51
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Rathmann C, Schlösser AS, Schiller J, Bogdanov M, Brüser T. Tat transport in Escherichia coli requires zwitterionic phosphatidylethanolamine but no specific negatively charged phospholipid. FEBS Lett 2017; 591:2848-2858. [PMID: 28815570 DOI: 10.1002/1873-3468.12794] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 08/04/2017] [Accepted: 08/09/2017] [Indexed: 02/04/2023]
Abstract
Translocation of folded proteins by the Tat system of Escherichia coli is believed to rely on the presence of phosphatidylethanolamine (PE) and the negatively charged phospholipids cardiolipin (CL) and phosphatidylglycerol (PG). Here, we show that while PE is indeed essential for activity, the Tat system is fully functional in a clsA/clsB/clsC deletion strain lacking CL, and in a pgsA deletion strain lacking both PG and CL during aerobic growth on complex media. In contrast to early studies that relied on strains with reduced lipid levels, this study therefore demonstrates that PG and CL are dispensable for Tat transport. The lack of these lipids may be compensated by other anionic phospholipids such as phosphatidic acid, CDP-diacylglycerol or N-acyl-PE.
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Affiliation(s)
| | | | - Jürgen Schiller
- Institute of Medical Physics and Biophysics, University of Leipzig, Germany
| | - Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, McGovern Medical School, Houston, TX, USA
| | - Thomas Brüser
- Institute of Microbiology, Leibniz University Hannover, Germany
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52
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Musatov A, Sedlák E. Role of cardiolipin in stability of integral membrane proteins. Biochimie 2017; 142:102-111. [PMID: 28842204 DOI: 10.1016/j.biochi.2017.08.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 08/21/2017] [Indexed: 01/13/2023]
Abstract
Cardiolipin (CL) is a unique phospholipid with a dimeric structure having four acyl chains and two phosphate groups found almost exclusively in certain membranes of bacteria and of mitochondria of eukaryotes. CL interacts with numerous proteins and has been implicated in function and stabilization of several integral membrane proteins (IMPs). While both functional and stabilization roles of CL in IMPs has been generally acknowledged, there are, in fact, only limited number of quantitative analysis that support this function of CL. This is likely caused by relatively complex determination of parameters characterizing stability of IMPs and particularly intricate assessment of role of specific phospholipids such as CL in IMPs stability. This review aims to summarize quantitative findings regarding stabilization role of CL in IMPs reported up to now.
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Affiliation(s)
- Andrej Musatov
- Department of Biophysics, Institute of Experimental Physics Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia.
| | - Erik Sedlák
- Centre for Interdisciplinary Biosciences, P.J. Šafárik University, Jesenná 5, 040 01 Košice, Slovakia.
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53
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Hwang Fu YH, Huang WYC, Shen K, Groves JT, Miller T, Shan SO. Two-step membrane binding by the bacterial SRP receptor enable efficient and accurate Co-translational protein targeting. eLife 2017; 6. [PMID: 28753124 PMCID: PMC5533587 DOI: 10.7554/elife.25885] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Accepted: 06/28/2017] [Indexed: 01/25/2023] Open
Abstract
The signal recognition particle (SRP) delivers ~30% of the proteome to the eukaryotic endoplasmic reticulum, or the bacterial plasma membrane. The precise mechanism by which the bacterial SRP receptor, FtsY, interacts with and is regulated at the target membrane remain unclear. Here, quantitative analysis of FtsY-lipid interactions at single-molecule resolution revealed a two-step mechanism in which FtsY initially contacts membrane via a Dynamic mode, followed by an SRP-induced conformational transition to a Stable mode that activates FtsY for downstream steps. Importantly, mutational analyses revealed extensive auto-inhibitory mechanisms that prevent free FtsY from engaging membrane in the Stable mode; an engineered FtsY pre-organized into the Stable mode led to indiscriminate targeting in vitro and disrupted FtsY function in vivo. Our results show that the two-step lipid-binding mechanism uncouples the membrane association of FtsY from its conformational activation, thus optimizing the balance between the efficiency and fidelity of co-translational protein targeting. DOI:http://dx.doi.org/10.7554/eLife.25885.001
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Affiliation(s)
- Yu-Hsien Hwang Fu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - William Y C Huang
- Department of Chemistry, University of California at Berkeley, Berkeley, United States
| | - Kuang Shen
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Jay T Groves
- Department of Chemistry, University of California at Berkeley, Berkeley, United States
| | - Thomas Miller
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
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54
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Lopalco P, Stahl J, Annese C, Averhoff B, Corcelli A. Identification of unique cardiolipin and monolysocardiolipin species in Acinetobacter baumannii. Sci Rep 2017; 7:2972. [PMID: 28592862 PMCID: PMC5462836 DOI: 10.1038/s41598-017-03214-w] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 04/20/2017] [Indexed: 01/05/2023] Open
Abstract
Acidic glycerophospholipids play an important role in determining the resistance of Gram-negative bacteria to stress conditions and antibiotics. Acinetobacter baumannii, an opportunistic human pathogen which is responsible for an increasing number of nosocomial infections, exhibits broad antibiotic resistances. Here lipids of A. baumannii have been analyzed by combined MALDI-TOF/MS and TLC analyses; in addition GC-MS analyses of fatty acid methyl esters released by methanolysis of membrane phospholipids have been performed. The main glycerophospholipids are phosphatidylethanolamine, phosphatidylglycerol, acyl-phosphatidylglycerol and cardiolipin together with monolysocardiolipin, a lysophospholipid only rarely detected in bacterial membranes. The major acyl chains in the phospholipids are C16:0 and C18:1, plus minor amounts of short chain fatty acids. The structures of the cardiolipin and monolysocardiolipin have been elucidated by post source decay mass spectrometry analysis. A large variety of cardiolipin and monolysocardiolipin species were found in A. baumannii. Similar lysocardiolipin levels were found in the two clinical strains A. baumannii ATCC19606T and AYE whereas in the nonpathogenic strain Acinetobacter baylyi ADP1 lysocardiolipin levels were highly reduced.
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Affiliation(s)
- Patrizia Lopalco
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Julia Stahl
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Goethe-University Frankfurt am Main, Frankfurt, Germany
| | - Cosimo Annese
- Italian National Council for Research - Institute for the Chemistry of OrganoMetallic Compounds (CNR-ICCOM), Bari, Italy
| | - Beate Averhoff
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Goethe-University Frankfurt am Main, Frankfurt, Germany
| | - Angela Corcelli
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy. .,Italian National Council for Research - Institute for Chemical-Physical Processes (CNR- IPCF), Bari, Italy.
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55
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Abstract
The insertion and assembly of proteins into the inner membrane of bacteria are crucial for many cellular processes, including cellular respiration, signal transduction, and ion and pH homeostasis. This process requires efficient membrane targeting and insertion of proteins into the lipid bilayer in their correct orientation and proper conformation. Playing center stage in these events are the targeting components, signal recognition particle (SRP) and the SRP receptor FtsY, as well as the insertion components, the Sec translocon and the YidC insertase. Here, we will discuss new insights provided from the recent high-resolution structures of these proteins. In addition, we will review the mechanism by which a variety of proteins with different topologies are inserted into the inner membrane of Gram-negative bacteria. Finally, we report on the energetics of this process and provide information on how membrane insertion occurs in Gram-positive bacteria and Archaea. It should be noted that most of what we know about membrane protein assembly in bacteria is based on studies conducted in Escherichia coli.
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Affiliation(s)
- Andreas Kuhn
- Institute for Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Hans-Georg Koch
- Institute for Biochemistry and Molecular Biology, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany
| | - Ross E Dalbey
- Department of Chemistry, The Ohio State University, Columbus, OH 43210
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56
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Noguchi F, Tanifuji G, Brown MW, Fujikura K, Takishita K. Complex evolution of two types of cardiolipin synthase in the eukaryotic lineage stramenopiles. Mol Phylogenet Evol 2016; 101:133-141. [DOI: 10.1016/j.ympev.2016.05.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 03/29/2016] [Accepted: 05/06/2016] [Indexed: 02/06/2023]
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57
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Collinson I, Corey RA, Allen WJ. Channel crossing: how are proteins shipped across the bacterial plasma membrane? Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0025. [PMID: 26370937 PMCID: PMC4632601 DOI: 10.1098/rstb.2015.0025] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The structure of the first protein-conducting channel was determined more than a decade ago. Today, we are still puzzled by the outstanding problem of protein translocation—the dynamic mechanism underlying the consignment of proteins across and into membranes. This review is an attempt to summarize and understand the energy transducing capabilities of protein-translocating machines, with emphasis on bacterial systems: how polypeptides make headway against the lipid bilayer and how the process is coupled to the free energy associated with ATP hydrolysis and the transmembrane protein motive force. In order to explore how cargo is driven across the membrane, the known structures of the protein-translocation machines are set out against the background of the historic literature, and in the light of experiments conducted in their wake. The paper will focus on the bacterial general secretory (Sec) pathway (SecY-complex), and its eukaryotic counterpart (Sec61-complex), which ferry proteins across the membrane in an unfolded state, as well as the unrelated Tat system that assembles bespoke channels for the export of folded proteins.
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Affiliation(s)
- Ian Collinson
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Robin A Corey
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - William J Allen
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
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58
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Dajkovic A, Hinde E, MacKichan C, Carballido-Lopez R. Dynamic Organization of SecA and SecY Secretion Complexes in the B. subtilis Membrane. PLoS One 2016; 11:e0157899. [PMID: 27336478 PMCID: PMC4918944 DOI: 10.1371/journal.pone.0157899] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 06/07/2016] [Indexed: 12/21/2022] Open
Abstract
In prokaryotes, about one third of cellular proteins are translocated across the plasma membrane or inserted into it by concerted action of the cytoplasmic ATPase SecA and the universally conserved SecYEG heterotrimeric polypeptide-translocating pore. Secretion complexes have been reported to localize in specific subcellular sites in Bacillus subtilis. In this work, we used a combination of total internal reflection microscopy, scanning fluorescence correlation spectroscopy, and pair correlation function to study the localization and dynamics of SecA and SecY in growing Bacillus subtilis cells. Both SecA and SecY localized in transient and dynamic foci in the cytoplasmic membrane, which displayed no higher-level organization in helices. Foci of SecA and SecY were in constant flux with freely diffusing SecA and SecY molecules. Scanning FCS confirmed the existence of populations of cellular SecA and SecY molecules with a wide range of diffusion coefficients. Diffusion of SecY as an uncomplexed molecular species was short-lived and only local while SecY complexed with its protein partners traversed distances of over half a micrometer in the cell.
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Affiliation(s)
- Alex Dajkovic
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
- * E-mail:
| | - Elizabeth Hinde
- School of Medical Sciences, University of New South Wales, Sydney, Australia 2052
| | - Calum MacKichan
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
| | - Rut Carballido-Lopez
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
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59
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Lin TY, Weibel DB. Organization and function of anionic phospholipids in bacteria. Appl Microbiol Biotechnol 2016; 100:4255-67. [PMID: 27026177 DOI: 10.1007/s00253-016-7468-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 03/04/2016] [Accepted: 03/08/2016] [Indexed: 11/25/2022]
Abstract
In addition to playing a central role as a permeability barrier for controlling the diffusion of molecules and ions in and out of bacterial cells, phospholipid (PL) membranes regulate the spatial and temporal position and function of membrane proteins that play an essential role in a variety of cellular functions. Based on the very large number of membrane-associated proteins encoded in genomes, an understanding of the role of PLs may be central to understanding bacterial cell biology. This area of microbiology has received considerable attention over the past two decades, and the local enrichment of anionic PLs has emerged as a candidate mechanism for biomolecular organization in bacterial cells. In this review, we summarize the current understanding of anionic PLs in bacteria, including their biosynthesis, subcellular localization, and physiological relevance, discuss evidence and mechanisms for enriching anionic PLs in membranes, and conclude with an assessment of future directions for this area of bacterial biochemistry, biophysics, and cell biology.
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Affiliation(s)
- Ti-Yu Lin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Douglas B Weibel
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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60
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Corey RA, Allen WJ, Komar J, Masiulis S, Menzies S, Robson A, Collinson I. Unlocking the Bacterial SecY Translocon. Structure 2016; 24:518-527. [PMID: 26973090 PMCID: PMC4826270 DOI: 10.1016/j.str.2016.02.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 01/26/2016] [Accepted: 02/05/2016] [Indexed: 11/25/2022]
Abstract
The Sec translocon performs protein secretion and membrane protein insertion at the plasma membrane of bacteria and archaea (SecYEG/β), and the endoplasmic reticular membrane of eukaryotes (Sec61). Despite numerous structures of the complex, the mechanism underlying translocation of pre-proteins, driven by the ATPase SecA in bacteria, remains unresolved. Here we present a series of biochemical and computational analyses exploring the consequences of signal sequence binding to SecYEG. The data demonstrate that a signal sequence-induced movement of transmembrane helix 7 unlocks the translocon and that this conformational change is communicated to the cytoplasmic faces of SecY and SecE, involved in SecA binding. Our findings progress the current understanding of the dynamic action of the translocon during the translocation initiation process. The results suggest that the converging effects of the signal sequence and SecA at the cytoplasmic face of SecYEG are decisive for the intercalation and translocation of pre-protein through the SecY channel. Validation of previously observed signal sequence-induced “unlocking” of SecYEG Conformational changes upon SecYEG unlocking are relayed to SecA binding site Unlocking the translocon perturbs the interaction between SecY and SecE Conformational changes distinct between secretion and membrane protein insertion
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Affiliation(s)
- Robin A Corey
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - William J Allen
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Joanna Komar
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Simonas Masiulis
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Sam Menzies
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Alice Robson
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Ian Collinson
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
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61
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Kuhn P, Draycheva A, Vogt A, Petriman NA, Sturm L, Drepper F, Warscheid B, Wintermeyer W, Koch HG. Ribosome binding induces repositioning of the signal recognition particle receptor on the translocon. J Cell Biol 2016; 211:91-104. [PMID: 26459600 PMCID: PMC4602035 DOI: 10.1083/jcb.201502103] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The cotranslational transfer of nascent membrane proteins to the SecYEG translocon is facilitated by a reorientation of the SecY-bound signal recognition particle (SRP) receptor, FtsY, which accompanies the formation of a quaternary targeting complex consisting of SecYEG, FtsY, SRP, and the ribosome. Cotranslational protein targeting delivers proteins to the bacterial cytoplasmic membrane or to the eukaryotic endoplasmic reticulum membrane. The signal recognition particle (SRP) binds to signal sequences emerging from the ribosomal tunnel and targets the ribosome-nascent-chain complex (RNC) to the SRP receptor, termed FtsY in bacteria. FtsY interacts with the fifth cytosolic loop of SecY in the SecYEG translocon, but the functional role of the interaction is unclear. By using photo-cross-linking and fluorescence resonance energy transfer measurements, we show that FtsY–SecY complex formation is guanosine triphosphate independent but requires a phospholipid environment. Binding of an SRP–RNC complex exposing a hydrophobic transmembrane segment induces a rearrangement of the SecY–FtsY complex, which allows the subsequent contact between SecY and ribosomal protein uL23. These results suggest that direct RNC transfer to the translocon is guided by the interaction between SRP and translocon-bound FtsY in a quaternary targeting complex.
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Affiliation(s)
- Patrick Kuhn
- Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Albena Draycheva
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Andreas Vogt
- Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Narcis-Adrian Petriman
- Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Lukas Sturm
- Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Friedel Drepper
- Department of Biochemistry and Functional Proteomics, Faculty of Biology and BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Bettina Warscheid
- Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Department of Biochemistry and Functional Proteomics, Faculty of Biology and BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Wolfgang Wintermeyer
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Hans-Georg Koch
- Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
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62
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Subramani S, Perdreau-Dahl H, Morth JP. The magnesium transporter A is activated by cardiolipin and is highly sensitive to free magnesium in vitro. eLife 2016; 5. [PMID: 26780187 PMCID: PMC4758953 DOI: 10.7554/elife.11407] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 01/16/2016] [Indexed: 01/19/2023] Open
Abstract
The magnesium transporter A (MgtA) is a specialized P-type ATPase, believed to import Mg2+ into the cytoplasm. In Salmonella typhimurium and Escherichia coli, the virulence determining two-component system PhoQ/PhoP regulates the transcription of mgtA gene by sensing Mg2+ concentrations in the periplasm. However, the factors that affect MgtA function are not known. This study demonstrates, for the first time, that MgtA is highly dependent on anionic phospholipids and in particular, cardiolipin. Colocalization studies confirm that MgtA is found in the cardiolipin lipid domains in the membrane. The head group of cardiolipin plays major role in activation of MgtA suggesting that cardiolipin may act as a Mg2+ chaperone for MgtA. We further show that MgtA is highly sensitive to free Mg2+ (Mg2+free) levels in the solution. MgtA is activated when the Mg2+free concentration is reduced below 10 μM and is strongly inhibited above 1 mM, indicating that Mg2+free acts as product inhibitor. Combined, our findings conclude that MgtA may act as a sensor as well as a transporter of Mg2+. DOI:http://dx.doi.org/10.7554/eLife.11407.001 Magnesium is an essential element for living cells, meaning that organisms from bacteria to humans need magnesium to survive. All cells are surrounded by a membrane made of fatty molecules called lipids, which is also embedded with proteins. Magnesium, like other metal ions, is transported inside cells across the cell’s membrane by specific membrane proteins. A species of gut bacteria called E. coli has two separate magnesium transport systems: one that works at high concentrations of magnesium and one at lower concentrations. The latter system involves a membrane protein called magnesium transporter A (or MgtA for short), which works like a molecular pump. However, it was not known exactly how this transporter was affected by magnesium nor how sensitive it was to this divalent metal ion. It was also unclear whether MgtA worked alone in the bacterial membrane or if it worked in conjunction with other molecules. Now Subramani et al. have managed to show that MgtA can sense magnesium ions down to micromolar concentrations, which is the equivalent to a pinch (1 gram) of magnesium salt in 10,000 liters of water. The experiments also showed that this detection system depended on a specific lipid molecule in the membrane called cardiolipin. MgtA and cardiolipin were found together in the membrane of living E. coli suggesting that the two do indeed work together. The discovery that a membrane transporter that pumps ions needs cardiolipin to work suggests that cells could indirectly control the movement of ions by changing the levels of specific lipids in their membranes. Subramani et al. now hope to use techniques, such as X-ray crystallography, to visualize how magnesium and cardiolipin bind to MtgA and explore how the three molecules work together as a complete system. Information about these interactions could in the future help researchers understand how these bacteria try to protect themself in the hostile environment in the human gut or cells of the immune systems. Further studies of this system could be used to develop biological sensors for magnesium or to design antibiotics that interfere with the magnesium transporter to treat bacterial infections. DOI:http://dx.doi.org/10.7554/eLife.11407.002
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Affiliation(s)
- Saranya Subramani
- Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway
| | - Harmonie Perdreau-Dahl
- Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway.,Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
| | - Jens Preben Morth
- Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway.,Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
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63
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Zheng Z, Blum A, Banerjee T, Wang Q, Dantis V, Oliver D. Determination of the Oligomeric State of SecYEG Protein Secretion Channel Complex Using in Vivo Photo- and Disulfide Cross-linking. J Biol Chem 2016; 291:5997-6010. [PMID: 26747607 DOI: 10.1074/jbc.m115.694844] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Indexed: 11/06/2022] Open
Abstract
SecYEG protein of bacteria or Sec61αβγ of eukaryotes is a universally conserved heterotrimeric protein channel complex that accommodates the partitioning of membrane proteins into the lipid bilayer as well as the secretion of proteins to the trans side of the plasma or endoplasmic reticular membrane, respectively. SecYEG function is facilitated by cytosolic partners, mainly a nascent chain-ribosome complex or the SecA ATPase motor protein. Extensive efforts utilizing both biochemical and biophysical approaches have been made to determine whether SecYEG functions as a monomer or a dimer, but such approaches have often generated conflicting results. Here we have employed site-specific in vivo photo-cross-linking or cysteine cross-linking, along with co-immunoprecipitation or SecA footprinting techniques to readdress this issue. Our findings show that the SecY dimer to monomer ratio is relatively constant regardless of whether translocons are actively engaged with protein substrate or not. Under the former conditions the SecY dimer can be captured associated with a translocon-jammed substrate, indicative of SecY dimer function. Furthermore, SecA ATPase can be cross-linked to two copies of SecY when the complex contains a translocation intermediate. Collectively, our results suggest that SecYEG dimers are functional units of the translocon.
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Affiliation(s)
- Zeliang Zheng
- From the Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459
| | - Amy Blum
- From the Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459
| | - Tithi Banerjee
- From the Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459
| | - Qianyu Wang
- From the Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459
| | - Virginia Dantis
- From the Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459
| | - Donald Oliver
- From the Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459.
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64
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Enzyme function is regulated by its localization. Comput Biol Chem 2015; 59 Pt B:113-22. [DOI: 10.1016/j.compbiolchem.2015.08.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 08/04/2015] [Accepted: 08/05/2015] [Indexed: 11/21/2022]
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65
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Prabudiansyah I, Kusters I, Caforio A, Driessen AJ. Characterization of the annular lipid shell of the Sec translocon. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2050-6. [DOI: 10.1016/j.bbamem.2015.06.024] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 06/24/2015] [Accepted: 06/26/2015] [Indexed: 11/16/2022]
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Kopečná J, Pilný J, Krynická V, Tomčala A, Kis M, Gombos Z, Komenda J, Sobotka R. Lack of Phosphatidylglycerol Inhibits Chlorophyll Biosynthesis at Multiple Sites and Limits Chlorophyllide Reutilization in Synechocystis sp. Strain PCC 6803. PLANT PHYSIOLOGY 2015; 169:1307-17. [PMID: 26269547 PMCID: PMC4587476 DOI: 10.1104/pp.15.01150] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 08/11/2015] [Indexed: 05/20/2023]
Abstract
The negatively charged lipid phosphatidylglycerol (PG) constitutes up to 10% of total lipids in photosynthetic membranes, and its deprivation in cyanobacteria is accompanied by chlorophyll (Chl) depletion. Indeed, radioactive labeling of the PG-depleted ΔpgsA mutant of Synechocystis sp. strain PCC 6803, which is not able to synthesize PG, proved the inhibition of Chl biosynthesis caused by restriction on the formation of 5-aminolevulinic acid and protochlorophyllide. Although the mutant accumulated chlorophyllide, the last Chl precursor, we showed that it originated from dephytylation of existing Chl and not from the block in the Chl biosynthesis. The lack of de novo-produced Chl under PG depletion was accompanied by a significantly weakened biosynthesis of both monomeric and trimeric photosystem I (PSI) complexes, although the decrease in cellular content was manifested only for the trimeric form. However, our analysis of ΔpgsA mutant, which lacked trimeric PSI because of the absence of the PsaL subunit, suggested that the virtual stability of monomeric PSI is a result of disintegration of PSI trimers. Interestingly, the loss of trimeric PSI was accompanied by accumulation of monomeric PSI associated with the newly synthesized CP43 subunit of photosystem II. We conclude that the absence of PG results in the inhibition of Chl biosynthetic pathway, which impairs synthesis of PSI, despite the accumulation of chlorophyllide released from the degraded Chl proteins. Based on the knowledge about the role of PG in prokaryotes, we hypothesize that the synthesis of Chl and PSI complexes are colocated in a membrane microdomain requiring PG for integrity.
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Affiliation(s)
- Jana Kopečná
- Institute of Microbiology, Centre Algatech, 37981 Trebon, Czech Republic (J.Kop., J.P., V.K., J.Kom., R.S.);Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic (V.K., A.T., J.Kom., R.S.);Biology Centre, Institute of Parasitology, 37005 Ceske Budejovice, Czech Republic (A.T.); andInstitute of Plant Biology, Biological Research Centre, H-6701 Szeged, Hungary (M.K., Z.G.)
| | - Jan Pilný
- Institute of Microbiology, Centre Algatech, 37981 Trebon, Czech Republic (J.Kop., J.P., V.K., J.Kom., R.S.);Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic (V.K., A.T., J.Kom., R.S.);Biology Centre, Institute of Parasitology, 37005 Ceske Budejovice, Czech Republic (A.T.); andInstitute of Plant Biology, Biological Research Centre, H-6701 Szeged, Hungary (M.K., Z.G.)
| | - Vendula Krynická
- Institute of Microbiology, Centre Algatech, 37981 Trebon, Czech Republic (J.Kop., J.P., V.K., J.Kom., R.S.);Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic (V.K., A.T., J.Kom., R.S.);Biology Centre, Institute of Parasitology, 37005 Ceske Budejovice, Czech Republic (A.T.); andInstitute of Plant Biology, Biological Research Centre, H-6701 Szeged, Hungary (M.K., Z.G.)
| | - Aleš Tomčala
- Institute of Microbiology, Centre Algatech, 37981 Trebon, Czech Republic (J.Kop., J.P., V.K., J.Kom., R.S.);Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic (V.K., A.T., J.Kom., R.S.);Biology Centre, Institute of Parasitology, 37005 Ceske Budejovice, Czech Republic (A.T.); andInstitute of Plant Biology, Biological Research Centre, H-6701 Szeged, Hungary (M.K., Z.G.)
| | - Mihály Kis
- Institute of Microbiology, Centre Algatech, 37981 Trebon, Czech Republic (J.Kop., J.P., V.K., J.Kom., R.S.);Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic (V.K., A.T., J.Kom., R.S.);Biology Centre, Institute of Parasitology, 37005 Ceske Budejovice, Czech Republic (A.T.); andInstitute of Plant Biology, Biological Research Centre, H-6701 Szeged, Hungary (M.K., Z.G.)
| | - Zoltan Gombos
- Institute of Microbiology, Centre Algatech, 37981 Trebon, Czech Republic (J.Kop., J.P., V.K., J.Kom., R.S.);Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic (V.K., A.T., J.Kom., R.S.);Biology Centre, Institute of Parasitology, 37005 Ceske Budejovice, Czech Republic (A.T.); andInstitute of Plant Biology, Biological Research Centre, H-6701 Szeged, Hungary (M.K., Z.G.)
| | - Josef Komenda
- Institute of Microbiology, Centre Algatech, 37981 Trebon, Czech Republic (J.Kop., J.P., V.K., J.Kom., R.S.);Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic (V.K., A.T., J.Kom., R.S.);Biology Centre, Institute of Parasitology, 37005 Ceske Budejovice, Czech Republic (A.T.); andInstitute of Plant Biology, Biological Research Centre, H-6701 Szeged, Hungary (M.K., Z.G.)
| | - Roman Sobotka
- Institute of Microbiology, Centre Algatech, 37981 Trebon, Czech Republic (J.Kop., J.P., V.K., J.Kom., R.S.);Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic (V.K., A.T., J.Kom., R.S.);Biology Centre, Institute of Parasitology, 37005 Ceske Budejovice, Czech Republic (A.T.); andInstitute of Plant Biology, Biological Research Centre, H-6701 Szeged, Hungary (M.K., Z.G.)
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A Cardiolipin-Deficient Mutant of Rhodobacter sphaeroides Has an Altered Cell Shape and Is Impaired in Biofilm Formation. J Bacteriol 2015; 197:3446-55. [PMID: 26283770 DOI: 10.1128/jb.00420-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 08/13/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Cell shape has been suggested to play an important role in the regulation of bacterial attachment to surfaces and the formation of communities associated with surfaces. We found that a cardiolipin synthase (Δcls) mutant of the rod-shaped bacterium Rhodobacter sphaeroides--in which synthesis of the anionic, highly curved phospholipid cardiolipin (CL) is reduced by 90%--produces ellipsoid-shaped cells that are impaired in biofilm formation. Reducing the concentration of CL did not cause significant defects in R. sphaeroides cell growth, swimming motility, lipopolysaccharide and exopolysaccharide production, surface adhesion protein expression, and membrane permeability. Complementation of the CL-deficient mutant by ectopically expressing CL synthase restored cells to their rod shape and increased biofilm formation. Treating R. sphaeroides cells with a low concentration (10 μg/ml) of the small-molecule MreB inhibitor S-(3,4-dichlorobenzyl)isothiourea produced ellipsoid-shaped cells that had no obvious growth defect yet reduced R. sphaeroides biofilm formation. This study demonstrates that CL plays a role in R. sphaeroides cell shape determination, biofilm formation, and the ability of the bacterium to adapt to its environment. IMPORTANCE Membrane composition plays a fundamental role in the adaptation of many bacteria to environmental stress. In this study, we build a new connection between the anionic phospholipid cardiolipin (CL) and cellular adaptation in Rhodobacter sphaeroides. We demonstrate that CL plays a role in the regulation of R. sphaeroides morphology and is important for the ability of this bacterium to form biofilms. This study correlates CL concentration, cell shape, and biofilm formation and provides the first example of how membrane composition in bacteria alters cell morphology and influences adaptation. This study also provides insight into the potential of phospholipid biosynthesis as a target for new chemical strategies designed to alter or prevent biofilm formation.
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Kagan VE, Tyurina YY, Tyurin VA, Mohammadyani D, Angeli JPF, Baranov SV, Klein-Seetharaman J, Friedlander RM, Mallampalli RK, Conrad M, Bayir H. Cardiolipin signaling mechanisms: collapse of asymmetry and oxidation. Antioxid Redox Signal 2015; 22:1667-80. [PMID: 25566681 PMCID: PMC4486147 DOI: 10.1089/ars.2014.6219] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
SIGNIFICANCE An ancient anionic phospholipid, cardiolipin (CL), ubiquitously present in prokaryotic and eukaryotic membranes, is essential for several structural and functional purposes. RECENT ADVANCES The emerging role of CLs in signaling has become the focus of many studies. CRITICAL ISSUES In this work, we describe two major pathways through which mitochondrial CLs may fulfill the signaling functions via utilization of their (i) asymmetric distribution across membranes and translocations, leading to the surface externalization and (ii) ability to undergo oxidation reactions to yield the signature products recognizable by the executionary machinery of cells. FUTURE DIRECTIONS We present a concept that CLs and their oxidation/hydrolysis products constitute a rich communication language utilized by mitochondria of eukaryotic cells for diversified regulation of cell physiology and metabolism as well as for inter-cellular interactions.
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Affiliation(s)
- Valerian E Kagan
- 1Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania.,2Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania.,3Department of Radiation Oncology, University of Pittsburgh, Pittsburgh, Pennsylvania.,4Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Yulia Y Tyurina
- 1Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Vladimir A Tyurin
- 1Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Dariush Mohammadyani
- 5Department of Bioengineering, Acute Lung Injury Center of Excellence, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jose Pedro Friedmann Angeli
- 6Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Developmental Genetics, Neuherberg, Germany
| | - Sergei V Baranov
- 7Department of Neurosurgery, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Judith Klein-Seetharaman
- 8Division of Metabolic and Vascular Health, Medical School, University of Warwick, Coventry, United Kingdom
| | | | - Rama K Mallampalli
- 9Department of Medicine, Acute Lung Injury Center of Excellence, University of Pittsburgh, and VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania
| | - Marcus Conrad
- 6Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Developmental Genetics, Neuherberg, Germany
| | - Hülya Bayir
- 10Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
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Matsumoto K, Hara H, Fishov I, Mileykovskaya E, Norris V. The membrane: transertion as an organizing principle in membrane heterogeneity. Front Microbiol 2015; 6:572. [PMID: 26124753 PMCID: PMC4464175 DOI: 10.3389/fmicb.2015.00572] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/25/2015] [Indexed: 01/05/2023] Open
Abstract
The bacterial membrane exhibits a significantly heterogeneous distribution of lipids and proteins. This heterogeneity results mainly from lipid-lipid, protein-protein, and lipid-protein associations which are orchestrated by the coupled transcription, translation and insertion of nascent proteins into and through membrane (transertion). Transertion is central not only to the individual assembly and disassembly of large physically linked groups of macromolecules (alias hyperstructures) but also to the interactions between these hyperstructures. We review here these interactions in the context of the processes in Bacillus subtilis and Escherichia coli of nutrient sensing, membrane synthesis, cytoskeletal dynamics, DNA replication, chromosome segregation, and cell division.
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Affiliation(s)
- Kouji Matsumoto
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, SaitamaJapan
| | - Hiroshi Hara
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, SaitamaJapan
| | - Itzhak Fishov
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-ShevaIsrael
| | - Eugenia Mileykovskaya
- Department of Biochemistry and Molecular Biology, University of Texas Medical School at HoustonHouston, TX, USA
| | - Vic Norris
- Laboratory of Microbiology Signals and Microenvironment EA 4312, Department of Science, University of Rouen, Mont-Saint-AignanFrance
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Walter B, Hristou A, Nowaczyk MM, Schünemann D. In vitro reconstitution of co-translational D1 insertion reveals a role of the cpSec-Alb3 translocase and Vipp1 in photosystem II biogenesis. Biochem J 2015; 468:315-24. [PMID: 25803492 DOI: 10.1042/bj20141425] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Photosystem II (PS II) is a multi-subunit complex localized in the thylakoid membrane that performs the light-dependent photosynthetic charge separation. The PS II reaction centre comprises, among others, the D1 protein. De novo synthesis and repair of PS II require efficient mechanisms for transport and insertion of plastid encoded D1 into the thylakoid membrane. To elucidate the process of D1 insertion, we used an in vitro translation system derived from pea chloroplasts to reconstitute the D1 insertion. Thereby, truncated D1 encoding psbA mRNAs lacking a stop codon were translated in the presence of thylakoid membranes and the translation was stalled by addition of chloramphenicol. The generated ribosome nascent chain complexes (RNCs) were tightly associated with the thylakoids. Subsequently, these D1 insertion intermediates were enriched from solubilized thylakoids by sucrose cushion centrifugation. Immunological analyses demonstrated the presence of the cpSec translocase, Alb3, cpFtsY, cpSRP54 and Vipp1 (vesicle-inducing protein in plastids 1) in the enriched D1 insertion intermediates. A complex formation between cpSecY, Alb3, cpFtsY and Vipp1 in thylakoid membranes was shown by gel filtration chromatography, BN (Blue Native)/SDS-PAGE and co-immunoprecipitation experiments. Furthermore, a stimulating effect of recombinant Vipp1 on the formation of a D1 insertion intermediate was observed in vitro. These results suggest a co-operative function of these proteins in D1 insertion.
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Affiliation(s)
- Björn Walter
- *Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Athina Hristou
- *Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Marc M Nowaczyk
- †Plant Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Danja Schünemann
- *Molecular Biology of Plant Organelles, Ruhr-University Bochum, 44780 Bochum, Germany
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Gorczyca M, Korchowiec B, Korchowiec J, Trojan S, Rubio-Magnieto J, Luis SV, Rogalska E. A Study of the Interaction between a Family of Gemini Amphiphilic Pseudopeptides and Model Monomolecular Film Membranes Formed with a Cardiolipin. J Phys Chem B 2015; 119:6668-79. [PMID: 25959677 DOI: 10.1021/acs.jpcb.5b02575] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The interaction between five gemini amphiphilic pseudopeptides (GAPs) differing by the length of the central spacer and a model membrane lipid, 1,3-bis[1,2-dimyristoyl-sn-glycero-3-phospho]-sn-glycerol (cardiolipin) were studied with the aim to evaluate their possible antimicrobial properties. To this end, monomolecular films were formed at the air/water interface with pure cardiolipin or cardiolipin/GAPs mixtures; film properties were determined using surface pressure and surface potential measurements, as well as polarization-modulation infrared reflection-absorption spectroscopy. Moreover, to better understand the GAPs-phospholipid interaction at the molecular level, molecular dynamics simulations were performed. The results obtained indicate that the length of the central spacer has an effect on the interaction of GAPs with cardiolipin and on the properties of the lipid film. The GAPs with the longer linkers can be expected to be useful for biological membrane modification and for possible antimicrobial applications.
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Affiliation(s)
- Marcelina Gorczyca
- †Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland
| | - Beata Korchowiec
- ‡Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland
| | - Jacek Korchowiec
- †Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland
| | - Sonia Trojan
- †Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland
| | - Jenifer Rubio-Magnieto
- §Departamento de Química Inorgánica y Orgánica, Universitat Jaume I, Avda. Sos Baynat, s/n, 12071 Castellón, Spain
| | - Santiago V Luis
- §Departamento de Química Inorgánica y Orgánica, Universitat Jaume I, Avda. Sos Baynat, s/n, 12071 Castellón, Spain
| | - Ewa Rogalska
- ∥Structure et Réactivité des Systèmes Moléculaires Complexes, BP 239, CNRS/Université de Lorraine, 54506 Vandoeuvre-lès-Nancy cedex, France
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Komar J, Botte M, Collinson I, Schaffitzel C, Berger I. ACEMBLing a multiprotein transmembrane complex: the functional SecYEG-SecDF-YajC-YidC Holotranslocon protein secretase/insertase. Methods Enzymol 2015; 556:23-49. [PMID: 25857776 DOI: 10.1016/bs.mie.2014.12.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Membrane proteins constitute about one third of the proteome. The ubiquitous Sec machinery facilitates protein movement across or integration of proteins into the cytoplasmic membrane. In Escherichia coli post- and co-translational targeting pathways converge at the protein-conducting channel, consisting of a central pore, SecYEG, which can recruit accessory domains SecDF-YajC and YidC, to form the holotranslocon (HTL) supercomplex. Detailed analysis of HTL function and architecture remained elusive until recently, largely due to the lack of a purified, recombinant complex. ACEMBL is an advanced DNA recombineering-based expression vector system we developed for producing challenging multiprotein complexes. ACEMBL affords the means to combine multiple expression elements including promoter DNAs, tags, genes of interest, and terminators in a combinatorial manner until optimal multigene expression plasmids are constructed that yield correctly assembled, homogenous, and active multiprotein complex specimens. We utilized ACEMBL for recombinant HTL overproduction. We developed protocols for detergent solubilizing and purifying the HTL. Highly purified complex was then used to reveal HTL function and the interactions between its constituents. HTL activity in protein secretion and membrane protein insertion was analyzed in both the presence and absence of the proton-motive force. Setting up ACEMBL for the assembly of multigene expression constructs that achieve high yields of functional multisubunit membrane protein complex is straightforward. Here, we used ACEMBL for obtaining active HTL supercomplex in high quality and quantity. The concept can likewise be applied to obtain many other assemblies of similar complexity, by overexpression in prokaryotic, and also eukaryotic hosts.
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Affiliation(s)
- Joanna Komar
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Mathieu Botte
- European Molecular Biology Laboratory, Grenoble, France; Unit for Virus Host-Cell Interactions, University of Grenoble Alpes-EMBL-CNRS, Unité mixte de Recherche, Grenoble, France
| | - Ian Collinson
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Christiane Schaffitzel
- School of Biochemistry, University of Bristol, Bristol, United Kingdom; European Molecular Biology Laboratory, Grenoble, France; Unit for Virus Host-Cell Interactions, University of Grenoble Alpes-EMBL-CNRS, Unité mixte de Recherche, Grenoble, France
| | - Imre Berger
- School of Biochemistry, University of Bristol, Bristol, United Kingdom; European Molecular Biology Laboratory, Grenoble, France; Unit for Virus Host-Cell Interactions, University of Grenoble Alpes-EMBL-CNRS, Unité mixte de Recherche, Grenoble, France.
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Kalli AC, Sansom MSP, Reithmeier RAF. Molecular dynamics simulations of the bacterial UraA H+-uracil symporter in lipid bilayers reveal a closed state and a selective interaction with cardiolipin. PLoS Comput Biol 2015; 11:e1004123. [PMID: 25729859 PMCID: PMC4346270 DOI: 10.1371/journal.pcbi.1004123] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 01/09/2015] [Indexed: 11/25/2022] Open
Abstract
The Escherichia coli UraA H+-uracil symporter is a member of the nucleobase/ascorbate transporter (NAT) family of proteins, and is responsible for the proton-driven uptake of uracil. Multiscale molecular dynamics simulations of the UraA symporter in phospholipid bilayers consisting of: 1) 1-palmitoyl 2-oleoyl-phosphatidylcholine (POPC); 2) 1-palmitoyl 2-oleoyl-phosphatidylethanolamine (POPE); and 3) a mixture of 75% POPE, 20% 1-palmitoyl 2-oleoyl-phosphatidylglycerol (POPG); and 5% 1-palmitoyl 2-oleoyl-diphosphatidylglycerol/cardiolipin (CL) to mimic the lipid composition of the bacterial inner membrane, were performed using the MARTINI coarse-grained force field to self-assemble lipids around the crystal structure of this membrane transport protein, followed by atomistic simulations. The overall fold of the protein in lipid bilayers remained similar to the crystal structure in detergent on the timescale of our simulations. Simulations were performed in the absence of uracil, and resulted in a closed state of the transporter, due to relative movement of the gate and core domains. Anionic lipids, including POPG and especially CL, were found to associate with UraA, involving interactions between specific basic residues in loop regions and phosphate oxygens of the CL head group. In particular, three CL binding sites were identified on UraA: two in the inner leaflet and a single site in the outer leaflet. Mutation of basic residues in the binding sites resulted in the loss of CL binding in the simulations. CL may play a role as a “proton trap” that channels protons to and from this transporter within CL-enriched areas of the inner bacterial membrane. Symporters are proteins that are responsible for the co-transport of ions and small molecule solutes across cell membranes. UraA is an example of a symporter, and is responsible for the proton-driven uptake of uracil in bacteria like E. coli. Despite its importance as a member of a large family of nucleobase/ascorbate transporters (NAT) and the existence of structural and functional data, the mechanism by which UraA transports uracil across the bacterial membrane, and in particular the role of its diverse and complex lipid environment in the transport mechanism, remains elusive. In this study, we have used a multiscale computational methodology to examine the dynamics of UraA and to elucidate its interactions with lipids that resemble its native environment in the bacterial inner membrane. Our results demonstrate that negatively-charged lipids in the membrane (phosphatidylglycerol and cardiolipin) associate preferentially with UraA and may play a role in its function. Additionally, our simulations resulted in a closed state of UraA, a likely intermediate in the transport mechanism that may not be readily accessible by experimental methods.
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Affiliation(s)
- Antreas C. Kalli
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- * E-mail:
| | - Mark S. P. Sansom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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Abstract
Cardiolipin (CL) is an anionic phospholipid with a characteristically large curvature and is of growing interest for two primary reasons: (i) it binds to and regulates many peripheral membrane proteins in bacteria and mitochondria, and (ii) it is distributed asymmetrically in rod-shaped cells and is concentrated at the poles and division septum. Despite the growing number of studies of CL, its function in bacteria remains unknown. 10-N-Nonyl acridine orange (NAO) is widely used to image CL in bacteria and mitochondria, as its interaction with CL is reported to produce a characteristic red-shifted fluorescence emission. Using a suite of biophysical techniques, we quantitatively studied the interaction of NAO with anionic phospholipids under physiologically relevant conditions. We found that NAO is promiscuous in its binding and has photophysical properties that are largely insensitive to the structure of diverse anionic phospholipids to which it binds. Being unable to rely solely on NAO to characterize the localization of CL in Escherichia coli cells, we instead used quantitative fluorescence microscopy, mass spectrometry, and mutants deficient in specific classes of anionic phospholipids. We found CL and phosphatidylglycerol (PG) concentrated in the polar regions of E. coli cell membranes; depletion of CL by genetic approaches increased the concentration of PG at the poles. Previous studies suggested that some CL-binding proteins also have a high affinity for PG and display a pattern of cellular localization that is not influenced by depletion of CL. Framed within the context of these previous experiments, our results suggest that PG may play an essential role in bacterial physiology by maintaining the anionic character of polar membranes.
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75
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Santos TMA, Lin TY, Rajendran M, Anderson SM, Weibel DB. Polar localization of Escherichia coli chemoreceptors requires an intact Tol-Pal complex. Mol Microbiol 2014; 92:985-1004. [PMID: 24720726 DOI: 10.1111/mmi.12609] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/05/2014] [Indexed: 11/29/2022]
Abstract
Subcellular biomolecular localization is critical for the metabolic and structural properties of the cell. The functional implications of the spatiotemporal distribution of protein complexes during the bacterial cell cycle have long been acknowledged; however, the molecular mechanisms for generating and maintaining their dynamic localization in bacteria are not completely understood. Here we demonstrate that the trans-envelope Tol-Pal complex, a widely conserved component of the cell envelope of Gram-negative bacteria, is required to maintain the polar positioning of chemoreceptor clusters in Escherichia coli. Localization of the chemoreceptors was independent of phospholipid composition of the membrane and the curvature of the cell wall. Instead, our data indicate that chemoreceptors interact with components of the Tol-Pal complex and that this interaction is required to polarly localize chemoreceptor clusters. We found that disruption of the Tol-Pal complex perturbs the polar localization of chemoreceptors, alters cell motility, and affects chemotaxis. We propose that the E. coli Tol-Pal complex restricts mobility of the chemoreceptor clusters at the cell poles and may be involved in regulatory mechanisms that co-ordinate cell division and segregation of the chemosensory machinery.
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Affiliation(s)
- Thiago M A Santos
- Department of Biochemistry, University of Wisconsin-Madison, 440 Henry Mall, Madison, WI, 53706, USA
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76
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Moser R, Aktas M, Fritz C, Narberhaus F. Discovery of a bifunctional cardiolipin/phosphatidylethanolamine synthase in bacteria. Mol Microbiol 2014; 92:959-72. [DOI: 10.1111/mmi.12603] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/03/2014] [Indexed: 01/22/2023]
Affiliation(s)
- Roman Moser
- Microbial Biology; Ruhr University Bochum; Bochum Germany
| | - Meriyem Aktas
- Microbial Biology; Ruhr University Bochum; Bochum Germany
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Denks K, Vogt A, Sachelaru I, Petriman NA, Kudva R, Koch HG. The Sec translocon mediated protein transport in prokaryotes and eukaryotes. Mol Membr Biol 2014; 31:58-84. [DOI: 10.3109/09687688.2014.907455] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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78
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Membrane protein insertion and proton-motive-force-dependent secretion through the bacterial holo-translocon SecYEG-SecDF-YajC-YidC. Proc Natl Acad Sci U S A 2014; 111:4844-9. [PMID: 24550475 DOI: 10.1073/pnas.1315901111] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The SecY/61 complex forms the protein-channel component of the ubiquitous protein secretion and membrane protein insertion apparatus. The bacterial version SecYEG interacts with the highly conserved YidC and SecDF-YajC subcomplex, which facilitates translocation into and across the membrane. Together, they form the holo-translocon (HTL), which we have successfully overexpressed and purified. In contrast to the homo-dimeric SecYEG, the HTL is a hetero-dimer composed of single copies of SecYEG and SecDF-YajC-YidC. The activities of the HTL differ from the archetypal SecYEG complex. It is more effective in cotranslational insertion of membrane proteins and the posttranslational secretion of a β-barreled outer-membrane protein driven by SecA and ATP becomes much more dependent on the proton-motive force. The activity of the translocating copy of SecYEG may therefore be modulated by association with different accessory subcomplexes: SecYEG (forming SecYEG dimers) or SecDF-YajC-YidC (forming the HTL). This versatility may provide a means to refine the secretion and insertion capabilities according to the substrate. A similar modularity may also be exploited for the translocation or insertion of a wide range of substrates across and into the endoplasmic reticular and mitochondrial membranes of eukaryotes.
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79
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Moser R, Aktas M, Narberhaus F. Phosphatidylcholine biosynthesis inXanthomonas campestrisvia a yeast-like acylation pathway. Mol Microbiol 2014; 91:736-50. [DOI: 10.1111/mmi.12492] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/10/2013] [Indexed: 12/01/2022]
Affiliation(s)
- Roman Moser
- Microbial Biology; Ruhr University Bochum; Bochum Germany
| | - Meriyem Aktas
- Microbial Biology; Ruhr University Bochum; Bochum Germany
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80
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Renner LD, Eswaramoorthy P, Ramamurthi KS, Weibel DB. Studying biomolecule localization by engineering bacterial cell wall curvature. PLoS One 2013; 8:e84143. [PMID: 24391905 PMCID: PMC3877235 DOI: 10.1371/journal.pone.0084143] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 11/12/2013] [Indexed: 11/22/2022] Open
Abstract
In this article we describe two techniques for exploring the relationship between bacterial cell shape and the intracellular organization of proteins. First, we created microchannels in a layer of agarose to reshape live bacterial cells and predictably control their mean cell wall curvature, and quantified the influence of curvature on the localization and distribution of proteins in vivo. Second, we used agarose microchambers to reshape bacteria whose cell wall had been chemically and enzymatically removed. By combining microstructures with different geometries and fluorescence microscopy, we determined the relationship between bacterial shape and the localization for two different membrane-associated proteins: i) the cell-shape related protein MreB of Escherichia coli, which is positioned along the long axis of the rod-shaped cell; and ii) the negative curvature-sensing cell division protein DivIVA of Bacillus subtilis, which is positioned primarily at cell division sites. Our studies of intracellular organization in live cells of E. coli and B. subtilis demonstrate that MreB is largely excluded from areas of high negative curvature, whereas DivIVA localizes preferentially to regions of high negative curvature. These studies highlight a unique approach for studying the relationship between cell shape and intracellular organization in intact, live bacteria.
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Affiliation(s)
- Lars D. Renner
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Technical University Dresden and the Max-Bergmann-Centre for Biomaterials, Dresden, Germany
| | - Prahathees Eswaramoorthy
- National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Kumaran S. Ramamurthi
- National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Douglas B. Weibel
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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81
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Focal targeting by human β-defensin 2 disrupts localized virulence factor assembly sites in Enterococcus faecalis. Proc Natl Acad Sci U S A 2013; 110:20230-5. [PMID: 24191013 DOI: 10.1073/pnas.1319066110] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Virulence factor secretion and assembly occurs at spatially restricted foci in some Gram-positive bacteria. Given the essentiality of the general secretion pathway in bacteria and the contribution of virulence factors to disease progression, the foci that coordinate these processes are attractive antimicrobial targets. In this study, we show in Enterococcus faecalis that SecA and Sortase A, required for the attachment of virulence factors to the cell wall, localize to discrete domains near the septum or nascent septal site as the bacteria proceed through the cell cycle. We also demonstrate that cationic human β-defensins interact with E. faecalis at discrete septal foci, and this exposure disrupts sites of localized secretion and sorting. Modification of anionic lipids by multiple peptide resistance factor, a protein that confers antimicrobial peptide resistance by electrostatic repulsion, renders E. faecalis more resistant to killing by defensins and less susceptible to focal targeting by the cationic antimicrobial peptides. These data suggest a paradigm in which focal targeting by antimicrobial peptides is linked to their killing efficiency and to disruption of virulence factor assembly.
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82
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Saraogi I, Shan SO. Co-translational protein targeting to the bacterial membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:1433-41. [PMID: 24513458 DOI: 10.1016/j.bbamcr.2013.10.013] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Revised: 10/09/2013] [Accepted: 10/16/2013] [Indexed: 12/18/2022]
Abstract
Co-translational protein targeting by the Signal Recognition Particle (SRP) is an essential cellular pathway that couples the synthesis of nascent proteins to their proper cellular localization. The bacterial SRP, which contains the minimal ribonucleoprotein core of this universally conserved targeting machine, has served as a paradigm for understanding the molecular basis of protein localization in all cells. In this review, we highlight recent biochemical and structural insights into the molecular mechanisms by which fundamental challenges faced by protein targeting machineries are met in the SRP pathway. Collectively, these studies elucidate how an essential SRP RNA and two regulatory GTPases in the SRP and SRP receptor (SR) enable this targeting machinery to recognize, sense and respond to its biological effectors, i.e. the cargo protein, the target membrane and the translocation machinery, thus driving efficient and faithful co-translational protein targeting. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Ishu Saraogi
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
| | - Shu-ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
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83
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Moraxella catarrhalis expresses a cardiolipin synthase that impacts adherence to human epithelial cells. J Bacteriol 2013; 196:107-20. [PMID: 24142255 DOI: 10.1128/jb.00298-13] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The major phospholipid constituents of Moraxella catarrhalis membranes are phosphatidylglycerol, phosphatidylethanolamine, and cardiolipin (CL). However, very little is known regarding the synthesis and function of these phospholipids in M. catarrhalis. In this study, we discovered that M. catarrhalis expresses a cardiolipin synthase (CLS), termed MclS, that is responsible for the synthesis of CL within the bacterium. The nucleotide sequence of mclS is highly conserved among M. catarrhalis isolates and is predicted to encode a protein with significant amino acid similarity to the recently characterized YmdC/ClsC protein of Escherichia coli. Isogenic mclS mutant strains were generated in M. catarrhalis isolates O35E, O12E, and McGHS1 and contained no observable levels of CL. Site-directed mutagenesis of a highly conserved HKD motif of MclS also resulted in a CL-deficient strain. Moraxella catarrhalis, which depends on adherence to epithelial cells for colonization of the human host, displays significantly reduced levels of adherence to HEp-2 and A549 cell lines in the mclS mutant strains compared to wild-type bacteria. The reduction in adherence appears to be attributed to the absence of CL. These findings mark the first instance in which a CLS has been related to a virulence-associated trait.
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84
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Hizlan D, Robson A, Whitehouse S, Gold VA, Vonck J, Mills D, Kühlbrandt W, Collinson I. Structure of the SecY complex unlocked by a preprotein mimic. Cell Rep 2013; 1:21-8. [PMID: 22576621 PMCID: PMC3333808 DOI: 10.1016/j.celrep.2011.11.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/06/2011] [Accepted: 11/08/2011] [Indexed: 11/26/2022] Open
Abstract
The Sec complex forms the core of a conserved machinery coordinating the passage of proteins across or into biological membranes. The bacterial complex SecYEG interacts with the ATPase SecA or translating ribosomes to translocate secretory and membrane proteins accordingly. A truncated preprotein competes with the physiological full-length substrate and primes the protein-channel complex for transport. We have employed electron cryomicroscopy of two-dimensional crystals to determine the structure of the complex unlocked by the preprotein. Its visualization in the native environment of the membrane preserves the active arrangement of SecYEG dimers, in which only one of the two channels is occupied by the polypeptide substrate. The signal sequence could be identified along with the corresponding conformational changes in SecY, including relocation of transmembrane segments 2b and 7 as well as the plug, which presumably then promote channel opening. Therefore, we propose that the structure describes the translocon unlocked by preprotein and poised for protein translocation.
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Affiliation(s)
- Dilem Hizlan
- Max Planck Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Straße 3, D-60438 Frankfurt am Main, Germany
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85
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Kudva R, Denks K, Kuhn P, Vogt A, Müller M, Koch HG. Protein translocation across the inner membrane of Gram-negative bacteria: the Sec and Tat dependent protein transport pathways. Res Microbiol 2013; 164:505-34. [DOI: 10.1016/j.resmic.2013.03.016] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/11/2013] [Indexed: 11/28/2022]
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86
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Solov'eva TF, Novikova OD, Portnyagina OY. Biogenesis of β-barrel integral proteins of bacterial outer membrane. BIOCHEMISTRY (MOSCOW) 2013; 77:1221-36. [PMID: 23240560 DOI: 10.1134/s0006297912110016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gram-negative bacteria are enveloped by two membranes, the inner (cytoplasmic) (CM) and the outer (OM). The majority of integral outer membrane proteins are arranged in β-barrels of cylindrical shape composed of amphipathic antiparallel β-strands. In bacteria, β-barrel proteins function as water-filled pores, active transporters, enzymes, receptors, and structural proteins. Proteins of bacterial OM are synthesized in the cytoplasm as unfolded polypeptides with an N-terminal sequence that marks them for transport across the CM. Precursors of membrane proteins move through the aqueous medium of the cytosol and periplasm under the protection of chaperones (SecB, Skp, SurA, and DegP), then cross the CM via the Sec system composed of a polypeptide-conducting channel (SecYEG) and ATPase (SecA), the latter providing the energy for the translocation of the pre-protein. Pre-protein folding and incorporation in the OM require the participation of the Bam-complex, probably without the use of energy. This review summarizes current data on the biogenesis of the β-barrel proteins of bacterial OM. Data on the structure of the proteins included in the multicomponent system for delivery of the OM proteins to their destination in the cell and on their complexes with partners, including pre-proteins, are presented. Molecular models constructed on the basis of structural, genetic, and biochemical studies that describe the mechanisms of β-barrel protein assembly by this molecular transport machinery are also considered.
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Affiliation(s)
- T F Solov'eva
- Elyakov Pacific Institute of Bioorganic Chemistry, Russian Academy of Sciences, Vladivostok, 690022, Russia.
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87
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Crosstalk between DnaA protein, the initiator of Escherichia coli chromosomal replication, and acidic phospholipids present in bacterial membranes. Int J Mol Sci 2013; 14:8517-37. [PMID: 23595001 PMCID: PMC3645759 DOI: 10.3390/ijms14048517] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 04/03/2013] [Accepted: 04/06/2013] [Indexed: 11/16/2022] Open
Abstract
Anionic (i.e., acidic) phospholipids such as phosphotidylglycerol (PG) and cardiolipin (CL), participate in several cellular functions. Here we review intriguing in vitro and in vivo evidence that suggest emergent roles for acidic phospholipids in regulating DnaA protein-mediated initiation of Escherichia coli chromosomal replication. In vitro acidic phospholipids in a fluid bilayer promote the conversion of inactive ADP-DnaA to replicatively proficient ATP-DnaA, yet both PG and CL also can inhibit the DNA-binding activity of DnaA protein. We discuss how cellular acidic phospholipids may positively and negatively influence the initiation activity of DnaA protein to help assure chromosomal replication occurs once, but only once, per cell-cycle. Fluorescence microscopy has revealed that PG and CL exist in domains located at the cell poles and mid-cell, and several studies link membrane curvature with sub-cellular localization of various integral and peripheral membrane proteins. E. coli DnaA itself is found at the cell membrane and forms helical structures along the longitudinal axis of the cell. We propose that there is cross-talk between acidic phospholipids in the bacterial membrane and DnaA protein as a means to help control the spatial and temporal regulation of chromosomal replication in bacteria.
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88
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Abstract
The motor ATPase SecA drives protein secretion through the bacterial Sec complex. The PPXD (pre-protein cross-linking domain) of the enzyme has been observed in different positions, effectively opening and closing a clamp for the polypeptide substrate. We set out to explore the implicated dynamic role of the PPXD in protein translocation by examining the effects of its immobilization, either in the position occupied in SecA alone with the clamp held open or when in complex with SecYEG with the clamp closed. We show that the conformational change from the former to the latter is necessary for high-affinity association with SecYEG and a corresponding activation of ATPase activity, presumably due to the PPXD contacting the NBDs (nucleotide-binding domains). In either state, the immobilization prevents pre-protein transport. However, when the PPXD was attached to an alternative position in the associated SecYEG complex, with the clamp closed, the transport capability was preserved. Therefore large-scale conformational changes of this domain are required for the initiation process, but not for translocation itself. The results allow us to refine a model for protein translocation, in which the mobility of the PPXD facilitates the transfer of pre-protein from SecA to SecYEG.
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89
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The role of lipid domains in bacterial cell processes. Int J Mol Sci 2013; 14:4050-65. [PMID: 23429192 PMCID: PMC3588084 DOI: 10.3390/ijms14024050] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 01/25/2013] [Accepted: 01/28/2013] [Indexed: 12/13/2022] Open
Abstract
Membranes are vital structures for cellular life forms. As thin, hydrophobic films, they provide a physical barrier separating the aqueous cytoplasm from the outside world or from the interiors of other cellular compartments. They maintain a selective permeability for the import and export of water-soluble compounds, enabling the living cell to maintain a stable chemical environment for biological processes. Cell membranes are primarily composed of two crucial substances, lipids and proteins. Bacterial membranes can sense environmental changes or communication signals from other cells and they support different cell processes, including cell division, differentiation, protein secretion and supplementary protein functions. The original fluid mosaic model of membrane structure has been recently revised because it has become apparent that domains of different lipid composition are present in both eukaryotic and prokaryotic cell membranes. In this review, we summarize different aspects of phospholipid domain formation in bacterial membranes, mainly in Gram-negative Escherichia coli and Gram-positive Bacillus subtilis. We describe the role of these lipid domains in membrane dynamics and the localization of specific proteins and protein complexes in relation to the regulation of cellular function.
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90
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Abstract
The signal recognition particle (SRP) and its receptor compose a universally conserved and essential cellular machinery that couples the synthesis of nascent proteins to their proper membrane localization. The past decade has witnessed an explosion in in-depth mechanistic investigations of this targeting machine at increasingly higher resolutions. In this review, we summarize recent work that elucidates how the SRP and SRP receptor interact with the cargo protein and the target membrane, respectively, and how these interactions are coupled to a novel GTPase cycle in the SRP·SRP receptor complex to provide the driving force and enhance the fidelity of this fundamental cellular pathway. We also discuss emerging frontiers in which important questions remain to be addressed.
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Affiliation(s)
- David Akopian
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Kuang Shen
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Xin Zhang
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Shu-ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
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91
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Akopian D, Dalal K, Shen K, Duong F, Shan SO. SecYEG activates GTPases to drive the completion of cotranslational protein targeting. ACTA ACUST UNITED AC 2013; 200:397-405. [PMID: 23401005 PMCID: PMC3575545 DOI: 10.1083/jcb.201208045] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
SecYEG drives conformational changes in the cotranslational targeting complex to activate it for GTP hydrolysis and the handover of the translating ribosome. Signal recognition particle (SRP) and its receptor (SR) comprise a highly conserved cellular machine that cotranslationally targets proteins to a protein-conducting channel, the bacterial SecYEG or eukaryotic Sec61p complex, at the target membrane. Whether SecYEG is a passive recipient of the translating ribosome or actively regulates this targeting machinery remains unclear. Here we show that SecYEG drives conformational changes in the cargo-loaded SRP–SR targeting complex that activate it for GTP hydrolysis and for handover of the translating ribosome. These results provide the first evidence that SecYEG actively drives the efficient delivery and unloading of translating ribosomes at the target membrane.
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Affiliation(s)
- David Akopian
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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92
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Visualizing a multidrug resistance protein, EmrE, with major bacterial lipids using Brewster angle microscopy. Chem Phys Lipids 2013; 167-168:33-42. [DOI: 10.1016/j.chemphyslip.2013.01.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 12/22/2012] [Accepted: 01/18/2013] [Indexed: 11/17/2022]
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93
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Whitehouse S, Gold VAM, Robson A, Allen WJ, Sessions RB, Collinson I. Mobility of the SecA 2-helix-finger is not essential for polypeptide translocation via the SecYEG complex. ACTA ACUST UNITED AC 2012; 199:919-29. [PMID: 23209305 PMCID: PMC3518217 DOI: 10.1083/jcb.201205191] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Polypeptide translocation in bacteria, once underway, requires only one copy each of SecA and SecYEG and does not require the mobility of the SecA 2-helix-finger. The bacterial ATPase SecA and protein channel complex SecYEG form the core of an essential protein translocation machinery. The nature of the conformational changes induced by each stage of the hydrolytic cycle of ATP and how they are coupled to protein translocation are not well understood. The structure of the SecA–SecYEG complex revealed a 2-helix-finger (2HF) of SecA in an ideal position to contact the substrate protein and push it through the membrane. Surprisingly, immobilization of this finger at the edge of the protein channel had no effect on translocation, whereas its imposition inside the channel blocked transport. This analysis resolves the stoichiometry of the active complex, demonstrating that after the initiation process translocation requires only one copy each of SecA and SecYEG. The results also have important implications on the mechanism of energy transduction and the power stroke driving transport. Evidently, the 2HF is not a highly mobile transducing element of polypeptide translocation.
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Affiliation(s)
- Sarah Whitehouse
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, England, UK
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94
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Discovery of a cardiolipin synthase utilizing phosphatidylethanolamine and phosphatidylglycerol as substrates. Proc Natl Acad Sci U S A 2012; 109:16504-9. [PMID: 22988102 DOI: 10.1073/pnas.1212797109] [Citation(s) in RCA: 170] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Depending on growth phase and culture conditions, cardiolipin (CL) makes up 5-15% of the phospholipids in Escherichia coli with the remainder being primarily phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). In E. coli, the cls and ybhO genes (renamed clsA and clsB, respectively) each encode a CL synthase (Cls) that catalyzes the condensation of two PG molecules to form CL and glycerol. However, a ΔclsAB mutant still makes CL in the stationary phase, indicating the existence of additional Cls. We identified a third Cls encoded by ymdC (renamed clsC). ClsC has sequence homology with ClsA and ClsB, which all belong to the phospholipase D superfamily. The ΔclsABC mutant lacks detectible CL regardless of growth phase or growth conditions. CL can be restored to near wild-type levels in stationary phase in the triple mutant by expressing either clsA or clsB. Expression of clsC alone resulted in a low level of CL in the stationary phase, which increased to near wild-type levels by coexpression of its neighboring gene, ymdB. CL synthesis by all Cls is increased with increasing medium osmolarity during logarithmic growth and in stationary phase. However, only ClsA contributes detectible levels of CL at low osmolarity during logarithmic growth. Mutation of the putative catalytic motif of ClsC prevents CL formation. Unlike eukaryotic Cls (that use PG and CDP-diacylglycerol as substrates) or ClsA, the combined YmdB-ClsC used PE as the phosphatidyl donor to PG to form CL, which demonstrates a third and unique mode for CL synthesis.
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95
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Govindarajan S, Nevo-Dinur K, Amster-Choder O. Compartmentalization and spatiotemporal organization of macromolecules in bacteria. FEMS Microbiol Rev 2012; 36:1005-22. [DOI: 10.1111/j.1574-6976.2012.00348.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 06/27/2012] [Accepted: 06/28/2012] [Indexed: 12/18/2022] Open
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96
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Elkehal R, Becker T, Sommer MS, Königer M, Schleiff E. Specific lipids influence the import capacity of the chloroplast outer envelope precursor protein translocon. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1823:1033-40. [PMID: 22425965 DOI: 10.1016/j.bbamcr.2012.02.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 01/30/2012] [Accepted: 02/29/2012] [Indexed: 11/29/2022]
Abstract
Recent studies demonstrated that lipids influence the assembly and efficiency of membrane-embedded macromolecular complexes. Similarly, lipids have been found to influence chloroplast precursor protein binding to the membrane surface and to be associated with the Translocon of the Outer membrane of Chloroplasts (TOC). We used a system based on chloroplast outer envelope vesicles from Pisum sativum to obtain an initial understanding of the influence of lipids on precursor protein translocation across the outer envelope. The ability of the model precursor proteins p(OE33)titin and pSSU to be recognized and translocated in this simplified system was investigated. We demonstrate that transport across the outer membrane can be observed in the absence of the inner envelope translocon. The translocation, however, was significantly slower than that observed for chloroplasts. Enrichment of outer envelope vesicles with different lipids natively found in chloroplast membranes altered the binding and transport behavior. Further, the results obtained using outer envelope vesicles were consistent with the results observed for the reconstituted isolated TOC complex. Based on both approaches we concluded that the lipids sulfoquinovosyldiacylglycerol (SQDG) and phosphatidylinositol (PI) increased TOC-mediated binding and import for both precursor proteins. In contrast, enrichment in digalactosyldiacylglycerol (DGDG) improved TOC-mediated binding for pSSU, but decreased import for both precursor proteins. Optimal import occurred only in a narrow concentration range of DGDG.
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Affiliation(s)
- Rajae Elkehal
- Center of Membrane Proteomic, Molecular Cell Biology of Plants, Goethe-University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
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97
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Arias-Cartin R, Grimaldi S, Arnoux P, Guigliarelli B, Magalon A. Cardiolipin binding in bacterial respiratory complexes: structural and functional implications. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1937-49. [PMID: 22561115 DOI: 10.1016/j.bbabio.2012.04.005] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 04/10/2012] [Accepted: 04/10/2012] [Indexed: 10/28/2022]
Abstract
The structural and functional integrity of biological membranes is vital to life. The interplay of lipids and membrane proteins is crucial for numerous fundamental processes ranging from respiration, photosynthesis, signal transduction, solute transport to motility. Evidence is accumulating that specific lipids play important roles in membrane proteins, but how specific lipids interact with and enable membrane proteins to achieve their full functionality remains unclear. X-ray structures of membrane proteins have revealed tight and specific binding of lipids. For instance, cardiolipin, an anionic phospholipid, has been found to be associated to a number of eukaryotic and prokaryotic respiratory complexes. Moreover, polar and septal accumulation of cardiolipin in a number of prokaryotes may ensure proper spatial segregation and/or activity of proteins. In this review, we describe current knowledge of the functions associated with cardiolipin binding to respiratory complexes in prokaryotes as a frame to discuss how specific lipid binding may tune their reactivity towards quinone and participate to supercomplex formation of both aerobic and anaerobic respiratory chains. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
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Affiliation(s)
- Rodrigo Arias-Cartin
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
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98
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Tian HF, Feng JM, Wen JF. The evolution of cardiolipin biosynthesis and maturation pathways and its implications for the evolution of eukaryotes. BMC Evol Biol 2012; 12:32. [PMID: 22409430 PMCID: PMC3378450 DOI: 10.1186/1471-2148-12-32] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 03/13/2012] [Indexed: 11/18/2022] Open
Abstract
Background Cardiolipin (CL) is an important component in mitochondrial inner and bacterial membranes. Its appearance in these two biomembranes has been considered as evidence of the endosymbiotic origin of mitochondria. But CL was reported to be synthesized through two distinct enzymes--CLS_cap and CLS_pld in eukaryotes and bacteria. Therefore, how the CL biosynthesis pathway evolved is an interesting question. Results Phylogenetic distribution investigation of CL synthase (CLS) showed: most bacteria have CLS_pld pathway, but in partial bacteria including proteobacteria and actinobacteria CLS_cap pathway has already appeared; in eukaryotes, Supergroup Opisthokonta and Archaeplastida, and Subgroup Stramenopiles, which all contain multicellular organisms, possess CLS_cap pathway, while Supergroup Amoebozoa and Excavata and Subgroup Alveolata, which all consist exclusively of unicellular eukaryotes, bear CLS_pld pathway; amitochondriate protists in any supergroups have neither. Phylogenetic analysis indicated the CLS_cap in eukaryotes have the closest relationship with those of alpha proteobacteria, while the CLS_pld in eukaryotes share a common ancestor but have no close correlation with those of any particular bacteria. Conclusions The first eukaryote common ancestor (FECA) inherited the CLS_pld from its bacterial ancestor (e. g. the bacterial partner according to any of the hypotheses about eukaryote evolution); later, when the FECA evolved into the last eukaryote common ancestor (LECA), the endosymbiotic mitochondria (alpha proteobacteria) brought in CLS_cap, and then in some LECA individuals the CLS_cap substituted the CLS_pld, and these LECAs would evolve into the protist lineages from which multicellular eukaryotes could arise, while in the other LECAs the CLS_pld was retained and the CLS_cap was lost, and these LECAs would evolve into the protist lineages possessing CLS_pld. Besides, our work indicated CL maturation pathway arose after the emergence of eukaryotes probably through mechanisms such as duplication of other genes, and gene duplication and loss occurred frequently at different lineage levels, increasing the pathway diversity probably to fit the complicated cellular process in various cells. Our work also implies the classification putting Stramenopiles and Alveolata together to form Chromalveolata may be unreasonable; the absence of CL synthesis and maturation pathways in amitochondriate protists is most probably due to secondary loss.
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Affiliation(s)
- Hai-Feng Tian
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan Province 650223, China
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The variable subdomain of Escherichia coli SecA functions to regulate SecA ATPase activity and ADP release. J Bacteriol 2012; 194:2205-13. [PMID: 22389482 DOI: 10.1128/jb.00039-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial SecA proteins can be categorized by the presence or absence of a variable subdomain (VAR) located within nucleotide-binding domain II of the SecA DEAD motor. Here we show that VAR is dispensable for SecA function, since the VAR deletion mutant secAΔ519-547 displayed a wild-type rate of cellular growth and protein export. Loss or gain of VAR is extremely rare in the history of bacterial evolution, indicating that it appears to contribute to secA function within the relevant species in their natural environments. VAR removal also results in additional secA phenotypes: azide resistance (Azi(r)) and suppression of signal sequence defects (PrlD). The SecAΔ(519-547) protein was found to be modestly hyperactive for SecA ATPase activities and displayed an accelerated rate of ADP release, consistent with the biochemical basis of azide resistance. Based on our findings, we discuss models whereby VAR allosterically regulates SecA DEAD motor function at SecYEG.
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Two copies of the SecY channel and acidic lipids are necessary to activate the SecA translocation ATPase. Proc Natl Acad Sci U S A 2012; 109:4104-9. [PMID: 22378651 DOI: 10.1073/pnas.1117783109] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The SecA ATPase associates with the SecY complex to push preproteins across the bacterial membrane. Because a single SecY is sufficient to create the conducting channel, the function of SecY oligomerization remains unclear. Here, we have analyzed the translocation reaction using nanodiscs. We show that one SecY copy is sufficient to bind SecA and the preprotein, but only the SecY dimer together with acidic lipids supports the activation of the SecA translocation ATPase. In discs, the dimer is predominantly arranged in a back-to-back manner and remains active even if a constituent SecY copy is defective for SecA binding. In membrane vesicles and in intact cells, the coproduction of two inactive SecYs, one for channel gating and the other for SecA binding, recreates a functional translocation unit. These results indisputably argue that the SecY dimer is crucial for the activation of SecA, which is necessary for preprotein transport.
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