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Sun K, White JC, He E, Van Gestel CAM, Qiu H. Surface Defects Regulate the in Vivo Bioenergetic Response of Earthworm Eisenia fetida Coelomocytes to Molybdenum Disulfide Nanosheets. ACS NANO 2023; 17:2639-2652. [PMID: 36651861 DOI: 10.1021/acsnano.2c10623] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Two-dimensional molybdenum disulfide (2D MoS2) nanomaterials are seeing increased use in several areas, and this will lead to their inevitable release into soils. Surface defects can occur on MoS2 nanosheets during synthesis or during environmental aging processes. The mechanisms of MoS2 nanosheet toxicity to soil invertebrates and the role of surface defects in that toxicity have not been fully elucidated. We integrated traditional toxicity end points, targeted energy metabolomics, and transcriptomics to compare the mechanistic differences in the toxicity of defect-free and defect-rich MoS2 nanosheets (DF-MoS2 and DR-MoS2) to Eisenia fetida using a coelomocyte-based in vivo assessment model. After organism-level exposure to DF-MoS2 for 96 h at 10 and 100 mg Mo/L, cellular reactive oxygen species (ROS) levels were elevated by 25.6-96.6% and the activity of mitochondrial respiratory electron transport chain (Mito-RETC) complex III was inhibited by 9.7-19.4%. The tricarboxylic acid cycling and glycolysis were also disrupted. DF-MoS2 preferentially up-regulated subcellular component motility processes related to microtubules and caused mitochondrial fission. Unlike DF-MoS2, DR-MoS2 triggered an increased degree of mitochondrial fusion, as well as more severe oxidative stress. The activities of Mito-RETC complexes (I, III, IV, V) associated with oxidative phosphorylation were significantly inhibited by 22.8-68.6%. Meanwhile, apoptotic pathways were activated upon DR-MoS2 exposure, which together with the depolarization of mitochondrial membrane potential, mediated significant apoptosis. In turn, genes related to cellular homeostasis and energy release were up-regulated to compensate for DR-MoS2-induced energy deprivation. Our study indicates that MoS2 nanosheets have nanospecific effects on E. fetida and also that the role of surface defects from synthesis or that accumulate from environmental impacts needs to be fully considered when evaluating the toxicity of these 2D materials.
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Affiliation(s)
- Kailun Sun
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Jason C White
- The Connecticut Agricultural Experiment Station, New Haven, Connecticut 06504, United States
| | - Erkai He
- School of Geographic Sciences, East China Normal University, Shanghai, 200241, China
| | - Cornelis A M Van Gestel
- Amsterdam Institute for Life and Environment (A-LIFE), Faculty of Science, Vrije Universiteit, Amsterdam, 1081 HV, The Netherlands
| | - Hao Qiu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
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2
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Sun H, Zheng M, Liu J, Fan W, He H, Huang F. Melatonin promoted osteogenesis of human periodontal ligament cells by regulating mitochondrial functions through the translocase of the outer mitochondrial membrane 20. J Periodontal Res 2023; 58:53-69. [PMID: 36373245 DOI: 10.1111/jre.13068] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 10/08/2022] [Accepted: 10/19/2022] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND OBJECTIVE Melatonin plays an important role in various beneficial functions, including promoting differentiation. However, effects on osteogenic differentiation, especially in human periodontal cells (hPDLCs), still remain inconclusive. Mitochondria are highly dynamic organelles that play an important role in various biological processes in cells, including energy metabolism and oxidative stress reaction. Furthermore, the translocase of the outer mitochondrial membrane 20 (TOM20) is responsible for recognizing and transporting precursor proteins. Thus, the objective of this study was to evaluate the functionality of melatonin on osteogenesis in human periodontal cells and to explore the involved mechanism of mitochondria. METHODS The hPDLCs were extracted and identified by flow cytometry and multilineage differentiation. We divided hPDLCs into control group, osteogenic induction group, and osteogenesis with melatonin treatment group (100, 10, and 1 μM). Then we used a specific siRNA to achieve interference of TOM20. Alizarin red and Alkaline phosphatase staining and activity assays were performed to evaluate osteogenic differentiation. Osteogenesis-related genes and proteins were measured by qPCR and western blot. Mitochondrial functions were tested using ATP, NAD+/NADH, JC-1, and Seahorse Mito Stress Test kits. Finally, TOM20 and mitochondrial dynamics-related molecules expression were also assessed by qPCR and western blot. RESULTS Our results showed that melatonin-treated hPDLCs had higher calcification and ALP activity as well as upregulated OCN and Runx2 expression at mRNA and protein levels, which was the most obvious in 1 μM melatonin-treated group. Meanwhile, melatonin supplement elevated intracellular ATP production and mitochondrial membrane potential by increasing mitochondrial oxidative metabolism, hence causing a lower NAD+ /NADH ratio. In addition, we also found that melatonin treatment raised TOM20 level and osteogenesis and mitochondrial functions were both suppressed after knocking down TOM20. CONCLUSION We found that melatonin promoted osteogenesis of hPDLCs and 1 μM melatonin had the most remarkable effect. Melatonin treatment can reinforce mitochondrial functions by upregulating TOM20.
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Affiliation(s)
- Haoyun Sun
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
| | - Miaomiao Zheng
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
| | - Jiawei Liu
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
| | - Wenguo Fan
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
| | - Hongwen He
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
| | - Fang Huang
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
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Increased mitochondrial protein import and cardiolipin remodelling upon early mtUPR. PLoS Genet 2021; 17:e1009664. [PMID: 34214073 PMCID: PMC8282050 DOI: 10.1371/journal.pgen.1009664] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 07/15/2021] [Accepted: 06/11/2021] [Indexed: 12/11/2022] Open
Abstract
Mitochondrial defects can cause a variety of human diseases and protective mechanisms exist to maintain mitochondrial functionality. Imbalances in mitochondrial proteostasis trigger a transcriptional program, termed mitochondrial unfolded protein response (mtUPR). However, the temporal sequence of events in mtUPR is unclear and the consequences on mitochondrial protein import are controversial. Here, we have quantitatively analyzed all main import pathways into mitochondria after different time spans of mtUPR induction. Kinetic analyses reveal that protein import into all mitochondrial subcompartments strongly increases early upon mtUPR and that this is accompanied by rapid remodelling of the mitochondrial signature lipid cardiolipin. Genetic inactivation of cardiolipin synthesis precluded stimulation of protein import and compromised cellular fitness. At late stages of mtUPR upon sustained stress, mitochondrial protein import efficiency declined. Our work clarifies the enigma of protein import upon mtUPR and identifies sequential mtUPR stages, in which an early increase in protein biogenesis to restore mitochondrial proteostasis is followed by late stages characterized by a decrease in import capacity upon prolonged stress induction. Mitochondria are essential organelles and involved in numerous important functions like ATP production, biosynthesis of metabolites and co-factors or regulation of programmed cell death. To fulfill this plethora of different tasks, mitochondria require an extensive proteome, which is build by import of nuclear-encoded precursor proteins from the cytosol. Mitochondrial defects can cause a variety of severe human disorders that often affect tissues with high energy demand e.g. heart, muscle or brain. However, protective mechanisms exist that are triggered upon mitochondrial dysfunction: Imbalances in mitochondrial proteostasis are sensed by the cell and elicit a nuclear transcriptional response, termed mitochondrial unfolded protein response (mtUPR). Transcription of mitochondrial chaperones and proteases is increased to counteract mitochondrial dysfunctions. In this study, we investigated if mtUPR progresses in different temporal stages and how protein import is affected upon mtUPR. We discover that mtUPR is subdivided into an early phase, in which protein import increases and a late phase, in which it declines. Stimulation of protein import is accompanied by an increase and remodelling of the mitochondrial signature lipid cardiolipin. Our work establishes a novel model how cells respond to dysfunctional mitochondria, in which cardiolipin and protein import are modulated as first protective measures.
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Baysal C, Pérez-González A, Eseverri Á, Jiang X, Medina V, Caro E, Rubio L, Christou P, Zhu C. Recognition motifs rather than phylogenetic origin influence the ability of targeting peptides to import nuclear-encoded recombinant proteins into rice mitochondria. Transgenic Res 2020; 29:37-52. [PMID: 31598902 PMCID: PMC7000509 DOI: 10.1007/s11248-019-00176-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 10/01/2019] [Indexed: 10/30/2022]
Abstract
Mitochondria fulfil essential functions in respiration and metabolism as well as regulating stress responses and apoptosis. Most native mitochondrial proteins are encoded by nuclear genes and are imported into mitochondria via one of several receptors that recognize N-terminal signal peptides. The targeting of recombinant proteins to mitochondria therefore requires the presence of an appropriate N-terminal peptide, but little is known about mitochondrial import in monocotyledonous plants such as rice (Oryza sativa). To gain insight into this phenomenon, we targeted nuclear-encoded enhanced green fluorescent protein (eGFP) to rice mitochondria using six mitochondrial pre-sequences with diverse phylogenetic origins, and investigated their effectiveness by immunoblot analysis as well as confocal and electron microscopy. We found that the ATPA and COX4 (Saccharomyces cerevisiae), SU9 (Neurospora crassa), pFA (Arabidopsis thaliana) and OsSCSb (Oryza sativa) peptides successfully directed most of the eGFP to the mitochondria, whereas the MTS2 peptide (Nicotiana plumbaginifolia) showed little or no evidence of targeting ability even though it is a native plant sequence. Our data therefore indicate that the presence of particular recognition motifs may be required for mitochondrial targeting, whereas the phylogenetic origin of the pre-sequences probably does not play a key role in the success of mitochondrial targeting in dedifferentiated rice callus and plants.
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Affiliation(s)
- Can Baysal
- Department of Plant Production and Forestry Science, University of Lleida-Agrotecnio Center, Av. Alcalde Rovira Roure, 191, 25198, Lleida, Spain
| | - Ana Pérez-González
- Centre for Plant Biotechnology and Genomics, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain
| | - Álvaro Eseverri
- Centre for Plant Biotechnology and Genomics, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain
| | - Xi Jiang
- Centre for Plant Biotechnology and Genomics, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain
| | - Vicente Medina
- Department of Plant Production and Forestry Science, University of Lleida-Agrotecnio Center, Av. Alcalde Rovira Roure, 191, 25198, Lleida, Spain
| | - Elena Caro
- Centre for Plant Biotechnology and Genomics, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain
| | - Luis Rubio
- Centre for Plant Biotechnology and Genomics, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain
| | - Paul Christou
- Department of Plant Production and Forestry Science, University of Lleida-Agrotecnio Center, Av. Alcalde Rovira Roure, 191, 25198, Lleida, Spain
- ICREA, Catalan Institute for Research and Advanced Studies, Passeig Lluís Companys 23, 08010, Barcelona, Spain
| | - Changfu Zhu
- Department of Plant Production and Forestry Science, University of Lleida-Agrotecnio Center, Av. Alcalde Rovira Roure, 191, 25198, Lleida, Spain.
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Mazure NM. VDAC in cancer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:665-673. [PMID: 28283400 DOI: 10.1016/j.bbabio.2017.03.002] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 02/21/2017] [Accepted: 03/03/2017] [Indexed: 12/23/2022]
Abstract
The voltage-dependent anion channel (VDAC) is a pore located at the outer membrane of the mitochondrion. It allows the entry and exit of numerous ions and metabolites between the cytosol and the mitochondrion. Flux through the pore occurs in an active way: first, it depends on the open or closed state and second, on the negative or positive charges of the different ion species passing through the pore. The flux of essential metabolites, such as ATP, determines the functioning of the mitochondria to a noxious stimulus. Moreover, VDAC acts as a platform for many proteins and in so doing supports glycolysis and prevents apoptosis by interacting with hexokinase, or members of the Bcl-2 family, respectively. VDAC is thus involved in the choice the cells make to survive or die, which is particularly relevant to cancer cells. For these reasons, VDAC has become a potential therapeutic target to fight cancer but also other diseases in which mitochondrial metabolism is modified. This article is part of a Special Issue entitled Mitochondria in Cancer, edited by Giuseppe Gasparre, Rodrigue Rossignol and Pierre Sonveaux.
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Affiliation(s)
- N M Mazure
- Institute for Research on Cancer and Aging, Nice (IRCAN), CNRS UMR7284, INSERM U1081, University of Nice, France; CNRS GDR 3697 Micronit, France.
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Kozjak-Pavlovic V, Dian-Lothrop EA, Meinecke M, Kepp O, Ross K, Rajalingam K, Harsman A, Hauf E, Brinkmann V, Günther D, Herrmann I, Hurwitz R, Rassow J, Wagner R, Rudel T. Bacterial porin disrupts mitochondrial membrane potential and sensitizes host cells to apoptosis. PLoS Pathog 2009; 5:e1000629. [PMID: 19851451 PMCID: PMC2759283 DOI: 10.1371/journal.ppat.1000629] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 09/24/2009] [Indexed: 11/28/2022] Open
Abstract
The bacterial PorB porin, an ATP-binding β-barrel protein of pathogenic Neisseria gonorrhoeae, triggers host cell apoptosis by an unknown mechanism. PorB is targeted to and imported by host cell mitochondria, causing the breakdown of the mitochondrial membrane potential (ΔΨm). Here, we show that PorB induces the condensation of the mitochondrial matrix and the loss of cristae structures, sensitizing cells to the induction of apoptosis via signaling pathways activated by BH3-only proteins. PorB is imported into mitochondria through the general translocase TOM but, unexpectedly, is not recognized by the SAM sorting machinery, usually required for the assembly of β-barrel proteins in the mitochondrial outer membrane. PorB integrates into the mitochondrial inner membrane, leading to the breakdown of ΔΨm. The PorB channel is regulated by nucleotides and an isogenic PorB mutant defective in ATP-binding failed to induce ΔΨm loss and apoptosis, demonstrating that dissipation of ΔΨm is a requirement for cell death caused by neisserial infection. PorB is a bacterial porin that plays an important role in the pathogenicity of Neisseria gonorrhoeae. Upon infection with these bacteria, PorB is transported into mitochondria of infected cells, causing the loss of mitochondrial membrane potential and eventually leading to apoptotic cell death. Here, we show that PorB enters mitochondria through the TOM complex, similar to other mitochondria-targeted proteins, but then bypasses the SAM complex machinery that assembles all other porin-like proteins into the outer mitochondrial membrane. This leads to the accumulation of PorB in the intermembrane space and the integration of a fraction of PorB into the inner mitochondrial membrane (IMM). In the IMM, ATP-regulated pores are formed, leading to dissipation of membrane potential and the loss of cristae structure in affected mitochondria, the necessary first steps in induction of apoptosis. Our work offers, for the first time, a detailed analysis of the mechanism by which PorB targets and damages host cell mitochondria.
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Affiliation(s)
- Vera Kozjak-Pavlovic
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
| | | | - Michael Meinecke
- Department of Biology/Chemistry, Division of Biophysics, University of Osnabrück, Osnabrück, Germany
| | - Oliver Kepp
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Katharina Ross
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Krishnaraj Rajalingam
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Anke Harsman
- Protein Purification Core Facility, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Eva Hauf
- Microscopy Core Facility, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Volker Brinkmann
- Microscopy Core Facility, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Dirk Günther
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Ines Herrmann
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Robert Hurwitz
- Protein Purification Core Facility, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Joachim Rassow
- Institute for Physiological Chemistry, Ruhr-University Bochum, Bochum, Germany
| | - Richard Wagner
- Department of Biology/Chemistry, Division of Biophysics, University of Osnabrück, Osnabrück, Germany
| | - Thomas Rudel
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
- * E-mail:
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Gabriel K, Pfanner N. The mitochondrial machinery for import of precursor proteins. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2008; 390:99-117. [PMID: 17951683 DOI: 10.1007/978-1-59745-466-7_7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Mitochondria contain a small genome that codes for approx 1% of the total number of proteins that reside in the mitochondria. Hence, most mitochondrial proteins are encoded for by the nuclear genome. After transcription in the nucleus these proteins are synthesized by cytosolic ribosomes. Like proteins destined for other organellar compartments, mitochondrially destined proteins possess targeting signals within their primary or secondary structure that direct them to the organelle with the assistance of cytosolic factors. Very specialized and discriminatory protein translocase complexes in the mitochondrial membranes, intermembrane space, and matrix are then engaged for the translocation, sorting, integration, processing, and folding of the newly imported proteins. The principles of protein targeting into mitochondria have been and are still being unraveled, mostly by studies with the yeast Saccharomyces cerevisiae and the fungus Neurospora crassa. In this chapter the major principles of mitochondrial protein targeting as currently understood will be discussed as a foundation for the experimental methods discussed later in this volume.
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Affiliation(s)
- Kipros Gabriel
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Freiburg, Germany
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Lister R, Carrie C, Duncan O, Ho LHM, Howell KA, Murcha MW, Whelan J. Functional definition of outer membrane proteins involved in preprotein import into mitochondria. THE PLANT CELL 2007; 19:3739-59. [PMID: 17981999 PMCID: PMC2174869 DOI: 10.1105/tpc.107.050534] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The role of plant mitochondrial outer membrane proteins in the process of preprotein import was investigated, as some of the principal components characterized in yeast have been shown to be absent or evolutionarily distinct in plants. Three outer membrane proteins of Arabidopsis thaliana mitochondria were studied: TOM20 (translocase of the outer mitochondrial membrane), METAXIN, and mtOM64 (outer mitochondrial membrane protein of 64 kD). A single functional Arabidopsis TOM20 gene is sufficient to produce a normal multisubunit translocase of the outer membrane complex. Simultaneous inactivation of two of the three TOM20 genes changed the rate of import for some precursor proteins, revealing limited isoform subfunctionalization. Inactivation of all three TOM20 genes resulted in severely reduced rates of import for some but not all precursor proteins. The outer membrane protein METAXIN was characterized to play a role in the import of mitochondrial precursor proteins and likely plays a role in the assembly of beta-barrel proteins into the outer membrane. An outer mitochondrial membrane protein of 64 kD (mtOM64) with high sequence similarity to a chloroplast import receptor was shown to interact with a variety of precursor proteins. All three proteins have domains exposed to the cytosol and interacted with a variety of precursor proteins, as determined by pull-down and yeast two-hybrid interaction assays. Furthermore, inactivation of one resulted in protein abundance changes in the others, suggesting functional redundancy. Thus, it is proposed that all three components directly interact with precursor proteins to participate in early stages of mitochondrial protein import.
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Affiliation(s)
- Ryan Lister
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009, Western Australia, Australia
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Peixoto PMV, Graña F, Roy TJ, Dunn CD, Flores M, Jensen RE, Campo ML. Awaking TIM22, a Dynamic Ligand-gated Channel for Protein Insertion in the Mitochondrial Inner Membrane. J Biol Chem 2007; 282:18694-701. [PMID: 17462993 DOI: 10.1074/jbc.m700775200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aqueous channels are at the core of the translocase of the outer membrane (TOM) and the translocase of the inner membrane for the transport of preproteins (TIM23), the translocases mediating the transport of proteins across the outer and inner mitochondrial membranes. Yet, the existence of a channel associated to the translocase of the inner membrane for the insertion of multitopic protein (TIM22) complex has been arguable, as its function relates to the insertion of multispanning proteins into the inner membrane. For the first time, we report conditions for detecting a channel activity associated to the TIM22 translocase in organelle, i.e. intact mitoplasts. An internal signal peptide in the intermembrane space of mitochondria is a requisite to inducing this channel, which is otherwise silent. The channel showed slightly cationic and high conductance activity of 1000 pS with a predominant half-open substate. Despite their different composition, the channels of the three mitochondrial translocases were thus remarkably similar, in agreement with their common task as pores transiently trapping proteins en route to their final destination. The opening of the TIM22 channel was a step-up process depending on the signal peptide concentration. Interestingly, low membrane potentials kept the channel fully open, providing a threshold level of the peptide is present. Our results portray TIM22 as a dynamic channel solely active in the presence of its cargo proteins. In its fully open conformation, favored by the combined action of internal signal peptide and low membrane potential, the channel could embrace the in-transit protein. As insertion progressed and initial interaction with the signal peptide faded, the channel would close, sustaining its role as a shunt that places trapped proteins into the membrane.
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Affiliation(s)
- Pablo M V Peixoto
- Department of Biochemistry and Molecular Biology, University of Extremadura, 10071 Cáceres, Spain
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10
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Curran JE, Johnson MP, Dyer TD, Göring HHH, Kent JW, Charlesworth JC, Borg AJ, Jowett JBM, Cole SA, MacCluer JW, Kissebah AH, Moses EK, Blangero J. Genetic determinants of mitochondrial content. Hum Mol Genet 2007; 16:1504-14. [PMID: 17468176 DOI: 10.1093/hmg/ddm101] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The mitochondria are the major cellular site of energy production and respiration. Recent research has focused on investigating the role of mitochondria in disease development and it has become increasingly evident that mitochondrial dysfunction contributes to a variety of human diseases. Mitochondrial DNA (mtDNA) quantity is very important for maintaining mitochondrial function and meeting the energy needs of the body. We have measured mitochondrial content in 1259 Mexican American individuals (from 42 extended families) and have shown that mtDNA quantity (a surrogate measure of mitochondrial integrity) has a large genetic component. We performed a genome scan and a genome-wide quantitative transcriptomic scan to identify QTLs influencing mitochondrial content. A variance components linkage-based genome scan utilizing 439 STR markers was used to localize a QTL for mitochondrial content on chromosome 10q (LOD = 3.83). Significant linkage to the mitochondrial genome was also detected for mitochondrial transmission (LOD = 3.39). For replication, we measured mitochondrial content in an independent Caucasian population (1088 individuals) finding evidence for linkage in these same regions. As part of the San Antonio Family Heart Study, we obtained genome-wide quantitative transcriptional profiles from 1240 individuals. Using lymphocyte samples, we quantitated 20 413 transcripts and examined correlations between the expression levels of these transcripts and mitochondrial content using the variance components method. Using regression analysis allowing for residual genetic components, we identified 829 transcripts (including many novel genes) influencing mitochondrial content that vary in their general biological actions, from cell signaling to cell trafficking and ion binding.
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Affiliation(s)
- Joanne E Curran
- Department of Genetics, Southwest Foundation for Biomedical Research, San Antonio, TX 78227, USA.
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11
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Vogt S, Troitzsch D, Abdul-Khaliq H, Moosdorf R. Heat stress attenuates ATP-depletion and pH-decrease during cardioplegic arrest. J Surg Res 2007; 139:176-81. [PMID: 17336331 DOI: 10.1016/j.jss.2006.07.041] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 07/27/2006] [Accepted: 07/28/2006] [Indexed: 11/17/2022]
Abstract
BACKGROUND The capacity of heat stress induction to improve myocardial tolerance against ischemia is well known. We investigated cardiac energy metabolism after hsp 72(+)/73(+) induction in isolated perfused neonatal rabbit hearts subjected to prolonged cold cardioplegic ischemia. METHODS Hearts from neonatal rabbits were excised, isolated perfused and arrested by 2-h cold cardioplegic ischemia. Rectal temperature of eight neonatal rabbits was raised to 42.0 to 42.5 degrees C for heat shock protein expression in a whole body water bath for 15 min before the onset of arrest. Another set of eight rabbits without hyperthermia pretreatment served as control. Recovery of left ventricle function was assessed by aortic flow, cardiac output, and max dP/dt. Status of high-energy phosphates was measured by (31)phosphorus nuclear magnetic resonance-spectroscopy. RESULTS Immunoblot analysis revealed clear hsp 72+/73+ induction after a brief period of systemic hyperthermia. Heat stress pretreatment resulted in a better recovery of left ventricular function (aortic flow and cardiac output improvement P < 0.05, max dP/dt P < 0.01) than in controls at 60 min after reperfusion. During ischemia and reperfusion, myocardial energy metabolism was better preserved in hearts after hsp induction as a consequence of increased gamma-, alpha-, and beta-ATP as well as phosphocreatine-values over controls. The ischemia-induced pH-decrease was attenuated. CONCLUSION These data contribute to the evidence of heat stress mediated beneficial effects on functional myocardial recovery and improved cardiac energy metabolism after prolonged cold cardioplegic ischemia. More importantly, the attenuation of ischemic pH reduction and better restoration suggest an involvement of mitochondrial membrane potential alterations.
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Affiliation(s)
- Sebastian Vogt
- Biomedical Research Center, Cardiovascular Research Lab and Heart Surgery, University Hospital, Philipps-University Marburg, Marburg, Germany.
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12
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Barth C, Le P, Fisher PR. Mitochondrial biology and disease in Dictyostelium. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 263:207-52. [PMID: 17725968 DOI: 10.1016/s0074-7696(07)63005-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The cellular slime mold Dictyostelium discoideum has become an increasingly useful model for the study of mitochondrial biology and disease. Dictyostelium is an amoebazoan, a sister clade to the animal and fungal lineages. The mitochondrial biology of Dictyostelium exhibits some features which are unique, others which are common to all eukaryotes, and still others that are otherwise found only in the plant or the animal lineages. The AT-rich mitochondrial genome of Dictyostelium is larger than its mammalian counterpart and contains 56kb (compared to 17kb in mammals) encoding tRNAs, rRNAs, and 33 polypeptides (compared to 13 in mammals). It produces a single primary transcript that is cotranscriptionally processed into multiple monocistronic, dicistronic, and tricistronic mRNAs, tRNAs, and rRNAs. The mitochondrial fission mechanism employed by Dictyostelium involves both the extramitochondrial dynamin-based system used by plant, animal, and fungal mitochondria and the ancient FtsZ-based intramitochondrial fission process inherited from the bacterial ancestor. The mitochondrial protein-import apparatus is homologous to that of other eukaryote, and mitochondria in Dictyostelium play an important role in the programmed cell death pathways. Mitochondrial disease in Dictyostelium has been created both by targeted gene disruptions and by antisense RNA and RNAi inhibition of expression of essential nucleus-encoded mitochondrial proteins. This has revealed a regular pattern of aberrant mitochondrial disease phenotypes caused not by ATP insufficiency per se, but by chronic activation of the universal eukaryotic energy-sensing protein kinase AMPK. This novel insight into the cytopathological mechanisms of mitochondrial dysfunction suggests new possibilities for therapeutic intervention in mitochondrial and neurodegenerative diseases.
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Affiliation(s)
- Christian Barth
- Department of Microbiology, La Trobe University, Melbourne VIC 3086, Australia
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Abstract
It is widely recognized that much of the information for determining the final subcellular localization of proteins is found in their amino acid sequences. Thus the prediction of protein localization sites is of both theoretical and practical interest. In most cases, the prediction has been attempted in two ways: one is based on the knowledge of experimentally characterized targeting signals, while the other utilizes the statistical differences of general sequence characteristics, such as amino acid composition, between localization sites. Both approaches have limitations, and it is recommended to check the results of various prediction methods based on different principles as well as training data. Recently, increased proteomic analyses of localization sites have provided new data to assess the current status of predictive methods. In this chapter we discuss these issues and close with an example illustrating the use of the WoLF PSORT web server for localization prediction.
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Affiliation(s)
- Kenta Nakai
- Laboratory of Functional Analysis in silico, Human Genome Center, Institute of Medical Science, University of Tokyo, Tokyo, Japan
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Martinez-Caballero S, Grigoriev SM, Herrmann JM, Campo ML, Kinnally KW. Tim17p regulates the twin pore structure and voltage gating of the mitochondrial protein import complex TIM23. J Biol Chem 2006; 282:3584-93. [PMID: 17148445 DOI: 10.1074/jbc.m607551200] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The TIM23 complex mediates import of preproteins into mitochondria, but little is known of the mechanistic properties of this translocase. Here patch clamping reconstituted inner membranes allowed for first time insights into the structure and function of the preprotein translocase. Our findings indicate that the TIM23 channel has "twin pores" (two equal sized pores that cooperatively gate) thereby strikingly resembling TOM, the translocase of the outer membrane. Tim17p and Tim23p are homologues, but their functions differ. Tim23p acts as receptor for preproteins and may largely constitute the preprotein-conducting passageway. Conversely depletion of Tim17p induces a collapse of the twin pores into a single pore, whereas N terminus deletion or C terminus truncation results in variable sized pores that cooperatively gate. Further analysis of Tim17p mutants indicates that the N terminus is vital for both voltage sensing and protein sorting. These results suggest that although Tim23p is the main structural unit of the pore Tim17p is required for twin pore structure and provides the voltage gate for the TIM23 channel.
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Affiliation(s)
- Sonia Martinez-Caballero
- Department of Basic Sciences, New York University College of Dentistry, New York, New York 10010, USA
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15
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Emelyanov VV, Vyssokikh MY. On the nature of obligate intracellular symbiosis of rickettsiae--Rickettsia prowazekii cells import mitochondrial porin. BIOCHEMISTRY (MOSCOW) 2006; 71:730-5. [PMID: 16903827 DOI: 10.1134/s0006297906070054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Mitochondrial porin was identified in Rickettsia prowazekii by Western blot analysis of whole cells and membrane fractions with monoclonal antibody against porin VDAC 1 of animal mitochondria. Using the BLAST server, no protein sequences homologous to mitochondrial porin were found among the rickettsial genomes. Rickettsiae also do not contain their own porin. The protein imported by rickettsiae is weakly extracted by nonionic detergents and, like porin in mitochondria, is insensitive to proteinase K in whole cells. Immunocytochemical analysis showed that it localizes to the outer membrane of the bacterial cells. These data support an earlier suggestion about import by rickettsiae of indispensable proteins from cytoplasm of the host cell as a molecular basis of obligate intracellular parasitism. They are also consistent with the hypothesis invoking a transfer of genes specifying surface proteins from the last common ancestor of rickettsiae and mitochondria to the host genome, and preservation by rickettsiae of the primitive ability to import these proteins.
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Affiliation(s)
- V V Emelyanov
- Gamaleya Institute of Epidemiology and Microbiology, Russian Academy of Medical Sciences, Moscow, 123098, Russia.
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Mukhopadhyay A, Yang CS, Weiner H. Binding of mitochondrial leader sequences to Tom20 assessed using a bacterial two-hybrid system shows that hydrophobic interactions are essential and that some mutated leaders that do not bind Tom20 can still be imported. Protein Sci 2006; 15:2739-48. [PMID: 17088320 PMCID: PMC2242433 DOI: 10.1110/ps.062462006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Previous studies pointed to the importance of leucine residues in the binding of mitochondrial leader sequences to Tom20, an outer membrane protein translocator that initially binds the leader during import. A bacteria two-hybrid assay was here employed to determine if this could be an alternative way to investigate the binding of leader to the receptor. Leucine to alanine and arginine to glutamine mutations were made in the leader sequence from rat liver aldehyde dehydrogenase (pALDH). The leucine residues in the C-terminal of pALDH leader were found to be essential for TOM20 binding. The hydrophobic residues of another mitochondrial leader F1beta-ATPase that were important for Tom20 binding were found at the C-terminus of the leader. In contrast, it was the leucines in the N-terminus of the leader of ornithine transcarbamylase that were essential for binding. Modeling the peptides to the structure of Tom20 showed that the hydrophobic residues from the three proteins could all fit into the hydrophobic binding pocket. The mutants of pALDH that did not bind to Tom20 were still imported in vivo in transformed HeLa cells or in vitro into isolated mitochondria. In contrast, the mutant from pOTC was imported less well ( approximately 50%) while the mutant from F1beta-ATPase was not imported to any measurable extent. Binding to Tom20 might not be a prerequisite for import; however, it also is possible that import can occur even if binding to a receptor component is poor, so long as the leader binds tightly to another component of the translocator.
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Affiliation(s)
- Abhijit Mukhopadhyay
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-2063, USA
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Léon S, Goodman JM, Subramani S. Uniqueness of the mechanism of protein import into the peroxisome matrix: transport of folded, co-factor-bound and oligomeric proteins by shuttling receptors. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1552-64. [PMID: 17011644 DOI: 10.1016/j.bbamcr.2006.08.037] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Revised: 08/18/2006] [Accepted: 08/23/2006] [Indexed: 11/30/2022]
Abstract
Based on earlier suggestions that peroxisomes may have arisen from endosymbionts that later lost their DNA, it was expected that protein transport into this organelle would have parallels to systems found in other organelles of endosymbiont origin, such as mitochondria and chloroplasts. This review highlights three features of peroxisomal matrix protein import that make it unique in comparison with these other subcellular compartments - the ability of this organelle to transport folded, co-factor-bound and oligomeric proteins, the dynamics of the import receptors during the matrix protein import cycle and the existence of a peroxisomal quality-control pathway, which insures that the peroxisome membrane is cleared of cargo-free receptors.
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Affiliation(s)
- Sébastien Léon
- Section of Molecular Biology, Division of Biological Sciences, University California, Room 3230 Bonner Hall, 9500 Gilman Drive, UC San Diego, La Jolla, CA 92093-0322, USA
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Meisinger C, Wiedemann N, Rissler M, Strub A, Milenkovic D, Schönfisch B, Müller H, Kozjak V, Pfanner N. Mitochondrial Protein Sorting. J Biol Chem 2006; 281:22819-26. [PMID: 16760475 DOI: 10.1074/jbc.m602679200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial outer membrane contains two distinct machineries for protein import and protein sorting that function in a sequential manner: the general translocase of the outer membrane (TOM complex) and the sorting and assembly machinery (SAM complex), which is dedicated to beta-barrel proteins. The SAM(core) complex consists of three subunits, Sam35, Sam37, and Sam50, that can associate with a fourth subunit, the morphology component Mdm10, to form the SAM(holo) complex. Whereas the SAM(core) complex is required for the biogenesis of all beta-barrel proteins, Mdm10 and the SAM(holo) complex play a selective role in beta-barrel biogenesis by promoting assembly of Tom40 but not of porin. We report that Tom7, a conserved subunit of the TOM complex, functions in an antagonistic manner to Mdm10 in biogenesis of Tom40 and porin. We show that Tom7 promotes segregation of Mdm10 from the SAM(holo) complex into a low molecular mass form. Upon deletion of Tom7, the fraction of Mdm10 in the SAM(holo) complex is significantly increased, explaining the opposing functions of Tom7 and Mdm10 in beta-barrel sorting. Thus the role of Tom7 is not limited to the TOM complex. Tom7 functions in mitochondrial protein biogenesis by a new mechanism, segregation of a sorting component, leading to a differentiation of beta-barrel assembly.
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Affiliation(s)
- Chris Meisinger
- Institut für Biochemie und Molekularbiologie and the Fakultät für Biologie, Universität Freiburg, 79104 Freiburg
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Minetti CASA, Remeta DP. Energetics of membrane protein folding and stability. Arch Biochem Biophys 2006; 453:32-53. [PMID: 16712771 DOI: 10.1016/j.abb.2006.03.023] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Accepted: 03/23/2006] [Indexed: 11/24/2022]
Abstract
The critical role of membrane proteins in a myriad of biological and physiological functions has spawned numerous investigations over the past several decades with the long-term goal of identifying the molecular origins and energetic forces that stabilize these proteins within the membrane. Parallel structural and thermodynamics studies on several systems have provided significant insight regarding the driving forces governing folding, assembly, insertion, and translocation of membrane proteins. The present review surveys families of membrane-associated proteins including alpha-helical and beta-barrel structures, viral surface receptors, and pore-forming toxins, citing representative proteins within each of these classes for further scrutiny in terms of structure-function relationships and global conformational stability. This overview presents seminal findings from pioneering studies on the energetics of membrane protein folding and stability to modern techniques that are exploiting the use of molecular genetics and single molecule studies. An overall consensus regarding the molecular origins of membrane protein stability is that a number of intrinsic properties resemble features of soluble proteins, yet there are distinct energetic differences arising from specific intra- and intermolecular interactions within the membrane. The combined efforts from structural, energetics, and dynamics approaches offer unique insights and improve our fundamental understanding of the driving forces dictating membrane protein folding and stability.
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Affiliation(s)
- Conceição A S A Minetti
- Rutgers-The State University of New Jersey, Department of Chemistry and Chemical Biology, Piscataway, NJ 08854, USA.
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Mogensen JE, Kleinschmidt JH, Schmidt MA, Otzen DE. Misfolding of a bacterial autotransporter. Protein Sci 2005; 14:2814-27. [PMID: 16199663 PMCID: PMC2253222 DOI: 10.1110/ps.051628705] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 08/09/2005] [Accepted: 08/15/2005] [Indexed: 10/25/2022]
Abstract
The adhesin involved in diffuse adherence (AIDA) is an autotransporter protein that confers the diffuse adherence phenotype to certain diarrheagenic Escherichia coli strains. It consists of a 49 amino acid signal peptide, a 797 amino acid passenger domain, and a 440 amino acid beta-domain integrated into the outer membrane. The beta-domain consists of two parts: the beta(1)-domain, which is predicted to form two beta-strands on the bacterial cell surface, and the beta(2)-domain, which constitutes the transmembrane domain. We have previously shown that the beta-domain can be folded from the urea-denatured state when bound to a nickel column during purification. It has not been possible to achieve proper refolding of the beta-domain in solution; instead, a misfolded state C is formed. Here, we characterize this misfolded state in greater detail, showing that despite being misfolded, C can be analyzed as a conventional conformational state, with cooperative unfolding in urea and SDS as well as showing simple exponential kinetics during its formation in the presence of lipid vesicles and detergent micelles. The kinetics of formation of C is sensitive to the lipid composition in vesicles. We have also attempted to identify biological factors that might aid folding of the beta-domain to the properly folded state. However, no purified periplasmic or cytosolic chaperone was found to increase folding yields, and no factor in a periplasmic extract was identified that could bind to C. We conclude that it is the exposure to the unique spatial arrangement of the bacterial cell that leads to proper refolding of the beta-domain.
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Affiliation(s)
- Jesper E Mogensen
- Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark
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Murcha MW, Elhafez D, Millar AH, Whelan J. The C-terminal region of TIM17 links the outer and inner mitochondrial membranes in Arabidopsis and is essential for protein import. J Biol Chem 2005; 280:16476-83. [PMID: 15722347 DOI: 10.1074/jbc.m413299200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The translocase of the inner membrane 17 (AtTIM17-2) protein from Arabidopsis has been shown to link the outer and inner mitochondrial membranes. This was demonstrated by several approaches: (i) In vitro organelle import assays indicated the imported AtTIM17-2 protein remained protease accessible in the outer membrane when inserted into the inner membrane. (ii) N-terminal and C-terminal tagging indicated that it was the C-terminal region that was located in the outer membrane. (iii) Antibodies raised to the C-terminal 100 amino acids recognize a 31-kDa protein from purified mitochondria, but cross-reactivity was abolished when mitochondria were protease-treated to remove outer membrane-exposed proteins. Antibodies to AtTIM17-2 inhibited import of proteins via the general import pathway into outer membrane-ruptured mitochondria, but did not inhibit protein import via the carrier import pathway. Together these results indicate that the C-terminal region of AtTIM17-2 is exposed on the outer surface of the outer membrane, and the C-terminal region is essential for protein import into mitochondria.
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Affiliation(s)
- Monika W Murcha
- Plant Molecular Biology Group, School of Biomedical and Chemicals Sciences, University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia
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