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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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52
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Protein trafficking in the mitochondrial intermembrane space: mechanisms and links to human disease. Biochem J 2017; 474:2533-2545. [PMID: 28701417 PMCID: PMC5509380 DOI: 10.1042/bcj20160627] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 05/03/2017] [Accepted: 05/09/2017] [Indexed: 01/20/2023]
Abstract
Mitochondria fulfill a diverse range of functions in cells including oxygen metabolism, homeostasis of inorganic ions and execution of apoptosis. Biogenesis of mitochondria relies on protein import pathways that are ensured by dedicated multiprotein translocase complexes localized in all sub-compartments of these organelles. The key components and pathways involved in protein targeting and assembly have been characterized in great detail over the last three decades. This includes the oxidative folding machinery in the intermembrane space, which contributes to the redox-dependent control of proteostasis. Here, we focus on several components of this system and discuss recent evidence suggesting links to human proteopathy.
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53
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Straub SP, Stiller SB, Wiedemann N, Pfanner N. Dynamic organization of the mitochondrial protein import machinery. Biol Chem 2017; 397:1097-1114. [PMID: 27289000 DOI: 10.1515/hsz-2016-0145] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Accepted: 05/17/2016] [Indexed: 01/12/2023]
Abstract
Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.
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54
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Abstract
The human mitochondrial glutamate dehydrogenase isoenzymes (hGDH1 and hGDH2) are abundant matrix-localized proteins encoded by nuclear genes. The proteins are synthesized in the cytoplasm, with an atypically long N-terminal mitochondrial targeting sequence (MTS). The results of secondary structure predictions suggest the presence of two α-helices within the N-terminal region of the MTS. Results from deletion analyses indicate that individual helices have limited ability to direct protein import and matrix localization, but that there is a synergistic interaction when both helices are present [Biochem. J. (2016) 473: , 2813-2829]. Mutagenesis of the MTS cleavage sites blocked post-import removal of the presequences, but did not impede import. The authors propose that the high matrix levels of hGDH can be attributed to the unusual length and secondary structure of the MTS.
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55
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Tang K, Zhao Y, Li H, Zhu M, Li W, Liu W, Zhu G, Xu D, Peng W, Xu YW. Translocase of Inner Membrane 50 Functions as a Novel Protective Regulator of Pathological Cardiac Hypertrophy. J Am Heart Assoc 2017; 6:JAHA.116.004346. [PMID: 28432072 PMCID: PMC5532988 DOI: 10.1161/jaha.116.004346] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
BACKGROUND Translocase of inner membrane 50 (TIM50) is a member of the translocase of inner membrane (TIM) complex in the mitochondria. Previous research has demonstrated the role of TIM50 in the regulation of oxidative stress and cardiac morphology. However, the role of TIM50 in pathological cardiac hypertrophy remains unknown. METHODS AND RESULTS In the present study we found that the expression of TIM50 was downregulated in hypertrophic hearts. Using genetic loss-of-function animal models, we demonstrated that TIM50 deficiency increased heart and cardiomyocyte size with more severe cardiac fibrosis compared with wild-type littermates. Moreover, we generated cardiomyocyte-specific TIM50 transgenic mice in which the hypertrophic and fibrotic phenotypes were all alleviated. Next, we tested reactive oxygen species generation and the activities of the antioxidant enzymes superoxide dismutase and catalase, and also respiratory chain complexes I, II, and IV, finding that all the activities were regulated by TIM50. Meanwhile, expression of the ASK1-JNK/P38 axis was increased in TIM50-deficient mice, and TIM50 overexpression decreased the activity of the ASK1-JNK/P38 axis. Finally, we treated mice with the antioxidant N-acetyl cysteine to reduce oxidative stress. After N-acetyl cysteine treatment, the deteriorative hypertrophic and fibrotic phenotypes caused by TIM50 deficiency were all remarkably reversed. CONCLUSIONS These data indicated that TIM50 could attenuate pathological cardiac hypertrophy primarily by reducing oxidative stress. TIM50 could be a promising target for the prevention and therapy of cardiac hypertrophy and heart failure.
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Affiliation(s)
- Kai Tang
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yifan Zhao
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Hailing Li
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Mengyun Zhu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Weiming Li
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Weijing Liu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Guofu Zhu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Dachun Xu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Wenhui Peng
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Ya-Wei Xu
- Department of Cardiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
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56
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The proteome of baker's yeast mitochondria. Mitochondrion 2017; 33:15-21. [DOI: 10.1016/j.mito.2016.08.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 08/12/2016] [Accepted: 08/13/2016] [Indexed: 01/29/2023]
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57
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Role of Tim17 Transmembrane Regions in Regulating the Architecture of Presequence Translocase and Mitochondrial DNA Stability. Mol Cell Biol 2017; 37:MCB.00491-16. [PMID: 27994013 DOI: 10.1128/mcb.00491-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 12/11/2016] [Indexed: 12/11/2022] Open
Abstract
Mitochondrial life cycle and protein import are intricate cellular processes, which require precise coordination between the transport machineries of outer and inner mitochondrial membranes. Presequence translocase performs the indispensable function of translocating preproteins having N-terminal targeting sequences across the inner membrane. Tim23 forms the core of the voltage-gated import channel, while Tim17 is presumed to maintain the stoichiometry of the translocase. However, mechanistic insights into how Tim17 coordinates these regulatory events within the complex remained elusive. We demonstrate that Tim17 harbors conserved G/AXXXG/A motifs within its transmembrane regions and plays an imperative role in the translocase assembly through interaction with Tim23. Tandem motifs are highly essential, as most of the amino acid substitutions lead to nonviability due to the complete destabilization of the TIM23 channel. Importantly, Tim17 transmembrane regions regulate the dynamic assembly of translocase to form either the TIM23 (PAM)-complex or TIM23 (SORT)-complex by recruiting the presequence translocase-associated motor (PAM) machinery or Tim21, respectively. To a greater significance, tim17 mutants displayed mitochondrial DNA (mtDNA) instability, membrane potential loss, and defective import, resulting in organellar dysfunction. We conclude that the integrity of Tim17 transmembrane regions is critical for mitochondrial function and protein turnover.
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58
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Demishtein-Zohary K, Günsel U, Marom M, Banerjee R, Neupert W, Azem A, Mokranjac D. Role of Tim17 in coupling the import motor to the translocation channel of the mitochondrial presequence translocase. eLife 2017; 6. [PMID: 28165323 PMCID: PMC5308891 DOI: 10.7554/elife.22696] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 02/06/2017] [Indexed: 12/24/2022] Open
Abstract
The majority of mitochondrial proteins use N-terminal presequences for targeting to mitochondria and are translocated by the presequence translocase. During translocation, proteins, threaded through the channel in the inner membrane, are handed over to the import motor at the matrix face. Tim17 is an essential, membrane-embedded subunit of the translocase; however, its function is only poorly understood. Here, we functionally dissected its four predicted transmembrane (TM) segments. Mutations in TM1 and TM2 impaired the interaction of Tim17 with Tim23, component of the translocation channel, whereas mutations in TM3 compromised binding of the import motor. We identified residues in the matrix-facing region of Tim17 involved in binding of the import motor. Our results reveal functionally distinct roles of different regions of Tim17 and suggest how they may be involved in handing over the proteins, during their translocation into mitochondria, from the channel to the import motor of the presequence translocase. DOI:http://dx.doi.org/10.7554/eLife.22696.001
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Affiliation(s)
- Keren Demishtein-Zohary
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Umut Günsel
- BMC-Physiological Chemistry, LMU Munich, Martinsried, Germany
| | - Milit Marom
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Rupa Banerjee
- BMC-Physiological Chemistry, LMU Munich, Martinsried, Germany
| | - Walter Neupert
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Abdussalam Azem
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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59
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Abstract
The budding yeast Saccharomyces cerevisiae is an important model organism to study cellular structure and function. Due to its excellent accessibility to genetics and biochemical and microscopic analyses, studies with yeast have provided fundamental insights into mitochondrial biology. Yeast offers additional advantages because it can grow under fermenting conditions when oxidative phosphorylation is not obligatory and because the majority of mitochondrial structure and function are largely conserved during evolution. Isolation of mitochondria is an important technique for mitochondrial studies. This chapter focuses on procedures for the isolation and purification of intact yeast mitochondria that can be used for numerous functional assays as well as for analyses of mitochondrial ultrastructure.
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Affiliation(s)
- Toshiaki Izawa
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany.
| | - Ann-Katrin Unger
- Cell Biology and Electron Microscopy, Institut für Zellbiologie, Universität Bayreuth, 95440, Bayreuth, Germany
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60
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Schendzielorz AB, Schulz C, Lytovchenko O, Clancy A, Guiard B, Ieva R, van der Laan M, Rehling P. Two distinct membrane potential-dependent steps drive mitochondrial matrix protein translocation. J Cell Biol 2016; 216:83-92. [PMID: 28011846 PMCID: PMC5223606 DOI: 10.1083/jcb.201607066] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/30/2016] [Accepted: 11/28/2016] [Indexed: 12/03/2022] Open
Abstract
Schendzielorz et al. report that mitochondrial precursors display different dependencies on the membrane potential (Δψ) for translocation. Two distinct Δψ-dependent steps promote precursor translocation, the first driving presequence translocation and the second acting on the mature portion of the polypeptide chain. Two driving forces energize precursor translocation across the inner mitochondrial membrane. Although the membrane potential (Δψ) is considered to drive translocation of positively charged presequences through the TIM23 complex (presequence translocase), the activity of the Hsp70-powered import motor is crucial for the translocation of the mature protein portion into the matrix. In this study, we show that mitochondrial matrix proteins display surprisingly different dependencies on the Δψ. However, a precursor’s hypersensitivity to a reduction of the Δψ is not linked to the respective presequence, but rather to the mature portion of the polypeptide chain. The presequence translocase constituent Pam17 is specifically recruited by the receptor Tim50 to promote the transport of hypersensitive precursors into the matrix. Our analyses show that two distinct Δψ-driven translocation steps energize precursor passage across the inner mitochondrial membrane. The Δψ- and Pam17-dependent import step identified in this study is positioned between the two known energy-dependent steps: Δψ-driven presequence translocation and adenosine triphosphate–driven import motor activity.
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Affiliation(s)
- Alexander Benjamin Schendzielorz
- Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany
| | - Christian Schulz
- Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany
| | - Oleksandr Lytovchenko
- Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany
| | - Anne Clancy
- Department of Molecular Biology, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany
| | - Bernard Guiard
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91190 Gif-sur-Yvette, France
| | - Raffaele Ieva
- Laboratoire de Microbiologie et Génétique Moléculaire, Centre de Biologie Intégrative, Université de Toulouse, Centre National de la Recherche Scientifique, Unité Propre de Service, 31062 Toulouse, France.,Institute of Biochemistry and Molecular Biology, Center for Biochemistry and Molecular Cell Research, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Martin van der Laan
- Institute of Biochemistry and Molecular Biology, Center for Biochemistry and Molecular Cell Research, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Center Göttingen, Georg-August-Universität Göttingen, 37073 Göttingen, Germany .,Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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61
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Shahrour MA, Staretz-Chacham O, Dayan D, Stephen J, Weech A, Damseh N, Pri Chen H, Edvardson S, Mazaheri S, Saada A, Hershkovitz E, Shaag A, Huizing M, Abu-Libdeh B, Gahl WA, Azem A, Anikster Y, Vilboux T, Elpeleg O, Malicdan MC. Mitochondrial epileptic encephalopathy, 3-methylglutaconic aciduria and variable complex V deficiency associated with TIMM50 mutations. Clin Genet 2016; 91:690-696. [PMID: 27573165 DOI: 10.1111/cge.12855] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 08/24/2016] [Accepted: 08/25/2016] [Indexed: 11/26/2022]
Abstract
Mitochondrial encephalopathies are a heterogeneous group of disorders that, usually carry grave prognosis. Recently a homozygous mutation, Gly372Ser, in the TIMM50 gene, was reported in an abstract form, in three sibs who suffered from intractable epilepsy and developmental delay accompanied by 3-methylglutaconic aciduria. We now report on four patients from two unrelated families who presented with severe intellectual disability and seizure disorder, accompanied by slightly elevated lactate level, 3-methylglutaconic aciduria and variable deficiency of mitochondrial complex V. Using exome analysis we identified two homozygous missense mutations, Arg217Trp and Thr252Met, in the TIMM50 gene. The TIMM50 protein is a subunit of TIM23 complex, the mitochondrial import machinery. It serves as the major receptor in the intermembrane space, binding to proteins which cross the mitochondrial inner membrane on their way to the matrix. The mutations, which affected evolutionary conserved residues and segregated with the disease in the families, were neither present in large cohorts of control exome analyses nor in our ethnic specific exome cohort. Given the phenotypic similarity, we conclude that missense mutations in TIMM50 are likely manifesting by severe intellectual disability and epilepsy accompanied by 3-methylglutaconic aciduria and variable mitochondrial complex V deficiency. 3-methylglutaconic aciduria is emerging as an important biomarker for mitochondrial dysfunction, in particular for mitochondrial membrane defects.
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Affiliation(s)
- M A Shahrour
- Department of Pediatrics, Al-Makassed Islamic Hospital, Jerusalem, Israel
| | - O Staretz-Chacham
- Metabolic Disease Unit, Soroka Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheba, Israel
| | - D Dayan
- Department of Biochemistry & Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - J Stephen
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - A Weech
- NIH Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - N Damseh
- Department of Pediatrics, Al-Makassed Islamic Hospital, Jerusalem, Israel
| | - H Pri Chen
- Department of Biochemistry & Molecular Biology, Tel Aviv University, Tel Aviv, Israel.,Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.,Graduate Partnerships Program, Tel Aviv University, Tel Aviv, Israel, and the National Institutes of Health, Bethesda, MD, USA
| | - S Edvardson
- Pediatric Neurology Unit, Hadassah, Hebrew University Medical Center Jerusalem, Jerusalem, Israel
| | - S Mazaheri
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - A Saada
- Monique and Jacques Roboh Department of Genetic Research, Hadassah, Hebrew University Medical Center Jerusalem, Jerusalem, Israel
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- NIH Intramural Sequencing Center (NISC), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - E Hershkovitz
- Metabolic Disease Unit, Soroka Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheba, Israel
| | - A Shaag
- NIH Intramural Sequencing Center (NISC), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - M Huizing
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - B Abu-Libdeh
- Department of Pediatrics, Al-Makassed Islamic Hospital, Jerusalem, Israel
| | - W A Gahl
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.,NIH Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - A Azem
- Department of Biochemistry & Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Y Anikster
- Metabolic Disease Unit, Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Tel-Hashomer, Israel.,Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - T Vilboux
- NIH Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.,Division of Medical Genomics, Inova Translational Medicine Institute, Fairfax, VA, USA
| | - O Elpeleg
- NIH Intramural Sequencing Center (NISC), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - M C Malicdan
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.,NIH Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
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62
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Manganas P, MacPherson L, Tokatlidis K. Oxidative protein biogenesis and redox regulation in the mitochondrial intermembrane space. Cell Tissue Res 2016; 367:43-57. [PMID: 27632163 PMCID: PMC5203823 DOI: 10.1007/s00441-016-2488-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 08/05/2016] [Indexed: 12/22/2022]
Abstract
Mitochondria are organelles that play a central role in cellular metabolism, as they are responsible for processes such as iron/sulfur cluster biogenesis, respiration and apoptosis. Here, we describe briefly the various protein import pathways for sorting of mitochondrial proteins into the different subcompartments, with an emphasis on the targeting to the intermembrane space. The discovery of a dedicated redox-controlled pathway in the intermembrane space that links protein import to oxidative protein folding raises important questions on the redox regulation of this process. We discuss the salient features of redox regulation in the intermembrane space and how such mechanisms may be linked to the more general redox homeostasis balance that is crucial not only for normal cell physiology but also for cellular dysfunction.
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Affiliation(s)
- Phanee Manganas
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Lisa MacPherson
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Kostas Tokatlidis
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
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63
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Demishtein-Zohary K, Azem A. The TIM23 mitochondrial protein import complex: function and dysfunction. Cell Tissue Res 2016; 367:33-41. [DOI: 10.1007/s00441-016-2486-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 08/05/2016] [Indexed: 01/16/2023]
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64
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van Dooren GG, Yeoh LM, Striepen B, McFadden GI. The Import of Proteins into the Mitochondrion of Toxoplasma gondii. J Biol Chem 2016; 291:19335-50. [PMID: 27458014 DOI: 10.1074/jbc.m116.725069] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Indexed: 11/06/2022] Open
Abstract
Outside of well characterized model eukaryotes, relatively little is known about the translocons that transport proteins across the two membranes that surround the mitochondrion. Apicomplexans are a phylum of intracellular parasites that cause major diseases in humans and animals and are evolutionarily distant from model eukaryotes such as yeast. Apicomplexans harbor a mitochondrion that is essential for parasite survival and is a validated drug target. Here, we demonstrate that the apicomplexan Toxoplasma gondii harbors homologues of proteins from all the major mitochondrial protein translocons present in yeast, suggesting these arose early in eukaryotic evolution. We demonstrate that a T. gondii homologue of Tom22 (TgTom22), a central component of the translocon of the outer mitochondrial membrane (TOM) complex, is essential for parasite survival, mitochondrial protein import, and assembly of the TOM complex. We also identify and characterize a T. gondii homologue of Tom7 (TgTom7) that is important for parasite survival and mitochondrial protein import. Contrary to the role of Tom7 in yeast, TgTom7 is important for TOM complex stability, suggesting the role of this protein has diverged during eukaryotic evolution. Together, our study identifies conserved and modified features of mitochondrial protein import in apicomplexan parasites.
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Affiliation(s)
- Giel G van Dooren
- From the Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia,
| | - Lee M Yeoh
- the School of BioSciences, University of Melbourne, Parkville, Victoria 3010, Australia, and
| | - Boris Striepen
- the Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602
| | - Geoffrey I McFadden
- the School of BioSciences, University of Melbourne, Parkville, Victoria 3010, Australia, and
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65
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Sinha D, Srivastava S, D'Silva P. Functional Diversity of Human Mitochondrial J-proteins Is Independent of Their Association with the Inner Membrane Presequence Translocase. J Biol Chem 2016; 291:17345-59. [PMID: 27330077 DOI: 10.1074/jbc.m116.738146] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Indexed: 01/30/2023] Open
Abstract
Mitochondrial J-proteins play a critical role in governing Hsp70 activity and, hence, are essential for organellar protein translocation and folding. In contrast to yeast, which has a single J-protein Pam18, humans involve two J-proteins, DnaJC15 and DnaJC19, associated with contrasting cellular phenotype, to transport proteins into the mitochondria. Mutation in DnaJC19 results in dilated cardiomyopathy and ataxia syndrome, whereas expression of DnaJC15 regulates the response of cancer cells to chemotherapy. In the present study we have comparatively assessed the biochemical properties of the J-protein paralogs in relation to their association with the import channel. Both DnaJC15 and DnaJC19 formed two distinct subcomplexes with Magmas at the import channel. Knockdown analysis suggested an essential role for Magmas and DnaJC19 in organellar protein translocation and mitochondria biogenesis, whereas DnaJC15 had dispensable supportive function. The J-proteins were found to have equal affinity for Magmas and could stimulate mitochondrial Hsp70 ATPase activity by equivalent levels. Interestingly, we observed that DnaJC15 exhibits bifunctional properties. At the translocation channel, it involves conserved interactions and mechanism to translocate the precursors into mitochondria. In addition to protein transport, DnaJC15 also showed a dual role in yeast where its expression elicited enhanced sensitivity of cells to cisplatin that required the presence of a functional J-domain. The amount of DnaJC15 expressed in the cell was directly proportional to the sensitivity of cells. Our analysis indicates that the differential cellular phenotype displayed by human mitochondrial J-proteins is independent of their activity and association with Magmas at the translocation channel.
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Affiliation(s)
- Devanjan Sinha
- From the Department of Biochemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India
| | - Shubhi Srivastava
- From the Department of Biochemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India
| | - Patrick D'Silva
- From the Department of Biochemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India
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66
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Complex formation and turnover of mitochondrial transporters and ion channels. J Bioenerg Biomembr 2016; 49:101-111. [DOI: 10.1007/s10863-016-9648-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 01/19/2016] [Indexed: 02/07/2023]
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67
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Zhang YJ, Zhang SF, He ZP, Lin L, Wang DZ. Proteomic analysis provides new insights into the adaptive response of a dinoflagellate Prorocentrum donghaiense to changing ambient nitrogen. PLANT, CELL & ENVIRONMENT 2015; 38:2128-2142. [PMID: 25789726 DOI: 10.1111/pce.12538] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 03/05/2015] [Indexed: 06/04/2023]
Abstract
Nitrogen (N) is the major nutrient limiting phytoplankton growth and productivity over large ocean areas. Dinoflagellates are important primary producers and major causative agents of harmful algal blooms in the ocean. However, very little is known about their adaptive response to changing ambient N. Here, we compared the protein profiles of a marine dinoflagellate Prorocentrum donghaiense grown in inorganic N-replete, N-deplete and N-resupplied conditions using 2-D fluorescence differential gel electrophoresis. The results showed that cell density, chlorophyll a and particulate organic N contents presented low levels in N-deplete cells, while particulate organic carbon content and glutamine synthetase (GS) activity maintained high levels. Comparison of the protein profiles of N-replete, N-deplete and N-resupplied cells indicated that proteins involved in photosynthesis, carbon fixation, protein and lipid synthesis were down-regulated, while proteins participating in N reallocation and transport activity were up-regulated in N-deplete cells. High expressions of GS and 60 kDa chaperonin as well as high GS activity in N-deplete cells indicated their central role in N stress adaptation. Overall, in contrast with other photosynthetic eukaryotic algae, P. donghaiense possessed a specific ability to regulate intracellular carbon and N metabolism in response to extreme ambient N deficiency.
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Affiliation(s)
- Ying-Jiao Zhang
- State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, 361102, China
- Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China
| | - Shu-Fei Zhang
- State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, 361102, China
| | - Zhi-Ping He
- State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, 361102, China
| | - Lin Lin
- State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, 361102, China
| | - Da-Zhi Wang
- State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, 361102, China
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Li J, Sha B. The structure of Tim50(164-361) suggests the mechanism by which Tim50 receives mitochondrial presequences. Acta Crystallogr F Struct Biol Commun 2015; 71:1146-51. [PMID: 26323300 PMCID: PMC4555921 DOI: 10.1107/s2053230x15013102] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 07/07/2015] [Indexed: 01/04/2023] Open
Abstract
Mitochondrial preproteins are transported through the translocase of the outer membrane (TOM) complex. Tim50 and Tim23 then transfer preproteins with N-terminal targeting presequences through the intermembrane space (IMS) across the inner membrane. The crystal structure of the IMS domain of Tim50 [Tim50(164-361)] has previously been determined to 1.83 Å resolution. Here, the crystal structure of Tim50(164-361) at 2.67 Å resolution that was crystallized using a different condition is reported. Compared with the previously determined Tim50(164-361) structure, significant conformational changes occur within the protruding β-hairpin of Tim50 and the nearby helix A2. These findings indicate that the IMS domain of Tim50 exhibits significant structural plasticity within the putative presequence-binding groove, which may play important roles in the function of Tim50 as a receptor protein in the TIM complex that interacts with the presequence and multiple other proteins. More interestingly, the crystal packing indicates that helix A1 from the neighboring monomer docks into the putative presequence-binding groove of Tim50(164-361), which may mimic the scenario of Tim50 and the presequence complex. Tim50 may recognize and bind the presequence helix by utilizing the inner side of the protruding β-hairpin through hydrophobic interactions. Therefore, the protruding β-hairpin of Tim50 may play critical roles in receiving the presequence and recruiting Tim23 for subsequent protein translocations.
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Affiliation(s)
- Jingzhi Li
- Department of Cell, Developmental and Integrative Biology (CDIB), University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Bingdong Sha
- Department of Cell, Developmental and Integrative Biology (CDIB), University of Alabama at Birmingham, Birmingham, AL 35294, USA
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69
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Singha UK, Hamilton V, Chaudhuri M. Tim62, a Novel Mitochondrial Protein in Trypanosoma brucei, Is Essential for Assembly and Stability of the TbTim17 Protein Complex. J Biol Chem 2015; 290:23226-39. [PMID: 26240144 DOI: 10.1074/jbc.m115.663492] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Indexed: 11/06/2022] Open
Abstract
Trypanosoma brucei, the causative agent of human African trypanosomiasis, possesses non-canonical mitochondrial protein import machinery. Previously, we characterized the essential translocase of the mitochondrial inner membrane (TIM) consisting of Tim17 in T. brucei. TbTim17 is associated with TbTim62. Here we show that TbTim62, a novel protein, is localized in the mitochondrial inner membrane, and its import into mitochondria depends on TbTim17. Knockdown (KD) of TbTim62 decreased the steady-state levels of TbTim17 post-transcriptionally. Further analysis showed that import of TbTim17 into mitochondria was not inhibited, but its half-life was reduced >4-fold due to TbTim62 KD. Blue-native gel electrophoresis revealed that TbTim62 is present primarily in ∼150-kDa and also in ∼1100-kDa protein complexes, whereas TbTim17 is present in multiple complexes within the range of ∼300 to ∼1100 kDa. TbTim62 KD reduced the levels of both TbTim62 as well as TbTim17 protein complexes. Interestingly, TbTim17 was accumulated as lower molecular mass complexes in TbTim62 KD mitochondria. Furthermore, depletion of TbTim62 hampered the assembly of the ectopically expressed TbTim17-2X-myc into TbTim17 protein complex. Co-immunoprecipitation analysis revealed that association of TbTim17 with mHSP70 was markedly reduced in TbTim62 KD mitochondria. All together our results demonstrate that TbTim62, a unique mitochondrial protein in T. brucei, is required for the formation of a stable TbTim17 protein complex. TbTim62 KD destabilizes this complex, and unassembled TbTim17 degrades. Therefore, TbTim62 acts as a novel regulatory factor to maintain the levels of TIM in T. brucei mitochondria.
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Affiliation(s)
- Ujjal K Singha
- From the Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee 37208
| | - VaNae Hamilton
- From the Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee 37208
| | - Minu Chaudhuri
- From the Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee 37208
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A presequence-binding groove in Tom70 supports import of Mdl1 into mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1850-9. [PMID: 25958336 DOI: 10.1016/j.bbamcr.2015.04.021] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 04/23/2015] [Accepted: 04/30/2015] [Indexed: 11/21/2022]
Abstract
The translocase of the outer mitochondrial membrane (TOM complex) is the general entry gate into mitochondria for almost all imported proteins. A variety of specific receptors allow the TOM complex to recognize targeting signals of various precursor proteins that are transported along different import pathways. Aside from the well-characterized presequence receptors Tom20 and Tom22 a third TOM receptor, Tom70, binds proteins of the carrier family containing multiple transmembrane segments. Here we demonstrate that Tom70 directly binds to presequence peptides using a dedicated groove. A single point mutation in the cavity of this pocket (M551R) reduces the presequence binding affinity of Tom70 ten-fold and selectively impairs import of the presequence-containing precursor Mdl1 but not the ADP/ATP carrier (AAC). Hence Tom70 contributes to the presequence import pathway by recognition of the targeting signal of the Mdl1 precursor.
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71
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Schulz C, Schendzielorz A, Rehling P. Unlocking the presequence import pathway. Trends Cell Biol 2015; 25:265-75. [DOI: 10.1016/j.tcb.2014.12.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 11/26/2014] [Accepted: 12/01/2014] [Indexed: 10/24/2022]
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72
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Cooperation of protein machineries in mitochondrial protein sorting. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1119-29. [DOI: 10.1016/j.bbamcr.2015.01.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 01/16/2015] [Accepted: 01/20/2015] [Indexed: 02/07/2023]
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73
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Micevski D, Zammit JE, Truscott KN, Dougan DA. Anti-adaptors use distinct modes of binding to inhibit the RssB-dependent turnover of RpoS (σ(S)) by ClpXP. Front Mol Biosci 2015; 2:15. [PMID: 25988182 PMCID: PMC4428439 DOI: 10.3389/fmolb.2015.00015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 04/08/2015] [Indexed: 12/26/2022] Open
Abstract
In Escherichia coli, σS is the master regulator of the general stress response. The level of σS changes in response to multiple stress conditions and it is regulated at many levels including protein turnover. In the absence of stress, σS is rapidly degraded by the AAA+ protease, ClpXP in a regulated manner that depends on the adaptor protein RssB. This two-component response regulator mediates the recognition of σS and its delivery to ClpXP. The turnover of σS however, can be inhibited in a stress specific manner, by one of three anti-adaptor proteins. Each anti-adaptor binds to RssB and inhibits its activity, but how this is achieved is not fully understood at a molecular level. Here, we describe details of the interaction between each anti-adaptor and RssB that leads to the stabilization of σS. By defining the domains of RssB using partial proteolysis we demonstrate that each anti-adaptor uses a distinct mode of binding to inhibit RssB activity. IraD docks specifically to the N-terminal domain of RssB, IraP interacts primarily with the C-terminal domain, while IraM interacts with both domains. Despite these differences in binding, we propose that docking of each anti-adaptor induces a conformational change in RssB, which resembles the inactive dimer of RssB. This dimer-like state of RssB not only prevents substrate binding but also triggers substrate release from a pre-bound complex.
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Affiliation(s)
- Dimce Micevski
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University Melbourne, VIC, Australia
| | - Jessica E Zammit
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University Melbourne, VIC, Australia
| | - Kaye N Truscott
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University Melbourne, VIC, Australia
| | - David A Dougan
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University Melbourne, VIC, Australia
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74
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A Perspective on Transport of Proteins into Mitochondria: A Myriad of Open Questions. J Mol Biol 2015; 427:1135-58. [DOI: 10.1016/j.jmb.2015.02.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 01/30/2015] [Accepted: 02/02/2015] [Indexed: 11/22/2022]
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75
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Horvath SE, Rampelt H, Oeljeklaus S, Warscheid B, van der Laan M, Pfanner N. Role of membrane contact sites in protein import into mitochondria. Protein Sci 2015; 24:277-97. [PMID: 25514890 DOI: 10.1002/pro.2625] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 12/08/2014] [Indexed: 12/13/2022]
Abstract
Mitochondria import more than 1,000 different proteins from the cytosol. The proteins are synthesized as precursors on cytosolic ribosomes and are translocated by protein transport machineries of the mitochondrial membranes. Five main pathways for protein import into mitochondria have been identified. Most pathways use the translocase of the outer mitochondrial membrane (TOM) as the entry gate into mitochondria. Depending on specific signals contained in the precursors, the proteins are subsequently transferred to different intramitochondrial translocases. In this article, we discuss the connection between protein import and mitochondrial membrane architecture. Mitochondria possess two membranes. It is a long-standing question how contact sites between outer and inner membranes are formed and which role the contact sites play in the translocation of precursor proteins. A major translocation contact site is formed between the TOM complex and the presequence translocase of the inner membrane (TIM23 complex), promoting transfer of presequence-carrying preproteins to the mitochondrial inner membrane and matrix. Recent findings led to the identification of contact sites that involve the mitochondrial contact site and cristae organizing system (MICOS) of the inner membrane. MICOS plays a dual role. It is crucial for maintaining the inner membrane cristae architecture and forms contacts sites to the outer membrane that promote translocation of precursor proteins into the intermembrane space and outer membrane of mitochondria. The view is emerging that the mitochondrial protein translocases do not function as independent units, but are embedded in a network of interactions with machineries that control mitochondrial activity and architecture.
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Affiliation(s)
- Susanne E Horvath
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104, Freiburg, Germany
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76
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Lu YW, Claypool SM. Disorders of phospholipid metabolism: an emerging class of mitochondrial disease due to defects in nuclear genes. Front Genet 2015; 6:3. [PMID: 25691889 PMCID: PMC4315098 DOI: 10.3389/fgene.2015.00003] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 01/06/2015] [Indexed: 01/14/2023] Open
Abstract
The human nuclear and mitochondrial genomes co-exist within each cell. While the mitochondrial genome encodes for a limited number of proteins, transfer RNAs, and ribosomal RNAs, the vast majority of mitochondrial proteins are encoded in the nuclear genome. Of the multitude of mitochondrial disorders known to date, only a fifth are maternally inherited. The recent characterization of the mitochondrial proteome therefore serves as an important step toward delineating the nosology of a large spectrum of phenotypically heterogeneous diseases. Following the identification of the first nuclear gene defect to underlie a mitochondrial disorder, a plenitude of genetic variants that provoke mitochondrial pathophysiology have been molecularly elucidated and classified into six categories that impact: (1) oxidative phosphorylation (subunits and assembly factors); (2) mitochondrial DNA maintenance and expression; (3) mitochondrial protein import and assembly; (4) mitochondrial quality control (chaperones and proteases); (5) iron–sulfur cluster homeostasis; and (6) mitochondrial dynamics (fission and fusion). Here, we propose that an additional class of genetic variant be included in the classification schema to acknowledge the role of genetic defects in phospholipid biosynthesis, remodeling, and metabolism in mitochondrial pathophysiology. This seventh class includes a small but notable group of nuclear-encoded proteins whose dysfunction impacts normal mitochondrial phospholipid metabolism. The resulting human disorders present with a diverse array of pathologic consequences that reflect the variety of functions that phospholipids have in mitochondria and highlight the important role of proper membrane homeostasis in mitochondrial biology.
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Affiliation(s)
- Ya-Wen Lu
- Department of Physiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
| | - Steven M Claypool
- Department of Physiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
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77
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Bleier L, Wittig I, Heide H, Steger M, Brandt U, Dröse S. Generator-specific targets of mitochondrial reactive oxygen species. Free Radic Biol Med 2015; 78:1-10. [PMID: 25451644 DOI: 10.1016/j.freeradbiomed.2014.10.511] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 10/13/2014] [Accepted: 10/14/2014] [Indexed: 10/24/2022]
Abstract
To understand the role of reactive oxygen species (ROS) in oxidative stress and redox signaling it is necessary to link their site of generation to the oxidative modification of specific targets. Here we have studied the selective modification of protein thiols by mitochondrial ROS that have been implicated as deleterious agents in a number of degenerative diseases and in the process of biological aging, but also as important players in cellular signal transduction. We hypothesized that this bipartite role might be based on different generator sites for "signaling" and "damaging" ROS and a directed release into different mitochondrial compartments. Because two main mitochondrial ROS generators, complex I (NADH:ubiquinone oxidoreductase) and complex III (ubiquinol:cytochrome c oxidoreductase; cytochrome bc1 complex), are known to predominantly release superoxide and the derived hydrogen peroxide (H2O2) into the mitochondrial matrix and the intermembrane space, respectively, we investigated whether these ROS generators selectively oxidize specific protein thiols. We used redox fluorescence difference gel electrophoresis analysis to identify redox-sensitive targets in the mitochondrial proteome of intact rat heart mitochondria. We observed that the modified target proteins were distinctly different when complex I or complex III was employed as the source of ROS. These proteins are potential targets involved in mitochondrial redox signaling and may serve as biomarkers to study the generator-dependent dual role of mitochondrial ROS in redox signaling and oxidative stress.
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Affiliation(s)
- Lea Bleier
- Molecular Bioenergetics Group, Goethe-University, D-60590 Frankfurt am Main, Germany
| | - Ilka Wittig
- Molecular Bioenergetics Group, Goethe-University, D-60590 Frankfurt am Main, Germany; Functional Proteomics, SFB815 Core Unit, Medical School, Goethe-University, D-60590 Frankfurt am Main, Germany
| | - Heinrich Heide
- Molecular Bioenergetics Group, Goethe-University, D-60590 Frankfurt am Main, Germany
| | - Mirco Steger
- Molecular Bioenergetics Group, Goethe-University, D-60590 Frankfurt am Main, Germany
| | - Ulrich Brandt
- Molecular Bioenergetics Group, Goethe-University, D-60590 Frankfurt am Main, Germany; Cluster of Excellence Frankfurt "Macromolecular Complexes," Goethe-University, D-60590 Frankfurt am Main, Germany; Radboud University Medical Center, Nijmegen Center for Mitochondrial Disorders, 6500 GA Nijmegen, The Netherlands
| | - Stefan Dröse
- Molecular Bioenergetics Group, Goethe-University, D-60590 Frankfurt am Main, Germany; Clinic of Anaesthesiology, Intensive Care Medicine and Pain Therapy, Goethe-University Hospital, Frankfurt am Main, Germany.
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78
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Thomas JL, Rajapaksha M, Mack VL, DeMars GA, Majzoub JA, Bose HS. Regulation of human 3β-hydroxysteroid dehydrogenase type 2 by adrenal corticosteroids and product-feedback by androstenedione in human adrenarche. J Pharmacol Exp Ther 2014; 352:67-76. [PMID: 25355646 DOI: 10.1124/jpet.114.219550] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In human adrenarche during childhood, the secretion of dehydroepiandrosterone (DHEA) from the adrenal gland increases due to its increased synthesis and/or decreased metabolism. DHEA is synthesized by 17α-hydroxylase/17,20-lyase, and is metabolized by 3β-hydroxysteroid dehydrogenase type 2 (3βHSD2). In this study, the inhibition of purified human 3βHSD2 by the adrenal steroids, androstenedione, cortisone, and cortisol, was investigated and related to changes in secondary enzyme structure. Solubilized, purified 3βHSD2 was inhibited competitively by androstenedione with high affinity, by cortisone at lower affinity, and by cortisol only at very high, nonphysiologic levels. When purified 3βHSD2 was bound to lipid vesicles, the competitive Ki values for androstenedione and cortisone were slightly decreased, and the Ki value of cortisol was decreased 2.5-fold, although still at a nonphysiologic level. The circular dichroism spectrum that measured 3βHSD2 secondary structure was significantly altered by the binding of cortisol, but not by androstenedione and cortisone. Our import studies show that 3βHSD2 binds in the intermitochondrial space as a membrane-associated protein. Androstenedione inhibits purified 3βHSD2 at physiologic levels, but similar actions for cortisol and cortisone are not supported. In summary, our results have clarified the mechanisms for limiting the metabolism of DHEA during human adrenarche.
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Affiliation(s)
- James L Thomas
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Maheshinie Rajapaksha
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Vance L Mack
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Geneva A DeMars
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Joseph A Majzoub
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Himangshu S Bose
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
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79
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Molecular basis of the dynamic structure of the TIM23 complex in the mitochondrial intermembrane space. Structure 2014; 22:1501-11. [PMID: 25263020 DOI: 10.1016/j.str.2014.07.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 07/04/2014] [Accepted: 07/19/2014] [Indexed: 11/20/2022]
Abstract
The presequence translocase TIM23 is a highly dynamic complex in which its subunits can adopt multiple conformations and undergo association-dissociation to facilitate import of proteins into mitochondria. Despite the importance of protein-protein interactions in TIM23, little is known about the molecular details of these processes. Using nuclear magnetic resonance spectroscopy, we characterized the dynamic interaction network of the intermembrane space domains of Tim23, Tim21, Tim50, and Tom22 at single-residue level. We show that Tim23(IMS) contains multiple sites to efficiently interact with the intermembrane space domain of Tim21 and to bind to Tim21, Tim50, and Tom22. In addition, we reveal the atomic details of the dynamic Tim23(IMS)-Tim21(IMS) complex. The combined data support a central role of the intermembrane space domain of Tim23 in the formation and regulation of the presequence translocase.
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80
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Mehnert CS, Rampelt H, Gebert M, Oeljeklaus S, Schrempp SG, Kochbeck L, Guiard B, Warscheid B, van der Laan M. The mitochondrial ADP/ATP carrier associates with the inner membrane presequence translocase in a stoichiometric manner. J Biol Chem 2014; 289:27352-27362. [PMID: 25124039 DOI: 10.1074/jbc.m114.556498] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The majority of mitochondrial proteins are synthesized with amino-terminal signal sequences. The presequence translocase of the inner membrane (TIM23 complex) mediates the import of these preproteins. The essential TIM23 core complex closely cooperates with partner protein complexes like the presequence translocase-associated import motor and the respiratory chain. The inner mitochondrial membrane also contains a large number of metabolite carriers, but their association with preprotein translocases has been controversial. We performed a comprehensive analysis of the TIM23 interactome based on stable isotope labeling with amino acids in cell culture. Subsequent biochemical studies on identified partner proteins showed that the mitochondrial ADP/ATP carrier associates with the membrane-embedded core of the TIM23 complex in a stoichiometric manner, revealing an unexpected connection of mitochondrial protein biogenesis to metabolite transport. Our data indicate that direct TIM23-AAC coupling may support preprotein import into mitochondria when respiratory activity is low.
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Affiliation(s)
- Carola S Mehnert
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Heike Rampelt
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany
| | - Michael Gebert
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Silke Oeljeklaus
- Institut für Biologie II, Fakultät für Biologie, Funktionelle Proteomik, and Universität Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, Universität Freiburg, 79104 Freiburg, Germany and
| | - Sandra G Schrempp
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Lioba Kochbeck
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany
| | - Bernard Guiard
- Centre de Génétique Moléculaire, CNRS, 91190 Gif-sur-Yvette, France
| | - Bettina Warscheid
- Institut für Biologie II, Fakultät für Biologie, Funktionelle Proteomik, and Universität Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, Universität Freiburg, 79104 Freiburg, Germany and
| | - Martin van der Laan
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, Universität Freiburg, 79104 Freiburg, Germany and.
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81
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Woellhaf MW, Hansen KG, Garth C, Herrmann JM. Import of ribosomal proteins into yeast mitochondria. Biochem Cell Biol 2014; 92:489-98. [PMID: 24943357 DOI: 10.1139/bcb-2014-0029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Mitochondrial ribosomes of baker's yeast contain at least 78 protein subunits. All but one of these proteins are nuclear-encoded, synthesized on cytosolic ribosomes, and imported into the matrix for biogenesis. The import of matrix proteins typically relies on N-terminal mitochondrial targeting sequences that form positively charged amphipathic helices. Interestingly, the N-terminal regions of many ribosomal proteins do not closely match the characteristics of matrix targeting sequences, suggesting that the import processes of these proteins might deviate to some extent from the general import route. So far, the biogenesis of only two ribosomal proteins, Mrpl32 and Mrp10, was studied experimentally and indeed showed surprising differences to the import of other preproteins. In this review article we summarize the current knowledge on the transport of proteins into the mitochondrial matrix, and thereby specifically focus on proteins of the mitochondrial ribosome.
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Affiliation(s)
- Michael W Woellhaf
- a Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663 Kaiserslautern, Germany
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82
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Song J, Tamura Y, Yoshihisa T, Endo T. A novel import route for an N-anchor mitochondrial outer membrane protein aided by the TIM23 complex. EMBO Rep 2014; 15:670-7. [PMID: 24781694 DOI: 10.1002/embr.201338142] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The membrane topology of Om45 in the yeast mitochondrial outer membrane (OM) is under debate. Here, we confirm that Om45 is anchored to the OM from the intermembrane space (IMS) by its N-terminal hydrophobic segment. We show that import of Om45 requires the presequence receptors, Tom20 and Tom22, and the import channel of Tom40. Unlike any of the known OM proteins, Om45 import requires the TIM23 complex in the inner membrane, a translocator for presequence-containing proteins, and the membrane potential (ΔΨ). Therefore, Om45 is anchored to the OM via the IMS by a novel import pathway involving the TIM23 complex.
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Affiliation(s)
- Jiyao Song
- Department of Chemistry, Graduate School of Science Nagoya University, Chikusa-ku Nagoya, Japan
| | - Yasushi Tamura
- Research Center for Materials Science Nagoya University, Chikusa-ku Nagoya, Japan
| | - Tohru Yoshihisa
- Graduate School of Life Science University of Hyogo, Hyogo, Japan
| | - Toshiya Endo
- Department of Chemistry, Graduate School of Science Nagoya University, Chikusa-ku Nagoya, Japan Structural Biology Research Center Nagoya University, Chikusa-ku Nagoya, Japan JST CREST Nagoya University, Chikusa-ku Nagoya, Japan
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83
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NMR analyses on the interactions of the yeast Tim50 C-terminal region with the presequence and Tim50 core domain. FEBS Lett 2014; 588:678-84. [PMID: 24462684 DOI: 10.1016/j.febslet.2013.12.037] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 12/28/2013] [Accepted: 12/31/2013] [Indexed: 11/21/2022]
Abstract
The mitochondrial targeting signal in the presequence of mitochondrial precursor proteins is recognized by Tom20 and subsequently by Tim50 in mitochondria. Yeast Tim50 contains two presequence binding sites in the conserved core domain and in the fungi-specific C-terminal presequence binding domain (PBD). We report the NMR analyses on interactions of a shorter variant of PBD (sPBD), a shorter variant of PBD, with presequences. The presequence is recognized by sPBD in a similar manner to Tom20. sPBD can also bind to the core domain of Tim50 through the presequence binding region, which could promote transfer of the presequence from sPBD to the core domain in Tim50.
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84
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Porcu S, Lapolla A, Biasutto L, Zoratti M, Piarulli F, Eliana G, Basso D, Roverso M, Seraglia R. A preliminary fastview of mitochondrial protein profile from healthy and type 2 diabetic subjects. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2014; 20:307-315. [PMID: 25420343 DOI: 10.1255/ejms.1285] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Type 2 diabetes results from the development of insulin resistance and a concomitant impairment of insulin secretion. Mitochondrial dysfunctions are thought to be the major contributor to the development of various pathologies, including type 1 and type 2 diabetes mellitus. Mitochondrial oxidative stress has been reported in models of both type 1 and type 2 diabetes mellitus and may play a central role in mitochondrial dysfunction. In the present study, we investigated the occurrence of protein alterations, due to the presence of type 2 diabetes, in mitochondria isolated from human peripheral blood mononuclear cells (PBMCs] by matrix-assisted laser desorp- tion/ionization mass spectrometry (MALDI-MS]. PBMCs may be suitable for this investigation because they have insulin receptors that quickly respond to changes in insulin concentration, and in the presence of insulin rapidly increase their rates of glucose utiliza- tion. In the presence of insulin-resistance conditions, such as type 2 diabetes mellitus, this mechanism is altered and the glycation of cytoplasmic as well as mitochondrial proteins may plausibly appear. Therefore, PBMCs may be useful tools to verify modifications or altered expression of mitochondrial proteins. Human mitochondria were obtained from 32 subjects, 16 healthy controls and 16 type 2 diabetic patients. Two different methods for mitochondria isolation and purification were employed and compared. Some proteins have been found to be differently expressed in the two groups of subjects under investigation and can be classified into two sets: i.e. proteins related to ATP synthase [e.g. 6.8kDa mitochondrial proteolipid [MLQ]; ATP-CF6 [m/z 12,597)] and proteins related to cell proliferation and apoptosis [e.g. TIMM9 [m/z 10,378); Bcl-2-like protein 2 (m/z20,742)].
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85
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Rainbolt TK, Atanassova N, Genereux JC, Wiseman RL. Stress-regulated translational attenuation adapts mitochondrial protein import through Tim17A degradation. Cell Metab 2013; 18:908-19. [PMID: 24315374 PMCID: PMC3904643 DOI: 10.1016/j.cmet.2013.11.006] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 08/08/2013] [Accepted: 11/06/2013] [Indexed: 12/28/2022]
Abstract
Stress-regulated signaling pathways protect mitochondrial proteostasis and function from pathologic insults. Despite the importance of stress-regulated signaling pathways in mitochondrial proteome maintenance, the molecular mechanisms by which these pathways maintain mitochondrial proteostasis remain largely unknown. We identify Tim17A as a stress-regulated subunit of the translocase of the inner membrane 23 (TIM23) mitochondrial protein import complex. We show that Tim17A protein levels are decreased downstream of stress-regulated translational attenuation induced by eukaryotic initiation factor 2α (eIF2α) phosphorylation through a mechanism dependent on the mitochondrial protease YME1L. Furthermore, we demonstrate that decreasing Tim17A attenuates TIM23-dependent protein import, promotes the induction of mitochondrial unfolded protein response (UPR)-associated proteostasis genes, and confers stress resistance in C. elegans and mammalian cells. Thus, our results indicate that Tim17A degradation is a stress-responsive mechanism by which cells adapt mitochondrial protein import efficiency and promote mitochondrial proteostasis in response to the numerous pathologic insults that induce stress-regulated translation attenuation.
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Affiliation(s)
- T Kelly Rainbolt
- Department of Molecular & Experimental Medicine, Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA 92037, USA
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86
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Ieva R, Heißwolf AK, Gebert M, Vögtle FN, Wollweber F, Mehnert CS, Oeljeklaus S, Warscheid B, Meisinger C, van der Laan M, Pfanner N. Mitochondrial inner membrane protease promotes assembly of presequence translocase by removing a carboxy-terminal targeting sequence. Nat Commun 2013; 4:2853. [DOI: 10.1038/ncomms3853] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2013] [Accepted: 11/01/2013] [Indexed: 01/04/2023] Open
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87
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Molecular insights revealing interaction of Tim23 and channel subunits of presequence translocase. Mol Cell Biol 2013; 33:4641-59. [PMID: 24061477 DOI: 10.1128/mcb.00876-13] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Tim23 is an essential channel-forming subunit of the presequence translocase recruiting multiple components for assembly of the core complex, thereby regulating the protein translocation process. However, understanding of the precise interaction of subunits associating with Tim23 remains largely elusive. Our findings highlight that transmembrane helix 1 (TM1) is required for homodimerization of Tim23, while, together with TM2, it is involved in preprotein binding within the channel. Based on our evidence, we predict that the TM1 and TM2 from each dimer are involved in the formation of the central translocation pore, aided by Tim17. Furthermore, TM2 is also involved in the recruitment of Tim21 and the presequence-associated motor (PAM) subcomplex to the Tim23 channel, while the matrix-exposed loop L1 generates specificity in their association with the core complex. Strikingly, our findings indicate that the C-terminal sequence of Tim23 is dispensable for growth and functions as an inhibitor for binding of Tim21. Our model conceptually explains the cooperative function between Tam41 and Pam17 subunits, while the antagonistic activity of Tim21 predominantly determines the bound and free forms of the PAM subcomplex during import.
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88
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Malhotra K, Sathappa M, Landin JS, Johnson AE, Alder NN. Structural changes in the mitochondrial Tim23 channel are coupled to the proton-motive force. Nat Struct Mol Biol 2013; 20:965-72. [DOI: 10.1038/nsmb.2613] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 05/14/2013] [Indexed: 01/11/2023]
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89
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Doyle SR, Kasinadhuni NRP, Chan CK, Grant WN. Evidence of evolutionary constraints that influences the sequence composition and diversity of mitochondrial matrix targeting signals. PLoS One 2013; 8:e67938. [PMID: 23825690 PMCID: PMC3692466 DOI: 10.1371/journal.pone.0067938] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 05/23/2013] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial targeting signals (MTSs) are responsible for trafficking nuclear encoded proteins to their final destination within mitochondria. These sequences are diverse, sharing little amino acid homology and vary significantly in length, and although the formation of a positively-charged amphiphilic alpha helix within the MTS is considered to be necessary and sufficient to mediate import, such a feature does not explain their diversity, nor how such diversity influences target sequence function, nor how such dissimilar signals interact with a single, evolutionarily conserved import mechanism. An in silico analysis of 296 N-terminal, matrix destined MTSs from Homo sapiens, Mus musculus, Saccharomyces cerevisiae, Arabidopsis thaliana, and Oryza sativa was undertaken to investigate relationships between MTSs, and/or, relationships between an individual targeting signal sequence and the protein that it imports. We present evidence that suggests MTS diversity is influenced in part by physiochemical and N-terminal characteristics of their mature sequences, and that some of these correlated characteristics are evolutionarily maintained across a number of taxa. Importantly, some of these associations begin to explain the variation in MTS length and composition.
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Affiliation(s)
- Stephen R Doyle
- La Trobe Institute for Molecular Sciences, La Trobe University, Bundoora, Australia.
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90
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Paul P, Simm S, Blaumeiser A, Scharf KD, Fragkostefanakis S, Mirus O, Schleiff E. The protein translocation systems in plants - composition and variability on the example of Solanum lycopersicum. BMC Genomics 2013; 14:189. [PMID: 23506162 PMCID: PMC3610429 DOI: 10.1186/1471-2164-14-189] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 02/25/2013] [Indexed: 11/22/2022] Open
Abstract
Background Protein translocation across membranes is a central process in all cells. In the past decades the molecular composition of the translocation systems in the membranes of the endoplasmic reticulum, peroxisomes, mitochondria and chloroplasts have been established based on the analysis of model organisms. Today, these results have to be transferred to other plant species. We bioinformatically determined the inventory of putative translocation factors in tomato (Solanum lycopersicum) by orthologue search and domain architecture analyses. In addition, we investigated the diversity of such systems by comparing our findings to the model organisms Saccharomyces cerevisiae, Arabidopsis thaliana and 12 other plant species. Results The literature search end up in a total of 130 translocation components in yeast and A. thaliana, which are either experimentally confirmed or homologous to experimentally confirmed factors. From our bioinformatic analysis (PGAP and OrthoMCL), we identified (co-)orthologues in plants, which in combination yielded 148 and 143 orthologues in A. thaliana and S. lycopersicum, respectively. Interestingly, we traced 82% overlap in findings from both approaches though we did not find any orthologues for 27% of the factors by either procedure. In turn, 29% of the factors displayed the presence of more than one (co-)orthologue in tomato. Moreover, our analysis revealed that the genomic composition of the translocation machineries in the bryophyte Physcomitrella patens resemble more to higher plants than to single celled green algae. The monocots (Z. mays and O. sativa) follow more or less a similar conservation pattern for encoding the translocon components. In contrast, a diverse pattern was observed in different eudicots. Conclusions The orthologue search shows in most cases a clear conservation of components of the translocation pathways/machineries. Only the Get-dependent integration of tail-anchored proteins seems to be distinct. Further, the complexity of the translocation pathway in terms of existing orthologues seems to vary among plant species. This might be the consequence of palaeoploidisation during evolution in plants; lineage specific whole genome duplications in Arabidopsis thaliana and triplications in Solanum lycopersicum.
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Affiliation(s)
- Puneet Paul
- Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, Frankfurt/Main, 60438, Germany
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91
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Lytovchenko O, Melin J, Schulz C, Kilisch M, Hutu DP, Rehling P. Signal recognition initiates reorganization of the presequence translocase during protein import. EMBO J 2013; 32:886-98. [PMID: 23403928 DOI: 10.1038/emboj.2013.23] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 01/17/2013] [Indexed: 11/09/2022] Open
Abstract
The mitochondrial presequence translocase interacts with presequence-containing precursors at the intermembrane space (IMS) side of the inner membrane to mediate their translocation into the matrix. Little is known as too how these matrix-targeting signals activate the translocase in order to initiate precursor transport. Therefore, we analysed how signal recognition by the presequence translocase initiates reorganization among Tim-proteins during import. Our analyses revealed that the presequence receptor Tim50 interacts with Tim21 in a signal-sensitive manner in a process that involves the IMS-domain of the Tim23 channel. The signal-driven release of Tim21 from Tim50 promotes recruitment of Pam17 and thus triggers formation of the motor-associated form of the TIM23 complex required for matrix transport.
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92
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Wiesemann K, Groß LE, Sommer M, Schleiff E, Sommer MS. self-assembling GFP: a versatile tool for plant (membrane) protein analyses. Methods Mol Biol 2013; 1033:131-144. [PMID: 23996175 DOI: 10.1007/978-1-62703-487-6_9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The investigation of cellular processes on the molecular level is important to understand the functional network within plant cells. self-assembling GFP has evolved to be a versatile tool for (membrane) protein analyses. Based on the autocatalytical reassembling property of the nonfluorescent strands 1-10 and 11, protein distribution and membrane protein topology can be analyzed in vivo. Here, we provide basic protocols to determine membrane protein topology in Arabidopsis thaliana protoplasts.
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Affiliation(s)
- Katharina Wiesemann
- Cluster of Excellence Frankfurt, Center for Membrane Proteomics, Department of Biosciences, Molecular Cell Biology, Goethe University, Frankfurt, Germany
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93
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Kulawiak B, Höpker J, Gebert M, Guiard B, Wiedemann N, Gebert N. The mitochondrial protein import machinery has multiple connections to the respiratory chain. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:612-26. [PMID: 23274250 DOI: 10.1016/j.bbabio.2012.12.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 12/12/2012] [Accepted: 12/17/2012] [Indexed: 01/09/2023]
Abstract
The mitochondrial inner membrane harbors the complexes of the respiratory chain and protein translocases required for the import of mitochondrial precursor proteins. These complexes are functionally interdependent, as the import of respiratory chain precursor proteins across and into the inner membrane requires the membrane potential. Vice versa the membrane potential is generated by the proton pumping complexes of the respiratory chain. Besides this basic codependency four different systems for protein import, processing and assembly show further connections to the respiratory chain. The mitochondrial intermembrane space import and assembly machinery oxidizes cysteine residues within the imported precursor proteins and is able to donate the liberated electrons to the respiratory chain. The presequence translocase of the inner membrane physically interacts with the respiratory chain. The mitochondrial processing peptidase is homologous to respiratory chain subunits and the carrier translocase of the inner membrane even shares a subunit with the respiratory chain. In this review we will summarize the import of mitochondrial precursor proteins and highlight these special links between the mitochondrial protein import machinery and the respiratory chain. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.
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Affiliation(s)
- Bogusz Kulawiak
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, Freiburg, Germany
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94
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Schusdziarra C, Blamowska M, Azem A, Hell K. Methylation-controlled J-protein MCJ acts in the import of proteins into human mitochondria. Hum Mol Genet 2012; 22:1348-57. [DOI: 10.1093/hmg/dds541] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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95
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Duncan MR, Fullerton M, Chaudhuri M. Tim50 in Trypanosoma brucei possesses a dual specificity phosphatase activity and is critical for mitochondrial protein import. J Biol Chem 2012; 288:3184-97. [PMID: 23212919 DOI: 10.1074/jbc.m112.436378] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In eukaryotes, proteins are imported into mitochondria via multiprotein translocases of the mitochondrial outer and inner membranes, TOM and TIM, respectively. Trypanosoma brucei, a hemoflagellated parasitic protozoan and the causative agent of African trypanosomiasis, imports about a thousand proteins into the mitochondrion; however, the mitochondrial protein import machinery in this organism is largely unidentified. Here, we characterized a homolog of Tim50 that is localized in the mitochondrial membrane in T. brucei. Similar to Tim50 proteins from fungi and mammals, Tim50 in T. brucei (TbTim50) possesses a mitochondrial targeting signal at its N terminus and a C-terminal domain phosphatase motif at its C terminus. Knockdown of TbTim50 reduced cell growth and inhibited import of proteins that contain N-terminal targeting signals. Co-immunoprecipitation analysis revealed that TbTim50 interacts with TbTim17. Unlike its fungal counterpart but similar to the human homolog of Tim50, recombinant TbTim50 possesses a dual specificity phosphatase activity with a greater affinity for protein tyrosine phosphate than for protein serine/threonine phosphate. Mutation of the aspartic acid residues to alanine in the C-terminal domain phosphatase motif (242)DXDX(V/T)(246) abolished activity for both type of substrates. TbTim50 knockdown increased and its overexpression decreased the level of voltage-dependent anion channel (VDAC). However, the VDAC level was unaltered when the phosphatase-inactive mutant of TbTim50 was overexpressed, suggesting that the phosphatase activity of TbTim50 plays a role in regulation of VDAC expression. In contrast, phosphatase activity of the TbTim50 is required neither for mitochondrial protein import nor for its interaction with TbTim17. Overall, our results show that TbTim50 plays additional roles in mitochondrial activities besides preprotein translocation.
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Affiliation(s)
- Melanie R Duncan
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee 37208, USA
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96
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Interaction of divalent metal ions with human translocase of inner membrane of mitochondria Tim50. Biochem Biophys Res Commun 2012; 428:365-70. [DOI: 10.1016/j.bbrc.2012.10.060] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Accepted: 10/15/2012] [Indexed: 11/21/2022]
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97
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Abstract
Good fortune let me be an innocent child during World War II, a hopeful adolescent with encouraging parents during the years of German recovery, and a self-determined adult in a period of peace, freedom, and wealth. My luck continued as a scientist who could entirely follow his fancy. My mind was always set on understanding how things are made. At a certain point, I found myself confronted with the question of how mitochondria and organelles, which cannot be formed de novo, are put together. Intracellular transport of proteins, their translocation across the mitochondrial membranes, and their folding and assembly were the processes that fascinated me. Now, after some 30 years, we have wonderful insights, unimagined views of a complex and at the same time simple machinery and its workings. We have glimpses of how orderly processes are established in the cell to assemble from single molecules our beautiful mitochondria that every day make some 50 kg of ATP for each of us. At the same time, we have learned amazing lessons from the tinkering of evolution that developed mitochondria from bacteria.
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Affiliation(s)
- Walter Neupert
- Ludwig-Maximilians-Universität München and Max Planck Institute of Biochemistry, Martinsried D-82152, Germany
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98
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Lowth BR, Kirstein-Miles J, Saiyed T, Brötz-Oesterhelt H, Morimoto RI, Truscott KN, Dougan DA. Substrate recognition and processing by a Walker B mutant of the human mitochondrial AAA+ protein CLPX. J Struct Biol 2012; 179:193-201. [PMID: 22710082 DOI: 10.1016/j.jsb.2012.06.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 05/14/2012] [Accepted: 06/07/2012] [Indexed: 10/28/2022]
Abstract
The mitochondrial matrix of mammalian cells contains several different ATP-dependent proteases, including CLPXP, some of which contribute to protein maturation and quality control. Currently however, the substrates and the physiological roles of mitochondrial CLPXP in humans, has remained elusive. Similarly, the mechanism by which these ATP-dependent proteases recognize their substrates currently remains unclear. Here we report the characterization of a Walker B mutation in human CLPX, in which the highly conserved glutamate was replaced with alanine. This mutant protein exhibits improved interaction with the model unfolded substrate casein and several putative physiological substrates in vitro. Although this mutant lacks ATPase activity, it retains the ability to mediate casein degradation by hCLPP, in a fashion similar to the small molecule ClpP-activator, ADEP. Our functional dissection of hCLPX structure, also identified that most model substrates are recognized by the N-terminal domain, although some substrates bypass this step and dock, directly to the pore-1 motif. Collectively these data reveal, that despite the difference between bacterial and human CLPXP complexes, human CLPXP exhibits a similar mode of substrate recognition and is deregulated by ADEPs.
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Affiliation(s)
- Bradley R Lowth
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
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99
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Dudek J, Rehling P, van der Laan M. Mitochondrial protein import: common principles and physiological networks. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:274-85. [PMID: 22683763 DOI: 10.1016/j.bbamcr.2012.05.028] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 05/24/2012] [Accepted: 05/28/2012] [Indexed: 11/28/2022]
Abstract
Most mitochondrial proteins are encoded in the nucleus. They are synthesized as precursor forms in the cytosol and must be imported into mitochondria with the help of different protein translocases. Distinct import signals within precursors direct each protein to the mitochondrial surface and subsequently onto specific transport routes to its final destination within these organelles. In this review we highlight common principles of mitochondrial protein import and address different mechanisms of protein integration into mitochondrial membranes. Over the last years it has become clear that mitochondrial protein translocases are not independently operating units, but in fact closely cooperate with each other. We discuss recent studies that indicate how the pathways for mitochondrial protein biogenesis are embedded into a functional network of various other physiological processes, such as energy metabolism, signal transduction, and maintenance of mitochondrial morphology. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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Affiliation(s)
- Jan Dudek
- Abteilung Biochemie II, Universität Göttingen, 37073 Göttingen, Germany
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Gebert M, Schrempp SG, Mehnert CS, Heißwolf AK, Oeljeklaus S, Ieva R, Bohnert M, von der Malsburg K, Wiese S, Kleinschroth T, Hunte C, Meyer HE, Haferkamp I, Guiard B, Warscheid B, Pfanner N, van der Laan M. Mgr2 promotes coupling of the mitochondrial presequence translocase to partner complexes. ACTA ACUST UNITED AC 2012; 197:595-604. [PMID: 22613836 PMCID: PMC3365495 DOI: 10.1083/jcb.201110047] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Many mitochondrial proteins are synthesized with N-terminal presequences in the cytosol. The presequence translocase of the inner mitochondrial membrane (TIM23) translocates preproteins into and across the membrane and associates with the matrix-localized import motor. The TIM23 complex consists of three core components and Tim21, which interacts with the translocase of the outer membrane (TOM) and the respiratory chain. We have identified a new subunit of the TIM23 complex, the inner membrane protein Mgr2. Mitochondria lacking Mgr2 were deficient in the Tim21-containing sorting form of the TIM23 complex. Mgr2 was required for binding of Tim21 to TIM23(CORE), revealing a binding chain of TIM23(CORE)-Mgr2/Tim21-respiratory chain. Mgr2-deficient yeast cells were defective in growth at elevated temperature, and the mitochondria were impaired in TOM-TIM23 coupling and the import of presequence-carrying preproteins. We conclude that Mgr2 is a coupling factor of the presequence translocase crucial for cell growth at elevated temperature and for efficient protein import.
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Affiliation(s)
- Michael Gebert
- Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Fakultät für Biologie, Funktionelle Proteomik, Universität Freiburg, 79104 Freiburg, Germany
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