X-ray Structure of Bacteriorhodopsin at 2.5 Angstroms from Microcrystals Grown in Lipidic Cubic Phases

Pebay‐Peyroula, Eva; Rummel, Gabriele; Rosenbusch, Jürg P.; Landau, Ehud M.

doi:10.1126/science.277.5332.1676

Cited by 884 publications

(715 citation statements)

References 43 publications

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“…A prominent example is bacteriorhodopsin (BR), a seven-a-helix bundle membrane protein (see e.g. [1][2][3]). In a-helix bundle proteins, multiple helices are aligned in the form of bundles and may contain polar residues at the interfaces between the helices that are not exposed to the lipid chains.…”

Section: Introductionmentioning

confidence: 99%

Membrane protein folding on the example of outer membrane protein A of Escherichia coli

Kleinschmidt¹

2003

Cellular and Molecular Life Sciences (CMLS)

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Abstract. The biophysical principles and mechanisms by which membrane proteins insert and fold into a biomembrane have mostly been studied with bacteriorhodopsin and outer membrane protein A (OmpA). This review describes the assembly process of the monomeric outer membrane proteins of Gram-negative bacteria, for which OmpA has served as an example. OmpA is a two-domain outer membrane protein composed of a 171-residue eight-stranded b-barrel transmembrane domain and a 154-residue periplasmic domain. OmpA is translocated in an unstructured form across the cytoplasmic membrane into the periplasm. In the periplasm, unfolded OmpA is kept in solution in complex with the molecular chaperone Skp. After binding of periplasmic lipopolysaccharide, OmpA insertion and folding occur spontaneously upon interaction of the complex with the phospholipid bilayer. Insertion and folding of the b-barrel transmembrane domain into the lipid bilayer are highly synchronized, i.e. the formation of large amounts of b-sheet secondary structure and b-barrel tertiary structure take place in parallel with the same rate constants, while OmpA inserts into the hydrophobic core of the membrane. In vitro, OmpA can successfully fold into a range of model membranes of very different phospholipid compositions, i.e. into bilayers of lipids of different headgroup structures and hydrophobic chain lengths. Three membrane-bound folding intermediates of OmpA were discovered in folding studies with dioleoylphosphatidylcholine bilayers. Their formation was monitored by time-resolved distance determinations by fluorescence quenching, and they were structurally distinguished by the relative positions of the five tryptophan residues of OmpA in projection to the membrane normal. Recent studies indicate a chaperone-assisted, highly synchronized mechanism of secondary and tertiary structure formation upon membrane insertion of b-barrel membrane proteins such as OmpA that involves at least three structurally distinct folding intermediates.

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Section: Introductionmentioning

confidence: 99%

Membrane protein folding on the example of outer membrane protein A of Escherichia coli

Kleinschmidt¹

2003

Cellular and Molecular Life Sciences (CMLS)

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Section: (Received 31 March 2000)mentioning

confidence: 99%

“…The property of cubic lipid bilayer phases to divide space into interwoven polar and apolar compartments is utilized for biological function, e.g., in mitochondria and the endoplasmic reticulum [3]. Recently, they have also been used as artificial matrices which enable membrane proteins such as bacteriorhodopsin to crystallize in a three-dimensional array [4].It was shown by Luzzati and co-workers [5] that the midsurfaces of the lipid bilayers are very close to cubic minimal surfaces, which have zero mean curvature everywhere. These surfaces occur in lipid-water systems due to the local symmetry of the lipid bilayer, which implies that the surface should curve to both sides in the same way.…”

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confidence: 99%

Stability of Inverse Bicontinuous Cubic Phases in Lipid-Water Mixtures

Schwarz

Gompper

2000

Phys. Rev. Lett.

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We investigate the stability of seven inverse bicontinuous cubic phases [G, D, P, C͑P͒, S, I-WP, F-RD] in lipid-water mixtures based on a curvature model of membranes. Lipid monolayers are described by parallel surfaces to triply periodic minimal surfaces. The phase behavior is determined by the distribution of the Gaussian curvature on the minimal surface and the porosity of each structure. Only G, D, and P are found to be stable, and to coexist along a triple line. The calculated phase diagram agrees very well with experimental results for 2:1 lauric acid͞DLPC. 61.30.Cz, 87.16.Dg Most of the many mesomorphic phases formed by lipid-water mixtures are of the inverse type, with the selfassembled lipid monolayers curving towards the aqueous regions [1]. In inverse bicontinuous cubic phases, a single lipid bilayer extends throughout the whole sample, dividing it into two percolating water labyrinths. Until now, the structures G, D, and P have been identified. The only known lipid-water system in which G, D, and P coexist is 2:1 lauric acid͞DLPC and water [2]. The property of cubic lipid bilayer phases to divide space into interwoven polar and apolar compartments is utilized for biological function, e.g., in mitochondria and the endoplasmic reticulum [3]. Recently, they have also been used as artificial matrices which enable membrane proteins such as bacteriorhodopsin to crystallize in a three-dimensional array [4].It was shown by Luzzati and co-workers [5] that the midsurfaces of the lipid bilayers are very close to cubic minimal surfaces, which have zero mean curvature everywhere. These surfaces occur in lipid-water systems due to the local symmetry of the lipid bilayer, which implies that the surface should curve to both sides in the same way. However, it is well known [6] that many more cubic minimal surfaces exist than the structures G, D, and P identified in lipid-water mixtures. What might be the reason why these other phases have not been observed thus far? Helfrich and Rennschuh [7] argued that, based on the curvature model for fluid membranes [8], structures with a narrow distribution of Gaussian curvature over the minimal midsurface should be most favorable. However, the relevant data was known to them only for G, D, and P, which are degenerate in this respect due to the existence of a Bonnet transformation. Recently, we obtained numerical representations for a large number of cubic minimal surfaces in the framework of a simple Ginzburg-Landau model [9]. In this Letter we use this data to investigate seven inverse bicontinuous cubic phases (G, D, P, C͑P͒, S, I-WP, F-RD). For an illustration of the G and S surfaces, see Fig. 1. We find that the width of the different distributions of Gaussian curvature is indeed smallest for G, D, and P and larger for all other structures considered.This proves for the first time why only G, D, and P should be observed experimentally.Our detailed investigation of the stability of bicontinuous cubic phases shows that the existence of the Bonnet transformation implies...

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“…Similarly, the bilayers of bicontinuous cubic phases in lipid-water mixtures by symmetry have no spontaneous curvature, so that their mid-surfaces can also be modelled by TPMS [11]. Bicontinuous cubic phases have gained renewed interest recently, for example as space partitioners in biological systems [12], as amphiphilic templates for mesoporous systems [13] and for the crystallization of membrane proteins [14].…”

Section: Introductionmentioning

confidence: 99%

Systematic approach to bicontinuous cubic phases in ternary amphiphilic systems

1999

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The Fourier approach and theories of space groups and color symmetries are used to systematically generate and compare bicontinuous cubic structures in the framework of a Ginzburg-Landau model for ternary amphiphilic systems. Both single and double structures are investigated; they correspond to systems with one or two monolayers in a unit cell, respectively. We show how and why single structures can be made to approach triply periodic minimal surfaces very closely, and give improved nodal approximations for G, D, I-WP and P surfaces. We demonstrate that the relative stability of the single structures can be calculated from the geometrical properties of their interfaces only. The single gyroid G turns out to be the most stable bicontinuous cubic phase since it has the smallest porosity. The representations are used to calculate distributions of the Gaussian curvature and 2 H-NMR bandshapes for C(P), C(D), S, C(Y) and F-RD surfaces.

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X-ray Structure of Bacteriorhodopsin at 2.5 Angstroms from Microcrystals Grown in Lipidic Cubic Phases

Cited by 884 publications

References 43 publications

Membrane protein folding on the example of outer membrane protein A of Escherichia coli

Membrane protein folding on the example of outer membrane protein A of Escherichia coli

Stability of Inverse Bicontinuous Cubic Phases in Lipid-Water Mixtures

Systematic approach to bicontinuous cubic phases in ternary amphiphilic systems

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