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Teh WK, Ding Y, Gubellini F, Filloux A, Poyart C, Givskov M, Dramsi S. Characterization of TelE, a T7SS LXG Effector Exhibiting a Conserved C-Terminal Glycine Zipper Motif Required for Toxicity. Microbiol Spectr 2023; 11:e0148123. [PMID: 37432124 PMCID: PMC10434224 DOI: 10.1128/spectrum.01481-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 06/22/2023] [Indexed: 07/12/2023] Open
Abstract
Streptococcus gallolyticus subsp. gallolyticus (SGG) is an opportunistic bacterial pathogen strongly associated with colorectal cancer. Here, through comparative genomics analysis, we demonstrated that the genetic locus encoding the type VIIb secretion system (T7SSb) machinery is uniquely present in SGG in two different arrangements. SGG UCN34 carrying the most prevalent T7SSb genetic arrangement was chosen as the reference strain. To identify the effectors secreted by this secretion system, we inactivated the essC gene encoding the motor of this machinery. A comparison of the proteins secreted by UCN34 wild type and its isogenic ΔessC mutant revealed six T7SSb effector proteins, including the expected WXG effector EsxA and three LXG-containing proteins. In this work, we characterized an LXG-family toxin named herein TelE promoting the loss of membrane integrity. Seven homologs of TelE harboring a conserved glycine zipper motif at the C terminus were identified in different SGG isolates. Scanning mutagenesis of this motif showed that the glycine residue at position 470 was crucial for TelE membrane destabilization activity. TelE activity was antagonized by a small protein TipE belonging to the DUF5085 family. Overall, we report herein a unique SGG T7SSb effector exhibiting a toxic activity against nonimmune bacteria. IMPORTANCE In this study, 38 clinical isolates of Streptococcus gallolyticus subsp. gallolyticus (SGG) were sequenced and a genetic locus encoding the type VIIb secretion system (T7SSb) was found conserved and absent from 16 genomes of the closely related S. gallolyticus subsp. pasteurianus (SGP). The T7SSb is a bona fide pathogenicity island. Here, we report that the model organism SGG strain UCN34 secretes six T7SSb effectors. One of the six effectors named TelE displayed a strong toxicity when overexpressed in Escherichia coli. Our results indicate that TelE is probably a pore-forming toxin whose activity can be antagonized by a specific immunity protein named TipE. Overall, we report a unique toxin-immunity protein pair and our data expand the range of effectors secreted through T7SSb.
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Affiliation(s)
- Wooi Keong Teh
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
| | - Yichen Ding
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
| | | | - Alain Filloux
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- Centre for Bacterial Resistance Biology, Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Claire Poyart
- Université de Paris, Assistance Publique Hôpitaux de Paris, Service de Bactériologie, Centre National de Référence des Streptocoques, Groupe Hospitalier Paris Centre site Cochin, Paris, France
| | - Michael Givskov
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- Costerton Biofilm Centre, Department of Immunology and Microbiology, University of Copenhagen, Denmark
| | - Shaynoor Dramsi
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Biology of Gram-positive Pathogens Unit, Paris, France
- Centre National de la Recherche Scientifique (CNRS) UMR2001, Paris, France
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2
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Yang L, Wagner T, Mechaly A, Boyko A, Bruch EM, Megrian D, Gubellini F, Alzari PM, Bellinzoni M. High resolution cryo-EM and crystallographic snapshots of the actinobacterial two-in-one 2-oxoglutarate dehydrogenase. Nat Commun 2023; 14:4851. [PMID: 37563123 PMCID: PMC10415282 DOI: 10.1038/s41467-023-40253-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 07/19/2023] [Indexed: 08/12/2023] Open
Abstract
Actinobacteria possess unique ways to regulate the oxoglutarate metabolic node. Contrary to most organisms in which three enzymes compose the 2-oxoglutarate dehydrogenase complex (ODH), actinobacteria rely on a two-in-one protein (OdhA) in which both the oxidative decarboxylation and succinyl transferase steps are carried out by the same polypeptide. Here we describe high-resolution cryo-EM and crystallographic snapshots of representative enzymes from Mycobacterium smegmatis and Corynebacterium glutamicum, showing that OdhA is an 800-kDa homohexamer that assembles into a three-blade propeller shape. The obligate trimeric and dimeric states of the acyltransferase and dehydrogenase domains, respectively, are critical for maintaining the overall assembly, where both domains interact via subtle readjustments of their interfaces. Complexes obtained with substrate analogues, reaction products and allosteric regulators illustrate how these domains operate. Furthermore, we provide additional insights into the phosphorylation-dependent regulation of this enzymatic machinery by the signalling protein OdhI.
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Affiliation(s)
- Lu Yang
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Unité de Microbiologie Structurale, F-75015, Paris, France
- Wuhan Institute of Biological Products Co. Ltd., Wuhan, 430207, PR China
| | - Tristan Wagner
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Unité de Microbiologie Structurale, F-75015, Paris, France
- Microbial Metabolism Group, Max Planck Institute for Marine Microbiology, Celsiusstraße 1, D-28359, Bremen, Germany
| | - Ariel Mechaly
- Institut Pasteur, Université Paris Cité, Plateforme de Cristallographie, F-75015, Paris, France
| | - Alexandra Boyko
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Unité de Microbiologie Structurale, F-75015, Paris, France
- BostonGene, Yerevan, Armenia
| | - Eduardo M Bruch
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Unité de Microbiologie Structurale, F-75015, Paris, France
- Sanofi, In vitro Biology, Integrated Drug Discovery, 350 Water St, Cambridge, MA, 02141, USA
| | - Daniela Megrian
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Unité de Microbiologie Structurale, F-75015, Paris, France
| | - Francesca Gubellini
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Unité de Microbiologie Structurale, F-75015, Paris, France
| | - Pedro M Alzari
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Unité de Microbiologie Structurale, F-75015, Paris, France
| | - Marco Bellinzoni
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Unité de Microbiologie Structurale, F-75015, Paris, France.
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Perry TN, Souabni H, Rapisarda C, Fronzes R, Giusti F, Popot JL, Zoonens M, Gubellini F. BAmSA: Visualising transmembrane regions in protein complexes using biotinylated amphipols and electron microscopy. Biochimica et Biophysica Acta (BBA) - Biomembranes 2019; 1861:466-477. [DOI: 10.1016/j.bbamem.2018.11.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 11/06/2018] [Accepted: 11/08/2018] [Indexed: 12/30/2022]
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Abstract
Bacterial secretion systems are responsible for releasing macromolecules to the extracellular milieu or directly into other cells. These membrane complexes are associated with pathogenicity and bacterial fitness. Understanding of these large assemblies has exponentially increased in the last few years thanks to electron microscopy. In fact, a revolution in this field has led to breakthroughs in characterizing the structures of secretion systems and other macromolecular machineries so as to obtain high-resolution images of complexes that could not be crystallized. In this review, we give a brief overview of structural advancements in the understanding of secretion systems, focusing in particular on cryo-electron microscopy, whether tomography or single-particle analysis. We describe how such techniques have contributed to knowledge of the mechanism of macromolecule secretion in bacteria and the impact they will have in the future.
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Affiliation(s)
- Chiara Rapisarda
- Structure et Fonction des Nanomachines Bactériennes, Institut Européen de Chimie et Biologie, 33607 Pessac, France; , .,CNRS UMR5234, Université de Bordeaux, 33076 Bordeaux, France
| | - Matteo Tassinari
- Institut Pasteur, Unité de Microbiologie Structurale, 75724 Paris, France; .,CNRS UMR3528, Institut Pasteur, 75015 Paris, France
| | - Francesca Gubellini
- Institut Pasteur, Unité de Microbiologie Structurale, 75724 Paris, France; .,CNRS UMR3528, Institut Pasteur, 75015 Paris, France
| | - Rémi Fronzes
- Structure et Fonction des Nanomachines Bactériennes, Institut Européen de Chimie et Biologie, 33607 Pessac, France; , .,CNRS UMR5234, Université de Bordeaux, 33076 Bordeaux, France
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Diallo A, Foster HR, Gromek KA, Perry TN, Dujeancourt A, Krasteva PV, Gubellini F, Falbel TG, Burton BM, Fronzes R. Bacterial transformation: ComFA is a DNA-dependent ATPase that forms complexes with ComFC and DprA. Mol Microbiol 2017; 105:741-754. [DOI: 10.1111/mmi.13732] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2017] [Indexed: 12/28/2022]
Affiliation(s)
- Amy Diallo
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
- Université Pierre et Marie Curie; Paris France
| | | | | | - Thomas N. Perry
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
| | - Annick Dujeancourt
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
| | - Petya V. Krasteva
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
| | - Francesca Gubellini
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
| | | | | | - Rémi Fronzes
- Institut Pasteur, G5 Groupe Biologie Structurale de la Sécrétion Bactérienne; Paris France
- CNRS, UMR3528, Institut Pasteur; 25-28 rue du Docteur Roux, Paris F-75015 France
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Low HH, Gubellini F, Rivera-Calzada A, Braun N, Connery S, Dujeancourt A, Lu F, Redzej A, Fronzes R, Orlova EV, Waksman G. Structure of a type IV secretion system. Nature 2014; 508:550-553. [PMID: 24670658 DOI: 10.1038/nature13081] [Citation(s) in RCA: 226] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 01/27/2014] [Indexed: 02/08/2023]
Abstract
Bacterial type IV secretion systems translocate virulence factors into eukaryotic cells, distribute genetic material between bacteria and have shown potential as a tool for the genetic modification of human cells. Given the complex choreography of the substrate through the secretion apparatus, the molecular mechanism of the type IV secretion system has proved difficult to dissect in the absence of structural data for the entire machinery. Here we use electron microscopy to reconstruct the type IV secretion system encoded by the Escherichia coli R388 conjugative plasmid. We show that eight proteins assemble in an intricate stoichiometric relationship to form an approximately 3 megadalton nanomachine that spans the entire cell envelope. The structure comprises an outer membrane-associated core complex connected by a central stalk to a substantial inner membrane complex that is dominated by a battery of 12 VirB4 ATPase subunits organized as side-by-side hexameric barrels. Our results show a secretion system with markedly different architecture, and consequently mechanism, to other known bacterial secretion systems.
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Affiliation(s)
- Harry H Low
- Institute of Structural and Molecular Biology, UCL and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Francesca Gubellini
- Institut Pasteur, G5 Biologie structurale de la sécrétion bactérienne and UMR 3528-CNRS, 25 rue du Docteur Roux, 75015 Paris, France
| | - Angel Rivera-Calzada
- Institute of Structural and Molecular Biology, UCL and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Nathalie Braun
- Institute of Structural and Molecular Biology, UCL and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Sarah Connery
- Institute of Structural and Molecular Biology, UCL and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Annick Dujeancourt
- Institut Pasteur, G5 Biologie structurale de la sécrétion bactérienne and UMR 3528-CNRS, 25 rue du Docteur Roux, 75015 Paris, France
| | - Fang Lu
- Institute of Structural and Molecular Biology, UCL and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Adam Redzej
- Institute of Structural and Molecular Biology, UCL and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Rémi Fronzes
- Institut Pasteur, G5 Biologie structurale de la sécrétion bactérienne and UMR 3528-CNRS, 25 rue du Docteur Roux, 75015 Paris, France
| | - Elena V Orlova
- Institute of Structural and Molecular Biology, UCL and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology, UCL and Birkbeck, Malet Street, London, WC1E 7HX, UK
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Gubellini F, Verdon G, Karpowich NK, Luff JD, Boël G, Gauthier N, Handelman SK, Ades SE, Hunt JF. Physiological response to membrane protein overexpression in E. coli. Mol Cell Proteomics 2011; 10:M111.007930. [PMID: 21719796 PMCID: PMC3205863 DOI: 10.1074/mcp.m111.007930] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Overexpression represents a principal bottleneck in structural and functional studies of integral membrane proteins (IMPs). Although E. coli remains the leading organism for convenient and economical protein overexpression, many IMPs exhibit toxicity on induction in this host and give low yields of properly folded protein. Different mechanisms related to membrane biogenesis and IMP folding have been proposed to contribute to these problems, but there is limited understanding of the physical and physiological constraints on IMP overexpression and folding in vivo. Therefore, we used a variety of genetic, genomic, and microscopy techniques to characterize the physiological responses of Escherichia coli MG1655 cells to overexpression of a set of soluble proteins and IMPs, including constructs exhibiting different levels of toxicity and producing different levels of properly folded versus misfolded product on induction. Genetic marker studies coupled with transcriptomic results indicate only minor perturbations in many of the physiological systems implicated in previous studies of IMP biogenesis. Overexpression of either IMPs or soluble proteins tends to block execution of the standard stationary-phase transcriptional program, although these effects are consistently stronger for the IMPs included in our study. However, these perturbations are not an impediment to successful protein overexpression. We present evidence that, at least for the target proteins included in our study, there is no inherent obstacle to IMP overexpression in E. coli at moderate levels suitable for structural studies and that the biochemical and conformational properties of the proteins themselves are the major obstacles to success. Toxicity associated with target protein activity produces selective pressure leading to preferential growth of cells harboring expression-reducing and inactivating mutations, which can produce chemical heterogeneity in the target protein population, potentially contributing to the difficulties encountered in IMP crystallization.
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Affiliation(s)
- Francesca Gubellini
- Department of Biological Sciences, 702A Fairchild Center, MC2434, Columbia University, New York, New York 10027, USA
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Seantier B, Dezi M, Gubellini F, Berquand A, Godefroy C, Dosset P, Lévy D, Milhiet PE. Transfer on hydrophobic substrates and AFM imaging of membrane proteins reconstituted in planar lipid bilayers. J Mol Recognit 2011; 24:461-6. [DOI: 10.1002/jmr.1070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Orelle C, Gubellini F, Durand A, Marco S, Lévy D, Gros P, Di Pietro A, Jault JM. Conformational change induced by ATP binding in the multidrug ATP-binding cassette transporter BmrA. Biochemistry 2008; 47:2404-12. [PMID: 18215075 DOI: 10.1021/bi702303s] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
ATP-binding cassette (ABC) transporters are involved in the transport of a wide variety of substrates, and ATP-driven dimerization of their nucleotide binding domains (NBDs) has been suggested to be one of the most energetic steps of their catalytic cycle. Taking advantage of the propensity of BmrA, a bacterial multidrug resistance ABC transporter, to form stable, highly ordered ring-shaped structures [Chami et al. (2002) J. Mol. Biol. 315, 1075-1085], we show here that addition of ATP in the presence of Mg2+ prevented ring formation or destroyed the previously formed rings. To pinpoint the catalytic step responsible for such an effect, two classes of hydrolysis-deficient mutants were further studied. In contrast to hydrolytically inactive glutamate mutants that behaved essentially as the wild-type, lysine Walker A mutants formed ring-shaped structures even in the presence of ATP-Mg. Although the latter mutants still bound ATP-Mg, and even slowly hydrolyzed it for the K380R mutant, they were most likely unable to undergo a proper NBD dimerization upon ATP-Mg addition. The ATP-driven dimerization step, which was still permitted in glutamate mutants and led to a stable conformation suitable to monitor the growth of 2D crystals, appeared therefore responsible for destabilization of the BmrA ring structures. Our results provide direct visual evidence that the ATP-induced NBD dimerization triggers a conformational change large enough in BmrA to destabilize the rings, which is consistent with the assumption that this step might constitute the "power stroke" for ABC transporters.
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Affiliation(s)
- Cédric Orelle
- Institut de Biologie et Chimie des Protéines, UMR 5086 CNRS-Université de Lyon 1 and IFR 128 BioSciences Gerland-Lyon Sud, 7 passage du Vercors, 69367 Lyon, France
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Busselez J, Cottevieille M, Cuniasse P, Gubellini F, Boisset N, Lévy D. Structural Basis for the PufX-Mediated Dimerization of Bacterial Photosynthetic Core Complexes. Structure 2007; 15:1674-83. [DOI: 10.1016/j.str.2007.09.026] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 09/19/2007] [Accepted: 09/20/2007] [Indexed: 11/26/2022]
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Berquand A, Lévy D, Gubellini F, Le Grimellec C, Milhiet PE. Influence of calcium on direct incorporation of membrane proteins into in-plane lipid bilayer. Ultramicroscopy 2007; 107:928-33. [PMID: 17544216 DOI: 10.1016/j.ultramic.2007.04.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Reconstitution of transmembrane proteins by direct incorporation into supported lipid bilayers (SLBs) is a new method to provide suitable samples for high-resolution atomic force microscopy (AFM) analysis of membrane proteins. First experiments have reported successful incorporation of proteins into detergent-destabilized SLBs. Here, we analyzed by AFM the incorporation of membrane proteins in the presence of calcium, a divalent cation functionally important for several membrane proteins. Using lipid-phase-separated membranes, we first show that calcium strongly stabilizes the SLBs decreasing the insertion of low cmc detergents, dodecyl-beta-maltoside, dodecyl-beta-thiomaltoside, and N-hexadecylphosphocholine (Fos-Choline-16) and further insertion of proteins. However, high yield of protein insertion is recovered in the presence of calcium by increasing the detergent concentration in the solution. These data revealed the importance of the calcium in the structure of SLBs and provided new insights into the mechanism of protein insertion into these model membranes.
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Gubellini F, Francia F, Turina P, Lévy D, Venturoli G, Melandri BA. Heterogeneity of photosynthetic membranes from Rhodobacter capsulatus: size dispersion and ATP synthase distribution. Biochim Biophys Acta 2007; 1767:1340-52. [PMID: 17961501 DOI: 10.1016/j.bbabio.2007.08.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Revised: 08/26/2007] [Accepted: 08/29/2007] [Indexed: 10/22/2022]
Abstract
The density distribution of photosynthetic membrane vesicles (chromatophores) from Rhodobacter capsulatus has been studied by isopicnic centrifugation. The average vesicle diameters, examined by electron microscopy, varied between 61 and 72 nm in different density fractions (70 nm in unfractionated chromatophores). The ATP synthase catalytic activities showed maxima displaced toward the higher density fractions relative to bacteriochlorophyll, resulting in higher specific activities in those fractions (about threefold). The amount of ATP synthase, measured by quantitative Western blotting, paralleled the catalytic activities. The average number of ATP synthases per chromatophore, evaluated on the basis of the Western blotting data and of vesicle density analysis, ranged between 8 and 13 (10 in unfractionated chromatophores). Poisson distribution analysis indicated that the probability of chromatophores devoid of ATP synthase was negligible. The effects of ATP synthase inhibition by efrapeptin on the time course of the transmembrane electric potential (evaluated as carotenoid electrochromic response) and on ATP synthesis were studied comparatively. The ATP produced after a flash and the total charge associated with the proton flow coupled to ATP synthesis were more resistant to efrapeptin than the initial value of the phosphorylating currents, indicating that several ATP synthases are fed by protons from the same vesicle.
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Affiliation(s)
- Francesca Gubellini
- Department of Biology, University of Bologna, Laboratory of Biochemistry and Biophysics, Via Irnerio, 42 I-40126, Bologna, Italy
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Piñol R, Jia L, Gubellini F, Lévy D, Albouy PA, Keller P, Cao A, Li MH. Self-Assembly of PEG-b-Liquid Crystal Polymer: The Role of Smectic Order in the Formation of Nanofibers. Macromolecules 2007. [DOI: 10.1021/ma071064y] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rafael Piñol
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China; and Laboratoire de Physique des Solides, CNRS UMR8502, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Lin Jia
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China; and Laboratoire de Physique des Solides, CNRS UMR8502, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Francesca Gubellini
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China; and Laboratoire de Physique des Solides, CNRS UMR8502, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Daniel Lévy
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China; and Laboratoire de Physique des Solides, CNRS UMR8502, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Pierre-Antoine Albouy
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China; and Laboratoire de Physique des Solides, CNRS UMR8502, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Patrick Keller
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China; and Laboratoire de Physique des Solides, CNRS UMR8502, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Amin Cao
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China; and Laboratoire de Physique des Solides, CNRS UMR8502, Université Paris-Sud, 91405 Orsay Cedex, France
| | - Min-Hui Li
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China; and Laboratoire de Physique des Solides, CNRS UMR8502, Université Paris-Sud, 91405 Orsay Cedex, France
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Gubellini F, Francia F, Busselez J, Venturoli G, Lévy D. Functional and structural analysis of the photosynthetic apparatus of Rhodobacter veldkampii. Biochemistry 2006; 45:10512-20. [PMID: 16939203 DOI: 10.1021/bi0610000] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the widely studied purple bacterium Rhodobacter sphaeroides, a small transmembrane protein, named PufX, is required for photosynthetic growth and is involved in the supramolecular dimeric organization of the core complex. We performed a structural and functional analysis of the photosynthetic apparatus of Rhodobacter veldkampii, a related species which evolved independently. Time-resolved optical spectroscopy of R. veldkampii chromatophores showed that the reaction center shares with R. sphaeroides spectral and redox properties and interacts with a cytochrome bc(1) complex through a Q-cycle mechanism. Kinetic analysis of flash-induced cytochrome b(561) reduction indicated a fast delivery of the reduced quinol produced by the reaction center to the cytochrome bc(1) complex. A core complex, along with two light-harvesting LH2 complexes significantly different in size, was purified and analyzed by sedimentation, size exclusion chromatography, mass spectroscopy, and electron microscopy. A PufX subunit identified by MALDI-TOF was found to be associated with the core complex. However, as shown by sedimentation and single-particle analysis by electron microscopy, the core complex is monomeric, suggesting that in R. veldkampii, PufX is involved in the photosynthetic growth but is unable to induce the dimerization of the core complex.
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Affiliation(s)
- Francesca Gubellini
- Institut Curie, UMR-CNRS 168 and LRC-CEA 34V, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
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Yang J, Piñol R, Gubellini F, Lévy D, Albouy PA, Keller P, Li MH. Formation of polymer vesicles by liquid crystal amphiphilic block copolymers. Langmuir 2006; 22:7907-11. [PMID: 16922582 DOI: 10.1021/la061436g] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We report the formation of polymer vesicles (or polymersomes) by a new class of amphiphilic block copolymers in which the hydrophobic block is a side-on nematic liquid crystal polymer. Two series of these block copolymers, named PEG-b-PA444 and PEG-b-PMAazo444, with different hydrophilic/hydrophobic ratios were synthesized and characterized in detail. Polymersomes and nanotubes were formed by adding water into a solution of copolymers in dioxane. Polymersomes in water were finally obtained by dialyzing the resulting mixture against water. These self-assemblies have been studied by classical TEM and cryo-TEM. For the PEG-b-PA444 series, polymersomes were observed for hydrophilic/hydrophobic ratios ranging from 40/60 to 19/81. For PEG-b-PMAazo444 series, polymersomes were observed for hydrophilic/hydrophobic ratios ranging from 26/74 to 18/82. For a PEG-b-PA444 sample with hydrophilic/hydrophobic ratio equal to 25/75, a tubular morphology with tube diameter of typically 100 nm and tube length of up to 10 mum was also observed together with polymersomes during addition of water into the polymer solution in dioxane.
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Affiliation(s)
- Jing Yang
- Institut Curie, CNRS UMR168, Laboratoire Physico-Chimie Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France
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Milhiet PE, Gubellini F, Berquand A, Dosset P, Rigaud JL, Le Grimellec C, Lévy D. High-resolution AFM of membrane proteins directly incorporated at high density in planar lipid bilayer. Biophys J 2006; 91:3268-75. [PMID: 16905620 PMCID: PMC1614478 DOI: 10.1529/biophysj.106.087791] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The heterologous expression and purification of membrane proteins represent major limitations for their functional and structural analysis. Here we describe a new method of incorporation of transmembrane proteins in planar lipid bilayer starting from 1 pmol of solubilized proteins. The principle relies on the direct incorporation of solubilized proteins into a preformed planar lipid bilayer destabilized by dodecyl-beta-maltoside or dodecyl-beta-thiomaltoside, two detergents widely used in membrane biochemistry. Successful incorporations are reported at 20 degrees C and at 4 degrees C with three bacterial photosynthetic multi-subunit membrane proteins. Height measurements by atomic force microscopy (AFM) of the extramembraneous domains protruding from the bilayer demonstrate that proteins are unidirectionally incorporated within the lipid bilayer through their more hydrophobic domains. Proteins are incorporated at high density into the bilayer and on incubation diffuse and segregate into protein close-packing areas. The high protein density allows high-resolution AFM topographs to be recorded and protein subunits organization delineated. This approach provides an alternative experimental platform to the classical methods of two-dimensional crystallization of membrane proteins for the structural analysis by AFM. Furthermore, the versatility and simplicity of the method are important intrinsic properties for the conception of biosensors and nanobiomaterials involving membrane proteins.
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Affiliation(s)
- Pierre-Emmanuel Milhiet
- Centre de Biochimie Structurale, Groupe Nanostructures et Complexes Membranaires, UMR 554 INSERM, UMR 5048 CNRS, Montpellier, France
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Turina P, Giovannini D, Gubellini F, Melandri BA. Physiological ligands ADP and Pi modulate the degree of intrinsic coupling in the ATP synthase of the photosynthetic bacterium Rhodobacter capsulatus. Biochemistry 2004; 43:11126-34. [PMID: 15323572 DOI: 10.1021/bi048975+] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The proton-pumping and the ATP hydrolysis activities of the ATP synthase of Rhodobacter capsulatus have been compared as a function of the ADP and P(i) concentrations. The proton pumping was measured either with the transmembrane pH difference probe, 9-amino-6-chloro-2-methoxyacridine, or with the transmembrane electric potential difference probe, bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol, obtaining consistent results. The comparison indicates that an intrinsic uncoupling of ATP synthase is induced when the concentration of either ligand is decreased. The half-maximal effect was found in the submicromolar range for ADP and at about 70 microM for P(i). It is proposed that a switch from a partially uncoupled state of ATP synthase to the coupled state is induced by the simultaneous binding of ADP and P(i).
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Affiliation(s)
- Paola Turina
- Department of Biology, Laboratory of Biochemistry and Biophysics, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy.
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