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Gross LE, Klinger A, Spies N, Ernst T, Flinner N, Simm S, Ladig R, Bodensohn U, Schleiff E. Insertion of plastidic β-barrel proteins into the outer envelopes of plastids involves an intermembrane space intermediate formed with Toc75-V/OEP80. Plant Cell 2021; 33:1657-1681. [PMID: 33624803 PMCID: PMC8254496 DOI: 10.1093/plcell/koab052] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/03/2021] [Indexed: 06/12/2023]
Abstract
The insertion of organellar membrane proteins with the correct topology requires the following: First, the proteins must contain topogenic signals for translocation across and insertion into the membrane. Second, proteinaceous complexes in the cytoplasm, membrane, and lumen of organelles are required to drive this process. Many complexes required for the intracellular distribution of membrane proteins have been described, but the signals and components required for the insertion of plastidic β-barrel-type proteins into the outer membrane are largely unknown. The discovery of common principles is difficult, as only a few plastidic β-barrel proteins exist. Here, we provide evidence that the plastidic outer envelope β-barrel proteins OEP21, OEP24, and OEP37 from pea (Pisum sativum) and Arabidopsis thaliana contain information defining the topology of the protein. The information required for the translocation of pea proteins across the outer envelope membrane is present within the six N-terminal β-strands. This process requires the action of translocon of the outer chloroplast (TOC) membrane. After translocation into the intermembrane space, β-barrel proteins interact with TOC75-V, as exemplified by OEP37 and P39, and are integrated into the membrane. The membrane insertion of plastidic β-barrel proteins is affected by mutation of the last β-strand, suggesting that this strand contributes to the insertion signal. These findings shed light on the elements and complexes involved in plastidic β-barrel protein import.
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Affiliation(s)
- Lucia E Gross
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Anna Klinger
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Nicole Spies
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Theresa Ernst
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Nadine Flinner
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Stefan Simm
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
- Frankfurt Institute for Advanced Studies, D-60438 Frankfurt, Germany
| | - Roman Ladig
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Uwe Bodensohn
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Enrico Schleiff
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
- Frankfurt Institute for Advanced Studies, D-60438 Frankfurt, Germany
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2
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Bodensohn US, Simm S, Fischer K, Jäschke M, Groß LE, Kramer K, Ehmann C, Rensing SA, Ladig R, Schleiff E. The intracellular distribution of the components of the GET system in vascular plants. Biochim Biophys Acta Mol Cell Res 2019; 1866:1650-1662. [PMID: 31233800 DOI: 10.1016/j.bbamcr.2019.06.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Revised: 06/17/2019] [Accepted: 06/19/2019] [Indexed: 12/16/2022]
Abstract
The guided entry of tail-anchored proteins (GET) pathway facilitates targeting and insertion of tail-anchored proteins into membranes. In plants, such a protein insertion machinery for the endoplasmic reticulum as well as constituents within mitochondrial and chloroplasts were discovered. Previous phylogenetic analysis revealed that Get3 sequences of Embryophyta form two clades representing cytosolic ("a") and organellar ("bc") GET3 homologs, respectively. Cellular fractionation of Arabidopsis thaliana seedlings and usage of the self-assembly GFP system in protoplasts verified the cytosolic (ATGet3a), plastidic (ATGet3b) and mitochondrial (ATGet3c) localization of the different homologs. The identified plant homologs of Get1 and Get4 in A. thaliana are localized in ER and cytosol, respectively, implicating a degree of conservation of the GET pathway in A. thaliana. Transient expression of Get3 homologs of Solanum lycopersicum, Medicago × varia or Physcomitrella patens with the self-assembly GFP technique in homologous and heterologous systems verified that multiple Get3 homologs with differing subcellular localizations are common in plants. Chloroplast localized Get3 homologs were detected in all tested plant systems. In contrast, mitochondrial localized Get3 homologs were not identified in S. lycopersicum, or P. patens, while we confirmed on the example of A. thaliana proteins that mitochondrial localized Get3 proteins are properly targeted in S. lycopersicum as well.
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Affiliation(s)
- Uwe S Bodensohn
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Stefan Simm
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany; Frankfurt Institute of Advanced Studies, Ruth-Moufang-Straße 1, D-60438 Frankfurt, Germany
| | - Ken Fischer
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Michelle Jäschke
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Lucia E Groß
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Katharina Kramer
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Christian Ehmann
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Stefan A Rensing
- Faculty of Biology, University of Marburg, Karl-von-Frisch-Str. 8, D-35043 Marburg, Germany
| | - Roman Ladig
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Enrico Schleiff
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany; Buchman Institute for Molecular Life Sciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 15, D-60438 Frankfurt, Germany; Frankfurt Institute of Advanced Studies, Ruth-Moufang-Straße 1, D-60438 Frankfurt, Germany.
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Wiesemann K, Simm S, Mirus O, Ladig R, Schleiff E. Regulation of two GTPases Toc159 and Toc34 in the translocon of the outer envelope of chloroplasts. Biochim Biophys Acta Proteins Proteom 2019; 1867:627-636. [PMID: 30611779 DOI: 10.1016/j.bbapap.2019.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 12/20/2018] [Accepted: 01/02/2019] [Indexed: 01/03/2023]
Abstract
The GTPases Toc159 and Toc34 of the translocon of the outer envelope of chloroplasts (TOC) are involved in recognition and transfer of precursor proteins at the cytosolic face of the organelle. Both proteins engage multiple interactions within the translocon during the translocation process, including dimeric states of their G-domains. The units of the Toc34 homodimer are involved in the recognition of the transit peptide representing the translocation signal of precursor proteins. This substrate recognition is part of the regulation of the GTPase cycle of Toc34. The Toc159 monomer and the Toc34 homodimer recognize the transit peptide of the small subunit of Rubisco at the N- and at the C-terminal region, respectively. Analysis of the transit peptide interaction by crosslinking shows that the heterodimer between both G-domains binds pSSU most efficiently. While substrate recognition by Toc34 homodimer was shown to regulate nucleotide exchange, we provide evidence that the high activation energy of the GTPase Toc159 is lowered by substrate recognition. The nucleotide affinity of Toc34G homodimer and Toc159G monomer are distinct, Toc34G homodimer recognizes GDP and Toc159G GTP with highest affinity. Moreover, the analysis of the nucleotide association rates of the monomeric and dimeric receptor units suggests that the heterodimer has an arrangement distinct from the homodimer of Toc34. Based on the biochemical parameters determined we propose a model for the order of events at the cytosolic side of TOC. The molecular processes described by this hypothesis range from transit peptide recognition to perception of the substrate by the translocation channel.
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Affiliation(s)
- Katharina Wiesemann
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Stefan Simm
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany; Frankfurt Institute for Advanced Studies, Ruth-Moufang-Straße 1, D-60438 Frankfurt, Germany
| | - Oliver Mirus
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Roman Ladig
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany; Cluster of Excellence Frankfurt, Goethe University, D-60438 Frankfurt, Germany
| | - Enrico Schleiff
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany; Frankfurt Institute for Advanced Studies, Ruth-Moufang-Straße 1, D-60438 Frankfurt, Germany; Cluster of Excellence Frankfurt, Goethe University, D-60438 Frankfurt, Germany; Buchmann Institute for Molecular Life Sciences, Goethe University, Max-von-Laue Str. 15, D-60438 Frankfurt, Germany.
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Brouwer E, Ngo G, Yadav S, Ladig R, Schleiff E. Tic22 from
Anabaena
sp. PCC 7120 with holdase function involved in outer membrane protein biogenesis shuttles between plasma membrane and Omp85. Mol Microbiol 2019; 111:1302-1316. [DOI: 10.1111/mmi.14222] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/07/2019] [Indexed: 11/30/2022]
Affiliation(s)
- Eva‐Maria Brouwer
- Institute for Molecular Biosciences Goethe University Frankfurt am Main Frankfurt am Main Germany
| | - Giang Ngo
- Institute for Molecular Biosciences Goethe University Frankfurt am Main Frankfurt am Main Germany
| | - Shivam Yadav
- Institute for Molecular Biosciences Goethe University Frankfurt am Main Frankfurt am Main Germany
- Centre of Advanced Studies in Botany, Institute of Science Banaras Hindu University Varanasi India
| | - Roman Ladig
- Institute for Molecular Biosciences Goethe University Frankfurt am Main Frankfurt am Main Germany
| | - Enrico Schleiff
- Institute for Molecular Biosciences Goethe University Frankfurt am Main Frankfurt am Main Germany
- Buchman Institute for Molecular Life Sciences Goethe University Frankfurt am Main Frankfurt am Main Germany
- Frankfurt Institute of Advanced Studies Frankfurt am Main Germany
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5
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Klinger A, Gosch V, Bodensohn U, Ladig R, Schleiff E. The signal distinguishing between targeting of outer membrane β-barrel protein to plastids and mitochondria in plants. Biochim Biophys Acta Mol Cell Res 2019; 1866:663-672. [PMID: 30633951 DOI: 10.1016/j.bbamcr.2019.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 12/03/2018] [Accepted: 01/07/2019] [Indexed: 12/15/2022]
Abstract
The proteome of the outer membrane of mitochondria and chloroplasts consists of membrane proteins anchored by α-helical or β-sheet elements. While proteins with α-helical transmembrane domains are present in all cellular membranes, proteins with β-barrel structure are specific for these two membranes. The organellar β-barrel proteins are encoded in the nuclear genome and thus, have to be targeted to the outer organellar membrane where they are recognized by surface exposed translocation complexes. In the last years, the signals that ensure proper targeting of these proteins have been investigated as essential base for an understanding of the regulation of cellular protein distribution. However, the organellar β-barrel proteins are unique as most of them do not contain a typical targeting information in form of an N-terminal cleavable targeting signal. Recently, it was discovered that targeting and surface recognition of mitochondrial β-barrel proteins in yeast, humans and plants depends on the hydrophobicity of the last β-hairpin of the β-barrel. However, we demonstrate that the hydrophobicity is not sufficient for the discrimination of targeting to chloroplasts or mitochondria. By domain swapping between mitochondrial and chloroplast targeted β-barrel proteins atVDAC1 and psOEP24 we demonstrate that the presence of a hydrophilic amino acid at the C-terminus of the penultimate β-strand is required for mitochondrial targeting. A mutation of the chloroplast β-barrel protein psOEP24 which mimics such profile is efficiently targeted to mitochondria. Thus, we present the properties of the signal for mitochondrial targeting of β-barrel proteins in plants.
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Affiliation(s)
- Anna Klinger
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Victoria Gosch
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Uwe Bodensohn
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Roman Ladig
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Enrico Schleiff
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany; Buchman Institute for Molecular Life Sciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 15, D-60438 Frankfurt, Germany; Frankfurt Institute of Advanced Studies, Ruth-Moufang-Straße 1, D-60438 Frankfurt, Germany.
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Hsueh YC, Nicolaisen K, Gross LE, Nöthen J, Schauer N, Vojta L, Ertel F, Koch I, Ladig R, Fulgosi H, Fernie AR, Schleiff E. The outer membrane Omp85-like protein P39 influences metabolic homeostasis in mature Arabidopsis thaliana. Plant Biol (Stuttg) 2018; 20:825-833. [PMID: 29758131 DOI: 10.1111/plb.12839] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 05/07/2018] [Indexed: 06/08/2023]
Abstract
The Omp85 proteins form a large membrane protein family in bacteria and eukaryotes. Omp85 proteins are composed of a C-terminal β-barrel-shaped membrane domain and one or more N-terminal polypeptide transport-associated (POTRA) domains. However, Arabidopsis thaliana contains two genes coding for Omp85 proteins without a POTRA domain. One gene is designated P39, according to the molecular weight of the encoded protein. The protein is targeted to plastids and it was established that p39 has electrophysiological properties similar to other Omp85 family members, particularly to that designated as Toc75V/Oep80. We analysed expression of the gene and characterised two T-DNA insertion mutants, focusing on alterations in photosynthetic activity, plastid ultrastructure, global expression profile and metabolome. We observed pronounced expression of P39, especially in veins. Mutants of P39 show growth aberrations, reduced photosynthetic activity and changes in plastid ultrastructure, particularly in the leaf tip. Further, they display global alteration of gene expression and metabolite content in leaves of mature plants. We conclude that the function of the plastid-localised and vein-specific Omp85 family protein p39 is important, but not essential, for maintenance of metabolic homeostasis of full-grown A. thaliana plants. Further, the function of p39 in veins influences the functionality of other plant tissues. The link connecting p39 function with metabolic regulation in mature A. thaliana is discussed.
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Affiliation(s)
- Y-C Hsueh
- Department of Molecular Cell Biology of Plants, Goethe University, Frankfurt, Germany
| | - K Nicolaisen
- Department of Molecular Cell Biology of Plants, Goethe University, Frankfurt, Germany
| | - L E Gross
- Department of Molecular Cell Biology of Plants, Goethe University, Frankfurt, Germany
| | - J Nöthen
- Department of Molecular Cell Biology of Plants, Goethe University, Frankfurt, Germany
- Department of Mathematics and Informatics, Goethe University, Frankfurt, Germany
| | - N Schauer
- MPI für Molekulare Pflanzenphysiologie, Potsdam, Germany
| | - L Vojta
- Division of Molecular Biology, Institute Ruđer Bošković, Zagreb, Croatia
| | - F Ertel
- Department of Molecular Cell Biology of Plants, Goethe University, Frankfurt, Germany
| | - I Koch
- Department of Mathematics and Informatics, Goethe University, Frankfurt, Germany
| | - R Ladig
- Department of Molecular Cell Biology of Plants, Goethe University, Frankfurt, Germany
| | - H Fulgosi
- Division of Molecular Biology, Institute Ruđer Bošković, Zagreb, Croatia
| | - A R Fernie
- MPI für Molekulare Pflanzenphysiologie, Potsdam, Germany
| | - E Schleiff
- Department of Molecular Cell Biology of Plants, Goethe University, Frankfurt, Germany
- Buchmann Institute for Molecular Life Sciences, Frankfurt, Germany
- Frankfurt Institute for Advanced Studies, Frankfurt, Germany
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Hsueh YC, Ehmann C, Flinner N, Ladig R, Schleiff E. The plastid outer membrane localized LPTD1 is important for glycerolipid remodelling under phosphate starvation. Plant Cell Environ 2017; 40:1643-1657. [PMID: 28433003 DOI: 10.1111/pce.12973] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 04/10/2017] [Accepted: 04/10/2017] [Indexed: 06/07/2023]
Abstract
Glycerolipid synthesis in plants is coordinated between plastids and the endoplasmic reticulum (ER). A central step within the glycerolipid synthesis is the transport of phosphatidic acid from ER to chloroplasts. The chloroplast outer envelope protein TGD4 belongs to the LptD family conserved in bacteria and plants and selectively binds and may transport phosphatidic acid. We describe a second LptD-family protein in A. thaliana (atLPTD1; At2g44640) characterized by a barrel domain with an amino-acid signature typical for cyanobacterial LptDs. It forms a cation selective channel in vitro with a diameter of about 9 Å. atLPTD1 levels are induced under phosphate starvation. Plants expressing an RNAi construct against atLPTD1 show a growth phenotype under normal conditions. Expressing the RNAi against atLPTD1 in the tgd4-1 background renders the plants more sensitive to light stress or phosphate limitation than the individual mutants. Moreover, lipid analysis revealed that digalactosyldiacylglycerol and sulfoquinovosyldiacylglycerol levels remain constant in the RNAi mutants under phosphate starvation, while these two lipids are enhanced in wild-type. Based on our results, we propose a function of atLPTD1 in the transport of lipids from ER to chloroplast under phosphate starvation, which is combinatory with the function of TGD4.
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Affiliation(s)
- Yi-Ching Hsueh
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, Max von Laue Str. 9, 60438, Frankfurt am Main, Germany
- Department of Physics, Syracuse University, 201 Physics Bldg., Syracuse, New York, NY, 13244-1130, USA
| | - Christian Ehmann
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, Max von Laue Str. 9, 60438, Frankfurt am Main, Germany
| | - Nadine Flinner
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, Max von Laue Str. 9, 60438, Frankfurt am Main, Germany
- Frankfurt Institute for Advanced Studies (FIAS), Ruth-Moufang-Straße 1, 60438, Frankfurt am Main, Germany
| | - Roman Ladig
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, Max von Laue Str. 9, 60438, Frankfurt am Main, Germany
| | - Enrico Schleiff
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, Max von Laue Str. 9, 60438, Frankfurt am Main, Germany
- Cluster of Excellence Frankfurt, Goethe University, Max von Laue Str. 9, 60438, Frankfurt am Main, Germany
- Buchman Institute of Molecular Life Sciences, Goethe University, Max von Laue Str. 15, 60438, Frankfurt am Main, Germany
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Ladig R, Sommer MS, Hahn A, Leisegang MS, Papasotiriou DG, Ibrahim M, Elkehal R, Karas M, Zickermann V, Gutensohn M, Brandt U, Klösgen RB, Schleiff E. A high-definition native polyacrylamide gel electrophoresis system for the analysis of membrane complexes. Plant J 2011; 67:181-94. [PMID: 21418111 DOI: 10.1111/j.1365-313x.2011.04577.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Native polyacrylamide gel electrophoresis (PAGE) is an important technique for the analysis of membrane protein complexes. A major breakthrough was the development of blue native (BN-) and high resolution clear native (hrCN-) PAGE techniques. Although these techniques are very powerful, they could not be applied to all systems with the same resolution. We have developed an alternative protocol for the analysis of membrane protein complexes of plant chloroplasts and cyanobacteria, which we termed histidine- and deoxycholate-based native (HDN-) PAGE. We compared the capacity of HDN-, BN- and hrCN-PAGE to resolve the well-studied respiratory chain complexes in mitochondria of bovine heart muscle and Yarrowia lipolytica, as well as thylakoid localized complexes of Medicago sativa, Pisum sativum and Anabaena sp. PCC7120. Moreover, we determined the assembly/composition of the Anabaena sp. PCC7120 thylakoids and envelope membranes by HDN-PAGE. The analysis of isolated chloroplast envelope complexes by HDN-PAGE permitted us to resolve complexes such as the translocon of the outer envelope migrating at approximately 700 kDa or of the inner envelope of about 230 and 400 kDa with high resolution. By immunodecoration and mass spectrometry of these complexes we present new insights into the assembly/composition of these translocation machineries. The HDN-PAGE technique thus provides an important tool for future analyses of membrane complexes such as protein translocons.
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Affiliation(s)
- Roman Ladig
- Institute of Biology - Plant Physiology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, D-06120 Halle/Saale, Germany
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Noack H, Bednarek T, Heidler J, Ladig R, Holtz J, Szibor M. TFAM-dependent and independent dynamics of mtDNA levels in C2C12 myoblasts caused by redox stress. Biochim Biophys Acta Gen Subj 2006; 1760:141-50. [PMID: 16439064 DOI: 10.1016/j.bbagen.2005.12.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Revised: 11/11/2005] [Accepted: 12/07/2005] [Indexed: 11/29/2022]
Abstract
TFAM is an essential protein factor for the initiation of transcription of the mtDNA. It also functions as a packaging factor, which stabilizes the mtDNA pool. To investigate the regulatory role of TFAM for regeneration and proliferation of the mtDNA pool, we exposed the muscle cell line C2C12 to a severe redox stress (H2O2) or to a moderate redox stress (GSH depletion), determined the dynamics of the mtDNA levels and correlated this with the TFAM protein levels. H2O2 caused a concentration-dependent loss of mtDNA molecules. The mtDNA levels recovered slowly within 3 days after H2O2 stress. The TFAM protein was less degraded than the mtDNA indicating an accumulation of TFAM protein per mtDNA after H2O2 stress. Overexpression of TFAM did not protect against the mtDNA loss after H2O2 stress but shortened the recovery time. GSH depletion led to a proliferation of the mtDNA pool. Although the mtDNA levels increased the TFAM protein levels were unaffected by the GSH depletion. We conclude that the accumulation of the TFAM protein after H2O2 stress contributes to the regeneration of the mtDNA pool but that other mechanisms, independent from the TFAM protein amount have to be postulated to explain the proliferation of the mtDNA pool after GSH depletion.
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Affiliation(s)
- Heiko Noack
- Institute of Pathophysiology, Martin-Luther-University Halle-Wittenberg, ZAMED, Heinrich-Damerow-Str. 1, 06097 Halle, Germany.
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