101
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The mechanism of collapse of heterogeneous lipid monolayers. Biophys J 2015; 107:1136-1145. [PMID: 25185549 DOI: 10.1016/j.bpj.2014.05.053] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 04/27/2014] [Accepted: 05/23/2014] [Indexed: 11/24/2022] Open
Abstract
Collapse of homogeneous lipid monolayers is known to proceed via wrinkling/buckling, followed by folding into bilayers in water. For heterogeneous monolayers with phase coexistence, the mechanism of collapse remains unclear. Here, we investigated collapse of lipid monolayers with coexisting liquid-liquid and liquid-solid domains using molecular dynamics simulations. The MARTINI coarse-grained model was employed to simulate monolayers of ∼80 nm in lateral dimension for 10-25 μs. The monolayer minimum surface tension decreased in the presence of solid domains, especially if they percolated. Liquid-ordered domains facilitated monolayer collapse due to the spontaneous curvature induced at a high cholesterol concentration. Upon collapse, bilayer folds formed in the liquid (disordered) phase; curved domains shifted the nucleation sites toward the phase boundary. The liquid (disordered) phase was preferentially transferred into bilayers, in agreement with the squeeze-out hypothesis. As a result, the composition and phase distribution were altered in the monolayer in equilibrium with bilayers compared to a flat monolayer at the same surface tension. The composition and phase behavior of the bilayers depended on the degree of monolayer compression. The monolayer-bilayer connection region was enriched in unsaturated lipids. Percolation of solid domains slowed down monolayer collapse by several orders of magnitude. These results are important for understanding the mechanism of two-to-three-dimensional transformations in heterogeneous thin films and the role of lateral organization in biological membranes. The study is directly relevant for the function of lung surfactant, and can explain the role of nanodomains in its surface activity and inhibition by an increased cholesterol concentration.
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102
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Galimzyanov TR, Molotkovsky RJ, Bozdaganyan ME, Cohen FS, Pohl P, Akimov SA. Elastic Membrane Deformations Govern Interleaflet Coupling of Lipid-Ordered Domains. PHYSICAL REVIEW LETTERS 2015; 115:088101. [PMID: 26340212 PMCID: PMC4750487 DOI: 10.1103/physrevlett.115.088101] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Indexed: 05/19/2023]
Abstract
The mechanism responsible for domain registration in two membrane leaflets has thus far remained enigmatic. Using continuum elasticity theory, we show that minimum line tension is achieved along the rim between thicker (ordered) and thinner (disordered) domains by shifting the rims in opposing leaflets by a few nanometers relative to each other. Increasing surface tension yields an increase in line tension, resulting in larger domains. Because domain registration is driven by lipid deformation energy, it does not require special lipid components or interactions at the membrane midplane.
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Affiliation(s)
- Timur R Galimzyanov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/5 Leninskiy prospekt, Moscow 119071, Russia
- National University of Science and Technology "MISiS", 4 Leninskiy prospekt, Moscow 119049, Russia
| | - Rodion J Molotkovsky
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/5 Leninskiy prospekt, Moscow 119071, Russia
| | - Marine E Bozdaganyan
- M.V. Lomonosov Moscow State University, 1 Leninskie Gory, Moscow 119991, Russia
- Federal Research Clinical Center of the Specialized Types of Health Care and Medical Technologies FMBA of Russia, 28 Orekhovyi bulvar, Moscow 115692, Russia
| | - Fredric S Cohen
- Rush University Medical Center, 1750 W. Harrison Street, Chicago, Illinois 60612, USA
| | - Peter Pohl
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40-42, Linz 4020, Austria
| | - Sergey A Akimov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/5 Leninskiy prospekt, Moscow 119071, Russia
- National University of Science and Technology "MISiS", 4 Leninskiy prospekt, Moscow 119049, Russia
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103
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Khakbaz P, Klauda JB. Probing the importance of lipid diversity in cell membranes via molecular simulation. Chem Phys Lipids 2015; 192:12-22. [PMID: 26260616 DOI: 10.1016/j.chemphyslip.2015.08.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 08/04/2015] [Accepted: 08/05/2015] [Indexed: 12/31/2022]
Abstract
Lipid membranes in prokaryotes and eukaryotes have a wide array of lipids that are necessary for proper membrane structure and function. In this paper, an introduction to lipid diversity in biology and a mini-review on how molecular simulations have been used to model biological membranes (primarily limited to one to three lipid types in most simulation-based models) is provided, which motivates the use of all-atom molecular dynamics (MD) simulations to study the effect of lipid diversity on properties of realistic membrane models of prokaryotes and eukaryotes. As an example, cytoplasmic membrane models of Escherichia coli were developed at different stages of the colony growth cycle (early-log, mid-log, stationary and overnight). The main difference between lipid compositions at each stage was the concentration of a cyclopropane-containing moiety on the sn-2 lipid acyl chain (cyC17:0). Triplicate MD simulations for each stage were run for 300 ns to study the influence of lipid diversity on the surface area per lipid, area compressibility modulus, deuterium order parameters, and electron density profiles. The overnight stage (also known as the death stage) had the highest average surface area per lipid, highest rigidity, and lowest bilayer thickness compare to other stages of E. coli cytoplasmic membrane. Although bilayer thickness did depend on the growth stage, the changes between these were small suggesting that the hydrophobic core of transmembrane proteins fit well with the membrane in all growth stages. Although it is still common practise in MD simulations of membrane proteins to use simple one- or two-component membranes, it can be important to use diverse lipid model membranes when membrane protein structure and function are influenced by changes in lipid membrane composition.
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Affiliation(s)
- Pouyan Khakbaz
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742, USA
| | - Jeffery B Klauda
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742, USA; Biophysics Program, University of Maryland, College Park, MD 20742, USA.
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104
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Giang H, Schick M. How cholesterol could be drawn to the cytoplasmic leaf of the plasma membrane by phosphatidylethanolamine. Biophys J 2015; 107:2337-44. [PMID: 25418302 DOI: 10.1016/j.bpj.2014.10.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 10/14/2014] [Accepted: 10/15/2014] [Indexed: 01/18/2023] Open
Abstract
In the mammalian plasma membrane, cholesterol can translocate rapidly between the exoplasmic and cytoplasmic leaves, so that its distribution between them should be given by the equality of its chemical potential in the leaves. Due to its favorable interaction with sphingomyelin, which is almost entirely in the outer leaf, one expects the great majority of cholesterol to be there also. Experimental results do not support this, implying that there is some mechanism attracting cholesterol to the inner leaf. We hypothesize that it is drawn there to reduce the bending free energy of the membrane caused by the presence of PE (phosphatidylethanolamine). It does this in two ways: first by simply diluting the amount of PE in the inner leaf, and second by ordering the tails of the PE to reduce its spontaneous curvature. Incorporating this mechanism into a model free energy for the bilayer, we find that between 50 and 60% of the total cholesterol should be in the inner leaf of human erythrocytes.
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Affiliation(s)
- Ha Giang
- Department of Physics, University of Washington, Seattle, Washington
| | - M Schick
- Department of Physics, University of Washington, Seattle, Washington.
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105
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Marquardt D, Geier B, Pabst G. Asymmetric lipid membranes: towards more realistic model systems. MEMBRANES 2015; 5:180-96. [PMID: 25955841 PMCID: PMC4496639 DOI: 10.3390/membranes5020180] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 04/28/2015] [Indexed: 01/23/2023]
Abstract
Despite the ubiquity of transbilayer asymmetry in natural cell membranes, the vast majority of existing research has utilized chemically well-defined symmetric liposomes, where the inner and outer bilayer leaflets have the same composition. Here, we review various aspects of asymmetry in nature and in model systems in anticipation for the next phase of model membrane studies.
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Affiliation(s)
- Drew Marquardt
- Institute of Molecular Biosciences, Biophysics Division, University of Graz, NAWI Graz, Humboldtstr 50/III, Graz, 8010, Austria.
- BioTechMed-Graz, Graz, 8010, Austria.
| | - Barbara Geier
- Institute of Molecular Biosciences, Biophysics Division, University of Graz, NAWI Graz, Humboldtstr 50/III, Graz, 8010, Austria.
- BioTechMed-Graz, Graz, 8010, Austria.
| | - Georg Pabst
- Institute of Molecular Biosciences, Biophysics Division, University of Graz, NAWI Graz, Humboldtstr 50/III, Graz, 8010, Austria.
- BioTechMed-Graz, Graz, 8010, Austria.
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106
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Sekereš J, Pleskot R, Pejchar P, Žárský V, Potocký M. The song of lipids and proteins: dynamic lipid-protein interfaces in the regulation of plant cell polarity at different scales. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:1587-98. [PMID: 25716697 DOI: 10.1093/jxb/erv052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Successful establishment and maintenance of cell polarity is crucial for many aspects of plant development, cellular morphogenesis, response to pathogen attack, and reproduction. Polar cell growth depends on integrating membrane and cell-wall dynamics with signal transduction pathways, changes in ion membrane transport, and regulation of vectorial vesicle trafficking and the dynamic actin cytoskeleton. In this review, we address the critical importance of protein-membrane crosstalk in the determination of plant cell polarity and summarize the role of membrane lipids, particularly minor acidic phospholipids, in regulation of the membrane traffic. We focus on the protein-membrane interface dynamics and discuss the current state of knowledge on three partially overlapping levels of descriptions. Finally, due to their multiscale and interdisciplinary nature, we stress the crucial importance of combining different strategies ranging from microscopic methods to computational modelling in protein-membrane studies.
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Affiliation(s)
- Juraj Sekereš
- 1 Institute of Experimental Botany, v. v. i., Academy of Sciences of the Czech Republic, Rozvojová 263, 16502 Prague 6, Czech Republic 2 Department of Experimental Plant Biology, Faculty of Science, Charles University in Prague, Viničná 5, 12844 Prague 2, Czech Republic
| | - Roman Pleskot
- 1 Institute of Experimental Botany, v. v. i., Academy of Sciences of the Czech Republic, Rozvojová 263, 16502 Prague 6, Czech Republic 3 Institute of Organic Chemistry and Biochemistry, v. v. i., Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 16610 Prague 6, Czech Republic
| | - Přemysl Pejchar
- 1 Institute of Experimental Botany, v. v. i., Academy of Sciences of the Czech Republic, Rozvojová 263, 16502 Prague 6, Czech Republic
| | - Viktor Žárský
- 1 Institute of Experimental Botany, v. v. i., Academy of Sciences of the Czech Republic, Rozvojová 263, 16502 Prague 6, Czech Republic 2 Department of Experimental Plant Biology, Faculty of Science, Charles University in Prague, Viničná 5, 12844 Prague 2, Czech Republic
| | - Martin Potocký
- 1 Institute of Experimental Botany, v. v. i., Academy of Sciences of the Czech Republic, Rozvojová 263, 16502 Prague 6, Czech Republic
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107
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Ackerman DG, Feigenson GW. Multiscale modeling of four-component lipid mixtures: domain composition, size, alignment, and properties of the phase interface. J Phys Chem B 2015; 119:4240-50. [PMID: 25564922 DOI: 10.1021/jp511083z] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Simplified lipid mixtures are often used to model the complex behavior of the cell plasma membrane. Indeed, as few as four components-a high-melting lipid, a nandomain-inducing low-melting lipid, a macrodomain-inducing low-melting lipid, and cholesterol (chol)-can give rise to a wide range of domain sizes and patterns that are highly sensitive to lipid compositions. Although these systems are studied extensively with experiments, the molecular-level details governing their phase behavior are not yet known. We address this issue by using molecular dynamics simulations to analyze how phase separation evolves in a four-component system as it transitions from small domains to large domains. To do so, we fix concentrations of the high-melting lipid 16:0,16:0-phosphatidylcholine (DPPC) and chol, and incrementally replace the nanodomain-inducing low-melting lipid 16:0,18:2-PC (PUPC) by the macrodomain-inducing low-melting lipid 18:2,18:2-PC (DUPC). Coarse-grained simulations of this four-component system reveal that lipid demixing increases as the amount of DUPC increases. Additionally, we find that domain size and interleaflet alignment change sharply over a narrow range of replacement of PUPC by DUPC, indicating that intraleaflet and interleaflet behaviors are coupled. Corresponding united atom simulations show that only lipids within ∼2 nm of the phase interface are significantly perturbed regardless of domain composition or size. Thus, whereas the fraction of interface-perturbed lipids is negligible for large domains, it is significant for smaller ones. Together, these results reveal characteristic traits of bilayer thermodynamic behavior in four-component mixtures, and provide a baseline for investigation of the effects of proteins and other lipids on membrane phase properties.
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Affiliation(s)
- David G Ackerman
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, United States
| | - Gerald W Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, United States
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108
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Ferraro M, Masetti M, Recanatini M, Cavalli A, Bottegoni G. Modeling lipid raft domains containing a mono-unsaturated phosphatidylethanolamine species. RSC Adv 2015. [DOI: 10.1039/c5ra02196k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
An advanced coarse-grained model for “atypical” lipid rafts was built and validated to be employed in studies of membrane-protein interactions.
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Affiliation(s)
- M. Ferraro
- D3 Compunet
- Istituto Italiano di Tecnologia
- Genova
- Italy
| | - M. Masetti
- Department of Pharmacy and Biotechnology
- Alma Mater Studiorum – Università di Bologna
- Bologna
- Italy
| | - M. Recanatini
- Department of Pharmacy and Biotechnology
- Alma Mater Studiorum – Università di Bologna
- Bologna
- Italy
| | - A. Cavalli
- D3 Compunet
- Istituto Italiano di Tecnologia
- Genova
- Italy
- Department of Pharmacy and Biotechnology
| | - G. Bottegoni
- D3 Compunet
- Istituto Italiano di Tecnologia
- Genova
- Italy
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109
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Baoukina S, Tieleman DP. Computer simulations of phase separation in lipid bilayers and monolayers. Methods Mol Biol 2015; 1232:307-322. [PMID: 25331143 DOI: 10.1007/978-1-4939-1752-5_21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Studying phase coexistence in lipid bilayers and monolayers is important for understanding lipid-lipid interactions underlying lateral organization in biological membranes. Computer simulations follow experimental approaches and use model lipid mixtures of simplified composition. Atomistic simulations give detailed information on the specificity of intermolecular interactions, while coarse-grained simulations achieve large time and length scales and provide a bridge towards state-of-the-art experimental techniques. Computer simulations allow characterizing the structure and composition of domains during phase transformations at Angstrom and picosecond resolution, and bring new insights into phase behavior of lipid membranes.
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Affiliation(s)
- Svetlana Baoukina
- Department of Biological Sciences, Centre for Molecular Simulation, University of Calgary, 2500 University Dr. NW, Calgary, AB, Canada, T2N 1N4,
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110
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Almeida PF. The many faces of lipid rafts. Biophys J 2014; 106:1841-3. [PMID: 24806915 DOI: 10.1016/j.bpj.2014.03.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 03/13/2014] [Accepted: 03/14/2014] [Indexed: 01/29/2023] Open
Affiliation(s)
- Paulo F Almeida
- Department of Chemistry and Biochemistry, University of North Carolina at Wilmington, Wilmington, North Carolina.
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111
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Deleu M, Crowet JM, Nasir MN, Lins L. Complementary biophysical tools to investigate lipid specificity in the interaction between bioactive molecules and the plasma membrane: A review. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:3171-3190. [DOI: 10.1016/j.bbamem.2014.08.023] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 08/05/2014] [Accepted: 08/21/2014] [Indexed: 02/08/2023]
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112
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Gueguen G, Destainville N, Manghi M. Mixed lipid bilayers with locally varying spontaneous curvature and bending. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2014; 37:31. [PMID: 25160487 DOI: 10.1140/epje/i2014-14076-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/21/2014] [Accepted: 08/06/2014] [Indexed: 06/03/2023]
Abstract
A model of lipid bilayers made of a mixture of two lipids with different average compositions on both leaflets, is developed. A Landau Hamiltonian describing the lipid-lipid interactions on each leaflet, with two lipidic fields ψ 1 and ψ 2, is coupled to a Helfrich one, accounting for the membrane elasticity, via both a local spontaneous curvature, which varies as C 0 + C 1(ψ 1 - ψ 2/2), and a bending modulus equal to κ 0 + κ 1(ψ 1 + ψ 2)/2. This model allows us to define curved patches as membrane domains where the asymmetry in composition, ψ 1 - ψ 2, is large, and thick and stiff patches where ψ 1 + ψ 2 is large. These thick patches are good candidates for being lipidic rafts, as observed in cell membranes, which are composed primarily of saturated lipids forming a liquid-ordered domain and are known to be thick and flat nano-domains. The lipid-lipid structure factors and correlation functions are computed for globally spherical membranes and planar ones and for a whole set of parameters including the surface tension and the coupling in the two leaflet compositions. Phase diagrams are established, within a Gaussian approximation, showing the occurrence of two types of Structure Disordered phases, with correlations between either curved or thick patches, and an Ordered phase, corresponding to the divergence of the structure factor at a finite wave vector. The varying bending modulus plays a central role for curved membranes, where the driving force κ 1 C 0 (2) is balanced by the line tension, to form raft domains of size ranging from 10 to 100 nm. For planar membranes, raft domains emerge via the cross-correlation with curved domains. A global picture emerges from curvature-induced mechanisms, described in the literature for planar membranes, to coupled curvature- and bending-induced mechanisms in curved membranes forming a closed vesicle.
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Affiliation(s)
- Guillaume Gueguen
- UPS, Laboratoire de Physique Théorique (IRSAMC), Université de Toulouse, F-31062, Toulouse, France
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113
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Durrant JD, Amaro RE. LipidWrapper: an algorithm for generating large-scale membrane models of arbitrary geometry. PLoS Comput Biol 2014; 10:e1003720. [PMID: 25032790 PMCID: PMC4102414 DOI: 10.1371/journal.pcbi.1003720] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 05/21/2014] [Indexed: 11/19/2022] Open
Abstract
As ever larger and more complex biological systems are modeled in silico, approximating physiological lipid bilayers with simple planar models becomes increasingly unrealistic. In order to build accurate large-scale models of subcellular environments, models of lipid membranes with carefully considered, biologically relevant curvature will be essential. In the current work, we present a multi-scale utility called LipidWrapper capable of creating curved membrane models with geometries derived from various sources, both experimental and theoretical. To demonstrate its utility, we use LipidWrapper to examine an important mechanism of influenza virulence. A copy of the program can be downloaded free of charge under the terms of the open-source FreeBSD License from http://nbcr.ucsd.edu/lipidwrapper. LipidWrapper has been tested on all major computer operating systems.
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Affiliation(s)
- Jacob D. Durrant
- Department of Chemistry & Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Rommie E. Amaro
- Department of Chemistry & Biochemistry, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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114
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Braun AR, Lacy MM, Ducas VC, Rhoades E, Sachs JN. α-Synuclein-induced membrane remodeling is driven by binding affinity, partition depth, and interleaflet order asymmetry. J Am Chem Soc 2014; 136:9962-72. [PMID: 24960410 PMCID: PMC4105054 DOI: 10.1021/ja5016958] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
We have investigated
the membrane remodeling capacity of the N-terminal
membrane-binding domain of α-synuclein (α-Syn100). Using fluorescence correlation spectroscopy and vesicle clearance
assays, we show that α-Syn100 fully tubulates POPG
vesicles, the first demonstration that the amphipathic helix on its
own is capable of this effect. We also show that at equal density
of membrane-bound protein, α-Syn has dramatically reduced affinity
for, and does not tubulate, vesicles composed of a 1:1 POPG:POPC mixture.
Coarse-grained molecular dynamics simulations suggested that the difference
between the pure POPG and mixture results may be attributed to differences
in the protein’s partition depth, the membrane’s hydrophobic
thickness, and disruption of acyl chain order. To explore the importance
of these attributes compared with the role of the reduced binding
energy, we created an α-Syn100 variant in which we
removed the hydrophobic core of the non-amyloid component (NAC) domain
and tested its impact on pure POPG vesicles. We observed a substantial
reduction in binding affinity and tubulation, and simulations of the
NAC-null protein suggested that the reduced binding energy increases
the protein mobility on the bilayer surface, likely impacting the
protein’s ability to assemble into organized pretubule structures.
We also used simulations to explore a potential role for interleaflet
coupling as an additional driving force for tubulation. We conclude
that symmetry across the leaflets in the tubulated state maximizes
the interaction energy of the two leaflets and relieves the strain
induced by the hydrophobic void beneath the amphipathic helix.
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Affiliation(s)
- Anthony R Braun
- Department of Biomedical Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States
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115
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Bennett WD, Tieleman DP. Computer simulations of lipid membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1765-76. [DOI: 10.1016/j.bbamem.2013.03.004] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 02/28/2013] [Accepted: 03/01/2013] [Indexed: 10/27/2022]
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116
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Rabinovich AL, Lyubartsev AP. Computer simulation of lipid membranes: Methodology and achievements. POLYMER SCIENCE SERIES C 2013. [DOI: 10.1134/s1811238213070060] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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117
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Molecular basis for the dissociation dynamics of protein A-immunoglobulin G1 complex. PLoS One 2013; 8:e66935. [PMID: 23776704 PMCID: PMC3680412 DOI: 10.1371/journal.pone.0066935] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 05/13/2013] [Indexed: 12/24/2022] Open
Abstract
Staphylococcus aureus protein A (SpA) is the most popular affinity ligand for immunoglobulin G1 (IgG1). However, the molecular basis for the dissociation dynamics of SpA-IgG1 complex is unclear. Herein, coarse-grained (CG) molecular dynamics (MD) simulations with the Martini force field were used to study the dissociation dynamics of the complex. The CG-MD simulations were first verified by the agreement in the structural and interactional properties of SpA and human IgG1 (hIgG1) in the association process between the CG-MD and all-atom MD at different NaCl concentrations. Then, the CG-MD simulation studies focused on the molecular insight into the dissociation dynamics of SpA-hIgG1 complex at pH 3.0. It is found that there are four steps in the dissociation process of the complex. First, there is a slight conformational adjustment of helix II in SpA. This is followed by the phenomena that the electrostatic interactions provided by the three hot spots (Glu143, Arg146 and Lys154) of helix II of SpA break up, leading to the dissociation of helix II from the binding site of hIgG1. Subsequently, breakup of the hydrophobic interactions between helix I (Phe132, Tyr133 and His137) in SpA and hIgG1 occurs, resulting in the disengagement of helix I from its binding site of hIgG1. Finally, the non-specific interactions between SpA and hIgG1 decrease slowly till disappearance, leading to the complete dissociation of the SpA-hIgG1 complex. This work has revealed that CG-MD coupled with the Martini force field is an effective method for studying the dissociation dynamics of protein-protein complex.
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118
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Formation of raft-like assemblies within clusters of influenza hemagglutinin observed by MD simulations. PLoS Comput Biol 2013; 9:e1003034. [PMID: 23592976 PMCID: PMC3623702 DOI: 10.1371/journal.pcbi.1003034] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 03/03/2013] [Indexed: 11/19/2022] Open
Abstract
The association of hemagglutinin (HA) with lipid rafts in the plasma membrane is an important feature of the assembly process of influenza virus A. Lipid rafts are thought to be small, fluctuating patches of membrane enriched in saturated phospholipids, sphingolipids, cholesterol and certain types of protein. However, raft-associating transmembrane (TM) proteins generally partition into Ld domains in model membranes, which are enriched in unsaturated lipids and depleted in saturated lipids and cholesterol. The reason for this apparent disparity in behavior is unclear, but model membranes differ from the plasma membrane in a number of ways. In particular, the higher protein concentration in the plasma membrane may influence the partitioning of membrane proteins for rafts. To investigate the effect of high local protein concentration, we have conducted coarse-grained molecular dynamics (CG MD) simulations of HA clusters in domain-forming bilayers. During the simulations, we observed a continuous increase in the proportion of raft-type lipids (saturated phospholipids and cholesterol) within the area of membrane spanned by the protein cluster. Lateral diffusion of unsaturated lipids was significantly attenuated within the cluster, while saturated lipids were relatively unaffected. On this basis, we suggest a possible explanation for the change in lipid distribution, namely that steric crowding by the slow-diffusing proteins increases the chemical potential for unsaturated lipids within the cluster region. We therefore suggest that a local aggregation of HA can be sufficient to drive association of the protein with raft-type lipids. This may also represent a general mechanism for the targeting of TM proteins to rafts in the plasma membrane, which is of functional importance in a wide range of cellular processes. The cell membrane is composed of a wide variety of lipids and proteins. Until recently, these were thought to be mixed evenly, but we now have evidence of the existence of “lipid rafts” — small, slow-moving areas of membrane in which certain types of lipid and protein accumulate. Rafts have many important biological functions in healthy cells, but also play a role in the assembly of influenza virus. For example, after the viral protein hemagglutinin is made inside the host cell, it accumulates in rafts. Exiting virus particles then take these portions of cell membrane with them as they leave the host cell. However, the mechanism by which proteins associate with lipid rafts is unclear. Here, we have used computers to simulate lipid membranes containing hemagglutinin. The simulations allow us to look in detail at the motions and interactions of individual proteins and lipids. We found that clusters of proteins altered the properties of nearby lipids, leading to accumulation of raft-type lipids. It therefore appears that aggregation of hemagglutinin may be enough to drive its association with rafts. This helps us to better understand both the influenza assembly process and the properties of lipid rafts.
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119
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Baoukina S, Mendez-Villuendas E, Bennett WFD, Tieleman DP. Computer simulations of the phase separation in model membranes. Faraday Discuss 2013; 161:63-75; discussion 113-50. [DOI: 10.1039/c2fd20117h] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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121
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Abstract
There is growing evidence that cell membranes can contain domains with different lipid and protein compositions and with different physical properties. Furthermore, it is increasingly appreciated that sphingolipids play a crucial role in the formation and properties of ordered lipid domains (rafts) in cell membranes. This review describes recent advances in our understanding of ordered membrane domains in both cells and model membranes. In addition, how the structure of sphingolipids influences their ability to participate in the formation of ordered domains, as well as how sphingolipid structure alters ordered domain properties, is described. The diversity of sphingolipid structure is likely to play an important role in modulating the biologically relevant properties of "rafts" in cell membranes.
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122
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de Jong DH, Singh G, Bennett WFD, Arnarez C, Wassenaar TA, Schäfer LV, Periole X, Tieleman DP, Marrink SJ. Improved Parameters for the Martini Coarse-Grained Protein Force Field. J Chem Theory Comput 2012; 9:687-97. [DOI: 10.1021/ct300646g] [Citation(s) in RCA: 922] [Impact Index Per Article: 76.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Djurre H. de Jong
- Groningen Biomolecular Sciences
and Biotechnology Institute and Zernike Institute for Advanced Materials,
University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Gurpreet Singh
- Department of Biological Sciences
and Institute for Biocomplexity and Informatics, University of Calgary,
2500 University Dr. NW, Calgary, AB, Canada, T2N 1N4
| | - W. F. Drew Bennett
- Department of Biological Sciences
and Institute for Biocomplexity and Informatics, University of Calgary,
2500 University Dr. NW, Calgary, AB, Canada, T2N 1N4
| | - Clement Arnarez
- Groningen Biomolecular Sciences
and Biotechnology Institute and Zernike Institute for Advanced Materials,
University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Tsjerk A. Wassenaar
- Groningen Biomolecular Sciences
and Biotechnology Institute and Zernike Institute for Advanced Materials,
University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Lars V. Schäfer
- Groningen Biomolecular Sciences
and Biotechnology Institute and Zernike Institute for Advanced Materials,
University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Xavier Periole
- Groningen Biomolecular Sciences
and Biotechnology Institute and Zernike Institute for Advanced Materials,
University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - D. Peter Tieleman
- Department of Biological Sciences
and Institute for Biocomplexity and Informatics, University of Calgary,
2500 University Dr. NW, Calgary, AB, Canada, T2N 1N4
| | - Siewert J. Marrink
- Groningen Biomolecular Sciences
and Biotechnology Institute and Zernike Institute for Advanced Materials,
University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
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123
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Polley A, Vemparala S, Rao M. Atomistic Simulations of a Multicomponent Asymmetric Lipid Bilayer. J Phys Chem B 2012; 116:13403-10. [DOI: 10.1021/jp3032868] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Anirban Polley
- Raman Research Institute, C. V. Raman Avenue, Bangalore 560 080, India
| | | | - Madan Rao
- Raman Research Institute, C. V. Raman Avenue, Bangalore 560 080, India
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore
560 065, India
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124
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Baoukina S, Mendez-Villuendas E, Tieleman DP. Molecular View of Phase Coexistence in Lipid Monolayers. J Am Chem Soc 2012; 134:17543-53. [DOI: 10.1021/ja304792p] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Svetlana Baoukina
- Department of Biological Sciences and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
| | - Eduardo Mendez-Villuendas
- Department of Biological Sciences and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
| | - D. Peter Tieleman
- Department of Biological Sciences and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
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125
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Hirose Y, Komura S, Andelman D. Concentration fluctuations and phase transitions in coupled modulated bilayers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:021916. [PMID: 23005794 DOI: 10.1103/physreve.86.021916] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Indexed: 06/01/2023]
Abstract
We consider the formation of finite-size domains in lipid bilayers consisting of saturated and hybrid lipids. First, we describe a monolayer model that includes a coupling between a compositional scalar field and a two-dimensional vectorial order parameter. Such a coupling yields an effective two-dimensional microemulsion free energy for the lipid monolayer, and its characteristic length of compositional modulations can be considered as the origin of finite-size domains in biological membranes. Next, we consider a coupled bilayer composed of two modulated monolayers and discuss the static and dynamic properties of concentration fluctuations above the transition temperature. We also investigate the micro-phase separation below the transition temperature and compare the micro-phase separated structures with statics and dynamics of concentration fluctuations above the transition.
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Affiliation(s)
- Yuichi Hirose
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
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126
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Jämbeck JPM, Lyubartsev AP. An Extension and Further Validation of an All-Atomistic Force Field for Biological Membranes. J Chem Theory Comput 2012; 8:2938-48. [PMID: 26592132 DOI: 10.1021/ct300342n] [Citation(s) in RCA: 346] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Biological membranes are versatile in composition and host intriguing molecular processes. In order to be able to study these systems, an accurate model Hamiltonian or force field (FF) is a necessity. Here, we report the results of our extension of earlier developed all-atomistic FF parameters for fully saturated phospholipids that complements an earlier parameter set for saturated phosphatidylcholine lipids (J. Phys. Chem. B, 2012, 116, 3164-3179). The FF, coined Slipids (Stockholm lipids), now also includes parameters for unsaturated phosphatidylcholine and phosphatidylethanolamine lipids, e.g., POPC, DOPC, SOPC, POPE, and DOPE. As the extended set of parameters is derived with the same philosophy as previously applied, the resulting FF has been developed in a fully consistent manner. The capabilities of Slipids are demonstrated by performing long simulations without applying any surface tension and using the correct isothermal-isobaric (NPT) ensemble for a range of temperatures and carefully comparing a number of properties with experimental findings. Results show that several structural properties are very well reproduced, such as scattering form factors, NMR order parameters, thicknesses, and area per lipid. Thermal dependencies of different thicknesses and area per lipid are reproduced as well. Lipid diffusion is systematically slightly underestimated, whereas the normalized lipid diffusion follows the experimental trends. This is believed to be due to the lack of collective movement in the relatively small bilayer patches used. Furthermore, the compatibility with amino acid FFs from the AMBER family is tested in explicit transmembrane complexes of the WALP23 peptide with DLPC and DOPC bilayers, and this shows that Slipids can be used to study more complex and biologically relevant systems.
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Affiliation(s)
- Joakim P M Jämbeck
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, SE-10691, Sweden
| | - Alexander P Lyubartsev
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, SE-10691, Sweden
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127
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Ward AB, Guvench O, Hills RD. Coarse grain lipid-protein molecular interactions and diffusion with MsbA flippase. Proteins 2012; 80:2178-90. [DOI: 10.1002/prot.24108] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Revised: 04/10/2012] [Accepted: 04/25/2012] [Indexed: 12/27/2022]
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128
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Rosetti C, Pastorino C. Comparison of Ternary Bilayer Mixtures with Asymmetric or Symmetric Unsaturated Phosphatidylcholine Lipids by Coarse Grained Molecular Dynamics Simulations. J Phys Chem B 2012; 116:3525-37. [DOI: 10.1021/jp212406u] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- C. Rosetti
- Departamento de Física, Centro Atómico Constituyentes CNEA, Av. Gral.
Paz 1499, 1650 San Martín, Buenos Aires, Argentina
- CONICET, Avda. Rivadavia 1917, C1033AAJ Cdad. de Buenos Aires, Buenos Aires,
Argentina
| | - C. Pastorino
- Departamento de Física, Centro Atómico Constituyentes CNEA, Av. Gral.
Paz 1499, 1650 San Martín, Buenos Aires, Argentina
- CONICET, Avda. Rivadavia 1917, C1033AAJ Cdad. de Buenos Aires, Buenos Aires,
Argentina
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129
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Schick M. Membrane heterogeneity: manifestation of a curvature-induced microemulsion. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:031902. [PMID: 22587118 DOI: 10.1103/physreve.85.031902] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Indexed: 05/31/2023]
Abstract
To explain the appearance of heterogeneities in the plasma membrane, I propose a hypothesis which begins with the observation that fluctuations in the membrane curvature are coupled to the difference between compositions of one leaf and the other. Because of this coupling, the most easily excited fluctuations can occur at nonzero wave numbers. When the coupling is sufficiently strong, it is well-known that it leads to microphase separation and modulated phases. I note that when the coupling is less strong, the tendency toward modulation remains manifest in a liquid phase that exhibits a transient structure of a characteristic size, that is, it is a microemulsion. The characteristic size of the fluctuating domains is estimated to be on the order of 100 nm, and experiments to verify this hypothesis are proposed.
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Affiliation(s)
- M Schick
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
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130
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Braun AR, Sevcsik E, Chin P, Rhoades E, Tristram-Nagle S, Sachs JN. α-Synuclein induces both positive mean curvature and negative Gaussian curvature in membranes. J Am Chem Soc 2012; 134:2613-20. [PMID: 22211521 DOI: 10.1021/ja208316h] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Using a combination of X-ray scattering, fluorescence correlation spectroscopy, coarse-grained molecular dynamics (MD) simulations and potential of mean force calculations, we have explored the membrane remodeling effects of monomeric α-synuclein (αS). Our initial findings from multiple approaches are that αS (1) causes a significant thinning of the bilayer and (2) stabilizes positive mean curvature, such that the maximum principle curvature matches that of synaptic vesicles, αS-induced tubules, and the synthetic lipid vesicles to which the protein binds most tightly. This suggests that αS binding to synaptic vesicles likely stabilizes their intrinsic curvature. We then show that αS induces local negative Gaussian curvature, an effect that occurs in regions of αS shown previously via NMR and corroborated by MD simulation to have significant conformational flexibility. The induction of negative Gaussian curvature, which has implications for all curvature-sensing and curvature-generating amphipathic α-helices, supports a hypothesis that connects helix insertion to fusion and fission of vesicles, processes that have recently been linked to αS function. Then, in an effort to explain these biophysical properties of αS, we promote an intrinsic curvature-field model that recasts long-range protein-protein interactions in terms of the interactions between the local curvature fields generated by lipid-protein complexes.
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Affiliation(s)
- Anthony R Braun
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
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131
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Demchenko AP. Modern views on the structure and dynamics of biological membranes. ACTA ACUST UNITED AC 2012. [DOI: 10.7124/bc.000029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- A. P. Demchenko
- Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine
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132
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Domański J, Marrink SJ, Schäfer LV. Transmembrane helices can induce domain formation in crowded model membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:984-94. [PMID: 21884678 DOI: 10.1016/j.bbamem.2011.08.021] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 07/27/2011] [Accepted: 08/15/2011] [Indexed: 12/29/2022]
Abstract
We studied compositionally heterogeneous multi-component model membranes comprised of saturated lipids, unsaturated lipids, cholesterol, and α-helical TM protein models using coarse-grained molecular dynamics simulations. Reducing the mismatch between the length of the saturated and unsaturated lipid tails reduced the driving force for segregation into liquid-ordered (l(o)) and liquid-disordered (l(d)) lipid domains. Cholesterol depletion had a similar effect, and binary lipid mixtures without cholesterol did not undergo large-scale phase separation under the simulation conditions. The phase-separating ternary dipalmitoyl-phosphatidylcholine (DPPC)/dilinoleoyl-PC (DLiPC)/cholesterol bilayer was found to segregate into l(o) and l(d) domains also in the presence of a high concentration of ΤΜ helices. The l(d) domain was highly crowded with TM helices (protein-to-lipid ratio ~1:5), slowing down lateral diffusion by a factor of 5-10 as compared to the dilute case, with anomalous (sub)-diffusion on the μs time scale. The membrane with the less strongly unsaturated palmitoyl-linoleoyl-PC instead of DLiPC, which in the absence of TM α-helices less strongly deviated from ideal mixing, could be brought closer to a miscibility critical point by introducing a high concentration of TM helices. Finally, the 7-TM protein bacteriorhodopsin was found to partition into the l(d) domains irrespective of hydrophobic matching. These results show that it is possible to directly study the lateral reorganization of lipids and proteins in compositionally heterogeneous and crowded model biomembranes with coarse-grained molecular dynamics simulations, a step toward simulations of realistic, compositionally complex cellular membranes. This article is part of a Special Issue entitled: Protein Folding in Membranes.
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Affiliation(s)
- Jan Domański
- Groningen Biomolecular Sciences and Biotechnology Institute, and Zernike Institute for Advanced Materials, University of Groningen, Nijemborgh 7, 9747 AG Groningen, The Netherlands
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133
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Qian S, Heller WT. Peptide-induced asymmetric distribution of charged lipids in a vesicle bilayer revealed by small-angle neutron scattering. J Phys Chem B 2011; 115:9831-7. [PMID: 21751797 DOI: 10.1021/jp204045t] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cellular membranes are complex mixtures of lipids, proteins, and other small molecules that provide functional, dynamic barriers between the cell and its environment, as well as between environments within the cell. The lipid composition of the membrane is highly specific and controlled in terms of both content and lipid localization. The membrane structure results from the complex interplay between the wide varieties of molecules present. Here, small-angle neutron scattering and selective deuterium labeling were used to probe the impact of the membrane-active peptides melittin and alamethicin on the structure of lipid bilayers composed of a mixture of the lipids dimyristoyl phosphatidylglycerol (DMPG) and chain-perdeuterated dimyristoyl phosphatidylcholine (DMPC). We found that both peptides enriched the outer leaflet of the bilayer with the negatively charged DMPG, creating an asymmetric distribution of lipids. The level of enrichment is peptide concentration-dependent and is stronger for melittin than it is for alamethicin. The enrichment between the inner and outer bilayer leaflets occurs at very low peptide concentrations and increases with peptide concentration, including when the peptide adopts a membrane-spanning, pore-forming state. The results suggest that these membrane-active peptides may have a secondary stressful effect on target cells at low concentrations that results from a disruption of the lipid distribution between the inner and outer leaflets of the bilayer that is independent of the formation of transmembrane pores.
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Affiliation(s)
- Shuo Qian
- Center for Structural Molecular Biology, Chemical Sciences and Neutron Scattering Science Divisions, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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