not devoid of conceptual difficulties.
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Affiliation(s)
- Sebastian Fiedler
- Leibniz Institute of Molecular Pharmacology (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Jana Broecker
- Leibniz Institute of Molecular Pharmacology (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Sandro Keller
- Leibniz Institute of Molecular Pharmacology (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
- Molecular Biophysics, University of Kaiserslautern, Erwin-Schrödinger-Str. 13, 67663 Kaiserslautern, Germany
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16
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Müh F, Rautter J, Lubitz W. Effects of zwitterionic detergents on the primary donor of bacterial reaction centers. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19961001208] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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17
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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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18
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Neutron diffraction measurements of skeletal muscle using the contrast variation technique: analysis of the equatorial diffraction patterns. J Struct Biol 2009; 167:25-35. [PMID: 19351558 DOI: 10.1016/j.jsb.2009.03.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 03/26/2009] [Accepted: 03/31/2009] [Indexed: 11/20/2022]
Abstract
Among various methods for structural studies of biological macromolecules, neutron scattering and diffraction have a unique feature in that the contrast between the scattering length density of the molecules and that of the solvent can be varied easily by changing the D2O content in the solvent. This "contrast variation" technique enables one to obtain information on variations of scattering length density of the molecules of interest. Here, in order to explore the possibilities of the contrast variation technique in neutron fiber diffraction, neutron diffraction measurements of skeletal muscles were performed. The neutron fiber diffraction patterns from frog sartorius muscles were measured in various D2O concentrations in the relaxed state where no tension of muscle is produced, and in the rigor state where all myosin heads of the thick filaments bind tightly to actin in the thin filaments. It was shown that in both states, there were reflections having distinct contrast matching points, indicating a variation in the scattering length density of the protein regions in the unit cell of the muscle structure. Analysis of the equatorial reflections by the two-dimensional projected scattering length density map calculations by Fourier synthesis and model calculations provided the phase information of the equatorial reflections, with which the projected scattering length density maps of the unit cell of the hexagonal filament array in both states were calculated. The analysis showed that the scattering length density of the thick filament region was higher than that of the thin filament region, and that the scattering length density of the thick filament backbone changed as muscle went from the relaxed state into the rigor state.
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19
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Müh F, Zouni A. Micelle formation in the presence of photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:2298-307. [DOI: 10.1016/j.bbamem.2008.05.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Revised: 05/26/2008] [Accepted: 05/29/2008] [Indexed: 11/16/2022]
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20
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Timmins P, Pebay-Peyroula E, Welte W. Detergent organisation in solutions and in crystals of membrane proteins. Biophys Chem 2008; 53:27-36. [PMID: 17020837 DOI: 10.1016/0301-4622(94)00073-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/1994] [Accepted: 02/20/1994] [Indexed: 11/23/2022]
Abstract
The use of neutron scattering in studying the organisation of detergents in pure micelles, in protein/detergent mixed micelles and in crystals of membrane proteins, is reviewed. Small angle scattering has been used to study the size, shape and composition of pure and mixed protein/detergent micelles as well as the effects of adding small amphiphiles. The technique of contrast variation applied to single crystals is described and its application to the determination of the organization of detergent in single crystals of membrane proteins is discussed. A better understanding of protein/detergent interactions should help in producing crystals of membrane proteins more easily as well as clues to the nature of protein/lipid interactions in vivo.
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Affiliation(s)
- P Timmins
- Institut Laue-Langevin, BP 156, 38042 Grenoble, France
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21
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Urboniene V, Vrublevskaja O, Trinkunas G, Gall A, Robert B, Valkunas L. Solvation effect of bacteriochlorophyll excitons in light-harvesting complex LH2. Biophys J 2007; 93:2188-98. [PMID: 17513366 PMCID: PMC1959563 DOI: 10.1529/biophysj.106.103093] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have characterized the influence of the protein environment on the spectral properties of the bacteriochlorophyll (Bchl) molecules of the peripheral light-harvesting (or LH2) complex from Rhodobacter sphaeroides. The spectral density functions of the pigments responsible for the 800 and 850 nm electronic transitions were determined from the temperature dependence of the Bchl absorption spectra in different environments (detergent micelles and native membranes). The spectral density function is virtually independent of the hydrophobic support that the protein experiences. The reorganization energy for the B850 Bchls is 220 cm(-1), which is almost twice that of the B800 Bchls, and its Huang-Rhys factor reaches 8.4. Around the transition point temperature, and at higher temperatures, both the static spectral inhomogeneity and the resonance interactions become temperature-dependent. The inhomogeneous distribution function of the transitions exhibits less temperature dependence when LH2 is embedded in membranes, suggesting that the lipid phase protects the protein. However, the temperature dependence of the fluorescence spectra of LH2 cannot be fitted using the same parameters determined from the analysis of the absorption spectra. Correct fitting requires the lowest exciton states to be additionally shifted to the red, suggesting the reorganization of the exciton spectrum.
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Affiliation(s)
- V Urboniene
- Department of General Physics and Spectroscopy, Vilnius University, Vilnius, Lithuania
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22
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Berger BW, Gendron CM, Lenhoff AM, Kaler EW. Effects of additives on surfactant phase behavior relevant to bacteriorhodopsin crystallization. Protein Sci 2006; 15:2682-96. [PMID: 17088325 PMCID: PMC2242436 DOI: 10.1110/ps.062370506] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The interactions leading to crystallization of the integral membrane protein bacteriorhodopsin solubilized in n-octyl-beta-D-glucoside were investigated. Osmotic second virial coefficients (B(22)) were measured by self-interaction chromatography using a wide range of additives and precipitants, including polyethylene glycol (PEG) and heptane-1,2,3-triol (HT). In all cases, attractive protein-detergent complex (PDC) interactions were observed near the surfactant cloud point temperature, and there is a correlation between the surfactant cloud point temperatures and PDC B(22) values. Light scattering, isothermal titration calorimetry, and tensiometry reveal that although the underlying reasons for the patterns of interaction may be different for various combinations of precipitants and additives, surfactant phase behavior plays an important role in promoting crystallization. In most cases, solution conditions that led to crystallization fell within a similar range of slightly negative B(22) values, suggesting that weakly attractive interactions are important as they are for soluble proteins. However, the sensitivity of the cloud point temperatures and resultant coexistence curves varied significantly as a function of precipitant type, which suggests that different types of forces are involved in driving phase separation depending on the precipitant used.
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Affiliation(s)
- Bryan W Berger
- Center for Molecular and Engineering Thermodynamics, Department of Chemical Engineering, University of Delaware, Newark, Delaware 19716, USA.
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23
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Lomize AL, Pogozheva ID, Lomize MA, Mosberg HI. Positioning of proteins in membranes: a computational approach. Protein Sci 2006; 15:1318-33. [PMID: 16731967 PMCID: PMC2242528 DOI: 10.1110/ps.062126106] [Citation(s) in RCA: 158] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
A new computational approach has been developed to determine the spatial arrangement of proteins in membranes by minimizing their transfer energies from water to the lipid bilayer. The membrane hydrocarbon core was approximated as a planar slab of adjustable thickness with decadiene-like interior and interfacial polarity profiles derived from published EPR studies. Applicability and accuracy of the method was verified for a set of 24 transmembrane proteins whose orientations in membranes have been studied by spin-labeling, chemical modification, fluorescence, ATR FTIR, NMR, cryo-microscopy, and neutron diffraction. Subsequently, the optimal rotational and translational positions were calculated for 109 transmembrane, five integral monotopic and 27 peripheral protein complexes with known 3D structures. This method can reliably distinguish transmembrane and integral monotopic proteins from water-soluble proteins based on their transfer energies and membrane penetration depths. The accuracies of calculated hydrophobic thicknesses and tilt angles were approximately 1 A and 2 degrees, respectively, judging from their deviations in different crystal forms of the same proteins. The hydrophobic thicknesses of transmembrane proteins ranged from 21.1 to 43.8 A depending on the type of biological membrane, while their tilt angles with respect to the bilayer normal varied from zero in symmetric complexes to 26 degrees in asymmetric structures. Calculated hydrophobic boundaries of proteins are located approximately 5 A lower than lipid phosphates and correspond to the zero membrane depth parameter of spin-labeled residues. Coordinates of all studied proteins with their membrane boundaries can be found in the Orientations of Proteins in Membranes (OPM) database:http://opm.phar.umich.edu/.
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Affiliation(s)
- Andrei L Lomize
- College of Pharmacy, University of Michigan, Ann Arbor, Michigan 48109-1065, USA.
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24
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Sørensen TLM, Olesen C, Jensen AML, Møller JV, Nissen P. Crystals of sarcoplasmic reticulum Ca(2+)-ATPase. J Biotechnol 2006; 124:704-16. [PMID: 16597471 DOI: 10.1016/j.jbiotec.2006.02.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2005] [Accepted: 02/01/2006] [Indexed: 11/24/2022]
Abstract
High-resolution structures of the Ca(2+)-ATPase have over the last 5 years added a structural dimension to our understanding of the function of this integral membrane protein. The Ca(2+)-ATPase is now by far the membrane protein where the most functionally different conformations have been described in precise structural detail. Here, we review our experience from solving Ca(2+)-ATPase structures: a purification scheme involving minimum handling of the protein to preserve natural and essential lipids, a rational approach to screening for crystals based on a limited number of polyethyleneglycols and many different salts, improving crystal quality using additives, collecting the data and finally solving the structures. We argue that certain of the lessons learned in the present study are very likely to be useful for crystallisation of eukaryotic membrane proteins in general.
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25
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Timmins P. Detergent Binding in Membrane Protein Crystals by Neutron Crystallography. NEUTRON SCATTERING IN BIOLOGY 2006. [DOI: 10.1007/3-540-29111-3_5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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26
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Galdiero S, Gouaux E. High resolution crystallographic studies of alpha-hemolysin-phospholipid complexes define heptamer-lipid head group interactions: implication for understanding protein-lipid interactions. Protein Sci 2005; 13:1503-11. [PMID: 15152085 PMCID: PMC2279993 DOI: 10.1110/ps.03561104] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The alpha-hemolysin is an archetypal pore-forming protein that is secreted from Staphylococcus aureus as a water-soluble monomer. When the monomer binds to the membrane of a susceptible cell, the membrane-bound molecules assemble into the lytic heptamer. Although a bilayer or a bilayer-like environment are essential to toxin assembly, there is no high resolution information on toxin-phospholipid complexes. We have determined the structures of detergent-solubilized alpha-hemolysin heptamer bound to glycerophosphocholine or dipropanoyl glycerophosphocholine at 1.75-1.80 A resolution and 110 K. The phosphocholine head group binds to each subunit in a crevice between the rim and the stem domains. The quaternary ammonium group interacts primarily with aromatic residues, whereas the phosphodiester moiety interacts with a conserved arginine residue. These structures provide a molecular basis for understanding why alpha-hemolysin preferentially assembles on membranes comprised of phosphocholine lipids.
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Affiliation(s)
- Stefania Galdiero
- Howard Hughes Medical Institute and Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.
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27
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Hantgan RR, Stahle MC, Connor JH, Lyles DS, Horita DA, Rocco M, Nagaswami C, Weisel JW, McLane MA. The disintegrin echistatin stabilizes integrin alphaIIbbeta3's open conformation and promotes its oligomerization. J Mol Biol 2004; 342:1625-36. [PMID: 15364586 DOI: 10.1016/j.jmb.2004.08.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Revised: 08/03/2004] [Accepted: 08/04/2004] [Indexed: 10/26/2022]
Abstract
We have employed echistatin, a 5.4 kDa snake venom disintegrin, as a model protein to investigate the paradox that small ligand-mimetics can bind to the resting alphaIIbbeta3 integrin while adhesive macromolecules cannot. We characterized the interactions between purified human alphaIIbbeta3 and two recombinant echistatin variants: rEch (1-49) M28L, chosen for its selectivity toward beta3-integrins, and rEch (1-40) M28L, a carboxy-terminal truncation mutant. While both contain an RGD integrin targeting sequence, only rEch (1-49) M28L was an effective inhibitor of alphaIIbbeta3 function. Electron microscopy of rotary shadowed specimens yielded a variety of alphaIIbbeta3 conformers ranging from compact, spherical particles (maximum dimension 22 nm) to the classical "head with two tails" forms (32 nm). The population of larger particles (42-56 nm) increased from 17% to 28% in the presence of rEch (1-49) M28L, indicative of ligand-induced oligomerization. Sedimentation velocity measurements demonstrated that both full length and truncated echistatin perturbed alphaIIbbeta3's solution structure, yielding slower-sedimenting open conformers. Dynamic light scattering showed that rEch (1-49) M28L protected alphaIIbbeta3 from thermal aggregation, raising its transition mid-point from 46 degrees C to 69 degrees C; a smaller shift resulted with rEch (1-40) M28L. Sedimentation equilibrium demonstrated that both echistatin ligands induced substantial alphaIIbbeta3 dimerization. van't Hoff analysis revealed a pattern of entropy/enthalpy compensation similar to tirofiban, a small RGD ligand-mimetic that binds tightly to alphaIIbbeta3, but yields smaller conformational perturbations than echistatin. We propose that echistatin may serve as a paradigm for understanding multidomain adhesive macromolecules because its ability to modulate alphaIIbbeta3's structure resides on an RGD loop, while full disintegrin activity requires an auxiliary site that includes the carboxy-terminal nine amino acid residues.
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Affiliation(s)
- Roy R Hantgan
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, NC 27517, USA.
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28
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Hong X, Weng YX, Li M. Determination of the topological shape of integral membrane protein light-harvesting complex LH2 from photosynthetic bacteria in the detergent solution by small-angle X-ray scattering. Biophys J 2004; 86:1082-8. [PMID: 14747343 PMCID: PMC1303901 DOI: 10.1016/s0006-3495(04)74183-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2003] [Accepted: 09/11/2003] [Indexed: 10/21/2022] Open
Abstract
The topological shape of the integral membrane protein light-harvesting complex LH2 from photosynthetic bacteria Rhodobacter spheroides 2.4.1 in detergent solution has been determined from synchrotron small-angle X-ray scattering data using direct curve-fitting by the ellipsoid, ab initio shape determination methods of simulated annealing algorithm and multipole expansion, respectively. The results indicate that the LH2 protein in aqueous solution is encapsulated by a monolayered detergent shell. The detergent-stabilized structure has the shape of an oblate plate, with a thickness of 40 A, a long axis of 110 A, and a short axis of 85 A. After correction for the detergent shell, the shape of the LH2 core is also an oblate plate with a height of 40 A, a long axis of 80 A, and a short axis of 55 A. In contrast to the cylindrical crystal structure with a height of 40 A and a diameter of 68 A, the molecular shape of the LH2 complex in detergent solution clearly deviates from the ringlike crystal structure, with an eccentricity found to be 0.59-consistent with the result of single molecular spectroscopy study of the isolated single LH2 molecules.
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Affiliation(s)
- Xinguo Hong
- Laboratory of Soft Matter Physics, Institute of Physics, and Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
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29
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Palazzo G, Mallardi A, Francia F, Dezi M, Venturoli G, Pierno M, Vignati E, Piazza R. Spontaneous emulsification of detergent solubilized reaction center: protein conformational changes precede droplet growth. Phys Chem Chem Phys 2004. [DOI: 10.1039/b314588n] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Milano F, Agostiano A, Mavelli F, Trotta M. Kinetics of the quinone binding reaction at the QB site of reaction centers from the purple bacteria Rhodobacter sphaeroides reconstituted in liposomes. ACTA ACUST UNITED AC 2003; 270:4595-605. [PMID: 14622246 DOI: 10.1046/j.1432-1033.2003.03845.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Transmembrane proton translocation in the photosynthetic membranes of the purple bacterium Rhodobacter sphaeroides is driven by light and performed by two transmembrane complexes; the photosynthetic reaction center and the ubiquinol-cytochrome c oxidoreductase complex, coupled by two mobile electron carriers; the cytochrome and the quinone. This paper focuses on the kinetics and thermodynamics of the interaction between the lipophylic electron carrier ubiquinone-10 and the photosynthetic enzyme reconstituted in liposomes. The collected data were simulated with an existing recognized kinetic scheme and the kinetic constants of the uptake (7.2 x 107 M(-1) x s(-1)) and release (40 s(-1)) processes of the ligand were inferred. The results obtained for the quinone release kinetic constant are comparable to the rate of the charge recombination reaction from the state D(+)QA(-). Values for the kinetic constants are discussed as part of the overall photocycle, suggesting that its bottleneck may not be the quinone uptake reaction in agreement with a previous report.
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Affiliation(s)
- Francesco Milano
- CNR, Istituto per i Processi Chimico-Fisici - Sezione di Bari Dipartimento di Chimica, Universitá di Bari, Italy
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31
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32
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Prince SM, Howard TD, Myles DAA, Wilkinson C, Papiz MZ, Freer AA, Cogdell RJ, Isaacs NW. Detergent structure in crystals of the integral membrane light-harvesting complex LH2 from Rhodopseudomonas acidophila strain 10050. J Mol Biol 2003; 326:307-15. [PMID: 12547211 DOI: 10.1016/s0022-2836(02)01361-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Integral membrane proteins are solubilized by their incorporation into a detergent micelle. The detergent micelle has a critical influence on the formation of a three-dimensional crystal lattice. The bulk detergent phase is not seen in X-ray crystal structures of integral membrane proteins, due to its disordered character. Here, we describe the detergent structure present in crystals of the peripheral light-harvesting complex of the purple bacteria Rhodopseudomonas acidophila strain 10050 at a maximal resolution of 12A as determined by neutron crystallography. The LH2 molecule has a toroidal shape and spans the membrane completely in vivo. A volume of 16% of the unit cell could be ascribed to detergent tails, localized on both the inner and outer hydrophobic surfaces of the molecule. The detergent tail volumes were found to be associated with individual LH2 molecules and had no direct role in the formation of the crystalline lattice.
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Affiliation(s)
- S M Prince
- Department of Chemistry, University of Glasgow, G12 8QQ, Glasgow, UK.
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33
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Snijder HJ, Timmins PA, Kalk KH, Dijkstra BW. Detergent organisation in crystals of monomeric outer membrane phospholipase A. J Struct Biol 2003; 141:122-31. [PMID: 12615538 DOI: 10.1016/s1047-8477(02)00579-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The structure of the detergent in crystals of outer membrane phospholipase A (OMPLA) has been determined using neutron diffraction contrast variation. Large crystals were soaked in stabilising solutions, each containing a different H(2)O/D(2)O contrast. From the neutron diffraction at five contrasts, the 12 A resolution structure of the detergent micelle around the protein molecule was determined. The hydrophobic beta-barrel surfaces of the protein molecules are covered by rings of detergent. These detergent belts are fused to neighbouring detergent rings forming a continuous three-dimensional network throughout the crystal. The thickness of the detergent layer around the protein varies from 7-20 A. The enzyme's active site is positioned just outside the hydrophobic detergent zone and is thus in a proper location to catalyse the hydrolysis of phospholipids in a natural membrane. Although the dimerisation face of OMPLA is covered with detergent, the detergent density is weak near the exposed polar patch, suggesting that burying this patch in the enzyme's dimer interface may be energetically favourable. Furthermore, these results indicate a crucial role for detergent coalescence during crystal formation and contribute to the understanding of membrane protein crystallisation.
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Affiliation(s)
- H J Snijder
- Laboratory of Biophysical Chemistry, BIOSON Research Institute and Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, The Netherlands
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34
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Response of membrane protein to the environment: the case of photosynthetic Reaction Centre. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2002. [DOI: 10.1016/s0928-4931(02)00178-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Jones MR, Fyfe PK, Roszak AW, Isaacs NW, Cogdell RJ. Protein-lipid interactions in the purple bacterial reaction centre. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1565:206-14. [PMID: 12409196 DOI: 10.1016/s0005-2736(02)00570-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The purple bacterial reaction centre uses the energy of sunlight to power energy-requiring reactions such as the synthesis of ATP. During the last 20 years, a combination of X-ray crystallography, spectroscopy and mutagenesis has provided a detailed insight into the mechanism of light energy transduction in the bacterial reaction centre. In recent years, structural techniques including X-ray crystallography and neutron scattering have also been used to examine the environment of the reaction centre. This mini-review focuses on recent studies of the surface of the reaction centre, and briefly discusses the importance of the specific protein-lipid interactions that have been resolved for integral membrane proteins.
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Affiliation(s)
- Michael R Jones
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, UK.
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36
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Lee AG. Ca2+ -ATPase structure in the E1 and E2 conformations: mechanism, helix-helix and helix-lipid interactions. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1565:246-66. [PMID: 12409199 DOI: 10.1016/s0005-2736(02)00573-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The determination of the crystal structure of the Ca(2+)-ATPase of sarcoplasmic reticulum (SR) in its Ca(2+)-bound [Nature 405 (2000) 647] and Ca(2+)-free forms [Nature 418 (2002) 605] gives the opportunity for an analysis of conformational changes on the Ca(2+)-ATPase and of helix-helix and helix-lipid interactions in the transmembrane (TM) region of the ATPase. The locations of the ends of the TM alpha-helices on the cytoplasmic side of the membrane are reasonably well defined by the location of Trp residues and by the location of Lys-262 that snorkels up to the surface. The locations of the lumenal ends of the helices are less clear. The position of Lys-972 on the lumenal side of helix M9 suggests that the hydrophobic thickness of the protein is only about 21 A, rather than the normal 30 A. The experimentally determined TM alpha-helices do not agree well with those predicted theoretically. Charged headgroups are required for strong interaction of lipids with the ATPase, consistent with the large number of charged residues located close to the lipid-water interface. Helix packing appears to be rather irregular. Packing of helices M8 and M10 is of the 3-4 ridges-into-grooves or knobs-into-holes types. Packing of helices M5 and M7 involves two Gly residues in M7 and one Gly residue in M5. Packing of the other helices generally involves just one or two residues on each helix at the crossing point. The irregular packing of the TM alpha-helices in the Ca(2+)-ATPase, combined with the diffuse structure of the ATPase on the lumenal side of the membrane, is suggested to lead to a relative low activation energy for changing the packing of the TM alpha-helices, with changes in TM alpha-helical packing being important in the process of transfer of Ca(2+) ions across the membrane. The inhibitor thapsigargin binds in a cleft between TM alpha-helices M3, M5 and M7. It is suggested that this and other similar clefts provide binding sites for a variety of hydrophobic molecules affecting the activity of the Ca(2+)-ATPase.
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Affiliation(s)
- A G Lee
- Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton, UK.
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37
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Williamson IM, Alvis SJ, East JM, Lee AG. Interactions of phospholipids with the potassium channel KcsA. Biophys J 2002; 83:2026-38. [PMID: 12324421 PMCID: PMC1302292 DOI: 10.1016/s0006-3495(02)73964-7] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The potassium channel KcsA from Streptomyces lividans has been reconstituted into bilayers of phosphatidylcholines and fluorescence spectroscopy has been used to characterize the response of KcsA to changes in bilayer thickness. The Trp residues in KcsA form two bands, one on each side of the membrane. Trp fluorescence emission spectra and the proportion of the Trp fluorescence intensity quenchable by I(-) hardly vary in the lipid chain length range C10 to C24, suggesting efficient hydrophobic matching between KcsA and the lipid bilayer over this range. Measurements of fluorescence quenching for KcsA reconstituted into mixtures of brominated and nonbrominated phospholipids have been analyzed to give binding constants of lipids for KcsA, relative to that for dioleoylphosphatidylcholine (di(C18:1)PC). Relative lipid binding constants increase by only a factor of three with increasing chain length from C10 to C22 with a decrease from C22 to C24. Strongest binding to di(C22:1)PC corresponds to a state in which the side chains of the lipid-exposed Trp residues are likely to be located within the hydrocarbon core of the lipid bilayer. It is suggested that matching of KcsA to thinner bilayers than di(C24:1)PC is achieved by tilting of the transmembrane alpha-helices in KcsA. Measurements of fluorescence quenching of KcsA in bilayers of brominated phospholipids as a function of phospholipid chain length suggest that in the chain length range C14 to C18 the Trp residues move further away from the center of the lipid bilayer with increasing chain length, which can be partly explained by a decrease in helix tilt angle with increasing bilayer thickness. In the chain length range C18 to C24 it is suggested that the Trp residues become more buried within the hydrocarbon core of the bilayer.
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Affiliation(s)
- Ian M Williamson
- Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, United Kingdom
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38
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39
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Abstract
Detergents are invaluable tools for studying membrane proteins. However, these deceptively simple, amphipathic molecules exhibit complex behavior when they self-associate and interact with other molecules. The phase behavior and assembled structures of detergents are markedly influenced not only by their unique chemical and physical properties but also by concentration, ionic conditions, and the presence of other lipids and proteins. In this minireview, we discuss the various aggregate forms detergents assume and some misconceptions about their structure. The distinction between detergents and the membrane lipids that they may (or may not) replace is emphasized in the most recent high resolution structures of membrane proteins. Detergents are clearly friends and foes, but with the knowledge of how they work, we can use the increasing variety of detergents to our advantage.
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Affiliation(s)
- R M Garavito
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319, USA.
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40
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Reifler MJ, Szalai VA, Peterson CN, Brudvig GW. Effects of tail-like substituents on the binding of competitive inhibitors to the Q(B) site of photosystem II. J Mol Recognit 2001; 14:157-65. [PMID: 11391786 DOI: 10.1002/jmr.529] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The QB quinone-binding site of photosystem II is an important target for herbicides. Two major classes of herbicides are based on s-triazine and phenylurea moieties. A small library of triazine and phenylurea compounds has been synthesized which have tail-like substituents in order to test the effects of charge, hydrophobicity and size of the tail on binding properties. It is found that a tail can be attached to one of the alkylamino groups of triazine-type herbicides or to the para position of phenylurea-type herbicides without loss of binding, provided that the tail is hydrophobic. This indicates that the herbicides must be oriented in the QB site such that these positions point toward the natural isoprenyl tail-binding pocket that extends out of the Q(B) site. In turn, the requirement that the tail must extend out of the QB site constrains the size of the other herbicide substituents in the pocket. This is in agreement with the presumed orientation and fit of ligands in the QB site. When longer hydrophobic tails are used, the binding penalty that occurs upon adding a charged substituent at the distal end is reduced. This allows the use of a series of tail substituents possessing a distal charge as an approximate molecular ruler to measure the distance from the QB site to the aqueous phase. Even a 10-carbon alkyl chain still shows a 4-fold effect from the presence or absence of a distal charge. Such a chain does not appear to be long enough to extend from the bulk aqueous phase to the QB site because binding is completely lost when a large hydrophilic domain (PEG(4000)) is attached to the distal end. Longer tails are effective only if they are sufficiently hydrophobic. An effort was made to use tailed herbicides for affinity binding of photosystem II. It was found that hydrophobic linkers promote nonspecific binding, but careful choice of solvent conditions, such as the use of excess nonionic detergent well above its critical micelle concentration, might obviate this problem during affinity-binding applications.
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Affiliation(s)
- M J Reifler
- Department of Chemistry, Yale University, New Haven, CT 06511-8107, USA
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41
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Gall A, Dellerue S, Lapouge K, Robert B, Bellissent-Funel MC. Small angle neutron scattering measurements on the membrane protein subunit B777 in a detergent microemulsion. Biopolymers 2001; 58:231-4. [PMID: 11169383 DOI: 10.1002/1097-0282(200103)58:3<231::aid-bip1000>3.0.co;2-#] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- A Gall
- Laboratoire Léon Brillouin (CEA-CNRS), CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France.
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42
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Fyfe PK, McAuley KE, Roszak AW, Isaacs NW, Cogdell RJ, Jones MR. Probing the interface between membrane proteins and membrane lipids by X-ray crystallography. Trends Biochem Sci 2001; 26:106-12. [PMID: 11166568 DOI: 10.1016/s0968-0004(00)01746-1] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Biological membranes are composed of a complex mixture of lipids and proteins, and the membrane lipids support several key biophysical functions, in addition to their obvious structural role. Recent results from X-ray crystallography are shedding new light on the precise molecular details of the protein-lipid interface.
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Affiliation(s)
- P K Fyfe
- Dept of Biochemistry, University of Bristol, BS8 1TD, Bristol, UK
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43
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Transfer of coenzyme Q0 from water to aqueous surfactant solutions: the case of Triton X-100. Colloids Surf B Biointerfaces 2001; 20:27-35. [PMID: 11084306 DOI: 10.1016/s0927-7765(00)00152-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The effect of UQ0 on the micellization equilibrium of Triton X-100 has been studied by the analysis of the UV absorption spectra of Triton X-100. In the range of the UQ0 concentration investigated, the critical micelle concentration (CMC) increases at increasing of the solute concentration. The dependence of the CMC on UQ0 concentration has been used to calculate the generalized Setchenov constant. Mixing and dilution enthalpies of aqueous solutions of UQ0 and Triton X-100 were measured and used to calculate the enthalpies of transfer of UQ0 from water to Triton X-100 aqueous solutions. From the dependence of the enthalpy of transfer on surfactant concentration, the distribution constant between aqueous and micellar phase and the standard enthalpy of transfer from water to Triton X-100 micelles were evaluated along with the standard transfer free energy and entropy. All measurements were carried out at 298 K.
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44
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Rosenbusch JP, Lustig A, Grabo M, Zulauf M, Regenass M. Approaches to determining membrane protein structures to high resolution: do selections of subpopulations occur? Micron 2001; 32:75-90. [PMID: 10900383 DOI: 10.1016/s0968-4328(00)00021-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Three different methods are currently used for the study of high-resolution structures of membrane proteins: X-ray crystallography, electron crystallography, and nuclear magnetic resonance (NMR) spectroscopy. Thus far, all methods combined have yielded a rather modest number of crystal structures that have been solved at the atomic level. It is hypothesized here that different methods may select different populations of proteins on the basis of various properties. Thus, protein stability may be a significant factor in the formation of three-dimensional (3D) crystals from detergent solutions, since exposure of hydrophobic protein zones to water may cause structural perturbation or denaturation in conformationally labile proteins. This is different in the formation of two-dimensional (2D) crystals where a protein remains protected in its native membrane environment. A biological selection mechanism may therefore be operative in that highly ordered lattices may form only if strong protein-protein interactions are relevant in vivo, thereby limiting the number of proteins that are amenable to electron crystallography. Keeping a protein in a bilayer environment throughout 3D crystallization maintains the lateral pressure existing in native membranes. This can be accomplished by using lipidic cubic phases. Alternatively, the hydrophobic interface of a membrane protein may be spared from contact with water by crystallization from organic solvents where the polar caps are protected in reverse micelles by using appropriate detergents. Some of the criteria that are useful in optimizing the various approaches are given. While the usefulness of complementary methods seems obvious, the results presented may be particularly critical in recognizing key problems in other structural approaches.
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Affiliation(s)
- J P Rosenbusch
- Biozentrum, University of Basel, Klingelbergstr. 70, CH-4056, Basel, Switzerland.
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45
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le Maire M, Champeil P, Moller JV. Interaction of membrane proteins and lipids with solubilizing detergents. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1508:86-111. [PMID: 11090820 DOI: 10.1016/s0304-4157(00)00010-1] [Citation(s) in RCA: 708] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Detergents are indispensable in the isolation of integral membrane proteins from biological membranes to study their intrinsic structural and functional properties. Solubilization involves a number of intermediary states that can be studied by a variety of physicochemical and kinetic methods; it usually starts by destabilization of the lipid component of the membranes, a process that is accompanied by a transition of detergent binding by the membrane from a noncooperative to a cooperative interaction already below the critical micellar concentration (CMC). This leads to the formation of membrane fragments of proteins and lipids with detergent-shielded edges. In the final stage of solubilization membrane proteins are present as protomers, with the membrane inserted sectors covered by detergent. We consider in detail the nature of this interaction and conclude that in general binding as a monolayer ring, rather than as a micelle, is the most probable mechanism. This mode of interaction is supported by neutron diffraction investigations on the disposition of detergent in 3-D crystals of membrane proteins. Finally, we briefly discuss the use of techniques such as analytical ultracentrifugation, size exclusion chromatography, and mass spectrometry relevant for the structural investigation of detergent solubilized membrane proteins.
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Affiliation(s)
- M le Maire
- Unite de recherche Associée 2096 (Centre National de la Recherche Scientifique et Commissariat a l'Energie Atomique), Cedex, France.
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46
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Fyfe PK, Jones MR. Re-emerging structures: continuing crystallography of the bacterial reaction centre. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1459:413-21. [PMID: 11004458 DOI: 10.1016/s0005-2728(00)00179-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction centre is nature's solar battery, and is found in a number of variations on a common theme in plants, algae and photosynthetic bacteria. During the last 20 years, a combination of X-ray crystallography, spectroscopy and mutagenesis has provided increasingly detailed insights into the mechanism of light energy transduction in the bacterial reaction centre. This mini-review looks at the application of X-ray crystallography to the bacterial reaction centre, focussing in particular on recent information on the structural consequences of site-directed mutagenesis, the roles played by water molecules in the reaction centre, the mechanism of ubiquinone reduction, and studies of the phospholipid environment of the protein.
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Affiliation(s)
- P K Fyfe
- Department of Biochemistry, School of Medical Sciences, University of Bristol, UK
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Hitscherich C, Kaplan J, Allaman M, Wiencek J, Loll PJ. Static light scattering studies of OmpF porin: implications for integral membrane protein crystallization. Protein Sci 2000; 9:1559-66. [PMID: 10975577 PMCID: PMC2144733 DOI: 10.1110/ps.9.8.1559] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Integral membrane proteins carry out some of the most important functions of living cells, yet relatively few details are known about their structures. This is due, in large part, to the difficulties associated with preparing membrane protein crystals suitable for X-ray diffraction analysis. Mechanistic studies of membrane protein crystallization may provide insights that will aid in determining future membrane protein structures. Accordingly, the solution behavior of the bacterial outer membrane protein OmpF porin was studied by static light scattering under conditions favorable for crystal growth. The second osmotic virial coefficient (B22) was found to be a predictor of the crystallization behavior of porin, as has previously been found for soluble proteins. Both tetragonal and trigonal porin crystals were found to form only within a narrow window of B22 values located at approximately -0.5 to -2 X 10(-4) mol mL g(-2), which is similar to the "crystallization slot" observed for soluble proteins. The B22 behavior of protein-free detergent micelles proved very similar to that of porin-detergent complexes, suggesting that the detergent's contribution dominates the behavior of protein-detergent complexes under crystallizing conditions. This observation implies that, for any given detergent, it may be possible to construct membrane protein crystallization screens of general utility by manipulating the solution properties so as to drive detergent B22 values into the crystallization slot. Such screens would limit the screening effort to the detergent systems most likely to yield crystals, thereby minimizing protein requirements and improving productivity.
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Affiliation(s)
- C Hitscherich
- Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City 52242, USA
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48
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de Foresta B, Gallay J, Sopkova J, Champeil P, Vincent M. Tryptophan octyl ester in detergent micelles of dodecylmaltoside: fluorescence properties and quenching by brominated detergent analogs. Biophys J 1999; 77:3071-84. [PMID: 10585929 PMCID: PMC1300578 DOI: 10.1016/s0006-3495(99)77138-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The fluorescence properties of tryptophan octyl ester (TOE), a hydrophobic model of Trp in proteins, were investigated in various mixed micelles of dodecylmaltoside (DM) and 7,8-dibromododecyl beta-maltoside (BrDM) or 10,11-dibromoundecanoyl beta-maltoside (BrUM). This study focuses on the mechanism via which these brominated detergents quench the fluorescence of TOE in a micellar system. The experiments were performed at a pH at which TOE is uncharged and almost completely bound to detergent micelles. TOE binding was monitored by its enhanced fluorescence in pure DM micelles or its quenched fluorescence in pure BrUM or BrDM micelles. In DM/BrUM and DM/BrDM mixed micelles, the fluorescence intensity of TOE decreased, as a nonlinear function of the molar fraction of brominated detergent, to almost zero in pure brominated detergent. The indole moiety of TOE is therefore highly accessible to the bromine atoms located on the detergent alkyl chain because quenching by bromines occurs by direct contact with the fluorophore. TOE is simultaneously poorly accessible to iodide (I(-)), a water-soluble collisional quencher. TOE time-resolved fluorescence intensity decay is heterogeneous in pure DM micelles, with four lifetimes (from 0.2 to 4.4 ns) at the maximum emission wavelength. Such heterogeneity may arise from dipolar relaxation processes in a motionally restricted medium, as suggested by the time-dependent (nanoseconds) red shift (11 nm) of the TOE emission spectrum, and from the existence of various TOE conformations. Time-resolved quenching experiments for TOE in mixed micelles showed that the excited-state lifetime values decreased only slightly with increases in the proportion of BrDM or BrUM. In contrast, the relative amplitude of the component with the longest lifetime decreased significantly relative to that of the short-lived species. This is consistent with a mainly static mechanism for the quenching of TOE by brominated detergents. Molecular modeling of TOE (in vacuum and in water) suggested that the indole ring was stabilized by folding back upon the octyl chain, forming a hairpin conformation. Within micelles, the presence of such folded conformations, making it possible for the entire molecule to be located in the hydrophobic part of the micelle, is consistent with the results of fluorescence quenching experiments. TOE rotational correlation time values, in the nanosecond range, were consistent with a hindered rotation of the indole moiety and a rotation of the complete TOE molecule in the pure DM or mixed detergent micelles. These results, obtained with a simple micellar model system, provide a basis for the interpretation of fluorescence quenching by brominated detergents in more complex systems such as protein- or peptide-detergent complexes.
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Affiliation(s)
- B de Foresta
- Section de Biophysique des Protéines et des Membranes, Département de Biologie Cellulaire et Moléculaire et URA 2096 (CNRS), CEA Saclay, 91191 Gif-sur-Yvette, France.
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50
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Arluison V, Batelier G, Riès-Kautt M, Grosjean H. RNA:pseudouridine synthetase Pus1 from Saccharomyces cerevisiae: oligomerization property and stoichiometry of the complex with yeast tRNA(Phe). Biochimie 1999; 81:751-6. [PMID: 10492022 DOI: 10.1016/s0300-9084(99)80133-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Yeast RNA:pseudouridine synthetase Pus1 catalyzes the formation of pseudouridines in tRNAs. We report here the quaternary structure of purified recombinant Pus1 in solution. At low concentration, in the absence of tRNA, Pus1 oligomerizes while at high concentration it precipitates. This oligomerization/aggregation can be prevented by addition of dodecyl-beta-D-maltoside or of yeast tRNA(Phe). The detergent does not significantly interfere with substrate binding or with activity of Pus1. The stoichiometry of the Pus1/tRNA(Phe) complex is 1/1. We conclude that the detergent covers an hydrophobic region of the RNA binding pocket responsible for Pus1 aggregation.
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Affiliation(s)
- V Arluison
- CNRS, Laboratoire d'Enzymologie et Biochimie Structurales, Gif-Sur-Yvette, France
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