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Covarrubias AA, Cuevas-Velazquez CL, Romero-Pérez PS, Rendón-Luna DF, Chater CCC. Structural disorder in plant proteins: where plasticity meets sessility. Cell Mol Life Sci 2017; 74:3119-3147. [PMID: 28643166 PMCID: PMC11107788 DOI: 10.1007/s00018-017-2557-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 06/01/2017] [Indexed: 01/08/2023]
Abstract
Plants are sessile organisms. This intriguing nature provokes the question of how they survive despite the continual perturbations caused by their constantly changing environment. The large amount of knowledge accumulated to date demonstrates the fascinating dynamic and plastic mechanisms, which underpin the diverse strategies selected in plants in response to the fluctuating environment. This phenotypic plasticity requires an efficient integration of external cues to their growth and developmental programs that can only be achieved through the dynamic and interactive coordination of various signaling networks. Given the versatility of intrinsic structural disorder within proteins, this feature appears as one of the leading characters of such complex functional circuits, critical for plant adaptation and survival in their wild habitats. In this review, we present information of those intrinsically disordered proteins (IDPs) from plants for which their high level of predicted structural disorder has been correlated with a particular function, or where there is experimental evidence linking this structural feature with its protein function. Using examples of plant IDPs involved in the control of cell cycle, metabolism, hormonal signaling and regulation of gene expression, development and responses to stress, we demonstrate the critical importance of IDPs throughout the life of the plant.
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Affiliation(s)
- Alejandra A Covarrubias
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62250, Cuernavaca, Mexico.
| | - Cesar L Cuevas-Velazquez
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62250, Cuernavaca, Mexico
| | - Paulette S Romero-Pérez
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62250, Cuernavaca, Mexico
| | - David F Rendón-Luna
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62250, Cuernavaca, Mexico
| | - Caspar C C Chater
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62250, Cuernavaca, Mexico
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2
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Króliczewski J, Piskozub M, Bartoszewski R, Króliczewska B. ALB3 Insertase Mediates Cytochrome b 6 Co-translational Import into the Thylakoid Membrane. Sci Rep 2016; 6:34557. [PMID: 27698412 PMCID: PMC5048292 DOI: 10.1038/srep34557] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 09/15/2016] [Indexed: 01/10/2023] Open
Abstract
The cytochrome b6 f complex occupies an electrochemically central position in the electron-transport chain bridging the photosynthetic reaction center of PS I and PS II. In plants, the subunits of these thylakoid membrane protein complexes are both chloroplast and nuclear encoded. How the chloroplast-encoded subunits of multi-spanning cytochrome b6 are targeted and inserted into the thylakoid membrane is not fully understood. Experimental approaches to evaluate the cytochrome b6 import mechanism in vivo have been limited to bacterial membranes and were not a part of the chloroplast environment. To evaluate the mechanism governing cytochrome b6 integration in vivo, we performed a comparative analysis of both native and synthetic cytochrome b6 insertion into purified thylakoids. Using biophysical and biochemical methods, we show that cytochrome b6 insertion into the thylakoid membrane is a non-spontaneous co-translational process that involves ALB3 insertase. Furthermore, we provided evidence that CSP41 (chloroplast stem-loop-binding protein of 41 kDa) interacts with RNC-cytochrome b6 complexes, and may be involved in cytochrome b6 (petB) transcript stabilization or processing.
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Affiliation(s)
- Jarosław Króliczewski
- Laboratory of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Wrocław Poland
| | - Małgorzata Piskozub
- Amplicon Sp. z o. o., Wrocław, Poland
- Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Rafał Bartoszewski
- Department of Biology and Pharmaceutical Botany, Medical University of Gdansk, Gdansk, Poland
| | - Bożena Króliczewska
- Department of Animal Physiology and Biostructure, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences, Wrocław, Poland
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3
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Bruno A, Scrima M, Novellino E, D'Errico G, D'Ursi AM, Limongelli V. The glycan role in the glycopeptide immunogenicity revealed by atomistic simulations and spectroscopic experiments on the multiple sclerosis biomarker CSF114(Glc). Sci Rep 2015; 5:9200. [PMID: 25776265 PMCID: PMC4361856 DOI: 10.1038/srep09200] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 02/24/2015] [Indexed: 12/22/2022] Open
Abstract
Glycoproteins are often recognized as not-self molecules by antibodies triggering the onset of severe autoimmune diseases such as Multiple Sclerosis (MS). Thus, the development of antigen-mimicking biomarkers represents an attractive strategy for an early diagnosis of the disease. An example is the synthetic glycopeptide CSF114(Glc), which was designed and tested as MS biomarker and whose clinical application was limited by its reduced ability to detect autoantibodies in MS patients. In the attempt to improve the efficacy of CSF114(Glc), we have characterized all the events leading to the final binding of the biomarker to the autoantibody using atomistic simulations, ESR and NMR experiments. The glycosydic moiety plays a primary role in the whole process. In particular, in an environment mimicking that used in the clinical tests the glycopeptide assumes a α-helix structure that is functional for the interaction with the antibody. In this conformation CSF114(Glc) binds the monoclonal antibody mAb8-18C5 similarly to the myelin oligodendrocyte glycoprotein MOG, which is a known MS auto-antigen, thus explaining its diagnostic activity. Our study offers new molecular bases to design more effective biomarkers and provides a most valid protocol to investigate other systems where the environment effect is determinant for the biological activity.
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Affiliation(s)
- Agostino Bruno
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, I-80131 Naples, Italy
| | - Mario Scrima
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano, Italy
| | - Ettore Novellino
- Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, I-80131 Naples, Italy
| | - Gerardino D'Errico
- Dipartimento di Scienze Chimiche, Università di Napoli "Federico II", Complesso di Monte Sant'Angelo, via Cinthia, 80126 Naples, Italy
| | - Anna Maria D'Ursi
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano, Italy
| | - Vittorio Limongelli
- 1] Department of Pharmacy, University of Naples "Federico II", via D. Montesano 49, I-80131 Naples, Italy [2] Università della Svizzera Italiana (USI), Faculty of Informatics, Institute of Computational Science, via G. Buffi 13, CH-6900 Lugano, Switzerland
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4
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Bychkova VE, Basova LV, Balobanov VA. How membrane surface affects protein structure. BIOCHEMISTRY (MOSCOW) 2015; 79:1483-514. [DOI: 10.1134/s0006297914130045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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5
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Membrane-induced changes in the holomyoglobin tertiary structure: interplay with function. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2014; 43:317-29. [DOI: 10.1007/s00249-014-0964-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 04/04/2014] [Accepted: 04/25/2014] [Indexed: 11/26/2022]
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6
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Kreutzberger AJ, Pokorny A. On the origin of multiphasic kinetics in peptide binding to phospholipid vesicles. J Phys Chem B 2012; 116:951-7. [PMID: 22242648 DOI: 10.1021/jp209080m] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We critically examined a series of exact kinetic models for their ability to describe binding of a typical α-helical amphipathic peptide to lipid bilayers. Binding of the model peptide lysette-26 was measured through fluorescence resonance energy transfer from a Trp residue on the peptide to a fluorescently labeled acceptor lipid included in vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. Experimental data was collected varying peptide and lipid concentrations over an order of magnitude. The kinetic models were fit to all the experimental data simultaneously. Of the four models examined, the simplest one that is sufficient to correctly describe the experimental data includes two coupled equilibria, one between peptide monomers in solution and bound to the lipid membrane, and a second one between lipid-bound peptides that oligomerize to form dimers. We found that individual kinetic binding curves are insufficient to distinguish among kinetic models of peptide binding to lipid bilayers but that a number of models can be excluded based on inspection of a simple set of experiments.
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Affiliation(s)
- Alex J Kreutzberger
- Department of Chemistry and Biochemistry, University of North Carolina Wilmington, Wilmington, North Carolina 28403, USA
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7
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Aoki S, Epand RM. Caveolin-1 hydrophobic segment peptides insertion into membrane mimetic systems: Role of Proline residue. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:12-8. [DOI: 10.1016/j.bbamem.2011.09.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 09/08/2011] [Accepted: 09/11/2011] [Indexed: 11/28/2022]
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Yamanaka M, Masanari M, Sambongi Y. Conferment of Folding Ability to a Naturally Unfolded Apocytochrome c through Introduction of Hydrophobic Amino Acid Residues. Biochemistry 2011; 50:2313-20. [DOI: 10.1021/bi101646m] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Masaru Yamanaka
- Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan
| | - Misa Masanari
- Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan
| | - Yoshihiro Sambongi
- Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan
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9
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Balobanov VA, Il’ina NB, Katina NS, Kashparov IA, Dolgikh DA, Bychkova VE. Kinetics of interactions between apomyoglobin and phospholipid membrane. Mol Biol 2010. [DOI: 10.1134/s0026893310040187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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Di Cianni A, Carotenuto A, Brancaccio D, Novellino E, Reubi JC, Beetschen K, Papini AM, Ginanneschi M. Novel Octreotide Dicarba-analogues with High Affinity and Different Selectivity for Somatostatin Receptors. J Med Chem 2010; 53:6188-97. [DOI: 10.1021/jm1005868] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Alessandra Di Cianni
- Laboratory of Peptides & Proteins, Chemistry & Biology, University of Firenze, Via della Lastruccia 13, I-50019 Sesto Fiorentino, Italy
- Department of Chemistry “Ugo Schiff”, University of Firenze, Via della Lastruccia 5-13, I-50019, Sesto Fiorentino, Italy
| | - Alfonso Carotenuto
- Department of Pharmaceutical Chemistry and Toxicology, University of Napoli, Via Domenico Montesano 49, I-80131 Napoli, Italy
| | - Diego Brancaccio
- Department of Pharmaceutical Chemistry and Toxicology, University of Napoli, Via Domenico Montesano 49, I-80131 Napoli, Italy
| | - Ettore Novellino
- Department of Pharmaceutical Chemistry and Toxicology, University of Napoli, Via Domenico Montesano 49, I-80131 Napoli, Italy
| | - Jean Claude Reubi
- Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Murtenstrasse 31, CH-3010 Berne, Switzerland
| | - Karin Beetschen
- Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Murtenstrasse 31, CH-3010 Berne, Switzerland
| | - Anna Maria Papini
- Laboratory of Peptides & Proteins, Chemistry & Biology, University of Firenze, Via della Lastruccia 13, I-50019 Sesto Fiorentino, Italy
- Department of Chemistry “Ugo Schiff”, University of Firenze, Via della Lastruccia 5-13, I-50019, Sesto Fiorentino, Italy
| | - Mauro Ginanneschi
- Laboratory of Peptides & Proteins, Chemistry & Biology, University of Firenze, Via della Lastruccia 13, I-50019 Sesto Fiorentino, Italy
- Department of Chemistry “Ugo Schiff”, University of Firenze, Via della Lastruccia 5-13, I-50019, Sesto Fiorentino, Italy
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11
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Abstract
To understand the mechanism of ionic detergent-induced protein denaturation, this study examines the action of sodium dodecyl sulfate on ferrocytochrome c conformation under neutral and strongly alkaline conditions. Equilibrium and stopped-flow kinetic results consistently suggest that tertiary structure unfolding in the submicellar and chain expansion in the micellar range of SDS concentrations are the two major and discrete events in the perturbation of protein structure. The nature of interaction between the detergent and the protein is predominantly hydrophobic in the submicellar and exclusively hydrophobic at micellar levels of SDS concentration. The observation that SDS also interacts with a highly denatured and negatively charged form of ferrocytochrome c suggests that the interaction is independent of structure, conformation, and ionization state of the protein. The expansion of the protein chain at micellar concentration of SDS is driven by coulombic repulsion between the protein-bound micelles, and the micelles and anionic amino acid side chains.
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Affiliation(s)
- Abani K Bhuyan
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India.
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12
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Interaction of a potyviral VPg with anionic phospholipid vesicles. Virology 2009; 395:114-20. [DOI: 10.1016/j.virol.2009.09.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 07/31/2009] [Accepted: 09/07/2009] [Indexed: 11/19/2022]
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13
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Yamamoto T, Nair P, Jacobsen NE, Davis P, Ma SW, Navratilova E, Moye S, Lai J, Yamamura HI, Vanderah TW, Porreca F, Hruby VJ. The importance of micelle-bound states for the bioactivities of bifunctional peptide derivatives for delta/mu opioid receptor agonists and neurokinin 1 receptor antagonists. J Med Chem 2008; 51:6334-47. [PMID: 18821747 DOI: 10.1021/jm800389v] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To provide new insight into the determining factors of membrane-bound peptide conformation that might play an important role in peptide-receptor docking and further biological behaviors, the dodecylphosphocholine (DPC) micelle-bound conformations of bifunctional peptide derivatives of delta-preferring opioid agonists and NK1 antagonists (1: Tyr-D-Ala-Gly-Phe-Met-Pro-Leu-Trp-O-3,5-Bzl(CF 3) 2; 2: Tyr-D-Ala-Gly-Phe-Met-Pro-Leu-Trp-NH-3,5-Bzl(CF 3) 2; 3: Tyr-D-Ala-Gly-Phe-Met-Pro-Leu-Trp-NH-Bzl) were determined based on 2D NMR studies. Although the differences in the primary sequence were limited to the C-terminus, the obtained NMR conformations were unexpectedly different for each compound. Moreover, their biological activities showed different trends in direct relation to the compound-specific conformations in DPC micelles. The important result is that not only were the NK1 antagonist activities different (the pharmacophore located at the C-terminus)but the opioid agonist activities (this pharmacophore was at the structurally preserved N-terminus) also were shifted, suggesting that a general conformational change in the bioactive state was induced due to relatively small and limited structural modifications.
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Affiliation(s)
- Takashi Yamamoto
- Department of Chemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, USA
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14
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Sedlák E. Characterization of the polyanion-induced molten globule-like state of cytochromec. Biopolymers 2007; 86:119-26. [PMID: 17330862 DOI: 10.1002/bip.20710] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cytochrome c (cyt c) undergoes a poly(vinylsulphate) (PVS)-induced transition at slightly acidic pH into a molten globule-like state that resembles the effect that negatively charged membrane surfaces have on this protein. In this work, the thermodynamic properties of the molten globule-like state of cyt c in complex with PVS are studied using differential scanning calorimetry, circular dichroism, fluorescence, and absorbance spectroscopy. The temperature-induced transition of the molten globule-like state of cyt c in the complex with PVS is characterized by a significantly lower calorimetric enthalpy than in the "typical" molten globule state of cyt c, i.e. free protein at pH 2.0 in high ionic strength. Moreover, the thermally-denatured state of cyt c in the complex at pH < 6 contains nearly 50% of the native secondary structure. The dependence of the transition temperature on the pH indicates a role for histidine residues in the destabilization of the cyt c structure in the PVS complex and in stabilization of the denatured state with the residual secondary structure. A comparison of the effects of small anions and polyanions demonstrates the importance of cooperativity among the anions in the destabilization of cyt c. Predictably, other hydrophilic flexible polyanions such as heparin, polyglutamate, and polyadenylate also have a destabilizing effect on the structure of cyt c. However, a correlation between the properties of the polyanions and their effect on the protein stability is still unclear.
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Affiliation(s)
- Erik Sedlák
- Department of Biochemistry, Faculty of Science UPJS, Moyzesova 11, 040 01 Kosice, Slovakia.
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15
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Peric M, Alves M, Bales BL. Combining precision spin-probe partitioning with time-resolved fluorescence quenching to study micelles. Chem Phys Lipids 2006; 142:1-13. [PMID: 16569402 DOI: 10.1016/j.chemphyslip.2006.02.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2005] [Revised: 02/16/2006] [Accepted: 02/17/2006] [Indexed: 10/25/2022]
Abstract
Micelles of lysomyristoylphosphatidylcholine (LMPC) and mixed micelles of LMPC with anionic detergent sodium dodecyl sulfate (SDS) have been characterized by spin-probe-partitioning electron paramagnetic resonance (SPPEPR) and time-resolved fluorescence quenching (TRFQ) experiments. SPPEPR is a novel new method to study structure and dynamics in lipid assemblies successfully applied here for the first time to micelles. Several improvements to the computer program used to analyze SPPEPR spectra have been incorporated that increase the precision in the extracted parameters considerably from which micelle properties such as effective water concentration and microviscosity may be estimated. In addition, with this increased precision, it is shown that it is feasible to study the rate of transfer of a small spin probe between micelles and the surrounding aqueous phase by SPPEPR. The rate of transfer of the spin probe di-tert-butyl nitroxide (DTBN) and the activation energy of the transfer process in LMPC and LMPC-SDS micelles have been determined with high precision. The rate of transfer increases with temperature and SDS molar fraction in mixed micelles, while it remains constant with LMPC concentration in pure LMPC micelles. The activation energy of DTBN transfer in pure lysophospholipid micelles does not change with LMPC concentration while it decreases with the increasing molar fraction of SDS in mixed LMPC-SDS micelles. Both this decrease in activation energy and the increase in the rate of transfer are rationalized in terms of an increasing micelle surface area per molecule (decreasing compactness) as SDS molecules are added. This decreasing compactness as a function of SDS content is confirmed by TRFQ measurements showing an aggregation number that decreases from 122 molecules for pure LMPC micelles to 80 molecules for pure SDS micelles. The same increase in surface area per molecule is predicted to increase the effective water concentration in the polar shell of the micelles. This increase in hydration with SDS molar fraction is confirmed by measuring the effective water concentration in the polar shell of the micelles from the hyperfine spacing of DTBN. This work demonstrates the potential to design mixed lysophospholipid surfactant micelles with variable physicochemical properties. Well-defined micellar substrates, in terms of their physicochemical properties, may improve the studies of protein structure and enzyme kinetics.
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Affiliation(s)
- Miroslav Peric
- Department of Physics and Astronomy and The Center for Supramolecular Studies, California State University at Northridge, Northridge, CA 91330-8268, United States.
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16
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Abstract
The kinetics of peptide-membrane association have been studied previously using stopped-flow tryptophan fluorescence; however, such experiments do not directly report the coil-to-helix transition process, which is a hallmark of peptide-membrane interaction. Herein, we report a new method for directly assessing the kinetics of the helix formation accompanied by the peptide-membrane association. This method is based on the technique of fluorescence resonance energy transfer (FRET) and an amino acid FRET pair, p-cyano-L-phenylalanine and tryptophan. To demonstrate the utility of this method, we have studied the membrane-mediated helix folding dynamics of a mutant of magainin 2, an antibiotic peptide found in the skin of the African clawed frog, Xenopus laevis. Our results indicate that the coil-to-helix transition occurs during the binding of the peptide to the lipid vesicle (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)], 3:1, wt/wt) but prior to the full insertion of the peptide into the hydrophobic region of the lipid bilayers.
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Affiliation(s)
- Matthew J Tucker
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
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17
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Liang L, Yao P, Jiang M, Zhang G, Yan Y. Interactions of apo cytochrome C with alternating copolymers of maleic acid and alkene. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:10662-70. [PMID: 16262334 DOI: 10.1021/la050973i] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Apo cytochrome c (apo cyt c) tends to aggregate at alkali pH. Poly(isobutylene-alt-maleic acid) (PIMA) is soluble molecularly, whereas poly(1-tetradecene-alt-maleic acid) (PTMA) forms particles that tend to dissociate by increasing pH and decreasing concentration. Dynamic light scattering and surface plasmon resonance are used to investigate the interactions of PIMA and PTMA with apo cyt c at different pH values to understand the mechanism of the interactions. When the positive or negative charges are in excess, the copolymer-protein complex particles can be stabilized by the charges on the surface. When the ratio of the positive to negative charges is close to the stoichiometric value, precipitation occurs. At pH 11.8, both PTMA and apo cyt c carry negative charges, but the hydrophobic interaction makes them form complexes. A competition exists between the interaction of the copolymer with apo cyt c and the self-aggregation of PTMA or apo cyt c alone. The interaction of PIMA or PTMA with apo cyt c at neutral and alkali pH destroys the aggregation of PTMA or apo cyt c and forms new complex particles.
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Affiliation(s)
- Li Liang
- Department of Macromolecular Science, Fudan University, Shanghai, China
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18
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Jiang X, Shang L, Wang Y, Dong S. Cytochrome c Superstructure Biocomposite Nucleated by Gold Nanoparticle: Thermal Stability and Voltammetric Behavior. Biomacromolecules 2005; 6:3030-6. [PMID: 16283723 DOI: 10.1021/bm050345f] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The thermal stability of cytochrome c (cyt c) after Au-nanoparticle-directed association has been studied by various spectroscopic (electronic absorption, resonance Raman, and circular dichroism) and electrochemical methods. The results show that the thermal stability of the Au-cyt c superstructure biocomposite formed by the electrostatic and hydrophobic interactions among the associated proteins increases significantly. It is mainly caused by strong hydrophobicity of the associated cyt c in Au-cyt c superstructure at high temperature, which results from the compact secondary structure and the packing of hydrophobic side chains around the Trp 59 and heme. In addition, the formation of bis-His configuration of heme is facilitated by the tightly self-associated state of cyt c in the Au-cyt c superstructure. The electrostatic coupling of the opposite charges among shells of the adsorbed proteins due to the formation of the superstructure biocomposite can reduce repulsions among the same charges in protein. These factors are also important for enhancing the stability of the associated cyt c. Furthermore, the voltammetric behavior of Au-cyt c at DNA modified glassy carbon electrode has been investigated for extending the application of Au-cyt c.
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Affiliation(s)
- Xiue Jiang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, ChineseAcademy of Sciences, Graduate School of the Chinese Academy of Sciences, Changchun, Jilin, 130022, China
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19
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Jiang X, Zhang L, Jiang J, Qu X, Wang E, Dong S. A Colloidal Au Monolayer Modulates the Conformation and Orientation of a Protein at the Electrode/Solution Interface. Chemphyschem 2005; 6:1613-21. [PMID: 16082663 DOI: 10.1002/cphc.200400652] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The orientation and conformation of adsorbed cytochrome c (cyt c) at the interface between an electrode modified with colloidal Au and a solution were studied by electrochemical, spectroscopic, and spectroelectrochemical techniques. The results indicate that the colloidal Au monolayer formed via preformation of an organic self-assembled monolayer (SAM) can increase the electronic coupling between the SAM and cyt c in the same manner as bifunctional molecular bridges, one functional group of which is bound to the electrode surface while the other interacts with the protein surface. The approach of cyt c to the modified electrode/solution interface can be assisted by strong interactions of the intrinsic charge of colloidal particles with cyt c, while the heme pocket remains almost unchanged due to the screening effect of the negatively charged field created by the intrinsic charge. The conformational changes of cyt c induced by its adsorption at a bare glassy carbon electrode/solution interface and the effect of the electric field on the ligation state of the heme can be avoided at the colloidal-Au-modified electrode/solution interface. Finally, a possible model for the adsorption orientation of cyt c at the colloidal-Au-modified electrode/solution interface is proposed.
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Affiliation(s)
- Xiue Jiang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Changchun, Jilin, 130022, China
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20
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Liang L, Yao P, Jiang M. Structural Transformation of Apocytochrome c Induced by Alternating Copolymers of Maleic Acid and Alkene. Biomacromolecules 2005; 6:2748-55. [PMID: 16153115 DOI: 10.1021/bm050250d] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Apocytochrome c interacts with two copolymers: poly(isobutylene-alt-maleic acid) (PIMA) and poly(1-tetradecene-alt-maleic acid) (PTMA). The interaction leads to apocytochrome c, a conformational change from random coil to alpha-helical structure. The alpha-helix content is influenced by the copolymer concentration, the length of alkyl chain of the copolymers, and pH of the medium. The electrostatic attraction between the copolymer and protein is an indispensable factor for the folding of the protein at acid pH. The hydrophobic interaction is an important factor over the entire pH range, especially when both the copolymer and protein carry negative charges at alkaline pH. The electrostatic and hydrophobic attractions between the copolymer and protein exclude water molecules, promoting the formation of hydrogen bonds within the helical structure. On the other hand, the hydrogen bonds formed between the ionized carboxyl of the copolymer and the amide of the protein partly restrain the formation of hydrogen bonds within the helical structure when the copolymer concentration is higher at pH 6.5 and 10.5.
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Affiliation(s)
- Li Liang
- Department of Macromolecular Science and Key Laboratory of Molecular Engineering of Polymer, Fudan University, Shanghai 200433, China
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21
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Model phospholipid membranes affect the tertiary structure of holomyoglobin: Conformational changes at pH 6.2. Mol Biol 2005. [DOI: 10.1007/s11008-005-0015-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Jiang X, Jiang J, Jin Y, Wang E, Dong S. Effect of Colloidal Gold Size on the Conformational Changes of Adsorbed Cytochrome c: Probing by Circular Dichroism, UV−Visible, and Infrared Spectroscopy. Biomacromolecules 2004; 6:46-53. [PMID: 15638503 DOI: 10.1021/bm049744l] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The conformational changes of bovine heart cytochrome c (cyt c) induced by the adsorption on gold nanoparticles with different sizes have been investigated by electronic absorption, circular dichroism (CD), and Fourier transform infrared spectra. The combination of these techniques can give complementary information about adsorption-induced conformational changes. The results show that there are different conformational changes for cyt c adsorbed on gold nanoparticles with different sizes due to the different interaction forces between cyt c and gold nanoparticles. The colloidal gold concentration-dependent conformation distribution curves of cyt c obtained by analysis of CD spectra using the singular value decomposition least-squares method show that the coverage of cyt c on the gold nanoparticles surface also affects the conformational changes of the adsorbed cyt c.
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Affiliation(s)
- Xiue Jiang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022 China
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23
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Chatterjee C, Majumder B, Mukhopadhyay C. Pulsed-Field Gradient and Saturation Transfer Difference NMR Study of Enkephalins in the Ganglioside GM1 Micelle. J Phys Chem B 2004. [DOI: 10.1021/jp037553r] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chiradip Chatterjee
- Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700 009, India, and NMR Facility, Department of Biophysics, Bose Institute, P1/12, CIT Scheme 7M, Kolkata 700 054, India
| | - Barun Majumder
- Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700 009, India, and NMR Facility, Department of Biophysics, Bose Institute, P1/12, CIT Scheme 7M, Kolkata 700 054, India
| | - Chaitali Mukhopadhyay
- Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700 009, India, and NMR Facility, Department of Biophysics, Bose Institute, P1/12, CIT Scheme 7M, Kolkata 700 054, India
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24
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Gong J, Yao P, Duan H, Jiang M, Gu S, Chunyu L. Structural transformation of cytochrome c and apo cytochrome c induced by sulfonated polystyrene. Biomacromolecules 2003; 4:1293-300. [PMID: 12959597 DOI: 10.1021/bm034090m] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The structural transformation of cytochrome c (cyt c) and its heme-free precursor, apo cyt c, induced by negatively charged sulfonated polystyrene (SPS) with different charge density (degree of sulfonation) and chain length was studied to understand the factors that influence the folding and unfolding of the protein. SPS forms stable transparent nanoparticles in aqueous solution. The hydrophobic association of the backbone chain and phenyl groups is balanced by the electrostatic repulsion of the sulfonate groups on the particle surface. The binding of cyt c to negatively charged SPS particles causes an extensive disruption of the native compact structure of cyt c: the cleavage of Fe-Met80 ligand, about 40% loss of the helical structure, and the disruption of the asymmetry environment of Trp59. On the other hand, SPS particle-bound apo cyt c undergoes a conformational change from the random coil to alpha-helical structure. The folding of apo cyt c in SPS particles was influenced by pH and ionic strength of the solution, SPS concentration, and the degree of sulfonation and chain length of SPS. The folding can reach more than 90% of the alpha-helix content of native cyt c in solution. Poly(sodium 4-styrenesulfonate) (PSS), which is 100% sulfonated polystyrene and cannot form hydrophobic cores in the solution, induces only two-thirds of the alpha-helix content compared with SPS. It appears that the electrostatic interaction between PSS/SPS and apo cyt c induces an early partially folded state of apo cyt c. The hydrophobic interaction between nonpolar residues in apo cyt c and the hydrophobic cores in SPS particles extends the alpha-helical structure of apo cyt c.
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Affiliation(s)
- Jie Gong
- Department of Macromolecular Science and the Key Laboratory of Molecular Engineering of Polymer, Fudan University, Shanghai 200433, China
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25
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Palian MM, Boguslavsky VI, O'Brien DF, Polt R. Glycopeptide-membrane interactions: glycosyl enkephalin analogues adopt turn conformations by NMR and CD in amphipathic media. J Am Chem Soc 2003; 125:5823-31. [PMID: 12733923 DOI: 10.1021/ja0268635] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Four enkephalin analogues (Tyr-D-Thr-Gly-Phe-Leu-Ser-CONH(2), 1, and the related O-linked glycopeptides bearing the monosaccharide beta-glucose, 2, the disaccharide beta-maltose, 3, and the trisaccharide beta-maltotriose, 4) were synthesized, purified by HPLC, and biophysical studies were conducted to examine their interactions with membrane model systems. Glycopeptide 2 has been previously reported to penetrate the blood-brain barrier (BBB), and produce potent analgesia superior to morphine in mice (J. Med. Chem.2000, 43, 2586-90 and J. Pharm. Exp. Ther. 2001, 299, 967-972). The parent peptide and its three glycopeptide derivatives were studied in aqueous solution and in the presence of micelles using 2-D NMR, CD, and molecular mechanics (Monte Carlo studies). Consistent with previous conformational studies on cyclic opioid agonist glycopeptides, it was seen that glycosylation did not significantly perturb the peptide backbone in aqueous solution, but all four compounds strongly associated with 5-30 mM SDS or DPC micelles, and underwent profound membrane-induced conformational changes. Interaction was also observed with POPC:POPE:cholesterol lipid vesicles (LUV) in equilibrium dialysis experiments. Although the peptide backbones of 1-4 possessed random coil structures in water, in the presence of the lipid phase they each formed a nearly identical pair of structures, all with a stable beta-turn motif at the C-terminus. Use of spin labels (Mn(2+) and 5-DOXYL-stearic acid) allowed for the determination of the position and orientation of the compounds relative to the surface of the micelle.
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Affiliation(s)
- Michael M Palian
- Carl S. Marvel Laboratories, Department of Chemistry, The University of Arizona, Tucson, Arizona 85721, USA
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26
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Sasahara K, McPhie P, Minton AP. Effect of dextran on protein stability and conformation attributed to macromolecular crowding. J Mol Biol 2003; 326:1227-37. [PMID: 12589765 DOI: 10.1016/s0022-2836(02)01443-2] [Citation(s) in RCA: 261] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thermally induced transition curves of hen egg-white lysozyme were measured in the presence of several concentrations of dextran at pH 2.0 by near-UV and far-UV CD. The transition curves were fitted to a two-state model by a non-linear, least-squares method to obtain the transition temperature (T(m)), enthalpy change (deltaH(u)(T(m))), and free energy change (deltaG(u)(T)) of the unfolding transition. An increase in T(m) and almost constant deltaH(u)(T(m)) values were observed in the presence of added dextran at concentrations exceeding ca 100 g l(-1). In addition, dextran-induced conformational changes of fully unfolded protein were investigated by CD spectroscopy. Addition of high concentrations of dextran to solutions of acid-unfolded cytochrome c at pH 2.0 results in a shift of the CD spectrum from that characteristic of the fully unfolded polypeptide to that characteristic of the more compact, salt-induced molten globule state, a result suggesting that the molten globule-like state is stabilized relative to the fully unfolded form in crowded environments. Both observations are in qualitative accord with predictions of a previously proposed model for the effect of intermolecular excluded volume (macromolecular crowding) on protein stability and conformation.
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Affiliation(s)
- Kenji Sasahara
- Section on Physical Biochemistry, Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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27
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Sim B, Cladera J, O'Shea P. Fibronectin interactions with osteoblasts: Identification of a non-integrin-mediated binding mechanism using a real-time fluorescence binding assay. ACTA ACUST UNITED AC 2003; 68:352-9. [PMID: 14704977 DOI: 10.1002/jbm.a.20022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Fibronectin (Fn) is an extracellular matrix protein that interacts with specific integrins on the cell surface, initiating signal transduction processes that lead to a reorganization of the cytoskeleton and the assembly of focal adhesions. Cell surface proteoglycans or glycosaminoglycans (GAGs) such as heparan sulfate are also known to participate in the interaction of Fn with the cell surface by binding to two different heparin-binding domains. The influence of Fn and GAGs on the spreading and differentiation of human osteoblasts was also previously described. In the current work, a method developed in our laboratory is established to evaluate the interaction between Fn and human osteoblasts and the influence of GAGs on such interactions. This technique makes use of fluoresceinphosphatidylethanolamine (FPE) such that when inserted into the lipidic bilayer, it acts as a fluorescent indicator of membrane interactions. The results indicate that the binding profile of Fn with the osteoblast cell surface is best represented by a hyperbolic single binding site model with a membrane affinity of 120 nM. Removal of cell surface heparan sulfate by treatment with heparitinase indicates that the cell surface moiety is directly involved in the binding process. Studies directed to assess the influence of heparin on the interaction of Fn with osteoblasts reveal that although it does not hamper Fn binding to the cell surface, it blocks the initial attachment to Fn-coated surfaces, indicating that binding to the integrin receptor alone is not enough to promote cell attachment but that the participation of the cell-surface GAGs is also a necessary condition.
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Affiliation(s)
- Bushra Sim
- School of Biomedical Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
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Sanghera N, Pinheiro TJT. Binding of prion protein to lipid membranes and implications for prion conversion. J Mol Biol 2002; 315:1241-56. [PMID: 11827491 DOI: 10.1006/jmbi.2001.5322] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The binding of the Syrian hamster prion protein, SHaPrP(90-231), to model lipid membranes was investigated by tryptophan fluorescence. Membranes composed of negatively charged or zwitterionic lipids, and raft-like membranes containing dipalmitoylphosphatidylcholine(1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), cholesterol and sphingomyelin, were investigated. It was found that SHaPrP(90-231) binds to negatively charged lipid membranes and raft-like membranes. Binding of PrP to negatively charged lipid membranes involves both electrostatic and hydrophobic lipid-protein interactions and results in partial insertion of PrP into the lipid bilayer. This membrane-inserted conformation of PrP is richer in beta-sheet structure and has a disruptive effect on the integrity of the lipid bilayer, leading to total release of vesicle contents. In contrast, the binding of PrP to raft-like membranes is driven by hydrophobic lipid-protein interactions and induces the formation of alpha-helical structure. This conformation of PrP with a high content of alpha-helix is formed only at pH 7 and does not destabilize the lipid bilayer. Our findings support the view that an interaction of PrP with lipid membranes could play a role in PrP conversion.
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Affiliation(s)
- Narinder Sanghera
- Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
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Asawakarn T, Cladera J, O'Shea P. Effects of the membrane dipole potential on the interaction of saquinavir with phospholipid membranes and plasma membrane receptors of Caco-2 cells. J Biol Chem 2001; 276:38457-63. [PMID: 11500495 DOI: 10.1074/jbc.m103269200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The combined use of the membrane surface potential fluorescent sensor fluorescein phosphatidylethanolamine (FPE) and the membrane dipole potential fluorescent sensor di-8-ANEPPS to characterize the interaction of molecules with model and cellular membranes and to asses the influence of the dipole potential on the interaction is reported. The study of the human immunodeficiency virus protease inhibitor saquinavir with Caco-2 cells and phospholipid membranes reveals that the compound interacts with the lipidic bilayer of model membranes with a simple hyperbolic binding profile but with Caco-2 cells in a cooperative way involving membrane receptors. Additional studies indicated that colchicine acts as a competitor ligand to saquinavir and suggests, in agreement with other reports, that the identity of the saquinavir "receptor" could be P-glycoprotein or the multiple drug resistance-associated protein. The modification of the magnitude of the membrane dipole potential using compounds such as cholesterol, phloretin, and 6-ketocholestanol influences the binding capacity of saquinavir. Furthermore, removal of cholesterol from the cell membrane using methyl-beta-cyclodextrin significantly decreases the binding capacity of saquinavir. Because removal of cholesterol from the cell membrane has been reported to disrupt membrane domains known as "rafts," our observations imply that the membrane dipole potential plays an important role as a modulator of molecule-membrane interactions in these membrane structures. Such a role is suggested to contribute to the altered behavior of receptor-mediated signaling systems in membrane rafts.
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Affiliation(s)
- T Asawakarn
- School of Biomedical Sciences, University of Nottingham, Nottingham NG 7 2UH, United Kingdom
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Woolhead CA, Mant A, Kim SJ, Robinson C, Rodger A. Conformation of a purified "spontaneously" inserting thylakoid membrane protein precursor in aqueous solvent and detergent micelles. J Biol Chem 2001; 276:14607-13. [PMID: 11278526 DOI: 10.1074/jbc.m009600200] [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: 11/06/2022] Open
Abstract
Subunit W of photosystem II (PsbW) is a single-span thylakoid membrane protein that is synthesized with a cleavable hydrophobic signal peptide and integrated into the thylakoid membrane by an apparently spontaneous mechanism. In this study, we have analyzed the secondary structure of the pre-protein at early stages of the insertion pathway, using purified recombinant pre-PsbW. We show that the protein remains soluble in Tris buffer after removal of detergent. Under these conditions pre-PsbW contains no detectable alpha-helix, whereas substantial alpha-helical structure is present in SDS micelles. In aqueous buffer, the tryptophan fluorescence emission characteristics are intermediate between those of solvent-exposed and hydrophobic environments, suggesting the formation of a partially folded structure. If denaturants are excluded from the purification protocol, pre-PsbW purifies instead as a 180-kDa oligomer with substantial alpha-helical structure. Mature-size PsbW was prepared by removal of the presequence, and we show that this protein also contains alpha-helix in detergent but in lower quantities than the pre-protein. We therefore propose that pre-PsbW contains alpha-helical structure in both the mature protein and the signal peptide in nonpolar environments. We propose that pre-PsbW acquires its alpha-helical structure only during the later, membrane-bound stages of the insertion pathway, after which it forms a "helical hairpin"-type loop intermediate in the thylakoid membrane.
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Affiliation(s)
- C A Woolhead
- Department of Chemistry and Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
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Orlandini E, Seno F, Banavar JR, Laio A, Maritan A. Deciphering the folding kinetics of transmembrane helical proteins. Proc Natl Acad Sci U S A 2000; 97:14229-34. [PMID: 11121029 PMCID: PMC18900 DOI: 10.1073/pnas.97.26.14229] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nearly a quarter of genomic sequences and almost half of all receptors that are likely to be targets for drug design are integral membrane proteins. Understanding the detailed mechanisms of the folding of membrane proteins is a largely unsolved, key problem in structural biology. Here, we introduce a general model and use computer simulations to study the equilibrium properties and the folding kinetics of a C(alpha)-based two-helix bundle fragment (comprised of 66 aa) of bacteriorhodopsin. Various intermediates are identified and their free energy are calculated together with the free energy barrier between them. In 40% of folding trajectories, the folding rate is considerably increased by the presence of nonobligatory intermediates acting as traps. In all cases, a substantial portion of the helices is rapidly formed. This initial stage is followed by a long period of consolidation of the helices accompanied by their correct packing within the membrane. Our results provide the framework for understanding the variety of folding pathways of helical transmembrane proteins.
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Affiliation(s)
- E Orlandini
- Istituto Nazionale Fisica della Materia (INFM), Dipartimento di Fisica, Università di Padova, Via Marzolo 8, 35131 Padova, Italy
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Sanghera N, Pinheiro TJ. Unfolding and refolding of cytochrome c driven by the interaction with lipid micelles. Protein Sci 2000; 9:1194-202. [PMID: 10892811 PMCID: PMC2144667 DOI: 10.1110/ps.9.6.1194] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Binding of native cyt c to L-PG micelles leads to a partially unfolded conformation of cyt c. This micelle-bound state has no stable tertiary structure, but remains as alpha-helical as native cyt c in solution. In contrast, binding of the acid-unfolded cyt c to L-PG micelles induces folding of the polypeptide, resulting in a similar helical state to that originated from the binding of native cyt c to L-PG micelles. Far-ultraviolet (UV) circular dichroism (CD) spectra showed that this common micelle-associated helical state (HL) has a native-like alpha-helix content, but is highly expanded without a tightly packed hydrophobic core, as revealed by tryptophan fluorescence, near-UV, and Soret CD spectroscopy. The kinetics of the interaction of native and acid-unfolded cyt c was investigated by stopped-flow tryptophan fluorescence. Formation of H(L) from the native state requires the disruption of the tightly packed hydrophobic core in the native protein. This micelle-induced unfolding of cyt c occurs at a rate approximately 0.1 s(-1), which is remarkably faster in the lipid environment compared with the expected rate of unfolding in solution. Refolding of acid-unfolded cyt c with L-PG micelles involves an early highly helical collapsed state formed during the burst phase (<3 ms), and the observed main kinetic event reports on the opening of this early compact intermediate prior to insertion into the lipid micelle.
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Affiliation(s)
- N Sanghera
- Department of Biological Sciences, University of Warwick, Coventry, United Kingdom
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Raza AS, Dharmasiri K, Smith DL. Identification of non-covalent structure in apocytochrome c by hydrogen exchange and mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2000; 35:612-617. [PMID: 10800050 DOI: 10.1002/(sici)1096-9888(200005)35:5<612::aid-jms972>3.0.co;2-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Apocytochrome c, the in vivo precursor to active cytochrome c, was analyzed by amide hydrogen exchange and mass spectrometry to search for fixed, non-covalent structure. The protein was incubated in H(2)O at pH 3.3 or 6.7 for various times, then exposed to D(2)O to initiate isotope labeling of unfolded regions. Following acid quenching of hydrogen exchange, the labeled apocytochrome c was digested with pepsin into fragments that were analyzed by directly coupled high-performance liquid chromatography/electrospray ionization mass spectrometry. The intermolecular distribution of deuterium and the deuterium levels in structurally distinctive populations were determined from the mass spectra of the peptic fragments. Spectra of peptic fragments derived from apocytochrome c incubated at pH 3.3 had single envelopes of isotope peaks with masses indicating that all of the amide hydrogens had been replaced with deuterium. These results showed that apocytochrome c at pH 3.3 offered little resistance to hydrogen exchange, indicating that it was unfolded with little fixed structure. However, mass spectra of peptic fragments including residues 81-94 of apocytochrome c incubated at pH 6.7 had two envelopes of isotope peaks, indicating that one population was unfolded and the other population was highly structured in this region. Mass spectra of peptic fragments including residues N-terminal to residue 81 indicated that this region of the protein remained unfolded with little fixed structure at pH 6.7.
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Affiliation(s)
- A S Raza
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0304, USA
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Bryson EA, Rankin SE, Goormaghtigh E, Ruysschaert JM, Watts A, Pinheiro TJ. Structure and dynamics of lipid-associated states of apocytochrome c. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:1390-6. [PMID: 10691976 DOI: 10.1046/j.1432-1327.2000.01138.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Apocytochrome c (apocyt c), which in aqueous solution is largely unstructured, acquires an alpha-helical conformation upon association with lipid membranes. The extent of alpha-helix induced in apocyt c is lipid-dependent and this folding process is driven by both electrostatic and hydrophobic lipid-protein interactions. The structural and dynamic properties of apocyt c in lipid membranes were investigated by attenuated total reflection Fourier transform infrared spectroscopy combined with amide H-D exchange kinetics. Apocyt c acquires a higher content of alpha-helical structure with negatively charged membranes than with zwitterionic ones. For all membranes studied here, the helices of these partially folded states of apocyt c have a preferential orientation perpendicular to the plane of the lipid membrane. The H-D exchange revealed that a small fraction of amide protons of apocyt c, possibly associated with a stable folded domain protected by the lipid, remained protected from exchange over 20 min. However, a large fraction of amide protons exchanged in less than 20 min, indicating that the helical states of apocyt c in lipid membranes are very dynamic.
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Affiliation(s)
- E A Bryson
- Department of Biological Sciences, University of Warwick, Coventry, UK
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