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Wikström M, Kelly AA, Georgiev A, Eriksson HM, Klement MR, Bogdanov M, Dowhan W, Wieslander A. Lipid-engineered Escherichia coli membranes reveal critical lipid headgroup size for protein function. J Biol Chem 2009; 284:954-65. [PMID: 18981182 PMCID: PMC2613627 DOI: 10.1074/jbc.m804482200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Revised: 10/23/2008] [Indexed: 11/06/2022] Open
Abstract
Escherichia coli membranes have a substantial bilayer curvature stress due to a large fraction of the nonbilayer-prone lipid phosphatidylethanolamine, and a mutant (AD93) lacking this lipid is severely crippled in several membrane-associated processes. Introduction of four lipid glycosyltransferases from Acholeplasma laidlawii and Arabidopsis thaliana, synthesizing large amounts of two nonbilayer-prone, and two bilayer-forming gluco- and galacto-lipids, (i) restored the curvature stress with the two nonbilayer lipids, and (ii) diluted the high negative lipid surface charge in all AD93 bilayers. Surprisingly, the bilayer-forming diglucosyl-diacylglycerol was almost as good in improving AD93 membrane processes as the two nonbilayer-prone glucosyl-diacylglycerol and galactosyl-diacylglycerol lipids, strongly suggesting that lipid surface charge dilution by these neutral lipids is very important for E. coli. Increased acyl chain length and unsaturation, plus cardiolipin (nonbilayer-prone) content, were probably also beneficial in the modified strains. However, despite a correct transmembrane topology for the transporter LacY in the diglucosyl-diacylglycerol clone, active transport failed in the absence of a nonbilayer-prone glycolipid. The corresponding digalactosyl-diacylglycerol bilayer lipid did not restore AD93 membrane processes, despite analogous acyl chain and cardiolipin contents. Chain ordering, probed by bis-pyrene lipids, was substantially lower in the digalactosyl-diacylglycerol strain lipids due to its extended headgroup. Hence, a low surface charge density of anionic lipids is important in E. coli membranes, but is inefficient if the headgroup of the diluting lipid is too large. This strongly indicates that a certain magnitude of the curvature stress is crucial for the bilayer in vivo.
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Affiliation(s)
- Malin Wikström
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
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Lindblom G, Orädd G. Lipid lateral diffusion and membrane heterogeneity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1788:234-44. [PMID: 18805393 DOI: 10.1016/j.bbamem.2008.08.016] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Revised: 08/13/2008] [Accepted: 08/21/2008] [Indexed: 11/24/2022]
Abstract
The pulsed field gradient (pfg)-NMR method for measurements of translational diffusion of molecules in macroscopically aligned lipid bilayers is described. This technique is proposed to have an appreciable potential for investigations in the field of lipid and membrane biology. Transport of molecules in the plane of the bilayer can be successfully studied, as well as lateral phase separation of lipids and their dynamics within the bilayer organizations. Lateral diffusion coefficients depend on lipid packing and acyl chain ordering and investigations of order parameters of perdeuterated acyl chains, using (2)H NMR quadrupole splittings, are useful complements. In this review we summarize some of our recent achievements obtained on lipid membranes. In particular, bilayers exhibiting two-phase coexistence of liquid disordered (l(d)) and liquid ordered (l(o)) phases are considered in detail. Methods for obtaining good oriented lipid bilayers, necessary for the pfg-NMR method to be efficiently used, are also briefly described. Among our major results, besides determinations of l(d) and l(o) phases, belongs the finding that the lateral diffusion is the same for all components, independent of the molecular structure (including cholesterol (CHOL)), if they reside in the same domain or phase in the membrane. Furthermore, quite unexpectedly CHOL seems to partition into the l(d)and l(o) phases to roughly the same extent, indicating that CHOL has no strong preference for any of these phases, i.e. CHOL seems to have similar interactions with all of the lipids. We propose that the lateral phase separation in bilayers containing one high-T(m) and one low-T(m) lipid together with CHOL is driven by the increasing difficulty of incorporating an unsaturated or prenyl lipid into the highly ordered bilayer formed by a saturated lipid and CHOL, i.e. the phase transition is entropy driven to keep the disorder of the hydrocarbon chains of the unsaturated lipid.
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Alley SH, Ces O, Barahona M, Templer RH. X-ray diffraction measurement of the monolayer spontaneous curvature of dioleoylphosphatidylglycerol. Chem Phys Lipids 2008; 154:64-7. [PMID: 18405663 DOI: 10.1016/j.chemphyslip.2008.03.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 03/05/2008] [Accepted: 03/12/2008] [Indexed: 11/17/2022]
Abstract
Phosphatidylglycerol (PG) is an anionic lipid commonly found in large proportions in the cell membranes of bacteria and plants and, to a lesser extent, in animal cells. PG plays an important role in the regulation and determination of the elastic properties of the membrane. Using small angle X-ray scattering experiments, we obtain that the monolayer spontaneous curvature of dioleoylphosphatidylglycerol (DOPG) is -1/150+/-0.021 nm(-1) when measured in 150 mM NaCl. When the experiments are carried out in 150 mM NaCl and 20mM MgCl(2), the value obtained for the monolayer spontaneous curvature is -1/8.7+/-0.037 nm(-1). These values are of importance in modelling the effects of curvature elastic stress in membrane lipid homeostasis in the bacterium Acholeplasma laidlawii [Alley, S.H., Barahona, M., Ces, O., Templer, R.H., in press. Biophysical regulation of lipid biosynthesis in the plasma membrane. Biophys. J.] and indicate that divalent cations can play a significant role in altering curvature elastic stress.
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Affiliation(s)
- Stephen H Alley
- Department of Bioengineering, Imperial College London, United Kingdom
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Abstract
We present a cellular model of lipid biosynthesis in the plasma membrane that couples biochemical and biophysical features of the enzymatic network of the cell-wall-less Mycoplasma Acholeplasma laidlawii. In particular, we formulate how the stored elastic energy of the lipid bilayer can modify the activity of curvature-sensitive enzymes through the binding of amphipathic alpha-helices. As the binding depends on lipid composition, this results in a biophysical feedback mechanism for the regulation of the stored elastic energy. The model shows that the presence of feedback increases the robustness of the steady state of the system, in the sense that biologically inviable nonbilayer states are less likely. We also show that the biophysical and biochemical features of the network have implications as to which enzymes are most efficient at implementing the regulation. The network imposes restrictions on the steady-state balance between bilayer and nonbilayer lipids and on the concentrations of particular lipids. Finally, we consider the influence of the length of the amphipathic alpha-helix on the efficacy of the feedback and propose experimental measurements and extensions of the modeling framework.
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Howe J, von Minden M, Gutsmann T, Koch MHJ, Wulf M, Gerber S, Milkereit G, Vill V, Brandenburg K. Structural preferences of dioleoyl glycolipids with mono- and disaccharide head groups. Chem Phys Lipids 2007; 149:52-8. [PMID: 17658504 DOI: 10.1016/j.chemphyslip.2007.06.214] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Revised: 05/24/2007] [Accepted: 06/05/2007] [Indexed: 11/16/2022]
Abstract
The structural preferences of 1,2-dioleoyl-sn-glycerol glycolipids with glucose, galactose, maltose, and cellobiose as sugar head group were investigated under near physiological conditions with Fourier-transform infrared spectroscopy (FT-IR) and synchrotron radiation small-angle X-ray scattering (SAXS). Whereas all glycolipids have a very high fluidity at temperatures above 0 degrees C, the mono- and disaccharide compounds differ considerably in their aggregate structures. The monosaccharide compounds adopt only inverted hexagonal (H(II)) structures in the temperature range 5-70 degrees C, while the disaccharide compounds adopt only multilamellar structures. Since these and similar glycolipids are frequently found in nature, these data should be of relevance for the function of their host cell membranes.
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Affiliation(s)
- Jörg Howe
- Forschungszentrum Borstel, LG Biophysik, D-23845 Borstel, Germany
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Zhao W, Róg T, Gurtovenko AA, Vattulainen I, Karttunen M. Atomic-scale structure and electrostatics of anionic palmitoyloleoylphosphatidylglycerol lipid bilayers with Na+ counterions. Biophys J 2006; 92:1114-24. [PMID: 17114222 PMCID: PMC1783877 DOI: 10.1529/biophysj.106.086272] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Anionic palmitoyloleoylphosphatidylglycerol (POPG) is one of the most abundant lipids in nature, yet its atomic-scale properties have not received significant attention. Here we report extensive 150-ns molecular dynamics simulations of a pure POPG lipid membrane with sodium counterions. It turns out that the average area per lipid of the POPG bilayer under physiological conditions is approximately 19% smaller than that of a bilayer built from its zwitterionic phosphatidylcholine analog, palmitoyloleoylphosphatidylcholine. This suggests that there are strong attractive interactions between anionic POPG lipids, which overcome the electrostatic repulsion between negative charges of PG headgroups. We demonstrate that interlipid counterion bridges and strong intra- and intermolecular hydrogen bonding play a key role in this seemingly counterintuitive behavior. In particular, the substantial strength and stability of ion-mediated binding between anionic lipid headgroups leads to complexation of PG molecules and ions and formation of large PG-ion clusters that act in a concerted manner. The ion-mediated binding seems to provide a possible molecular-level explanation for the low permeability of PG-containing bacterial membranes to organic solvents: highly polar interactions at the water/membrane interface are able to create a high free energy barrier for hydrophobic molecules such as benzene.
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Affiliation(s)
- Wei Zhao
- Biophysics and Statistical Mechanics Group, Laboratory of Computational Engineering, Helsinki Institute of Physics, Helsinki University of Technology, Espoo
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Storm P, Li L, Kinnunen P, Wieslander A. Lateral organization in Acholeplasma laidlawii lipid bilayer models containing endogenous pyrene probes. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:1699-709. [PMID: 12694183 DOI: 10.1046/j.1432-1033.2003.03527.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In membranes of the small prokaryote Acholeplasma laidlawii bilayer- and nonbilayer-prone glycolipids are major species, similar to chloroplast membranes. Enzymes of the glucolipid pathway keep certain important packing properties of the bilayer in vivo, visualized especially as a monolayer curvature stress ('spontaneous curvature'). Two key enzymes depend in a cooperative fashion on substantial amounts of the endogenous anionic lipid phosphatidylglycerol (PG) for activity. The lateral organization of five unsaturated A. laidlawii lipids was analyzed in liposome model bilayers with the use of endogenously produced pyrene-lipid probes, and extensive experimental designs. Of all lipids analyzed, PG especially promoted interactions with the precursor diacylglycerol (DAG), as revealed from pyrene excimer ratio (Ie/Im) responses. Significant interactions were also recorded within the major nonbilayer-prone monoglucosylDAG (MGlcDAG) lipids. The anionic precursor phosphatidic acid (PA) was without effects. Hence, a heterogeneous lateral lipid organization was present in these liquid-crystalline bilayers. The MGlcDAG synthase when binding at the PG bilayer interface, decreased acyl chain ordering (increase of membrane free volume) according to a bis-pyrene-lipid probe, but the enzyme did not influence the bulk lateral lipid organization as recorded from DAG or PG probes. It is concluded that the concentration of the substrate DAG by PG is beneficial for the MGlcDAG synthase, but that binding in a proper orientation/conformation seems most important for activity.
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Affiliation(s)
- Patrik Storm
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
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The anti-parallel, extended or splayed-chain conformation of amphiphilic lipids. Colloids Surf B Biointerfaces 2002. [DOI: 10.1016/s0927-7765(02)00034-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Rilfors L, Lindblom G. Regulation of lipid composition in biological membranes—biophysical studies of lipids and lipid synthesizing enzymes. Colloids Surf B Biointerfaces 2002. [DOI: 10.1016/s0927-7765(01)00310-1] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Orädd G, Rilfors L, Lindblom G. Initial acyl chain segments of gluco- and phospholipids differ in ordering in both lamellar and reversed hexagonal phases. Phys Chem Chem Phys 2001. [DOI: 10.1039/b106018j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Orädd G, Andersson A, Rilfors L, Lindblom G, Strandberg E, Andrén PE. alpha-methylene ordering of acyl chains differs in glucolipids and phosphatidylglycerol from Acholeplasma laidlawii membranes: (2)H-NMR quadrupole splittings from individual lipids in mixed bilayers. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1468:329-44. [PMID: 11018677 DOI: 10.1016/s0005-2736(00)00273-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A Acholeplasma laidlawii strain A-EF22 was grown in a medium supplemented with alpha-deuterated oleic acid. Phosphatidylglycerol (PG), the glucolipids monoglucosyldiacylglycerol (MGlcDAG), diglucosyldiacylglycerol (DGlcDAG) and monoacyldiglucosyldiacylglycerol, and the phosphoglucolipid glycerophosphoryldiglucosyldiacylglycerol (GPDGlcDAG) were purified, and the phase behaviour and molecular ordering for the individual lipids, as well as for mixtures of the lipids, were studied by (2)H-, (31)P-NMR and X-ray scattering methods. The chemical structure of all the A. laidlawii lipids, except PG, has been determined and verified previously; here also the chemical structure of PG was verified, utilising mass spectrometry and (1)H and (13)C high resolution NMR spectroscopy. For the first time, lipid dimers were found in the mass spectrometry measurements. The major findings in this work are: (1) addition of 50 mol% of PG to the non-lamellar-forming lipid MGlcDAG does not significantly alter the transition temperature between lamellar and non-lamellar phases; (2) the (2)H-NMR quadrupole splitting patterns obtained from the lamellar liquid crystalline phase are markedly different for PG on one hand, and DGlcDAG and GPDGlcDAG on the other hand; and (3) mixtures of PG and DGlcDAG or MGlcDAG give rise to (2)H-NMR spectra consisting of a superposition of splitting patterns of the individual lipids. These remarkable features show that the local ordering of the alpha-carbon of the acyl chains is different for PG than for MGlcDAG and DGlcDAG, and that this difference is preserved when PG is mixed with the glucolipids. The results obtained are interpreted in terms of differences in molecular shape and hydrophilicity of the different polar headgroups.
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Affiliation(s)
- G Orädd
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
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Staudegger E, Prenner EJ, Kriechbaum M, Degovics G, Lewis RN, McElhaney RN, Lohner K. X-ray studies on the interaction of the antimicrobial peptide gramicidin S with microbial lipid extracts: evidence for cubic phase formation. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1468:213-30. [PMID: 11018666 DOI: 10.1016/s0005-2736(00)00260-1] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We have investigated the effect of the interaction of the antimicrobial peptide gramicidin S (GS) on the thermotropic phase behavior of model lipid bilayer membranes generated from the total membrane lipids of Acholeplasma laidlawii B and Escherichia coli. The A. laidlawii B membrane lipids consist primarily of neutral glycolipids and anionic phospholipids, while the E. coli inner membrane lipids consist exclusively of zwitterionic and anionic phospholipids. We show that the addition of GS at a lipid-to-peptide molar ratio of 25 strongly promotes the formation of bicontinuous inverted cubic phases in both of these lipid model membranes, predominantly of space group Pn3m. In addition, the presence of GS causes a thinning of the liquid-crystalline bilayer and a reduction in the lattice spacing of the inverted cubic phase which can form in the GS-free membrane lipid extracts at sufficiently high temperatures. This latter finding implies that GS potentiates the formation of an inverted cubic phase by increasing the negative curvature stress in the host lipid bilayer. This effect may be an important aspect of the permeabilization and eventual disruption of the lipid bilayer phase of biological membranes, which appears to be the mechanism by which GS kills bacterial cells and lysis erythrocytes.
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Affiliation(s)
- E Staudegger
- Institut für Biophysik und Röntgenstrukturforschung, Osterreichische Akademie der Wissenschaften, Steyrergasse 171VI, A-8010 Graz, Austria
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Andersson AS, Rilfors L, Orädd G, Lindblom G. Total lipids with short and long acyl chains from Acholeplasma form nonlamellar phases. Biophys J 1998; 75:2877-87. [PMID: 9826609 PMCID: PMC1299960 DOI: 10.1016/s0006-3495(98)77730-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The cell-wall-less bacterium Acholeplasma laidlawii A-EF22 synthesizes eight glycerolipids. Some of them form lamellar phases, whereas others are able to form normal or reversed nonlamellar phases. In this study we examined the phase properties of total lipid extracts with limiting average acyl chain lengths of 15 and 19 carbon atoms. The temperature at which these extracts formed reversed hexagonal (HII) phases differed by 5-10 degreesC when the water contents were 20-30 wt%. Thus the cells adjust the ratio between lamellar-forming and nonlamellar-forming lipids to the acyl chain lengths. Because short acyl chains generally increase the potential of lipids to form bilayers, it was judged interesting to determine which of the A. laidlawii A lipids are able to form reversed nonlamellar phases with short acyl chains. The two candidates with this ability are monoacyldiglucosyldiacylglycerol (MADGlcDAG) and monoglucosyldiacylglycerol. The average acyl chain lengths were 14.7 and 15.1 carbon atoms, and the degrees of acyl chain unsaturation were 32 and 46 mol%, respectively. The only liquid crystalline phase formed by MADGlcDAG is an HII phase. Monoglucosyldiacylglycerol forms reversed cubic (Ia3d) and HII phases at high temperatures. Thus, even when the organism is grown with short fatty acids, it synthesizes two lipids that have the capacity to maintain the nonlamellar tendency of the lipid bilayer. MADGlcDAG in particular contributes very powerfully to this tendency.
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Affiliation(s)
- A S Andersson
- Department of Physical Chemistry, Umeâ University, S-901 87 Umeâ, Sweden.
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