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Horten P, Song K, Garlich J, Hardt R, Colina-Tenorio L, Horvath SE, Schulte U, Fakler B, van der Laan M, Becker T, Stuart RA, Pfanner N, Rampelt H. Identification of MIMAS, a multifunctional mega-assembly integrating metabolic and respiratory biogenesis factors of mitochondria. Cell Rep 2024; 43:113772. [PMID: 38393949 PMCID: PMC11010658 DOI: 10.1016/j.celrep.2024.113772] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 01/03/2024] [Accepted: 01/24/2024] [Indexed: 02/25/2024] Open
Abstract
The mitochondrial inner membrane plays central roles in bioenergetics and metabolism and contains several established membrane protein complexes. Here, we report the identification of a mega-complex of the inner membrane, termed mitochondrial multifunctional assembly (MIMAS). Its large size of 3 MDa explains why MIMAS has escaped detection in the analysis of mitochondria so far. MIMAS combines proteins of diverse functions from respiratory chain assembly to metabolite transport, dehydrogenases, and lipid biosynthesis but not the large established supercomplexes of the respiratory chain, ATP synthase, or prohibitin scaffold. MIMAS integrity depends on the non-bilayer phospholipid phosphatidylethanolamine, in contrast to respiratory supercomplexes whose stability depends on cardiolipin. Our findings suggest that MIMAS forms a protein-lipid mega-assembly in the mitochondrial inner membrane that integrates respiratory biogenesis and metabolic processes in a multifunctional platform.
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Affiliation(s)
- Patrick Horten
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Kuo Song
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Joshua Garlich
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233, USA
| | - Robert Hardt
- Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Bonn, 53115 Bonn, Germany
| | - Lilia Colina-Tenorio
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Susanne E Horvath
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Uwe Schulte
- Institute of Physiology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Martin van der Laan
- Medical Biochemistry and Molecular Biology, Center for Molecular Signaling, PZMS, Faculty of Medicine, Saarland University, 66421 Homburg, Germany
| | - Thomas Becker
- Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Bonn, 53115 Bonn, Germany
| | - Rosemary A Stuart
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233, USA
| | - Nikolaus Pfanner
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
| | - Heike Rampelt
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
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Kunová N, Havalová H, Ondrovičová G, Stojkovičová B, Bauer JA, Bauerová-Hlinková V, Pevala V, Kutejová E. Mitochondrial Processing Peptidases-Structure, Function and the Role in Human Diseases. Int J Mol Sci 2022; 23:1297. [PMID: 35163221 PMCID: PMC8835746 DOI: 10.3390/ijms23031297] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 01/21/2022] [Accepted: 01/22/2022] [Indexed: 12/21/2022] Open
Abstract
Mitochondrial proteins are encoded by both nuclear and mitochondrial DNA. While some of the essential subunits of the oxidative phosphorylation (OXPHOS) complexes responsible for cellular ATP production are synthesized directly in the mitochondria, most mitochondrial proteins are first translated in the cytosol and then imported into the organelle using a sophisticated transport system. These proteins are directed mainly by targeting presequences at their N-termini. These presequences need to be cleaved to allow the proper folding and assembly of the pre-proteins into functional protein complexes. In the mitochondria, the presequences are removed by several processing peptidases, including the mitochondrial processing peptidase (MPP), the inner membrane processing peptidase (IMP), the inter-membrane processing peptidase (MIP), and the mitochondrial rhomboid protease (Pcp1/PARL). Their proper functioning is essential for mitochondrial homeostasis as the disruption of any of them is lethal in yeast and severely impacts the lifespan and survival in humans. In this review, we focus on characterizing the structure, function, and substrate specificities of mitochondrial processing peptidases, as well as the connection of their malfunctions to severe human diseases.
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Affiliation(s)
| | | | | | | | | | | | | | - Eva Kutejová
- Department of Biochemistry and Protein Structure, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská Cesta 21, 845 51 Bratislava, Slovakia; (H.H.); (G.O.); (B.S.); (J.A.B.); (V.B.-H.); (V.P.)
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Heidorn-Czarna M, Maziak A, Janska H. Protein Processing in Plant Mitochondria Compared to Yeast and Mammals. FRONTIERS IN PLANT SCIENCE 2022; 13:824080. [PMID: 35185991 PMCID: PMC8847149 DOI: 10.3389/fpls.2022.824080] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 01/12/2022] [Indexed: 05/02/2023]
Abstract
Limited proteolysis, called protein processing, is an essential post-translational mechanism that controls protein localization, activity, and in consequence, function. This process is prevalent for mitochondrial proteins, mainly synthesized as precursor proteins with N-terminal sequences (presequences) that act as targeting signals and are removed upon import into the organelle. Mitochondria have a distinct and highly conserved proteolytic system that includes proteases with sole function in presequence processing and proteases, which show diverse mitochondrial functions with limited proteolysis as an additional one. In virtually all mitochondria, the primary processing of N-terminal signals is catalyzed by the well-characterized mitochondrial processing peptidase (MPP). Subsequently, a second proteolytic cleavage occurs, leading to more stabilized residues at the newly formed N-terminus. Lately, mitochondrial proteases, intermediate cleavage peptidase 55 (ICP55) and octapeptidyl protease 1 (OCT1), involved in proteolytic cleavage after MPP and their substrates have been described in the plant, yeast, and mammalian mitochondria. Mitochondrial proteins can also be processed by removing a peptide from their N- or C-terminus as a maturation step during insertion into the membrane or as a regulatory mechanism in maintaining their function. This type of limited proteolysis is characteristic for processing proteases, such as IMP and rhomboid proteases, or the general mitochondrial quality control proteases ATP23, m-AAA, i-AAA, and OMA1. Identification of processing protease substrates and defining their consensus cleavage motifs is now possible with the help of large-scale quantitative mass spectrometry-based N-terminomics, such as combined fractional diagonal chromatography (COFRADIC), charge-based fractional diagonal chromatography (ChaFRADIC), or terminal amine isotopic labeling of substrates (TAILS). This review summarizes the current knowledge on the characterization of mitochondrial processing peptidases and selected N-terminomics techniques used to uncover protease substrates in the plant, yeast, and mammalian mitochondria.
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Petrů M, Dohnálek V, Füssy Z, Doležal P. Fates of Sec, Tat, and YidC Translocases in Mitochondria and Other Eukaryotic Compartments. Mol Biol Evol 2021; 38:5241-5254. [PMID: 34436602 PMCID: PMC8662606 DOI: 10.1093/molbev/msab253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Formation of mitochondria by the conversion of a bacterial endosymbiont was a key moment in the evolution of eukaryotes. It was made possible by outsourcing the endosymbiont's genetic control to the host nucleus, while developing the import machinery for proteins synthesized on cytosolic ribosomes. The original protein export machines of the nascent organelle remained to be repurposed or were completely abandoned. This review follows the evolutionary fates of three prokaryotic inner membrane translocases Sec, Tat, and YidC. Homologs of all three translocases can still be found in current mitochondria, but with different importance for mitochondrial function. Although the mitochondrial YidC homolog, Oxa1, became an omnipresent independent insertase, the other two remained only sporadically present in mitochondria. Only a single substrate is known for the mitochondrial Tat and no function has yet been assigned for the mitochondrial Sec. Finally, this review compares these ancestral mitochondrial proteins with their paralogs operating in the plastids and the endomembrane system.
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Affiliation(s)
- Markéta Petrů
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Vít Dohnálek
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Zoltán Füssy
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Pavel Doležal
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
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5
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Gomez-Fabra Gala M, Vögtle FN. Mitochondrial proteases in human diseases. FEBS Lett 2021; 595:1205-1222. [PMID: 33453058 DOI: 10.1002/1873-3468.14039] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 12/17/2020] [Accepted: 12/18/2020] [Indexed: 12/15/2022]
Abstract
Mitochondria contain more than 1000 different proteins, including several proteolytic enzymes. These mitochondrial proteases form a complex system that performs limited and terminal proteolysis to build the mitochondrial proteome, maintain, and control its functions or degrade mitochondrial proteins and peptides. During protein biogenesis, presequence proteases cleave and degrade mitochondrial targeting signals to obtain mature functional proteins. Processing by proteases also exerts a regulatory role in modulation of mitochondrial functions and quality control enzymes degrade misfolded, aged, or superfluous proteins. Depending on their different functions and substrates, defects in mitochondrial proteases can affect the majority of the mitochondrial proteome or only a single protein. Consequently, mutations in mitochondrial proteases have been linked to several human diseases. This review gives an overview of the components and functions of the mitochondrial proteolytic machinery and highlights the pathological consequences of dysfunctional mitochondrial protein processing and turnover.
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Affiliation(s)
- Maria Gomez-Fabra Gala
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Germany.,Faculty of Biology, University of Freiburg, Germany.,Spemann Graduate School of Biology and Medicine, University of Freiburg, Germany
| | - Friederike-Nora Vögtle
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Germany.,CIBSS-Centre for Integrative Biological Signalling Studies, University of Freiburg, Germany
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6
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Lorenzi I, Oeljeklaus S, Aich A, Ronsör C, Callegari S, Dudek J, Warscheid B, Dennerlein S, Rehling P. The mitochondrial TMEM177 associates with COX20 during COX2 biogenesis. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2018; 1865:323-333. [PMID: 29154948 PMCID: PMC5764226 DOI: 10.1016/j.bbamcr.2017.11.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 11/10/2017] [Accepted: 11/14/2017] [Indexed: 12/17/2022]
Abstract
The three mitochondrial-encoded proteins, COX1, COX2, and COX3, form the core of the cytochrome c oxidase. Upon synthesis, COX2 engages with COX20 in the inner mitochondrial membrane, a scaffold protein that recruits metallochaperones for copper delivery to the CuA-Site of COX2. Here we identified the human protein, TMEM177 as a constituent of the COX20 interaction network. Loss or increase in the amount of TMEM177 affects COX20 abundance leading to reduced or increased COX20 levels respectively. TMEM177 associates with newly synthesized COX2 and SCO2 in a COX20-dependent manner. Our data shows that by unbalancing the amount of TMEM177, newly synthesized COX2 accumulates in a COX20-associated state. We conclude that TMEM177 promotes assembly of COX2 at the level of CuA-site formation.
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Affiliation(s)
- Isotta Lorenzi
- Department of Cellular Biochemistry, University Medical Centre Göttingen, GZMB, D-37073 Göttingen, Germany
| | - Silke Oeljeklaus
- Faculty of Biology, Department of Biochemistry and Functional Proteomics, University Freiburg, D-79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, D-79104 Freiburg, Germany
| | - Abhishek Aich
- Department of Cellular Biochemistry, University Medical Centre Göttingen, GZMB, D-37073 Göttingen, Germany
| | - Christin Ronsör
- Department of Cellular Biochemistry, University Medical Centre Göttingen, GZMB, D-37073 Göttingen, Germany
| | - Sylvie Callegari
- Department of Cellular Biochemistry, University Medical Centre Göttingen, GZMB, D-37073 Göttingen, Germany
| | - Jan Dudek
- Department of Cellular Biochemistry, University Medical Centre Göttingen, GZMB, D-37073 Göttingen, Germany
| | - Bettina Warscheid
- Faculty of Biology, Department of Biochemistry and Functional Proteomics, University Freiburg, D-79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, D-79104 Freiburg, Germany
| | - Sven Dennerlein
- Department of Cellular Biochemistry, University Medical Centre Göttingen, GZMB, D-37073 Göttingen, Germany.
| | - Peter Rehling
- Department of Cellular Biochemistry, University Medical Centre Göttingen, GZMB, D-37073 Göttingen, Germany; Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany.
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7
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A single-cysteine mutant and chimeras of essential Leishmania Erv can complement the loss of Erv1 but not of Mia40 in yeast. Redox Biol 2017; 15:363-374. [PMID: 29310075 PMCID: PMC5760468 DOI: 10.1016/j.redox.2017.12.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 12/17/2017] [Accepted: 12/21/2017] [Indexed: 11/21/2022] Open
Abstract
Mia40/CHCHD4 and Erv1/ALR are essential for oxidative protein folding in the mitochondrial intermembrane space of yeast and mammals. In contrast, many protists, including important apicomplexan and kinetoplastid parasites, lack Mia40. Furthermore, the Erv homolog of the model parasite Leishmania tarentolae (LtErv) was shown to be incompatible with Saccharomyces cerevisiae Mia40 (ScMia40). Here we addressed structure-function relationships of ScErv1 and LtErv as well as their compatibility with the oxidative protein folding system in yeast using chimeric, truncated, and mutant Erv constructs. Chimeras between the N-terminal arm of ScErv1 and a variety of truncated LtErv constructs were able to rescue yeast cells that lack ScErv1. Yeast cells were also viable when only a single cysteine residue was replaced in LtErvC17S. Thus, the presence and position of the C-terminal arm and the kinetoplastida-specific second (KISS) domain of LtErv did not interfere with its functionality in the yeast system, whereas a relatively conserved cysteine residue before the flavodomain rendered LtErv incompatible with ScMia40. The question whether parasite Erv homologs might also exert the function of Mia40 was addressed in another set of complementation assays. However, neither the KISS domain nor other truncated or mutant LtErv constructs were able to rescue yeast cells that lack ScMia40. The general relevance of Erv and its candidate substrate small Tim1 was analyzed for the related parasite L. infantum. Repeated unsuccessful knockout attempts suggest that both genes are essential in this human pathogen and underline the potential of mitochondrial protein import pathways for future intervention strategies.
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8
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Ribosome-Associated Mba1 Escorts Cox2 from Insertion Machinery to Maturing Assembly Intermediates. Mol Cell Biol 2016; 36:2782-2793. [PMID: 27550809 PMCID: PMC5086520 DOI: 10.1128/mcb.00361-16] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 07/08/2016] [Accepted: 08/17/2016] [Indexed: 01/25/2023] Open
Abstract
The three conserved core subunits of the cytochrome c oxidase are encoded by mitochondria in close to all eukaryotes. The Cox2 subunit spans the inner membrane twice, exposing the N and C termini to the intermembrane space. For this, the N terminus is exported cotranslationally by Oxa1 and subsequently undergoes proteolytic maturation in Saccharomyces cerevisiae. Little is known about the translocation of the C terminus, but Cox18 has been identified to be a critical protein in this process. Here we find that the scaffold protein Cox20, which promotes processing of Cox2, is in complex with the ribosome receptor Mba1 and translating mitochondrial ribosomes in a Cox2-dependent manner. The Mba1-Cox20 complex accumulates when export of the C terminus of Cox2 is blocked by the loss of the Cox18 protein. While Cox20 engages with Cox18, Mba1 is no longer present at this stage. Our analyses indicate that Cox20 associates with nascent Cox2 and Mba1 to promote Cox2 maturation cotranslationally. We suggest that Mba1 stabilizes the Cox20-ribosome complex and supports the handover of Cox2 to the Cox18 tail export machinery.
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9
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The versatility of the mitochondrial presequence processing machinery: cleavage, quality control and turnover. Cell Tissue Res 2016; 367:73-81. [DOI: 10.1007/s00441-016-2492-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/06/2016] [Accepted: 08/10/2016] [Indexed: 12/12/2022]
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Mani J, Meisinger C, Schneider A. Peeping at TOMs-Diverse Entry Gates to Mitochondria Provide Insights into the Evolution of Eukaryotes. Mol Biol Evol 2015; 33:337-51. [PMID: 26474847 DOI: 10.1093/molbev/msv219] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mitochondria are essential for eukaryotic life and more than 95% of their proteins are imported as precursors from the cytosol. The targeting signals for this posttranslational import are conserved in all eukaryotes. However, this conservation does not hold true for the protein translocase of the mitochondrial outer membrane that serves as entry gate for essentially all precursor proteins. Only two of its subunits, Tom40 and Tom22, are conserved and thus likely were present in the last eukaryotic common ancestor. Tom7 is found in representatives of all supergroups except the Excavates. This suggests that it was added to the core of the translocase after the Excavates segregated from all other eukaryotes. A comparative analysis of the biochemically and functionally characterized outer membrane translocases of yeast, plants, and trypanosomes, which represent three eukaryotic supergroups, shows that the receptors that recognize the conserved import signals differ strongly between the different systems. They present a remarkable example of convergent evolution at the molecular level. The structural diversity of the functionally conserved import receptors therefore provides insight into the early evolutionary history of mitochondria.
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Affiliation(s)
- Jan Mani
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Chris Meisinger
- Institut für Biochemie und Molekularbiologie, ZBMZ and BIOSS Centre for Biological Signalling Studies, Universität Freiburg, Freiburg, Germany
| | - André Schneider
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
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Höhr AIC, Straub SP, Warscheid B, Becker T, Wiedemann N. Assembly of β-barrel proteins in the mitochondrial outer membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:74-88. [PMID: 25305573 DOI: 10.1016/j.bbamcr.2014.10.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 09/25/2014] [Accepted: 10/01/2014] [Indexed: 12/15/2022]
Abstract
Mitochondria evolved through endosymbiosis of a Gram-negative progenitor with a host cell to generate eukaryotes. Therefore, the outer membrane of mitochondria and Gram-negative bacteria contain pore proteins with β-barrel topology. After synthesis in the cytosol, β-barrel precursor proteins are first transported into the mitochondrial intermembrane space. Folding and membrane integration of β-barrel proteins depend on the mitochondrial sorting and assembly machinery (SAM) located in the outer membrane, which is related to the β-barrel assembly machinery (BAM) in bacteria. The SAM complex recognizes β-barrel proteins by a β-signal in the C-terminal β-strand that is required to initiate β-barrel protein insertion into the outer membrane. In addition, the SAM complex is crucial to form membrane contacts with the inner mitochondrial membrane by interacting with the mitochondrial contact site and cristae organizing system (MICOS) and shares a subunit with the endoplasmic reticulum-mitochondria encounter structure (ERMES) that links the outer mitochondrial membrane to the endoplasmic reticulum (ER).
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Affiliation(s)
- Alexandra I C Höhr
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Sebastian P Straub
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Bettina Warscheid
- BIOSS Centre for Biological Signalling Studies, Universität Freiburg, 79104 Freiburg, Germany; Abteilung Biochemie und Funktionelle Proteomik, Institut für Biologie II, Fakultät für Biologie, Universität Freiburg, 79104 Freiburg, Germany
| | - Thomas Becker
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Universität Freiburg, 79104 Freiburg, Germany
| | - Nils Wiedemann
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Universität Freiburg, 79104 Freiburg, Germany.
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Herrmann JM, Riemer J. Three approaches to one problem: protein folding in the periplasm, the endoplasmic reticulum, and the intermembrane space. Antioxid Redox Signal 2014; 21:438-56. [PMID: 24483706 DOI: 10.1089/ars.2014.5841] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
SIGNIFICANCE The bacterial periplasm, the endoplasmic reticulum (ER), and the intermembrane space (IMS) of mitochondria contain dedicated machineries for the incorporation of disulfide bonds into polypeptides, which cooperate with chaperones, proteases, and assembly factors during protein biogenesis. RECENT ADVANCES The mitochondrial disulfide relay was identified only very recently. The current knowledge of the protein folding machinery of the IMS will be described in detail in this review and compared with the "more established" systems of the periplasm and the ER. CRITICAL ISSUES While the disulfide relays of all three compartments adhere to the same principle, the specific designs and functions of these systems differ considerably. In particular, the cooperation with other folding systems makes the situation in each compartment unique. FUTURE DIRECTIONS The biochemical properties of the oxidation machineries are relatively well understood. However, it still remains largely unclear as to how the quality control systems of "oxidizing" compartments orchestrate the activities of oxidoreductases, chaperones, proteases, and signaling molecules to ensure protein homeostasis.
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Affiliation(s)
- Johannes M Herrmann
- 1 Department of Cell Biology, University of Kaiserslautern , Kaiserslautern, Germany
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13
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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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14
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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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15
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Keil M, Bareth B, Woellhaf MW, Peleh V, Prestele M, Rehling P, Herrmann JM. Oxa1-ribosome complexes coordinate the assembly of cytochrome C oxidase in mitochondria. J Biol Chem 2012; 287:34484-93. [PMID: 22904327 DOI: 10.1074/jbc.m112.382630] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The terminal enzyme of the respiratory chain, cytochrome c oxidase, consists of a hydrophobic reaction center formed by three mitochondrially encoded subunits with which 9-10 nuclear encoded subunits are associated. The three core subunits are synthesized on mitochondrial ribosomes and inserted into the inner membrane in a co-translational reaction facilitated by the Oxa1 insertase. Oxa1 consists of an N-terminal insertase domain and a C-terminal ribosome-binding region. Mutants lacking the C-terminal region show specific defects in co-translational insertion, suggesting that the close contact of the ribosome with the insertase promotes co-translational insertion of nascent chains. In this study, we inserted flexible linkers of 100 or 200 amino acid residues between the insertase domain and ribosome-binding region of Oxa1 of Saccharomyces cerevisiae. In the absence of the ribosome receptor Mba1, these linkers caused a length-dependent decrease in mitochondrial respiratory activity caused by diminished levels of cytochrome c oxidase. Interestingly, considerable amounts of mitochondrial translation products were still integrated into the inner membrane in these linker mutants. However, they showed severe defects in later stages of the biogenesis process, presumably during assembly into functional complexes. Our observations suggest that the close proximity of Oxa1 to ribosomes is not only used to improve membrane insertion but is also critical for the productive assembly of the subunits of the cytochrome c oxidase. This points to a role for Oxa1 in the spatial coordination of the ribosome with assembly factors that are critical for enzyme biogenesis.
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Affiliation(s)
- Melanie Keil
- Department of Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
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16
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Wang Z, Yan S, Liu C, Chen F, Wang T. Proteomic analysis reveals an aflatoxin-triggered immune response in cotyledons of Arachis hypogaea infected with Aspergillus flavus. J Proteome Res 2012; 11:2739-53. [PMID: 22424419 DOI: 10.1021/pr201105d] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
An immune response is triggered in host cells when host receptors recognize conserved molecular motifs, pathogen-associated molecular patterns (PAMPs), such as β-glucans, and chitin at the cell surface of a pathogen. Effector-triggered immunity occurs when pathogens deliver effectors into the host cell to suppress the first immune signaling. Using a differential proteomic approach, we identified an array of proteins responding to aflatoxins in cotyledons of peanut (Arachis hypogaea) infected with aflatoxin-producing (toxigenic) but not nonaflatoxin-producing (atoxigenic) strains of Aspergillus flavus. These proteins are involved in immune signaling and PAMP perception, DNA and RNA stabilization, induction of defense, innate immunity, hypersensitive response, biosynthesis of phytoalexins, cell wall responses, peptidoglycan assembly, penetration resistance, condensed tannin synthesis, detoxification, and metabolic regulation. Gene expression analysis confirmed the differential abundance of proteins in peanut cotyledons supplemented with aflatoxins, with or without infection with the atoxigenic strain. Similarly, peanut germination and A. flavus growth were altered in response to aflatoxin B1. These findings show an additional immunity initiated by aflatoxins. With the PAMP- and effector-triggered immune responses, this immunity constitutes the third immune response of the immune system in peanut cotyledon cells. The system is also a three-grade coevolution of plant-pathogen interaction.
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Affiliation(s)
- Zizhang Wang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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17
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Herrmann JM, Riemer J. Mitochondrial disulfide relay: redox-regulated protein import into the intermembrane space. J Biol Chem 2011; 287:4426-33. [PMID: 22157015 DOI: 10.1074/jbc.r111.270678] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
99% of all mitochondrial proteins are synthesized in the cytosol, from where they are imported into mitochondria. In contrast to matrix proteins, many proteins of the intermembrane space (IMS) lack presequences and are imported in an oxidation-driven reaction by the mitochondrial disulfide relay. Incoming polypeptides are recognized and oxidized by the IMS-located receptor Mia40. Reoxidation of Mia40 is facilitated by the sulfhydryl oxidase Erv1 and the respiratory chain. Although structurally unrelated, the mitochondrial disulfide relay functionally resembles the Dsb (disufide bond) system of the bacterial periplasm, the compartment from which the IMS was derived 2 billion years ago.
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Affiliation(s)
- Johannes M Herrmann
- Department of Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663 Kaiserslautern, Germany.
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18
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Barros MH, Rak M, Paulela JA, Tzagoloff A. Characterization of Gtf1p, the connector subunit of yeast mitochondrial tRNA-dependent amidotransferase. J Biol Chem 2011; 286:32937-47. [PMID: 21799017 DOI: 10.1074/jbc.m111.265371] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bacterial GatCAB operon for tRNA-dependent amidotransferase (AdT) catalyzes the transamidation of mischarged glutamyl-tRNA(Gln) to glutaminyl-tRNA(Gln). Here we describe the phenotype of temperature-sensitive (ts) mutants of GTF1, a gene proposed to code for subunit F of mitochondrial AdT in Saccharomyces cerevisiae. The ts gtf1 mutants accumulate an electrophoretic variant of the mitochondrially encoded Cox2p subunit of cytochrome oxidase and an unstable form of the Atp8p subunit of the F(1)-F(0) ATP synthase that is degraded, thereby preventing assembly of the F(0) sector. Allotopic expression of recoded ATP8 and COX2 did not significantly improve growth of gtf1 mutants on respiratory substrates. However, ts gft1 mutants are partially rescued by overexpression of PET112 and HER2 that code for the yeast homologues of the catalytic subunits of bacterial AdT. Additionally, B66, a her2 point mutant has a phenotype similar to that of gtf1 mutants. These results provide genetic support for the essentiality, in vivo, of the GatF subunit of the heterotrimeric AdT that catalyzes formation of glutaminyl-tRNA(Gln) (Frechin, M., Senger, B., Brayé, M., Kern, D., Martin, R. P., and Becker, H. D. (2009) Genes Dev. 23, 1119-1130).
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Affiliation(s)
- Mario H Barros
- Department of Microbiology, University of São Paulo, 05508-900 São Paulo, Brazil
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19
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Napoli E, Ross-Inta C, Wong S, Omanska-Klusek A, Barrow C, Iwahashi C, Garcia-Arocena D, Sakaguchi D, Berry-Kravis E, Hagerman R, Hagerman PJ, Giulivi C. Altered zinc transport disrupts mitochondrial protein processing/import in fragile X-associated tremor/ataxia syndrome. Hum Mol Genet 2011; 20:3079-92. [PMID: 21558427 DOI: 10.1093/hmg/ddr211] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that affects individuals who are carriers of small CGG premutation expansions in the fragile X mental retardation 1 (FMR1) gene. Mitochondrial dysfunction was observed as an incipient pathological process occurring in individuals who do not display overt features of FXTAS (1). Fibroblasts from premutation carriers had lower oxidative phosphorylation capacity (35% of controls) and Complex IV activity (45%), and higher precursor-to-mature ratios (P:M) of nDNA-encoded mitochondrial proteins (3.1-fold). However, fibroblasts from carriers with FXTAS symptoms presented higher FMR1 mRNA expression (3-fold) and lower Complex V (38%) and aconitase activities (43%). Higher P:M of ATPase β-subunit (ATPB) and frataxin were also observed in cortex from patients that died with FXTAS symptoms. Biochemical findings observed in FXTAS cells (lower mature frataxin, lower Complex IV and aconitase activities) along with common phenotypic traits shared by Friedreich's ataxia and FXTAS carriers (e.g. gait ataxia, loss of coordination) are consistent with a defective iron homeostasis in both diseases. Higher P:M, and lower ZnT6 and mature frataxin protein expression suggested defective zinc and iron metabolism arising from altered ZnT protein expression, which in turn impairs the activity of mitochondrial Zn-dependent proteases, critical for the import and processing of cytosolic precursors, such as frataxin. In support of this hypothesis, Zn-treated fibroblasts showed a significant recovery of ATPB P:M, ATPase activity and doubling time, whereas Zn and desferrioxamine extended these recoveries and rescued Complex IV activity.
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Affiliation(s)
- Eleonora Napoli
- Department of Molecular Biosciences, School of Veterinary Medicine, School of Medicine, University of California Davis, Davis, CA 95616, USA
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20
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Midzak A, Rone M, Aghazadeh Y, Culty M, Papadopoulos V. Mitochondrial protein import and the genesis of steroidogenic mitochondria. Mol Cell Endocrinol 2011; 336:70-9. [PMID: 21147195 PMCID: PMC3057322 DOI: 10.1016/j.mce.2010.12.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2010] [Revised: 12/03/2010] [Accepted: 12/05/2010] [Indexed: 11/23/2022]
Abstract
The principal site of regulation of steroid hormone biosynthesis is the transfer of cholesterol from the outer to inner mitochondrial membrane. Hormonal stimulation of steroidogenic cells promotes this mitochondrial lipid import through a multi-protein complex, termed the transduceosome, spanning the two membranes. The transduceosome complex is assembled from multiple proteins, such as the steroidogenic acute regulatory (STAR) protein and translocator protein (TSPO), and requires their targeting to the mitochondria for transduceosome function. The vast majority of mitochondrial proteins, including those participating in cholesterol import, are encoded in the nucleus. Their subsequent mitochondrial incorporation is performed through a series of protein import machineries located in the outer and inner mitochondrial membranes. Here we review our current knowledge of the mitochondrial cholesterol import machinery of the transduceosome. This is complemented with descriptions of mitochondrial protein import machineries and mechanisms by which these machineries assemble the transduceosome in steroidogenic mitochondria.
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Affiliation(s)
- Andrew Midzak
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Department of Medicine, McGill University, Montreal, Quebec, H3G 1A4, Canada
| | - Malena Rone
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Department of Medicine, McGill University, Montreal, Quebec, H3G 1A4, Canada
| | - Yassaman Aghazadeh
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Department of Medicine, McGill University, Montreal, Quebec, H3G 1A4, Canada
| | - Martine Culty
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Department of Medicine, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Quebec, H3G 1A4, Canada
| | - Vassilios Papadopoulos
- Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Department of Medicine, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Department of Biochemistry, McGill University, Montreal, Quebec, H3G 1A4, Canada
- Correspondence at The Research Institute of the McGill University Health Center, Montreal General Hospital, 1650 Cedar Avenue, C10-148, Montreal, Quebec H3G 1A4, Canada. Tel: 514-934-1934 ext. 44580; Fax: 514-934-8261;
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21
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Müller JEN, Papic D, Ulrich T, Grin I, Schütz M, Oberhettinger P, Tommassen J, Linke D, Dimmer KS, Autenrieth IB, Rapaport D. Mitochondria can recognize and assemble fragments of a beta-barrel structure. Mol Biol Cell 2011; 22:1638-47. [PMID: 21460184 PMCID: PMC3093317 DOI: 10.1091/mbc.e10-12-0943] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The signal that directs newly synthesized mitochondrial β-barrel proteins from the cytosol to the organelle is poorly defined. The findings of this study demonstrate that, rather than a linear sequence, the structural information in four β-strands is sufficient for the mitochondria to recognize and assemble β-barrel protein. β-barrel proteins are found in the outer membranes of eukaryotic organelles of endosymbiotic origin as well as in the outer membrane of Gram-negative bacteria. Precursors of mitochondrial β-barrel proteins are synthesized in the cytosol and have to be targeted to the organelle. Currently, the signal that assures their specific targeting to mitochondria is poorly defined. To characterize the structural features needed for specific mitochondrial targeting and to test whether a full β-barrel structure is required, we expressed in yeast cells the β-barrel domain of the trimeric autotransporter Yersinia adhesin A (YadA). Trimeric autotransporters are found only in prokaryotes, where they are anchored to the outer membrane by a single 12-stranded β-barrel structure to which each monomer is contributing four β-strands. Importantly, we found that YadA is solely localized to the mitochondrial outer membrane, where it exists in a native trimeric conformation. These findings demonstrate that, rather than a linear sequence or a complete β-barrel structure, four β-strands are sufficient for the mitochondria to recognize and assemble a β-barrel protein. Remarkably, the evolutionary origin of mitochondria from bacteria enables them to import and assemble even proteins belonging to a class that is absent in eukaryotes.
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Affiliation(s)
- Jonas E N Müller
- Interfaculty Institute of Biochemistry, University of Tübingen, 72076 Tübingen, Germany
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22
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Poulsen JB, Andersen KR, Kjær KH, Durand F, Faou P, Vestergaard AL, Talbo GH, Hoogenraad N, Brodersen DE, Justesen J, Martensen PM. Human 2'-phosphodiesterase localizes to the mitochondrial matrix with a putative function in mitochondrial RNA turnover. Nucleic Acids Res 2011; 39:3754-70. [PMID: 21245038 PMCID: PMC3089451 DOI: 10.1093/nar/gkq1282] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The vertebrate 2-5A system is part of the innate immune system and central to cellular antiviral defense. Upon activation by viral double-stranded RNA, 5'-triphosphorylated, 2'-5'-linked oligoadenylate polyribonucleotides (2-5As) are synthesized by one of several 2'-5'-oligoadenylate synthetases. These unusual oligonucleotides activate RNase L, an unspecific endoribonuclease that mediates viral and cellular RNA breakdown. Subsequently, the 2-5As are removed by a 2'-phosphodiesterase (2'-PDE), an enzyme that apart from breaking 2'-5' bonds also degrades regular, 3'-5'-linked oligoadenylates. Interestingly, 2'-PDE shares both functionally and structurally characteristics with the CCR4-type exonuclease-endonuclease-phosphatase family of deadenylases. Here we show that 2'-PDE locates to the mitochondrial matrix of human cells, and comprise an active 3'-5' exoribonuclease exhibiting a preference for oligo-adenosine RNA like canonical cytoplasmic deadenylases. Furthermore, we document a marked negative association between 2'-PDE and mitochondrial mRNA levels following siRNA-directed knockdown and plasmid-mediated overexpression, respectively. The results indicate that 2'-PDE, apart from playing a role in the cellular immune system, may also function in mitochondrial RNA turnover.
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23
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Nilsson Cederholm S, Bäckman HG, Pesaresi P, Leister D, Glaser E. Deletion of an organellar peptidasome PreP affects early development in Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 2009; 71:497-508. [PMID: 19701724 DOI: 10.1007/s11103-009-9534-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 08/02/2009] [Indexed: 05/28/2023]
Abstract
A novel peptidasome PreP is responsible for degradation of targeting peptides and other unstructured peptides in mitochondria and chloroplasts. Arabidopsis thaliana contains two PreP isoforms, AtPreP1, and AtPreP2. Here we have characterized single and double prep knockout mutants. Immunoblot analysis of atprep1 and atprep2 mutants showed that both isoforms are expressed in all tissues with the highest expression in flowers and siliques; additionally, AtPreP1 accumulated to a much higher level in comparison to AtPreP2. The atprep2 mutant behaved like wild type, whereas deletion of AtPreP1 resulted in slightly pale-green seedlings. Analysis of the atprep1 atprep2 double mutant revealed a chlorotic phenotype in true leaves with diminished chlorophyll a and b content, but unchanged Chl a/b ratio indicating a proportional decrease of both PSI and PSII complexes. Mitochondrial respiratory rates (state 3) were lower and the mitochondria were partially uncoupled. EM pictures on cross sections of the first true leaves showed aberrant chloroplasts, including less grana stacking and less starch granules. Mitochondria with extremely variable size could also be observed. At later developmental stages the plants appeared almost normal. However, all through the development there was a statistically significant decrease of approximately 40% in the accumulated biomass in the double mutant plants in comparison to wild type. In mitochondria, deletion of AtPreP was not compensated by activation of any peptidolytic activity, whereas chloroplast membranes contained a minor peptidolytic activity not related to AtPreP. In summary, the AtPreP peptidasome is required for efficient plant growth and organelle function particularly during early development.
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24
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Gabriel K, Pfanner N. The mitochondrial machinery for import of precursor proteins. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2008; 390:99-117. [PMID: 17951683 DOI: 10.1007/978-1-59745-466-7_7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Mitochondria contain a small genome that codes for approx 1% of the total number of proteins that reside in the mitochondria. Hence, most mitochondrial proteins are encoded for by the nuclear genome. After transcription in the nucleus these proteins are synthesized by cytosolic ribosomes. Like proteins destined for other organellar compartments, mitochondrially destined proteins possess targeting signals within their primary or secondary structure that direct them to the organelle with the assistance of cytosolic factors. Very specialized and discriminatory protein translocase complexes in the mitochondrial membranes, intermembrane space, and matrix are then engaged for the translocation, sorting, integration, processing, and folding of the newly imported proteins. The principles of protein targeting into mitochondria have been and are still being unraveled, mostly by studies with the yeast Saccharomyces cerevisiae and the fungus Neurospora crassa. In this chapter the major principles of mitochondrial protein targeting as currently understood will be discussed as a foundation for the experimental methods discussed later in this volume.
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Affiliation(s)
- Kipros Gabriel
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Freiburg, Germany
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25
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Pusnik M, Small I, Read LK, Fabbro T, Schneider A. Pentatricopeptide repeat proteins in Trypanosoma brucei function in mitochondrial ribosomes. Mol Cell Biol 2007; 27:6876-88. [PMID: 17646387 PMCID: PMC2099244 DOI: 10.1128/mcb.00708-07] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The pentatricopeptide repeat (PPR), a degenerate 35-amino-acid motif, defines a novel eukaryotic protein family. Plants have 400 to 500 distinct PPR proteins, whereas other eukaryotes generally have fewer than 5. The few PPR proteins that have been studied have roles in organellar gene expression, probably via direct interaction with RNA. Here we show that the parasitic protozoan Trypanosoma brucei encodes 28 distinct PPR proteins, an extraordinarily high number for a nonplant organism. A comparative analysis shows that seven out of eight selected PPR proteins are mitochondrially localized and essential for oxidative phosphorylation. Six of these are required for the stabilization of mitochondrial rRNAs and, like ribosomes, are associated with the mitochondrial membranes. Furthermore, one of the PPR proteins copurifies with the large subunit rRNA. Finally, ablation of all of the PPR proteins that were tested induces degradation of the other PPR proteins, indicating that they function in concert. Our results show that a significant number of trypanosomal PPR proteins are individually essential for the maintenance and/or biogenesis of mitochondrial rRNAs.
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Affiliation(s)
- Mascha Pusnik
- Department of Biology/Cell and Developmental Biology, University of Fribourg, Chemin du Musée 10, CH-1700, Fribourg, Switzerland
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26
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Zara V, Dolce V, Capobianco L, Ferramosca A, Papatheodorou P, Rassow J, Palmieri F. Biogenesis of eel liver citrate carrier (CIC): negative charges can substitute for positive charges in the presequence. J Mol Biol 2006; 365:958-67. [PMID: 17113102 DOI: 10.1016/j.jmb.2006.10.077] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 10/20/2006] [Accepted: 10/21/2006] [Indexed: 11/22/2022]
Abstract
A family of structurally related carrier proteins mediates the flux of metabolites across the mitochondrial inner membrane. Differently from most other mitochondrial proteins, members of the carrier family are synthesized without an amino-terminal targeting sequence. However, in some mammalian and plant species, representatives were identified that carry a positively charged presequence. To obtain data on a carrier protein from lower vertebrates, we determined the primary structure of eel mitochondrial citrate carrier (CIC) and investigated its import pathway into the target organelle. The protein carries a cleavable presequence of 20 amino acids, including two positively charged residues. The cleavage site is recognized by a magnesium-dependent peptidase in the intermembrane space. The presequence is dispensable both for targeting and translocation, but prior to import into mitochondria, significantly increases the solubility of the precursor protein. This effect is completely retained if the positive charges are exchanged with negative charges. Following this observation, we found that several carrier proteins appear to carry non-cleavable presequences that may similarly act as charged intramolecular chaperones.
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Affiliation(s)
- Vincenzo Zara
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università di Lecce, Via Provinciale Lecce-Monteroni, I-73100 Lecce, Italy.
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27
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Luo W, Fang H, Green N. Substrate specificity of inner membrane peptidase in yeast mitochondria. Mol Genet Genomics 2006; 275:431-6. [PMID: 16450175 DOI: 10.1007/s00438-006-0099-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2005] [Accepted: 12/23/2005] [Indexed: 11/26/2022]
Abstract
The inner membrane protease (IMP) cleaves intra-organelle sorting peptides from precursor proteins in mitochondria of the yeast Saccharomyces cerevisiae. An unusual feature of the IMP is the presence of two catalytic subunits, Imp1p and Imp2p, which recognize distinct substrate sets even though both enzymes belong to the same protease family. This nonoverlapping substrate specificity was hypothesized to result from the recognition of distinct residues at the P'1 position (also termed +1 position) in the protease substrates. Here, we constructed an extensive series of mutations to obtain a profile of the critical cleavage site residues in IMP substrates and conclude that Imp1p, and not Imp2p, recognizes specific P'1 residues. In addition to its specificity for P'1 residues, Imp1p also shows substrate specificity for the P3 (-3) position. In contrast, Imp2p recognizes the P1 (-1) position and the P3 position. Based on this new understanding of IMP substrate specificity, we conducted a survey for candidate IMP substrates in mammalian mitochondria and found consensus Imp2p cleavage sites in mammalian precursors to cytochrome c1 and glycerol-3-phosphate (G-3-P) dehydrogenase. Presence of a putative Imp2p cleavage site in G-3-P dehydrogenase was surprising, as its yeast ortholog contains an Imp1p cleavage site. To address this issue experimentally, we performed the first co-expression of mammalian IMP with proposed mammalian IMP precursors in yeast and show that murine precursors to cytochrome c1 and G-3-P dehydrogenase are cleaved by murine Imp2p. These results suggest, surprisingly, G-3-P dehydrogenase has switched from Imp1p in yeast to Imp2p in mammals.
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Affiliation(s)
- Wentian Luo
- Department of Microbiology & Immunology, Vanderbilt University Medical Center, 1161 21st Ave. S., A5217MCN, Nashville, TN 37232-2363, USA
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28
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Michaelis G, Esser K, Tursun B, Stohn JP, Hanson S, Pratje E. Mitochondrial signal peptidases of yeast: the rhomboid peptidase Pcp1 and its substrate cytochrome C peroxidase. Gene 2005; 354:58-63. [PMID: 15979251 DOI: 10.1016/j.gene.2005.04.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Accepted: 04/15/2005] [Indexed: 11/15/2022]
Abstract
The rhomboid peptidase Pcp1 of yeast is the first mitochondrial enzyme of this new class of serine peptidases. Pcp1 is an integral part of the inner membrane and was identified by its signal peptidase activity responsible for processing of the intermediate of cytochrome c peroxidase (iCcp1) to the mature enzyme. Here we describe studies on the expression of the PCP1 gene. Proteolytic processing of Pcp1 itself was found. The precursor and the intermediate of Ccp1 were localized to the inner membrane. The results confirm our previous report on a two-step processing pathway of cytochrome c peroxidase and the identification of the signal peptidases involved.
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Affiliation(s)
- Georg Michaelis
- Botanisches Institut der Universität Düsseldorf, Universitätsstr.1, D-40225 Düsseldorf, Germany
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29
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Bota DA, Davies KJ. Protein degradation in mitochondria: implications for oxidative stress, aging and disease: a novel etiological classification of mitochondrial proteolytic disorders. Mitochondrion 2005; 1:33-49. [PMID: 16120267 DOI: 10.1016/s1567-7249(01)00005-8] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2001] [Accepted: 03/16/2001] [Indexed: 01/12/2023]
Abstract
The mitochondrial genome encodes just a small number of subunits of the respiratory chain. All the other mitochondrial proteins are encoded in the nucleus and produced in the cytosol. Various enzymes participate in the activation and intramitochondrial transport of imported proteins. To finally take their place in the various mitochondrial compartments, the targeting signals of imported proteins have to be cleaved by mitochondrial processing peptidases. Mitochondria must also be able to eliminate peptides that are internally synthesized in excess, as well as those that are improperly assembled, and those with abnormal conformation caused by mutation or oxidative damage. Damaged mitochondrial proteins can be removed in two ways: either through lysosomal autophagy, that can account for at most 25-30% of the biochemically estimated rates of average mitochondrial catabolism; or through an intramitochondrial proteinolytic pathway. Mitochondrial proteases have been extensively studied in yeast, but evidence in recent years has demonstrated the existence of similar systems in mammalian cells, and has pointed to the possible importance of mitochondrial proteolytic enzymes in human diseases and ageing. A number of mitochondrial diseases have been identified whose mechanisms involve proteolytic dysfunction. Similar mechanisms probably play a role in diminished resistance to oxidative stress, and in the aging process. In this paper we review current knowledge of mammalian mitochondrial proteolysis, under normal conditions and in several disease states, and we propose an etiological classification of human diseases characterized by a decline or loss of function of mitochondrial proteolytic enzymes.
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Affiliation(s)
- D A Bota
- Ethel Percy Andrus Gerontology Center and Division of Molecular Biology, University of Southern California, Los Angeles, CA-90089-0191, USA
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30
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Herrmann JM, Hell K. Chopped, trapped or tacked--protein translocation into the IMS of mitochondria. Trends Biochem Sci 2005; 30:205-11. [PMID: 15817397 DOI: 10.1016/j.tibs.2005.02.005] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
All proteins of the intermembrane space (IMS) of mitochondria are synthesized in the cytosol. The mechanisms by which these polypeptides are transported into the IMS are strikingly different from other protein-translocation processes in the cell. Recent studies suggest that IMS proteins reach their destination by three alternative principles that differ in the energy sources employed to drive the translocation reactions. The first class of proteins uses both hydrolysis of matrix ATP and the electrochemical potential of the inner membrane. The second class depends on the energy gain of protein folding, and the third on the association of the proteins to high-affinity binding sites in the IMS.
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Affiliation(s)
- Johannes M Herrmann
- Institut für Physiologische Chemie, Universität München, Butenandtstrasse 5, 81377 Munich, Germany.
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31
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Lister R, Hulett JM, Lithgow T, Whelan J. Protein import into mitochondria: origins and functions today (review). Mol Membr Biol 2005; 22:87-100. [PMID: 16092527 DOI: 10.1080/09687860500041247] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Mitochondria are organelles derived from alpha-proteobacteria over the course of one to two billion years. Mitochondria from the major eukaryotic lineages display some variation in functions and coding capacity but sequence analysis demonstrates them to be derived from a single common ancestral endosymbiont. The loss of assorted functions, the transfer of genes to the nucleus, and the acquisition of various 'eukaryotic' proteins have resulted in an organelle that contains approximately 1000 different proteins, with most of these proteins imported into the organelle across one or two membranes. A single translocase in the outer membrane and two translocases in the inner membrane mediate protein import. Comparative sequence analysis and functional complementation experiments suggest some components of the import pathways to be directly derived from the eubacterial endosymbiont's own proteins, and some to have arisen 'de novo' at the earliest stages of 'mitochondrification' of the endosymbiont. A third class of components appears lineage-specific, suggesting they were incorporated into the process of protein import long after mitochondria was established as an organelle and after the divergence of the various eukaryotic lineages. Protein sorting pathways inherited from the endosymbiont have been co-opted and play roles in intraorganelle protein sorting after import. The import apparatus of animals and fungi show significant similarity to one another, but vary considerably to the plant apparatus. Increasing complexity in the eukaryotic lineage, i.e., from single celled to multi-cellular life forms, has been accompanied by an expansion in genes encoding each component, resulting in small gene families encoding many components. The functional differences in these gene families remain to be elucidated, but point to a mosaic import apparatus that can be regulated by a variety of signals.
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Affiliation(s)
- Ryan Lister
- Plant Molecular Biology Group, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley, Western Australia, Australia
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32
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Herrmann JM, Funes S. Biogenesis of cytochrome oxidase—Sophisticated assembly lines in the mitochondrial inner membrane. Gene 2005; 354:43-52. [PMID: 15905047 DOI: 10.1016/j.gene.2005.03.017] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 02/02/2005] [Accepted: 03/23/2005] [Indexed: 11/18/2022]
Abstract
Biogenesis of the cytochrome oxidase complex in the mitochondrial inner membrane depends on the concerted action of a variety of proteins. Recent studies shed light on this biological assembly process revealing an astonishingly complex procedure by which the different subunits of the enzymes are put together and the required cofactors are supplied. In this review we present a hypothetical model for the assembly process of cytochrome oxidase based on the current knowledge of the functions of specific assembly factors. According to this model the two largest subunits of the complex are first equipped with their respective cofactors on independent assembly lines. Prior to their assembly with the residual subunits that complete the whole complex, these two subcomplexes remain bound to substrate-specific chaperones. We propose that these chaperones, Mss51 for subunit 1 and Cox20 for subunit 2, control the coordinate assembly process to prevent potentially harmful redox reactions of unassembled or misassembled subunits.
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Affiliation(s)
- Johannes M Herrmann
- Institute of Physiological Chemistry, Butenandtstrasse 5, 81377 München, University of Munich, Germany.
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33
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Otera H, Ohsakaya S, Nagaura ZI, Ishihara N, Mihara K. Export of mitochondrial AIF in response to proapoptotic stimuli depends on processing at the intermembrane space. EMBO J 2005; 24:1375-86. [PMID: 15775970 PMCID: PMC1142539 DOI: 10.1038/sj.emboj.7600614] [Citation(s) in RCA: 262] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Accepted: 02/10/2005] [Indexed: 01/05/2023] Open
Abstract
Apoptosis-inducing factor (AIF) is a mitochondrial intermembrane flavoprotein that is translocated to the nucleus in response to proapoptotic stimuli, where it induces nuclear apoptosis. Here we show that AIF is synthesized as an approximately 67-kDa preprotein with an N-terminal extension and imported into mitochondria, where it is processed to the approximately 62-kDa mature form. Topology analysis revealed that mature AIF is a type-I inner membrane protein with the N-terminus exposed to the matrix and the C-terminal portion to the intermembrane space. Upon induction of apoptosis, processing of mature AIF to an approximately 57-kDa form occurred caspase-independently in the intermembrane space, releasing the processed form into the cytoplasm. Bcl-2 or Bcl-XL inhibited both these events. These findings indicate that AIF release from mitochondria occurs by a two-step process: detachment from the inner membrane by apoptosis-induced processing in the intermembrane space and translocation into the cytoplasm. The results also suggest the presence of a unique protease that is regulated by proapoptotic stimuli in caspase-independent cell death.
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Affiliation(s)
- Hidenori Otera
- Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan
| | - Shigenori Ohsakaya
- Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan
| | - Zen-Ichiro Nagaura
- Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan
| | - Naotada Ishihara
- Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan
| | - Katsuyoshi Mihara
- Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan
- Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka 812-8582, Japan. Tel.: +81 92 642 6176; Fax: +81 92 642 6183; E-mail:
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34
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Esser K, Jan PS, Pratje E, Michaelis G. The mitochondrial IMP peptidase of yeast: functional analysis of domains and identification of Gut2 as a new natural substrate. Mol Genet Genomics 2004; 271:616-26. [PMID: 15118906 DOI: 10.1007/s00438-004-1011-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Accepted: 03/31/2004] [Indexed: 11/24/2022]
Abstract
The mitochondrial inner membrane peptidase IMP of Saccharomyces cerevisiae is required for proteolytic processing of certain mitochondrially and nucleus-encoded proteins during their export from the matrix into the inner membrane or the intermembrane space. The membrane-associated signal peptidase complex is composed of the two catalytic subunits, Imp1 and Imp2, and the Som1 protein. The IMP subunits are thought to function in membrane association, interaction and stabilisation of subunits, substrate specificity, and proteolysis. We have analysed inner membrane peptidase mutants and substrates to gain more insight into the functions of various domains and investigate the basis of substrate recognition. The results suggest that certain conserved glycine residues in the second and third conserved regions of Imp1 and Imp2 are important for stabilisation of the Imp complex and for the proteolytic activity of the subunits, respectively. The non-conserved C-terminal parts of the Imp subunits are important for their proteolytic activities. The C-terminal region of Imp2, comprising a predicted second transmembrane segment, is dispensable for the stability of Imp2 and Imp1, and cannot functionally substitute for the C-terminal segment of Imp1. Alteration of the Imp2 cleavage site in cytochrome c(1) (from A/M to N/D) reveals the specificity of the Imp2 peptidase. In addition, we have identified Gut2, the mitochondrial FAD-dependent glycerol-3-phosphate dehydrogenase, as a new substrate for Imp1. Failure to cleave the Gut2 precursor may contribute to the pet phenotype of certain imp mutants. Gut2 is associated with the inner membrane, and is essential for growth on glycerol-containing medium. Suggested functions of the analysed residues and domains of the IMP subunits, characteristics of the cleavage sites of substrates and implications for the phenotypes of imp mutants are discussed.
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Affiliation(s)
- K Esser
- Botanisches Institut, Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
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35
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Fiori A, Mason TL, Fox TD. Evidence that synthesis of the Saccharomyces cerevisiae mitochondrially encoded ribosomal protein Var1p may be membrane localized. EUKARYOTIC CELL 2003; 2:651-3. [PMID: 12796311 PMCID: PMC161437 DOI: 10.1128/ec.2.3.651-653.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The 5'-untranslated leaders of mitochondrial mRNAs appear to localize translation within the organelle. VAR1 is the only yeast mitochondrial gene encoding a major soluble protein. A chimeric mRNA bearing the VAR1 untranslated regions and the coding sequence for pre-Cox2p appears to be translated at the inner membrane surface. We propose that translation of the ribosomal protein Var1p is also likely to occur in close proximity to the inner membrane.
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Affiliation(s)
- Alessandro Fiori
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
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36
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Affiliation(s)
- Mark Paetzel
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA
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37
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Esser K, Tursun B, Ingenhoven M, Michaelis G, Pratje E. A novel two-step mechanism for removal of a mitochondrial signal sequence involves the mAAA complex and the putative rhomboid protease Pcp1. J Mol Biol 2002; 323:835-43. [PMID: 12417197 DOI: 10.1016/s0022-2836(02)01000-8] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The yeast protein cytochrome c peroxidase (Ccp1) is nuclearly encoded and imported into the mitochondrial intermembrane space, where it is involved in degradation of reactive oxygen species. It is known, that Ccp1 is synthesised as a precursor with a N-terminal pre-sequence, that is proteolytically removed during transport of the protein. Here we present evidence for a new processing pathway, involving novel signal peptidase activities. The mAAA protease subunits Yta10 (Afg3) and Yta12 (Rca1) were identified both to be essential for the first processing step. In addition, the Pcp1 (Ygr101w) gene product was found to be required for the second processing step, yielding the mature Ccp1 protein. The newly identified Pcp1 protein belongs to the rhomboid-GlpG superfamily of putative intramembrane peptidases. Inactivation of the protease motifs in mAAA and Pcp1 blocks the respective steps of proteolysis. A model of coupled Ccp1 transport and N-terminal processing by the mAAA complex and Pcp1 is discussed. Similar processing mechanisms may exist, because the mAAA subunits and the newly identified Pcp1 protein belong to ubiquitous protein families.
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Affiliation(s)
- Karlheinz Esser
- Botanisches Institut der Universität Düsseldorf, Universitätsstr. 1, Germany.
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38
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Stuart R. Insertion of proteins into the inner membrane of mitochondria: the role of the Oxa1 complex. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1592:79-87. [PMID: 12191770 DOI: 10.1016/s0167-4889(02)00266-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The inner mitochondrial membrane harbors a large number of proteins that display a wide range of topological arrangements. The majority of these proteins are encoded in the cell's nucleus, but a few polytopic proteins, all subunits of respiratory chain complexes are encoded by the mitochondrial genome. A number of distinct sorting mechanisms exist to direct these proteins into the mitochondrial inner membrane. One of these pathways involves the export of proteins from the matrix into the inner membrane and is used by both proteins synthesized within the mitochondria, as well as by a subset of nuclear encoded proteins. Prior to embarking on the export pathway, nuclear encoded proteins using this sorting route are initially imported into the mitochondrial matrix from the cytosol, their site of synthesis. Protein export from the matrix into the inner membrane bears similarities to Sec-independent protein export in bacteria and requires the function of the Oxa1 protein. Oxa1 is a component of a general protein insertion site in yeast mitochondrial inner membrane used by both nuclear and mitochondrial DNA encoded proteins. Oxa1 is a member of the conserved Oxa1/YidC/Alb3 protein family found throughout prokaryotes throughout eukaryotes (where it is found in mitochondria and chloroplasts). The evidence to demonstrate that the Oxa1/YidC/Alb3 protein family represents a novel evolutionarily conserved membrane insertion machinery is reviewed here.
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Affiliation(s)
- Rosemary Stuart
- Department of Biology, Marquette University, 530 N. 15th Street, Milwaukee, WI 53233, USA.
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39
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Saracco SA, Fox TD. Cox18p is required for export of the mitochondrially encoded Saccharomyces cerevisiae Cox2p C-tail and interacts with Pnt1p and Mss2p in the inner membrane. Mol Biol Cell 2002; 13:1122-31. [PMID: 11950926 PMCID: PMC102256 DOI: 10.1091/mbc.01-12-0580] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2001] [Revised: 12/03/2001] [Accepted: 12/24/2001] [Indexed: 11/11/2022] Open
Abstract
The amino- and carboxy-terminal domains of mitochondrially encoded cytochrome c oxidase subunit II (Cox2p) are translocated out of the matrix to the intermembrane space. We have carried out a genetic screen to identify components required to export the biosynthetic enzyme Arg8p, tethered to the Cox2p C terminus by a translational gene fusion inserted into mtDNA. We obtained multiple alleles of COX18, PNT1, and MSS2, as well as mutations in CBP1 and PET309. Focusing on Cox18p, we found that its activity is required to export the C-tail of Cox2p bearing a short C-terminal epitope tag. This is not a consequence of reduced membrane potential due to loss of cytochrome oxidase activity because Cox2p C-tail export was not blocked in mitochondria lacking Cox4p. Cox18p is not required to export the Cox2p N-tail, indicating that these two domains of Cox2p are translocated by genetically distinct mechanisms. Cox18p is a mitochondrial integral inner membrane protein. The inner membrane proteins Mss2p and Pnt1p both coimmunoprecipitate with Cox18p, suggesting that they work together in translocation of Cox2p domains, an inference supported by functional interactions among the three genes.
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Affiliation(s)
- Scott A Saracco
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853-2703, USA
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40
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Daley DO, Adams KL, Clifton R, Qualmann S, Millar AH, Palmer JD, Pratje E, Whelan J. Gene transfer from mitochondrion to nucleus: novel mechanisms for gene activation from Cox2. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 30:11-21. [PMID: 11967089 DOI: 10.1046/j.1365-313x.2002.01263.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The evolutionarily recent transfer of the gene for cytochrome c oxidase subunit 2 (cox2) from the mitochondrion to the nucleus in legumes is shown to have involved novel gene-activation steps. The acquired mitochondrial targeting presequence is bordered by two introns. Characterization of the import of soybean Cox2 indicates that the presequence is cleaved in a three-step process which is independent of assembly. The final processing step takes place only in the mitochondria of legume species, and not in several non-legume plants. The unusually long presequence of 136 amino acids consists of three regions: the first 20 amino acids are required for mitochondrial targeting and can be replaced by another presequence; the central portion of the presequence is required for efficient import of the Cox2 protein into mitochondria; and the last 12 amino acids, derived from the mitochondrially encoded protein, are required for correct maturation of the imported protein. The acquisition of a unique presequence, and the capacity for legume mitochondria to remove this presequence post-import, are considered to be essential adaptations for targeting of Cox2 to the mitochondrion and therefore activation of the transferred gene in the nucleus.
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Affiliation(s)
- Daniel O Daley
- Department of Biochemistry, University of Western Australia, Nedlands 6907, Australia
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41
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Chloroplast and Mitochondrial Type I Signal Peptidases. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1874-6047(02)80006-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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42
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Broadley SA, Demlow CM, Fox TD. Peripheral mitochondrial inner membrane protein, Mss2p, required for export of the mitochondrially coded Cox2p C tail in Saccharomyces cerevisiae. Mol Cell Biol 2001; 21:7663-72. [PMID: 11604502 PMCID: PMC99937 DOI: 10.1128/mcb.21.22.7663-7672.2001] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cytochrome oxidase subunit 2 (Cox2p) is synthesized on the matrix side of the mitochondrial inner membrane, and its N- and C-terminal domains are exported across the inner membrane by distinct mechanisms. The Saccharomyces cerevisiae nuclear gene MSS2 was previously shown to be necessary for Cox2p accumulation. We have used pulse-labeling studies and the expression of the ARG8(m) reporter at the COX2 locus in an mss2 mutant to demonstrate that Mss2p is not required for Cox2p synthesis but rather for its accumulation. Mutational inactivation of the proteolytic function of the matrix-localized Yta10p (Afg3p) AAA-protease partially stabilizes Cox2p in an mss2 mutant but does not restore assembly of cytochrome oxidase. In the absence of Mss2p, the Cox2p N terminus is exported, but Cox2p C-terminal export and assembly of Cox2p into cytochrome oxidase is blocked. Epitope-tagged Mss2p is tightly, but peripherally, associated with the inner membrane and protected by it from externally added proteases. Taken together, these data indicate that Mss2p plays a role in recognizing the Cox2p C tail in the matrix and promoting its export.
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Affiliation(s)
- S A Broadley
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
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43
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Affiliation(s)
- T Krimmer
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, 79104 Freiburg, Germany
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44
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Abstract
The vast majority of mitochondrial proteins are synthesized in the cytosol and are imported into mitochondria by protein machineries located in the mitochondrial membranes. It has become clear that hydrophilic as well as hydrophobic preproteins use a common translocase in the outer mitochondrial membrane, but diverge to two distinct translocases in the inner membrane. The translocases are dynamic, high-molecular-weight complexes that have to provide specific means for the recognition of preproteins, channel formation and generation of import-driving forces.
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Affiliation(s)
- N Pfanner
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany.
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45
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Bonnefoy N, Bsat N, Fox TD. Mitochondrial translation of Saccharomyces cerevisiae COX2 mRNA is controlled by the nucleotide sequence specifying the pre-Cox2p leader peptide. Mol Cell Biol 2001; 21:2359-72. [PMID: 11259585 PMCID: PMC86869 DOI: 10.1128/mcb.21.7.2359-2372.2001] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mitochondrial gene encoding yeast cytochrome oxidase subunit II (Cox2p) specifies a precursor protein with a 15-amino-acid leader peptide. Deletion of the entire leader peptide coding region is known to block Cox2p accumulation posttranscriptionally. Here, we examined in vivo the role of the pre-Cox2p leader peptide and the mRNA sequence that encodes it in the expression of a mitochondrial reporter gene, ARG8m, fused to the 91st codon of COX2. We found within the coding sequence antagonistic elements that control translation: the positive element includes sequences in the first 14 codons specifying the leader peptide, while the negative element appears to be within codons 15 to 91. Partial deletions, point mutations, and local frameshifts within the leader peptide coding region were placed in both the cox2::ARG8m reporter and in COX2 itself. Surprisingly, the mRNA sequence of the first six codons specifying the leader peptide plays an important role in positively controlling translation, while the amino acid sequence of the leader peptide itself is relatively unconstrained. Two mutations that partially block translation can be suppressed by nearby sequence substitutions that weaken a predicted stem structure and by overproduction of either the COX2 mRNA-specific translational activator Pet111p or the large-subunit mitochondrial ribosomal protein MrpL36p. We propose that regulatory elements embedded in the translated COX2 mRNA sequence could play a role, together with trans-acting factors, in coupling regulated synthesis of nascent pre-Cox2p to its insertion in the mitochondrial inner membrane.
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Affiliation(s)
- N Bonnefoy
- Centre de Génétique Moléculaire, Laboratoire propre du CNRS associé à l'Université Pierre et Marie Curie, 91198 Gif-sur-Yvette Cedex, France
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46
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Deng K, Shenoy SK, Tso SC, Yu L, Yu CA. Reconstitution of mitochondrial processing peptidase from the core proteins (subunits I and II) of bovine heart mitochondrial cytochrome bc(1) complex. J Biol Chem 2001; 276:6499-505. [PMID: 11073949 DOI: 10.1074/jbc.m007128200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mature core I and core II proteins of the bovine heart mitochondrial cytochrome bc(1) complex were individually overexpressed in Escherichia coli as soluble proteins using the expression vector pET-I and pET-II, respectively. Purified recombinant core I and core II alone show no mitochondrial processing peptidase (MPP) activity. When these two proteins are mixed together, MPP activity is observed. Maximum activity is obtained when the molar ratio of these two core proteins reaches 1. This indicates that only the two core subunits of thebc(1) complex are needed for MPP activity. The properties of reconstituted MPP are similar to those of Triton X-100-activated MPP in the bovine bc(1) complex. When Rieske iron-sulfur protein precursor is used as substrate for reconstituted MPP, the processing activity stops when the amount of product formation (subunit IX) equals the amount of reconstituted MPP used in the system. Addition of Triton X-100 to the product-inhibited reaction mixture restores MPP activity, indicating that Triton X-100 dissociates bound subunit IX from the active site of reconstituted MPP. The aromatic group, rather than the hydroxyl group, at Tyr(57) of core I is essential for reconstitutive activity.
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Affiliation(s)
- K Deng
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078, USA
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47
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Xoconostle-Cázares B, Ruiz-Medrano R, Lucas WJ. Proteolytic processing of CmPP36, a protein from the cytochrome b(5) reductase family, is required for entry into the phloem translocation pathway. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2000; 24:735-747. [PMID: 11135108 DOI: 10.1046/j.1365-313x.2000.00916.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Cucurbita maxima (pumpkin) phloem sap contains a 31 kDa protein that cross-reacts with antibodies directed against the red clover necrotic mosaic virus movement protein (RCNMV MP). Microsequence data from phloem-purified 31 kDa protein were used to isolate a complementary DNA: the open reading frame encodes a 36 kDa protein belonging to the cytochrome b(5) reductase (Cb5R) family; the gene was termed CmPP36. Western analyses established that CmPP36, RCNMV MP and CmPP16 (Xoconostle-Cázares et al., 1999, Science 283, 94-98) are immunologically related, probably due to a common epitope, represented by the NADH(+)-binding domain of CmPP36. An N-terminal 5 kDa membrane-targeting domain is cleaved to produce the 31 kDa Delta N-CmPP36 detected in the phloem sap. Microinjection experiments established that Delta N-CmPP36, but not CmPP36, is able to interact with plasmodesmata to mediate its cell-to-cell transport. Thus, intercellular movement of CmPP36 requires proteolytic processing in the companion cell to produce a soluble, movement-competent, protein. In contrast to RCNMV and CmPP16, Delta N-CmPP36 interacts with but does not mediate the trafficking of RNA. Northern and in situ RT-PCR studies established that CmPP36 mRNA is present in all plant organs, being highly abundant within vascular tissues. In roots of hydroponically grown pumpkin plants, CmPP36 mRNA levels respond to changes in available iron in the culture solution. Finally, enzymatic assays established that both CmPP36 and Delta N-CmPP36 could reduce Fe(3+)-citrate and Fe(3+)-EDTA in the presence of NADH(+). These findings are discussed in terms of the possible roles played by CmPP36 in phloem function.
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Affiliation(s)
- B Xoconostle-Cázares
- Section of Plant Biology, Division of Biological Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
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48
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Geissler A, Krimmer T, Bömer U, Guiard B, Rassow J, Pfanner N. Membrane potential-driven protein import into mitochondria. The sorting sequence of cytochrome b(2) modulates the deltapsi-dependence of translocation of the matrix-targeting sequence. Mol Biol Cell 2000; 11:3977-91. [PMID: 11071921 PMCID: PMC15051 DOI: 10.1091/mbc.11.11.3977] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The transport of preproteins into or across the mitochondrial inner membrane requires the membrane potential Deltapsi across this membrane. Two roles of Deltapsi in the import of cleavable preproteins have been described: an electrophoretic effect on the positively charged matrix-targeting sequences and the activation of the translocase subunit Tim23. We report the unexpected finding that deletion of a segment within the sorting sequence of cytochrome b(2), which is located behind the matrix-targeting sequence, strongly influenced the Deltapsi-dependence of import. The differential Deltapsi-dependence was independent of the submitochondrial destination of the preprotein and was not attributable to the requirement for mitochondrial Hsp70 or Tim23. With a series of preprotein constructs, the net charge of the sorting sequence was altered, but the Deltapsi-dependence of import was not affected. These results suggested that the sorting sequence contributed to the import driving mechanism in a manner distinct from the two known roles of Deltapsi. Indeed, a charge-neutral amino acid exchange in the hydrophobic segment of the sorting sequence generated a preprotein with an even better import, i.e. one with lower Deltapsi-dependence than the wild-type preprotein. The sorting sequence functioned early in the import pathway since it strongly influenced the efficiency of translocation of the matrix-targeting sequence across the inner membrane. These results suggest a model whereby an electrophoretic effect of Deltapsi on the matrix-targeting sequence is complemented by an import-stimulating activity of the sorting sequence.
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Affiliation(s)
- A Geissler
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, D-79104 Freiburg, Germany
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49
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Abstract
The biogenesis of mitochondria and the maintenance of mitochondrial functions depends on an autonomous proteolytic system in the organelle which is highly conserved throughout evolution. Components of this system include processing peptidases and ATP-dependent proteases, as well as molecular chaperone proteins and protein complexes with apparently regulatory functions. While processing peptidases mediate maturation of nuclear-encoded mitochondrial preproteins, quality control within various subcompartments of mitochondria is ensured by ATP-dependent proteases which selectively remove non-assembled or misfolded polypeptides. Moreover; these proteases appear to control the activity- or steady-state levels of specific regulatory proteins and thereby ensure mitochondrial genome integrity, gene expression and protein assembly.
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Affiliation(s)
- M Käser
- Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians-Universität München, Germany
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Klenotic PA, Carlos JL, Samuelson JC, Schuenemann TA, Tschantz WR, Paetzel M, Strynadka NC, Dalbey RE. The role of the conserved box E residues in the active site of the Escherichia coli type I signal peptidase. J Biol Chem 2000; 275:6490-8. [PMID: 10692453 DOI: 10.1074/jbc.275.9.6490] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type I signal peptidases are integral membrane proteins that function to remove signal peptides from secreted and membrane proteins. These enzymes carry out catalysis using a serine/lysine dyad instead of the prototypical serine/histidine/aspartic acid triad found in most serine proteases. Site-directed scanning mutagenesis was used to obtain a qualitative assessment of which residues in the fifth conserved region, Box E, of the Escherichia coli signal peptidase I are critical for maintaining a functional enzyme. First, we find that there is no requirement for activity for a salt bridge between the invariant Asp-273 and the Arg-146 residues. In addition, we show that the conserved Ser-278 is required for optimal activity as well as conserved salt bridge partners Asp-280 and Arg-282. Finally, Gly-272 is essential for signal peptidase I activity, consistent with it being located within van der Waals proximity to Ser-278 and general base Lys-145 side-chain atoms. We propose that replacement of the hydrogen side chain of Gly-272 with a methyl group results in steric crowding, perturbation of the active site conformation, and specifically, disruption of the Ser-90/Lys-145 hydrogen bond. A refined model is proposed for the catalytic dyad mechanism of signal peptidase I in which the general base Lys-145 is positioned by Ser-278, which in turn is held in place by Asp-280.
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Affiliation(s)
- P A Klenotic
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA
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