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Blum D, Reuter M, Schliebs W, Tomaschewski J, Erdmann R, Wagner R. Membrane binding and pore forming insertion of PEX5 into horizontal lipid bilayer. Biol Chem 2023; 404:157-167. [PMID: 36260915 DOI: 10.1515/hsz-2022-0183] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 08/29/2022] [Indexed: 11/15/2022]
Abstract
The assembly of the peroxisomal translocon involves the transition of a soluble form of the peroxisomal targeting receptor PEX5 into a membrane-bound form, which becomes an integral membrane component of the import pore for peroxisomal matrix proteins. How this transition occurs is still a mystery. We addressed this question using a artificial horizontal bilayer in combination with fluorescence time-correlated single photon counting (TCSPC) and electrophysiological channel recording. Purified human isoform PEX5L and truncated PEX5L(1-335) lacking the cargo binding domain were selectively labeled with thiol-reactive Atto-dyes. Diffusion coefficients of labeled protein in solution show that PEX5L is monomeric with a rather compact spherical conformation, while the truncated protein appeared in a more extended conformation. Labeled PEX5L and the truncated PEX5L(1-335) bind stably to horizontal bilayer thereby accumulating around 100-fold. The diffusion coefficients of the membrane-bound PEX5L forms are 3-4 times lower than in solution, indicating the formation of larger complexes. Electrophysiological single channel recording shows that membrane-bound labeled and non-labeled PEX5L, but not the truncated PEX5L(1-335), can form ion conducting membrane channels. The data suggest that PEX5L is the pore-forming component of the oligomeric peroxisomal translocon and that spontaneous PEX5L membrane surface binding might be an important step in its assembly.
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Affiliation(s)
- Daniel Blum
- MOLIFE Research Center, Jacobs, University Bremen, D-28759 Bremen, Germany
| | - Maren Reuter
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Medizinische Fakultät, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Wolfgang Schliebs
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Medizinische Fakultät, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Jana Tomaschewski
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Medizinische Fakultät, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Ralf Erdmann
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Medizinische Fakultät, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - Richard Wagner
- MOLIFE Research Center, Jacobs, University Bremen, D-28759 Bremen, Germany
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2
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Sayyed UMH, Mahalakshmi R. Mitochondrial protein translocation machinery: From TOM structural biogenesis to functional regulation. J Biol Chem 2022; 298:101870. [PMID: 35346689 PMCID: PMC9052162 DOI: 10.1016/j.jbc.2022.101870] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 03/13/2022] [Accepted: 03/14/2022] [Indexed: 01/15/2023] Open
Abstract
The human mitochondrial outer membrane is biophysically unique as it is the only membrane possessing transmembrane β-barrel proteins (mitochondrial outer membrane proteins, mOMPs) in the cell. The most vital of the three mOMPs is the core protein of the translocase of the outer mitochondrial membrane (TOM) complex. Identified first as MOM38 in Neurospora in 1990, the structure of Tom40, the core 19-stranded β-barrel translocation channel, was solved in 2017, after nearly three decades. Remarkably, the past four years have witnessed an exponential increase in structural and functional studies of yeast and human TOM complexes. In addition to being conserved across all eukaryotes, the TOM complex is the sole ATP-independent import machinery for nearly all of the ∼1000 to 1500 known mitochondrial proteins. Recent cryo-EM structures have provided detailed insight into both possible assembly mechanisms of the TOM core complex and organizational dynamics of the import machinery and now reveal novel regulatory interplay with other mOMPs. Functional characterization of the TOM complex using biochemical and structural approaches has also revealed mechanisms for substrate recognition and at least five defined import pathways for precursor proteins. In this review, we discuss the discovery, recently solved structures, molecular function, and regulation of the TOM complex and its constituents, along with the implications these advances have for alleviating human diseases.
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Affiliation(s)
- Ulfat Mohd Hanif Sayyed
- Molecular Biophysics Laboratory, Indian Institute of Science Education and Research, Bhopal, India
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3
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Hrd1 forms the retrotranslocation pore regulated by auto-ubiquitination and binding of misfolded proteins. Nat Cell Biol 2020; 22:274-281. [DOI: 10.1038/s41556-020-0473-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 01/20/2020] [Indexed: 01/01/2023]
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4
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Schmitt C, Bafna JA, Schmid B, Klingl S, Baier S, Hemmis B, Wagner R, Winterhalter M, Voll LM. Manipulation of charge distribution in the arginine and glutamate clusters of the OmpG pore alters sugar specificity and ion selectivity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183021. [PMID: 31306626 DOI: 10.1016/j.bbamem.2019.07.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 07/02/2019] [Accepted: 07/09/2019] [Indexed: 01/08/2023]
Abstract
OmpG is a general diffusion pore in the E. coli outer membrane with a molecular architecture comprising a 14-stranded β-barrel scaffold and unique structural features. In contrast to other non-specific porins, OmpG lacks a central constriction zone and has an exceptionally wide pore diameter of about 13 Å. The equatorial plane of OmpG harbors an annulus of four alternating basic and acidic patches whose function is only poorly characterized. We have investigated the role of charge distribution for ion selectivity and sugar transport with the help of OmpG variants mutated in the annulus. Substituting the glutamate residues of the annulus for histidines or alanines led to a strong reduction in cation selectivity. Replacement of the glutamates in the annulus by histidine residues also disfavored the passage of pentoses and hexoses relative to disaccharides. Our results demonstrate that despite the wide pore diameter, an annulus only consisting of two opposing basic patches confers reduced cation and monosaccharide transport compared to OmpG wild type. Furthermore, randomization of charged residues in the annulus had the potential to abolish pH-dependency of sugar transport. Our results indicate that E15, E31, R92, R111 and R211 in the annulus form electrostatic interactions with R228, E229 and D232 in loop L6 that influence pH-dependency of sugar transport.
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Affiliation(s)
- Christine Schmitt
- Division of Biochemistry and Applied Protein Center Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany; Department Biology, Division of Plant Physiology, Philipps-University Marburg, D-35043 Marburg, Germany.
| | - Jayesh Arun Bafna
- Department of Life Sciences and Chemistry, Jacobs University Bremen, D-28719 Bremen, Germany.
| | - Benedikt Schmid
- Division of Biotechnology and Applied Protein Center Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany.
| | - Stefan Klingl
- Division of Biotechnology and Applied Protein Center Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany.
| | - Steffen Baier
- Division of Biochemistry and Applied Protein Center Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
| | - Birgit Hemmis
- Department of Biology and Chemistry, University of Osnabrück, D-49069 Osnabrück, Germany
| | - Richard Wagner
- Department of Life Sciences and Chemistry, Jacobs University Bremen, D-28719 Bremen, Germany; Department of Biology and Chemistry, University of Osnabrück, D-49069 Osnabrück, Germany.
| | - Mathias Winterhalter
- Department of Life Sciences and Chemistry, Jacobs University Bremen, D-28719 Bremen, Germany.
| | - Lars M Voll
- Division of Biochemistry and Applied Protein Center Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany; Department Biology, Division of Plant Physiology, Philipps-University Marburg, D-35043 Marburg, Germany.
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5
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Lang S, Nguyen D, Pfeffer S, Förster F, Helms V, Zimmermann R. Functions and Mechanisms of the Human Ribosome-Translocon Complex. Subcell Biochem 2019; 93:83-141. [PMID: 31939150 DOI: 10.1007/978-3-030-28151-9_4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The membrane of the endoplasmic reticulum (ER) in human cells harbors the protein translocon, which facilitates membrane insertion and translocation of almost every newly synthesized polypeptide targeted to organelles of the secretory pathway. The translocon comprises the polypeptide-conducting Sec61 channel and several additional proteins, which are associated with the heterotrimeric Sec61 complex. This ensemble of proteins facilitates ER targeting of precursor polypeptides, Sec61 channel opening and closing, and modification of precursor polypeptides in transit through the Sec61 complex. Recently, cryoelectron tomography of translocons in native ER membranes has given unprecedented insights into the architecture and dynamics of the native, ribosome-associated translocon and the Sec61 channel. These structural data are discussed in light of different Sec61 channel activities including ribosome receptor function, membrane insertion or translocation of newly synthesized polypeptides as well as the possible roles of the Sec61 channel as a passive ER calcium leak channel and regulator of ATP/ADP exchange between cytosol and ER.
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Affiliation(s)
- Sven Lang
- Competence Center for Molecular Medicine, Saarland University Medical School, Building 44, 66421, Homburg, Germany.
| | - Duy Nguyen
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Stefan Pfeffer
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152, Martinsried, Germany
- ZMBH, 69120, Heidelberg, Germany
| | - Friedrich Förster
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152, Martinsried, Germany
- Center for Biomolecular Research, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Volkhard Helms
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Richard Zimmermann
- Competence Center for Molecular Medicine, Saarland University Medical School, Building 44, 66421, Homburg, Germany
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6
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Rondelli V, Del Favero E, Brocca P, Fragneto G, Trapp M, Mauri L, Ciampa M, Romani G, Braun C, Winterstein L, Schroeder I, Thiel G, Moroni A, Cantu' L. Directional K+ channel insertion in a single phospholipid bilayer: Neutron reflectometry and electrophysiology in the joint exploration of a model membrane functional platform. Biochim Biophys Acta Gen Subj 2018; 1862:1742-1750. [DOI: 10.1016/j.bbagen.2018.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/27/2018] [Accepted: 05/07/2018] [Indexed: 01/05/2023]
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7
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Abstract
There are a number of methods of investigating the function of recombinant proteins such as ion channels. However, after channel purification there are few methods to guarantee that the protein still functions. For ion channels, reconstituting back into planar lipid bilayers and demonstrating preserved function is a convenient and trusted method. It is cell free and even inaccessible, intracellular ion channels can be studied. We have used this method to study the function of recombinant channels of known subunit composition and have found it convenient for investigating the mode of action of ion channel modulators.
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Affiliation(s)
- Jacqueline Maher
- School of Pharmacy and Biomolecular Sciences, University Of Brighton, United Kingdom
| | - Marcus Allen
- Centre for Stress and Age-Related Disease, School of Pharmacy and Biomolecular Sciences, University of Brighton, United Kingdom.
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8
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Krüger V, Becker T, Becker L, Montilla-Martinez M, Ellenrieder L, Vögtle FN, Meyer HE, Ryan MT, Wiedemann N, Warscheid B, Pfanner N, Wagner R, Meisinger C. Identification of new channels by systematic analysis of the mitochondrial outer membrane. J Cell Biol 2017; 216:3485-3495. [PMID: 28916712 PMCID: PMC5674900 DOI: 10.1083/jcb.201706043] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 08/03/2017] [Accepted: 08/22/2017] [Indexed: 02/08/2023] Open
Abstract
Channels in the mitochondrial outer membrane exchange metabolites, ions, and proteins with the rest of the cell. Kruger et al. identify several new types of channel and suggest that the outer mitochondrial membrane is a more selective molecular sieve with a greater variety of channel-forming proteins than previously appreciated. The mitochondrial outer membrane is essential for communication between mitochondria and the rest of the cell and facilitates the transport of metabolites, ions, and proteins. All mitochondrial outer membrane channels known to date are β-barrel membrane proteins, including the abundant voltage-dependent anion channel and the cation-preferring protein-conducting channels Tom40, Sam50, and Mdm10. We analyzed outer membrane fractions of yeast mitochondria and identified four new channel activities: two anion-preferring channels and two cation-preferring channels. We characterized the cation-preferring channels at the molecular level. The mitochondrial import component Mim1 forms a channel that is predicted to have an α-helical structure for protein import. The short-chain dehydrogenase-related protein Ayr1 forms an NADPH-regulated channel. We conclude that the mitochondrial outer membrane contains a considerably larger variety of channel-forming proteins than assumed thus far. These findings challenge the traditional view of the outer membrane as an unspecific molecular sieve and indicate a higher degree of selectivity and regulation of metabolite fluxes at the mitochondrial boundary.
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Affiliation(s)
- Vivien Krüger
- Division of Biophysics, School of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany.,Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Thomas Becker
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Lars Becker
- Division of Biophysics, School of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany
| | | | - Lars Ellenrieder
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - F-Nora Vögtle
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Helmut E Meyer
- Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., Dortmund, Germany
| | - Michael T Ryan
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Nils Wiedemann
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Bettina Warscheid
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany.,Institute of Biology II, Biochemistry - Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Nikolaus Pfanner
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany .,BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Richard Wagner
- Division of Biophysics, School of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany .,Biophysics, Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Chris Meisinger
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
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9
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Denkert N, Schendzielorz AB, Barbot M, Versemann L, Richter F, Rehling P, Meinecke M. Cation selectivity of the presequence translocase channel Tim23 is crucial for efficient protein import. eLife 2017; 6. [PMID: 28857742 PMCID: PMC5578737 DOI: 10.7554/elife.28324] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 07/31/2017] [Indexed: 01/09/2023] Open
Abstract
Virtually all mitochondrial matrix proteins and a considerable number of inner membrane proteins carry a positively charged, N-terminal presequence and are imported by the TIM23 complex (presequence translocase) located in the inner mitochondrial membrane. The voltage-regulated Tim23 channel constitutes the actual protein-import pore wide enough to allow the passage of polypeptides with a secondary structure. In this study, we identify amino acids important for the cation selectivity of Tim23. Structure based mutants show that selectivity is provided by highly conserved, pore-lining amino acids. Mutations of these amino acid residues lead to reduced selectivity properties, reduced protein import capacity and they render the Tim23 channel insensitive to substrates. We thus show that the cation selectivity of the Tim23 channel is a key feature for substrate recognition and efficient protein import. The cells of animals, plants and other eukaryotic organisms contain compartments known as organelles that play many different roles. For example, compartments called mitochondria are responsible for supplying the chemical energy cells need to survive and grow. Two membranes surround each mitochondrion and energy is converted on the surface of the inner one. Mitochondria contain over 1,000 different proteins, most of which are produced in the main part of the cell and have to be transported into the mitochondria. A transport protein called Tim23 is part of a larger group or ‘complex’ of proteins that helps to import many other proteins into the mitochondria. This complex sits in the inner membrane, with the Tim23 protein forming a large, water-filled pore through its core that provides a route for proteins to pass through the membrane. Proteins are made of building blocks called amino acids. The proteins transported by the complex containing Tim23 all have a short chain of amino acids at one end known as an N-terminal presequence. However, it is not clear how the inside of the Tim23 channel identifies and transports this presequence to allow the right proteins to pass through the inner membrane. Denkert, Schendzielorz et al. studied the normal and mutant versions of a Tim23 channel from yeast to find out which parts of the protein are involved in detecting the N-terminal presequence after it enters the pore. The experiments show that there are several amino acids in Tim23 that play important roles in this process. Furthermore, mitochondria containing mutant Tim23 channels, that are less able to identify the N-terminal presequence, are impaired in their ability to import proteins. Tim23 proteins in humans and other organisms also contain most or all of the specific amino acids identified in this study, suggesting that the findings of Denkert, Schendzielorz et al. will also apply to other species. Furthermore, the experimental strategy used in this study could be adapted to investigate transport proteins in other cell compartments.
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Affiliation(s)
- Niels Denkert
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | | | - Mariam Barbot
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Lennart Versemann
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Frank Richter
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany.,Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Göttinger Zentrum für Molekulare Biowissenschaften, Göttingen, Germany
| | - Michael Meinecke
- Department of Cellular Biochemistry, University Medical Center Göttingen, Göttingen, Germany.,Göttinger Zentrum für Molekulare Biowissenschaften, Göttingen, Germany.,European Neuroscience Institute Göttingen, Göttingen, Germany
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10
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Harsman A, Schock A, Hemmis B, Wahl V, Jeshen I, Bartsch P, Schlereth A, Pertl-Obermeyer H, Goetze TA, Soll J, Philippar K, Wagner R. OEP40, a Regulated Glucose-permeable β-Barrel Solute Channel in the Chloroplast Outer Envelope Membrane. J Biol Chem 2016; 291:17848-60. [PMID: 27339897 DOI: 10.1074/jbc.m115.712398] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Indexed: 12/20/2022] Open
Abstract
Chloroplasts and mitochondria are unique endosymbiotic cellular organelles surrounded by two membranes. Essential metabolic networking between these compartments and their hosting cells requires the exchange of a large number of biochemical pathway intermediates in a directed and coordinated fashion across their inner and outer envelope membranes. Here, we describe the identification and functional characterization of a highly specific, regulated solute channel in the outer envelope of chloroplasts, named OEP40. Loss of OEP40 function in Arabidopsis thaliana results in early flowering under cold temperature. The reconstituted recombinant OEP40 protein forms a high conductance β-barrel ion channel with subconductant states in planar lipid bilayers. The OEP40 channel is slightly cation-selective PK+/PCl- ≈ 4:1 and rectifying (i⃗/i⃖ ≅ 2) with a slope conductance of Ḡmax ≅ 690 picosiemens. The OEP40 channel has a restriction zone diameter of ≅1.4 nm and is permeable for glucose, glucose 1-phosphate and glucose 6-phosphate, but not for maltose. Moreover, channel properties are regulated by trehalose 6-phosphate, which cannot permeate. Altogether, our results indicate that OEP40 is a "glucose-gate" in the outer envelope membrane of chloroplasts, facilitating selective metabolite exchange between chloroplasts and the surrounding cell.
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Affiliation(s)
- Anke Harsman
- From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück
| | - Annette Schock
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Birgit Hemmis
- From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück
| | - Vanessa Wahl
- the Department of Metabolic Networks, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Ingrid Jeshen
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Philipp Bartsch
- From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück
| | - Armin Schlereth
- the Department of Metabolic Networks, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Heidi Pertl-Obermeyer
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Tom Alexander Goetze
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Jürgen Soll
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Katrin Philippar
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Richard Wagner
- From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück,
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11
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Montilla-Martinez M, Beck S, Klümper J, Meinecke M, Schliebs W, Wagner R, Erdmann R. Distinct Pores for Peroxisomal Import of PTS1 and PTS2 Proteins. Cell Rep 2015; 13:2126-34. [PMID: 26673321 DOI: 10.1016/j.celrep.2015.11.016] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 09/10/2015] [Accepted: 11/03/2015] [Indexed: 11/29/2022] Open
Abstract
Two peroxisomal targeting signals, PTS1 and PTS2, recognized by cytosolic receptors Pex5 and cooperating Pex7/Pex18, direct folded proteins to the peroxisomal matrix. A pore consisting of the PTS1 receptor Pex5 and the docking protein Pex14 imports PTS1 proteins. We identified a distinct PTS2-specific pore, which contains the PTS2 co-receptor Pex18 and the Pex14/Pex17-docking complex as major constituents. The estimated maximal pore size of ∼ 4.7 nm is large enough to allow import of folded PTS2 proteins. PTS2 cargo proteins modulate complex gating, open probability, and subconductance states of the pore. While the PTS1 channel is transiently activated by arriving receptor-cargo complexes, the reconstituted PTS2 channel is constitutively present in an open state. However, the cargo-loaded PTS2 channel is largely impermeable to solutes and ions. Our results demonstrate that import of PTS1 and PTS2 proteins does not converge at the peroxisomal membrane as previously anticipated but is performed by distinct pores.
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Affiliation(s)
| | - Sabrina Beck
- Institut für Biochemie und Pathobiochemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Jessica Klümper
- Institut für Biochemie und Pathobiochemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Michael Meinecke
- Institut für Zelluläre Biochemie, Universitätsmedizin Göttingen, 37073 Göttingen, Germany
| | - Wolfgang Schliebs
- Institut für Biochemie und Pathobiochemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Richard Wagner
- Biophysik, Fachbereich Biologie/Chemie, Universität Osnabrück, 49069 Osnabrück, Germany; MOLIFE Research Center, Jacobs University Bremen, 28759 Bremen, Germany.
| | - Ralf Erdmann
- Institut für Biochemie und Pathobiochemie, Ruhr-Universität Bochum, 44780 Bochum, Germany.
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12
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Abstract
The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.
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13
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Krammer EM, Saidani H, Prévost M, Homblé F. Origin of ion selectivity in Phaseolus coccineus mitochondrial VDAC. Mitochondrion 2014; 19 Pt B:206-13. [PMID: 24742372 DOI: 10.1016/j.mito.2014.04.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Revised: 03/14/2014] [Accepted: 04/04/2014] [Indexed: 12/23/2022]
Abstract
The mitochondrial voltage-dependent a nion-selective channel (VDAC) is the major permeation pathway for small ions and metabolites. Although a wealth of electrophysiological data has been obtained on different VDAC species, the physical mechanisms of their ionic selectivity are still elusive. We addressed this issue using electrophysiological experiments performed on plant VDAC. A simple macroscopic electrodiffusion model accounting for ion diffusion and for an effective fixed charge of the channel describes well its selectivity. Brownian Dynamics simulations of ion permeation performed on plant and mammalian VDACs point to the role of specific charged residues located at about the middle of the pore.
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Affiliation(s)
- Eva-Maria Krammer
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Bld du Triomphe, 1050 Brussels, Belgium
| | - Hayet Saidani
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Bld du Triomphe, 1050 Brussels, Belgium
| | - Martine Prévost
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Bld du Triomphe, 1050 Brussels, Belgium
| | - Fabrice Homblé
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Bld du Triomphe, 1050 Brussels, Belgium.
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14
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Bartsch P, Harsman A, Wagner R. Single channel analysis of membrane proteins in artificial bilayer membranes. Methods Mol Biol 2013; 1033:345-61. [PMID: 23996188 DOI: 10.1007/978-1-62703-487-6_22] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The planar lipid bilayer technique is a powerful experimental approach for electrical single channel recordings of pore-forming membrane proteins in a chemically well-defined and easily modifiable environment. Here we provide a general survey of the basic materials and procedures required to set up a robust bilayer system and perform electrophysiological single channel recordings of reconstituted proteins suitable for the in-depth characterization of their functional properties.
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Affiliation(s)
- Philipp Bartsch
- Biophysics, Department of Biology/Chemistry, University of Osnabrueck, Osnabrueck, Germany
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15
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Lamichhane U, Islam T, Prasad S, Weingart H, Mahendran KR, Winterhalter M. Peptide translocation through the mesoscopic channel: binding kinetics at the single molecule level. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 42:363-9. [DOI: 10.1007/s00249-012-0885-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 11/30/2012] [Accepted: 12/13/2012] [Indexed: 12/21/2022]
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16
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Bartsch P, Walter C, Selenschik P, Honigmann A, Wagner R. Horizontal Bilayer for Electrical and Optical Recordings. MATERIALS 2012. [PMCID: PMC5449052 DOI: 10.3390/ma5122705] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Philipp Bartsch
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
- Ionovation GmbH, Westerbreite 7, Osnabrueck 49084, Germany
| | - Claudius Walter
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
- Ionovation GmbH, Westerbreite 7, Osnabrueck 49084, Germany
| | - Philipp Selenschik
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
| | - Alf Honigmann
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
| | - Richard Wagner
- Biophysics, Department of Biology/Chemistry, University Osnabrueck, Barbarastr. 13, Osnabrueck 49076, Germany; E-Mails: (P.B.); (C.W.); (P.S.); (A.H.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +49-541-969-2398; Fax: +49-541-969-2243
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17
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Sripada L, Tomar D, Singh R. Mitochondria: One of the destinations of miRNAs. Mitochondrion 2012; 12:593-9. [DOI: 10.1016/j.mito.2012.10.009] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 08/22/2012] [Accepted: 10/09/2012] [Indexed: 01/15/2023]
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18
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Harsman A, Niemann M, Pusnik M, Schmidt O, Burmann BM, Hiller S, Meisinger C, Schneider A, Wagner R. Bacterial origin of a mitochondrial outer membrane protein translocase: new perspectives from comparative single channel electrophysiology. J Biol Chem 2012; 287:31437-45. [PMID: 22778261 DOI: 10.1074/jbc.m112.392118] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondria are of bacterial ancestry and have to import most of their proteins from the cytosol. This process is mediated by Tom40, an essential protein that forms the protein-translocating pore in the outer mitochondrial membrane. Tom40 is conserved in virtually all eukaryotes, but its evolutionary origin is unclear because bacterial orthologues have not been identified so far. Recently, it was shown that the parasitic protozoon Trypanosoma brucei lacks a conventional Tom40 and instead employs the archaic translocase of the outer mitochondrial membrane (ATOM), a protein that shows similarities to both eukaryotic Tom40 and bacterial protein translocases of the Omp85 family. Here we present electrophysiological single channel data showing that ATOM forms a hydrophilic pore of large conductance and high open probability. Moreover, ATOM channels exhibit a preference for the passage of cationic molecules consistent with the idea that it may translocate unfolded proteins targeted by positively charged N-terminal presequences. This is further supported by the fact that the addition of a presequence peptide induces transient pore closure. An in-depth comparison of these single channel properties with those of other protein translocases reveals that ATOM closely resembles bacterial-type protein export channels rather than eukaryotic Tom40. Our results support the idea that ATOM represents an evolutionary intermediate between a bacterial Omp85-like protein export machinery and the conventional Tom40 that is found in mitochondria of other eukaryotes.
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Affiliation(s)
- Anke Harsman
- Biophysik, Fachbereich Biologie/Chemie, Universität Osnabrück, 49076 Osnabrück, Germany
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19
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Feld GK, Brown MJ, Krantz BA. Ratcheting up protein translocation with anthrax toxin. Protein Sci 2012; 21:606-24. [PMID: 22374876 DOI: 10.1002/pro.2052] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 02/21/2012] [Accepted: 02/22/2012] [Indexed: 01/09/2023]
Abstract
Energy-consuming nanomachines catalyze the directed movement of biopolymers in the cell. They are found both dissolved in the aqueous cytosol as well as embedded in lipid bilayers. Inquiries into the molecular mechanism of nanomachine-catalyzed biopolymer transport have revealed that these machines are equipped with molecular parts, including adjustable clamps, levers, and adaptors, which interact favorably with substrate polypeptides. Biological nanomachines that catalyze protein transport, known as translocases, often require that their substrate proteins unfold before translocation. An unstructured protein chain is likely entropically challenging to bind, push, or pull in a directional manner, especially in a way that produces an unfolding force. A number of ingenious solutions to this problem are now evident in the anthrax toxin system, a model used to study protein translocation. Here we highlight molecular ratchets and current research on anthrax toxin translocation. A picture is emerging of proton-gradient-driven anthrax toxin translocation, and its associated ratchet mechanism likely applies broadly to other systems. We suggest a cyclical thermodynamic order-to-disorder mechanism (akin to a heat-engine cycle) is central to underlying protein translocation: peptide substrates nonspecifically bind to molecular clamps, which possess adjustable affinities; polypeptide substrates compress into helical structures; these clamps undergo proton-gated switching; and the substrate subsequently expands regaining its unfolded state conformational entropy upon translocation.
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Affiliation(s)
- Geoffrey K Feld
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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