51
|
Affiliation(s)
- Katherine Labbé
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616; , ,
| | - Andrew Murley
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616; , ,
| | - Jodi Nunnari
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616; , ,
| |
Collapse
|
52
|
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).
Collapse
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.
| |
Collapse
|
53
|
Yamaoka S, Hara-Nishimura I. The mitochondrial Ras-related GTPase Miro: views from inside and outside the metazoan kingdom. FRONTIERS IN PLANT SCIENCE 2014; 5:350. [PMID: 25076955 PMCID: PMC4100572 DOI: 10.3389/fpls.2014.00350] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 06/30/2014] [Indexed: 05/24/2023]
Abstract
Miro GTPase, a member of the Ras superfamily, consists of two GTPase domains flanking a pair of EF hand motifs and a C-terminal transmembrane domain that anchors the protein to the mitochondrial outer membrane. Since the identification of Miro in humans, a series of studies in metazoans, including mammals and fruit flies, have shown that Miro plays a role in the calcium-dependent regulation of mitochondrial transport along microtubules. However, in non-metazoans, including yeasts, slime molds, and plants, Miro is primarily involved in the maintenance of mitochondrial morphology and homeostasis. Given the high level of conservation of Miro in eukaryotes and the variation in the molecular mechanisms of mitochondrial transport between eukaryotic lineages, Miro may have a common ancestral function in mitochondria, and its roles in the regulation of mitochondrial transport may have been acquired specifically by metazoans after the evolutionary divergence of eukaryotes.
Collapse
Affiliation(s)
- Shohei Yamaoka
- Graduate School of Biostudies, Kyoto UniversityKyoto, Japan
| | | |
Collapse
|
54
|
Klecker T, Böckler S, Westermann B. Making connections: interorganelle contacts orchestrate mitochondrial behavior. Trends Cell Biol 2014; 24:537-45. [PMID: 24786308 DOI: 10.1016/j.tcb.2014.04.004] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 04/01/2014] [Accepted: 04/02/2014] [Indexed: 01/07/2023]
Abstract
Mitochondria are highly dynamic organelles. During their life cycle they frequently fuse and divide, and damaged mitochondria are removed by autophagic degradation. These processes serve to maintain mitochondrial function and ensure optimal energy supply for the cell. It has recently become clear that this complex mitochondrial behavior is governed to a large extent by interactions with other organelles. In this review, we describe mitochondrial contacts with the endoplasmic reticulum (ER), plasma membrane, and peroxisomes. In particular, we highlight how mitochondrial fission, distribution, inheritance, and turnover are orchestrated by interorganellar contacts in yeast and metazoa. These interactions are pivotal for the integration of the dynamic mitochondrial network into the architecture of eukaryotic cells.
Collapse
Affiliation(s)
- Till Klecker
- Institut für Zellbiologie, Universität Bayreuth, 95440 Bayreuth, Germany
| | - Stefan Böckler
- Institut für Zellbiologie, Universität Bayreuth, 95440 Bayreuth, Germany
| | | |
Collapse
|
55
|
Lee J, Kim DH, Hwang I. Specific targeting of proteins to outer envelope membranes of endosymbiotic organelles, chloroplasts, and mitochondria. FRONTIERS IN PLANT SCIENCE 2014; 5:173. [PMID: 24808904 PMCID: PMC4010795 DOI: 10.3389/fpls.2014.00173] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 04/10/2014] [Indexed: 05/21/2023]
Abstract
Chloroplasts and mitochondria are endosymbiotic organelles thought to be derived from endosymbiotic bacteria. In present-day eukaryotic cells, these two organelles play pivotal roles in photosynthesis and ATP production. In addition to these major activities, numerous reactions, and cellular processes that are crucial for normal cellular functions occur in chloroplasts and mitochondria. To function properly, these organelles constantly communicate with the surrounding cellular compartments. This communication includes the import of proteins, the exchange of metabolites and ions, and interactions with other organelles, all of which heavily depend on membrane proteins localized to the outer envelope membranes. Therefore, correct and efficient targeting of these membrane proteins, which are encoded by the nuclear genome and translated in the cytosol, is critically important for organellar function. In this review, we summarize the current knowledge of the mechanisms of protein targeting to the outer membranes of mitochondria and chloroplasts in two different directions, as well as targeting signals and cytosolic factors.
Collapse
Affiliation(s)
- Junho Lee
- Cellular Systems Biology, Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
| | - Dae Heon Kim
- Cellular Systems Biology, Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
| | - Inhwan Hwang
- Cellular Systems Biology, Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
- Division of Integrative Biosciences and Bioengineering, Pohang University of Science and TechnologyPohang, South Korea
- *Correspondence: Inhwan Hwang, Cellular Systems Biology, Department of Life Sciences and Division of Integrative Biosciences and Bioengineering, Pohang University of Science and Technology, Hyojadong, Nam-Gu, Pohang 790-784, South Korea e-mail:
| |
Collapse
|
56
|
Flinner N, Ellenrieder L, Stiller SB, Becker T, Schleiff E, Mirus O. Mdm10 is an ancient eukaryotic porin co-occurring with the ERMES complex. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:3314-3325. [PMID: 24135058 DOI: 10.1016/j.bbamcr.2013.10.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 09/20/2013] [Accepted: 10/07/2013] [Indexed: 12/17/2022]
Abstract
Mitochondrial β-barrel proteins fulfill central functions in the outer membrane like metabolite exchange catalyzed by the voltage-dependent anion channel (VDAC) and protein biogenesis by the central components of the preprotein translocase of the outer membrane (Tom40) or of the sorting and assembly machinery (Sam50). The mitochondrial division and morphology protein Mdm10 is another essential outer membrane protein with proposed β-barrel fold, which has so far only been found in Fungi. Mdm10 is part of the endoplasmic reticulum mitochondria encounter structure (ERMES), which tethers the ER to mitochondria and associates with the SAM complex. In here, we provide evidence that Mdm10 phylogenetically belongs to the VDAC/Tom40 superfamily. Contrary to Tom40 and VDAC, Mdm10 exposes long loops towards both sides of the membrane. Analyses of single loop deletion mutants of Mdm10 in the yeast Saccharomyces cerevisiae reveal that the loops are dispensable for Mdm10 function. Sequences similar to fungal Mdm10 can be found in species from Excavates to Fungi, but neither in Metazoa nor in plants. Strikingly, the presence of Mdm10 coincides with the appearance of the other ERMES components. Mdm10's presence in both unikonts and bikonts indicates an introduction at an early time point in eukaryotic evolution.
Collapse
Affiliation(s)
- Nadine Flinner
- JWGU Frankfurt am Main, Cluster of Excellence Macromolecular Complexes, Centre of Membrane Proteomics, Department of Biosciences, Max-von-Laue Str. 9, 60438 Frankfurt, Germany
| | - Lars Ellenrieder
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, D-79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, D-79104 Freiburg, Germany
| | - Sebastian B Stiller
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, D-79104 Freiburg, Germany; Fakultät für Biologie, Universität Freiburg, D-79104 Freiburg, Germany
| | - Thomas Becker
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, D-79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Universität Freiburg, D-79104 Freiburg, Germany
| | - Enrico Schleiff
- JWGU Frankfurt am Main, Cluster of Excellence Macromolecular Complexes, Centre of Membrane Proteomics, Department of Biosciences, Max-von-Laue Str. 9, 60438 Frankfurt, Germany.
| | - Oliver Mirus
- JWGU Frankfurt am Main, Cluster of Excellence Macromolecular Complexes, Centre of Membrane Proteomics, Department of Biosciences, Max-von-Laue Str. 9, 60438 Frankfurt, Germany
| |
Collapse
|
57
|
Murcha MW, Wang Y, Narsai R, Whelan J. The plant mitochondrial protein import apparatus - the differences make it interesting. Biochim Biophys Acta Gen Subj 2013; 1840:1233-45. [PMID: 24080405 DOI: 10.1016/j.bbagen.2013.09.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 09/17/2013] [Accepted: 09/18/2013] [Indexed: 12/25/2022]
Abstract
BACKGROUND Mitochondria play essential roles in the life and death of almost all eukaryotic cells, ranging from single-celled to multi-cellular organisms that display tissue and developmental differentiation. As mitochondria only arose once in evolution, much can be learned from studying single celled model systems such as yeast and applying this knowledge to other organisms. However, two billion years of evolution have also resulted in substantial divergence in mitochondrial function between eukaryotic organisms. SCOPE OF REVIEW Here we review our current understanding of the mechanisms of mitochondrial protein import between plants and yeast (Saccharomyces cerevisiae) and identify a high level of conservation for the essential subunits of plant mitochondrial import apparatus. Furthermore, we investigate examples whereby divergence and acquisition of functions have arisen and highlight the emerging examples of interactions between the import apparatus and components of the respiratory chain. MAJOR CONCLUSIONS After more than three decades of research into the components and mechanisms of mitochondrial protein import of plants and yeast, the differences between these systems are examined. Specifically, expansions of the small gene families that encode the mitochondrial protein import apparatus in plants are detailed, and their essential role in seed viability is revealed. GENERAL SIGNIFICANCE These findings point to the essential role of the inner mitochondrial protein translocases in Arabidopsis, establishing their necessity for seed viability and the crucial role of mitochondrial biogenesis during germination. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.
Collapse
Affiliation(s)
- Monika W Murcha
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia.
| | - Yan Wang
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
| | - Reena Narsai
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia; Computational Systems Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia
| | - James Whelan
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia; Department of Botany, School of Life Science, La Trobe University, Bundoora 3086, Victoria, Australia
| |
Collapse
|
58
|
Horvath SE, Daum G. Lipids of mitochondria. Prog Lipid Res 2013; 52:590-614. [PMID: 24007978 DOI: 10.1016/j.plipres.2013.07.002] [Citation(s) in RCA: 606] [Impact Index Per Article: 55.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 07/31/2013] [Indexed: 01/06/2023]
Abstract
A unique organelle for studying membrane biochemistry is the mitochondrion whose functionality depends on a coordinated supply of proteins and lipids. Mitochondria are capable of synthesizing several lipids autonomously such as phosphatidylglycerol, cardiolipin and in part phosphatidylethanolamine, phosphatidic acid and CDP-diacylglycerol. Other mitochondrial membrane lipids such as phosphatidylcholine, phosphatidylserine, phosphatidylinositol, sterols and sphingolipids have to be imported. The mitochondrial lipid composition, the biosynthesis and the import of mitochondrial lipids as well as the regulation of these processes will be main issues of this review article. Furthermore, interactions of lipids and mitochondrial proteins which are highly important for various mitochondrial processes will be discussed. Malfunction or loss of enzymes involved in mitochondrial phospholipid biosynthesis lead to dysfunction of cell respiration, affect the assembly and stability of the mitochondrial protein import machinery and cause abnormal mitochondrial morphology or even lethality. Molecular aspects of these processes as well as diseases related to defects in the formation of mitochondrial membranes will be described.
Collapse
Affiliation(s)
- Susanne E Horvath
- Institute of Biochemistry, Graz University of Technology, Petersgasse 12/2, A-8010 Graz, Austria
| | | |
Collapse
|
59
|
Vevea JD, Swayne TC, Boldogh IR, Pon LA. Inheritance of the fittest mitochondria in yeast. Trends Cell Biol 2013; 24:53-60. [PMID: 23932848 DOI: 10.1016/j.tcb.2013.07.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 07/02/2013] [Accepted: 07/08/2013] [Indexed: 01/01/2023]
Abstract
Eukaryotic cells compartmentalize their biochemical processes within organelles, which have specific functions that must be maintained for overall cellular health. As the site of aerobic energy mobilization and essential biosynthetic activities, mitochondria are critical for cell survival and proliferation. Here, we describe mechanisms to control the quality and quantity of mitochondria within cells with an emphasis on findings from the budding yeast Saccharomyces cerevisiae. We also describe how mitochondrial quality and quantity control systems that operate during cell division affect lifespan and cell cycle progression.
Collapse
Affiliation(s)
- Jason D Vevea
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Theresa C Swayne
- Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY, USA
| | - Istvan R Boldogh
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Liza A Pon
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA; Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY, USA.
| |
Collapse
|
60
|
Wideman JG, Lackey SWK, Srayko MA, Norton KA, Nargang FE. Analysis of mutations in Neurospora crassa ERMES components reveals specific functions related to β-barrel protein assembly and maintenance of mitochondrial morphology. PLoS One 2013; 8:e71837. [PMID: 23940790 PMCID: PMC3733929 DOI: 10.1371/journal.pone.0071837] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Accepted: 07/03/2013] [Indexed: 11/22/2022] Open
Abstract
The endoplasmic reticulum mitochondria encounter structure (ERMES) tethers the er to mitochondria and contains four structural components: Mmm1, Mdm12, Mdm10, and Mmm2 (Mdm34). The Gem1 protein may play a role in regulating ERMES function. Saccharomyces cerevisiae and Neurospora crassa strains lacking any of Mmm1, Mdm12, or Mdm10 are known to show a variety of phenotypic defects including altered mitochondrial morphology and defects in the assembly of β-barrel proteins into the mitochondrial outer membrane. Here we examine ERMES complex components in N. crassa and show that Mmm1 is an ER membrane protein containing a Cys residue near its N-terminus that is conserved in the class Sordariomycetes. The residue occurs in the ER-lumen domain of the protein and is involved in the formation of disulphide bonds that give rise to Mmm1 dimers. Dimer formation is required for efficient assembly of Tom40 into the TOM complex. However, no effects are seen on porin assembly or mitochondrial morphology. This demonstrates a specificity of function and suggests a direct role for Mmm1 in Tom40 assembly. Mutation of a highly conserved region in the cytosolic domain of Mmm1 results in moderate defects in Tom40 and porin assembly, as well as a slight morphological phenotype. Previous reports have not examined the role of Mmm2 with respect to mitochondrial protein import and assembly. Here we show that absence of Mmm2 affects assembly of β-barrel proteins and that lack of any ERMES structural component results in defects in Tom22 assembly. Loss of N. crassa Gem1 has no effect on the assembly of these proteins but does affect mitochondrial morphology.
Collapse
Affiliation(s)
- Jeremy G. Wideman
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | | | - Martin A. Srayko
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Kacie A. Norton
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Frank E. Nargang
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| |
Collapse
|
61
|
Wideman JG, Gawryluk RM, Gray MW, Dacks JB. The Ancient and Widespread Nature of the ER–Mitochondria Encounter Structure. Mol Biol Evol 2013; 30:2044-9. [DOI: 10.1093/molbev/mst120] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
|
62
|
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.
Collapse
Affiliation(s)
- Bogusz Kulawiak
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, Freiburg, Germany
| | | | | | | | | | | |
Collapse
|
63
|
Klein A, Israel L, Lackey SWK, Nargang FE, Imhof A, Baumeister W, Neupert W, Thomas DR. Characterization of the insertase for β-barrel proteins of the outer mitochondrial membrane. ACTA ACUST UNITED AC 2012; 199:599-611. [PMID: 23128244 PMCID: PMC3494861 DOI: 10.1083/jcb.201207161] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Isolation of the intact TOB complex reveals a 1:1:1 stoichiometry of Tob55, Tob38, and Tob37 with a 140-kD molecular mass, providing new insight into complex structure and function. The TOB–SAM complex is an essential component of the mitochondrial outer membrane that mediates the insertion of β-barrel precursor proteins into the membrane. We report here its isolation and determine its size, composition, and structural organization. The complex from Neurospora crassa was composed of Tob55–Sam50, Tob38–Sam35, and Tob37–Sam37 in a stoichiometry of 1:1:1 and had a molecular mass of 140 kD. A very minor fraction of the purified complex was associated with one Mdm10 protein. Using molecular homology modeling for Tob55 and cryoelectron microscopy reconstructions of the TOB complex, we present a model of the TOB–SAM complex that integrates biochemical and structural data. We discuss our results and the structural model in the context of a possible mechanism of the TOB insertase.
Collapse
Affiliation(s)
- Astrid Klein
- Max-Planck Institut für Biochemie, Abteilung für zelluläre Biochemie, D-82152 Martinsried, Germany
| | | | | | | | | | | | | | | |
Collapse
|
64
|
Abstract
A protein's function is intimately linked to its correct subcellular location, yet the machinery required for protein synthesis is predominately cytosolic. How proteins are trafficked through the confines of the cell and integrated into the appropriate cellular compartments has puzzled and intrigued researchers for decades. Indeed, studies exploring this premise revealed elaborate cellular protein translocation and sorting systems, which ensure that all proteins are shuttled to the appropriate cellular destination, where they fulfill their specific functions. This holds true for mitochondria, where sophisticated molecular machines serve to recognize incoming precursor proteins and integrate them into the functional framework of the organelle. We summarize the recent progress in our understanding of mitochondrial protein sorting and the machineries and mechanisms that mediate and regulate this highly dynamic cellular process essential for survival of virtually all eukaryotic cells.
Collapse
|
65
|
Abstract
The most well-characterized organelle contact sites are those between the endoplasmic reticulum (ER) and mitochondria. Increased understanding is being gained of how ER-mitochondria contact sites are organized and which factors converge at this interface, some of which may provide a tethering function. The role of the ER-mitochondria junction in coordinating the functions of these two organelles is also becoming clearer, and it has been shown to be involved in the regulation of lipid synthesis, Ca(2+) signalling and the control of mitochondrial biogenesis and intracellular trafficking.
Collapse
|
66
|
Abstract
Cellular organelles need to communicate in order to co-ordinate homoeostasis of the compartmentalized eukaryotic cell. Such communication involves the formation of membrane contact sites between adjacent organelles, allowing privileged exchange of metabolites and information. Using a synthetic protein designed to artificially tether the ER (endoplasmic reticulum) to mitochondria, we have discovered a yeast protein complex naturally involved in establishing and maintaining contact sites between these two organelles. This protein complex is physiologically involved in a plethora of mitochondrial processes, suggesting that ER-mitochondria connections play a central co-ordinating role in the regulation of mitochondrial biology. Recent biochemical characterization of this protein complex led to the discovery that GTPases of the Miro family are part of ER-mitochondria connections. The yeast Miro GTPase Gem1 localizes to ER-mitochondria interface and influences the size and distribution of mitochondria. Thus Miro GTPases may serve as regulators of the ER-mitochondria connection.
Collapse
|
67
|
From evolution to pathogenesis: the link between β-barrel assembly machineries in the outer membrane of mitochondria and gram-negative bacteria. Int J Mol Sci 2012; 13:8038-8050. [PMID: 22942688 PMCID: PMC3430219 DOI: 10.3390/ijms13078038] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 06/21/2012] [Accepted: 06/21/2012] [Indexed: 01/29/2023] Open
Abstract
β-barrel proteins are the highly abundant in the outer membranes of Gram-negative bacteria and the mitochondria in eukaryotes. The assembly of β-barrels is mediated by two evolutionary conserved machineries; the β-barrel Assembly Machinery (BAM) in Gram-negative bacteria; and the Sorting and Assembly Machinery (SAM) in mitochondria. Although the BAM and SAM have functionally conserved roles in the membrane integration and folding of β-barrel proteins, apart from the central BamA and Sam50 proteins, the remaining components of each of the complexes have diverged remarkably. For example all of the accessory components of the BAM complex characterized to date are located in the bacterial periplasm, on the same side as the N-terminal domain of BamA. This is the same side of the membrane as the substrates that are delivered to the BAM. On the other hand, all of the accessory components of the SAM complex are located on the cytosolic side of the membrane, the opposite side of the membrane to the N-terminus of Sam50 and the substrate receiving side of the membrane. Despite the accessory subunits being located on opposite sides of the membrane in each system, it is clear that each system is functionally equivalent with bacterial proteins having the ability to use the eukaryotic SAM and vice versa. In this review, we summarize the similarities and differences between the BAM and SAM complexes, highlighting the possible selecting pressures on bacteria and eukaryotes during evolution. It is also now emerging that bacterial pathogens utilize the SAM to target toxins and effector proteins to host mitochondria and this will also be discussed from an evolutionary perspective.
Collapse
|
68
|
Dudek J, Rehling P, van der Laan M. Mitochondrial protein import: common principles and physiological networks. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:274-85. [PMID: 22683763 DOI: 10.1016/j.bbamcr.2012.05.028] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 05/24/2012] [Accepted: 05/28/2012] [Indexed: 11/28/2022]
Abstract
Most mitochondrial proteins are encoded in the nucleus. They are synthesized as precursor forms in the cytosol and must be imported into mitochondria with the help of different protein translocases. Distinct import signals within precursors direct each protein to the mitochondrial surface and subsequently onto specific transport routes to its final destination within these organelles. In this review we highlight common principles of mitochondrial protein import and address different mechanisms of protein integration into mitochondrial membranes. Over the last years it has become clear that mitochondrial protein translocases are not independently operating units, but in fact closely cooperate with each other. We discuss recent studies that indicate how the pathways for mitochondrial protein biogenesis are embedded into a functional network of various other physiological processes, such as energy metabolism, signal transduction, and maintenance of mitochondrial morphology. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
Collapse
Affiliation(s)
- Jan Dudek
- Abteilung Biochemie II, Universität Göttingen, 37073 Göttingen, Germany
| | | | | |
Collapse
|
69
|
Nguyen TT, Lewandowska A, Choi JY, Markgraf DF, Junker M, Bilgin M, Ejsing CS, Voelker DR, Rapoport TA, Shaw JM. Gem1 and ERMES do not directly affect phosphatidylserine transport from ER to mitochondria or mitochondrial inheritance. Traffic 2012; 13:880-90. [PMID: 22409400 PMCID: PMC3648210 DOI: 10.1111/j.1600-0854.2012.01352.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 03/08/2012] [Accepted: 03/12/2012] [Indexed: 11/27/2022]
Abstract
In yeast, a protein complex termed the ER-Mitochondria Encounter Structure (ERMES) tethers mitochondria to the endoplasmic reticulum. ERMES proteins are implicated in a variety of cellular functions including phospholipid synthesis, mitochondrial protein import, mitochondrial attachment to actin, polarized mitochondrial movement into daughter cells during division, and maintenance of mitochondrial DNA (mtDNA). The mitochondrial-anchored Gem1 GTPase has been proposed to regulate ERMES functions. Here, we show that ERMES and Gem1 have no direct role in the transport of phosphatidylserine (PS) from the ER to mitochondria during the synthesis of phosphatidylethanolamine (PE), as PS to PE conversion is not affected in ERMES or gem1 mutants. In addition, we report that mitochondrial inheritance defects in ERMES mutants are a secondary consequence of mitochondrial morphology defects, arguing against a primary role for ERMES in mitochondrial association with actin and mitochondrial movement. Finally, we show that ERMES complexes are long-lived, and do not depend on the presence of Gem1. Our findings suggest that the ERMES complex may have primarily a structural role in maintaining mitochondrial morphology.
Collapse
Affiliation(s)
- Tammy T Nguyen
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
70
|
Role of MINOS in mitochondrial membrane architecture and biogenesis. Trends Cell Biol 2012; 22:185-92. [DOI: 10.1016/j.tcb.2012.01.004] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 01/25/2012] [Accepted: 01/31/2012] [Indexed: 11/18/2022]
|
71
|
Rao S, Schmidt O, Harbauer AB, Schönfisch B, Guiard B, Pfanner N, Meisinger C. Biogenesis of the preprotein translocase of the outer mitochondrial membrane: protein kinase A phosphorylates the precursor of Tom40 and impairs its import. Mol Biol Cell 2012; 23:1618-27. [PMID: 22419819 PMCID: PMC3338429 DOI: 10.1091/mbc.e11-11-0933] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The translocase of the outer mitochondrial membrane (TOM) is essential for the import of proteins into mitochondria. Cytosolic protein kinase A phosphorylates the precursor of the channel-forming protein Tom40 and inhibits its import into mitochondria, thus regulating the biogenesis of the protein entry gate of mitochondria. The preprotein translocase of the outer mitochondrial membrane (TOM) functions as the main entry gate for the import of nuclear-encoded proteins into mitochondria. The major subunits of the TOM complex are the three receptors Tom20, Tom22, and Tom70 and the central channel-forming protein Tom40. Cytosolic kinases have been shown to regulate the biogenesis and activity of the Tom receptors. Casein kinase 2 stimulates the biogenesis of Tom22 and Tom20, whereas protein kinase A (PKA) impairs the receptor function of Tom70. Here we report that PKA exerts an inhibitory effect on the biogenesis of the β-barrel protein Tom40. Tom40 is synthesized as precursor on cytosolic ribosomes and subsequently imported into mitochondria. We show that PKA phosphorylates the precursor of Tom40. The phosphorylated Tom40 precursor is impaired in import into mitochondria, whereas the nonphosphorylated precursor is efficiently imported. We conclude that PKA plays a dual role in the regulation of the TOM complex. Phosphorylation by PKA not only impairs the receptor activity of Tom70, but it also inhibits the biogenesis of the channel protein Tom40.
Collapse
Affiliation(s)
- Sanjana Rao
- Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, 79104 Freiburg, Germany
| | | | | | | | | | | | | |
Collapse
|
72
|
Becker T, Böttinger L, Pfanner N. Mitochondrial protein import: from transport pathways to an integrated network. Trends Biochem Sci 2012; 37:85-91. [PMID: 22178138 DOI: 10.1016/j.tibs.2011.11.004] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2011] [Revised: 11/07/2011] [Accepted: 11/08/2011] [Indexed: 01/24/2023]
Abstract
Mitochondria, the powerhouses of the cell, import most of their proteins from the cytosol. It was originally assumed that mitochondria imported precursor proteins via a general pathway but recent studies have revealed a remarkable variety of import pathways and mechanisms. Currently, five different protein import pathways can be distinguished. However, the import machineries cooperate with each other and are connected to other systems that function in the respiratory chain, mitochondrial membrane organization, protein quality control and endoplasmic reticulum-mitochondria junctions. In this Opinion, we propose that mitochondrial protein import should not be seen as an independent task of the organelle and that a network of cooperating machineries is responsible for major mitochondrial functions.
Collapse
Affiliation(s)
- Thomas Becker
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany
| | | | | |
Collapse
|
73
|
Mitochondrial sorting and assembly machinery subunit Sam37 in Candida albicans: insight into the roles of mitochondria in fitness, cell wall integrity, and virulence. EUKARYOTIC CELL 2012; 11:532-44. [PMID: 22286093 DOI: 10.1128/ec.05292-11] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent studies indicate that mitochondrial functions impinge on cell wall integrity, drug tolerance, and virulence of human fungal pathogens. However, the mechanistic aspects of these processes are poorly understood. We focused on the mitochondrial outer membrane SAM (Sorting and Assembly Machinery) complex subunit Sam37 in Candida albicans. Inactivation of SAM37 in C. albicans leads to a large reduction in fitness, a phenotype not conserved with the model yeast Saccharomyces cerevisiae. Our data indicate that slow growth of the sam37ΔΔ mutant results from mitochondrial DNA loss, a new function for Sam37 in C. albicans, and from reduced activity of the essential SAM complex subunit Sam35. The sam37ΔΔ mutant was hypersensitive to drugs that target the cell wall and displayed altered cell wall structure, supporting a role for Sam37 in cell wall integrity in C. albicans. The sensitivity of the mutant to membrane-targeting antifungals was not significantly altered. The sam37ΔΔ mutant was avirulent in the mouse model, and bioinformatics showed that the fungal Sam37 proteins are distant from their animal counterparts and could thus represent potential drug targets. Our study provides the first direct evidence for a link between mitochondrial function and cell wall integrity in C. albicans and is further relevant for understanding mitochondrial function in fitness, antifungal drug tolerance, and virulence of this major pathogen. Beyond the relevance to fungal pathogenesis, this work also provides new insight into the mitochondrial and cellular roles of the SAM complex in fungi.
Collapse
|
74
|
Grimm S. The ER-mitochondria interface: the social network of cell death. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:327-34. [PMID: 22182703 DOI: 10.1016/j.bbamcr.2011.11.018] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/20/2011] [Accepted: 11/21/2011] [Indexed: 12/23/2022]
Abstract
When cellular organelles communicate bad things can happen. Recent findings uncovered that the junction between the endoplasmic reticulum (ER) and the mitochondria holds a crucial role for cell death regulation. Not only does this locale connect the two best-known organelles in apoptosis, numerous regulators of cell death are concentrated at this spot, providing a terrain for intense signal transfers. Ca2+ is the most prominent signalling factor that is released from the ER and, at high concentration, mediates the transfer of an apoptosis signal to mitochondria as the executioner organelle for cell death. An elaborate array of checks and balances is fine-tuning this process including Bcl-2 family members. Moreover, MAMs, "mitochondria-associated membranes", are distinct membrane sections at the ER that are in close contact with mitochondria and have been found to exchange lipids and lipid-derived molecules such as ceramide for apoptosis induction. Recent work has also described a reverse transfer of apoptosis signals, from mitochondria to the ER, via cytochrome c release and prolonged IP3R opening or through the mitochondrial fission factor Fis1 and Bap31 at the ER, which form the ARCosome, a novel caspase-activation complex.
Collapse
|
75
|
Jiang JH, Davies JK, Lithgow T, Strugnell RA, Gabriel K. Targeting of Neisserial PorB to the mitochondrial outer membrane: an insight on the evolution of β-barrel protein assembly machines. Mol Microbiol 2011; 82:976-87. [DOI: 10.1111/j.1365-2958.2011.07880.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
|
76
|
Lackey SWK, Wideman JG, Kennedy EK, Go NE, Nargang FE. The Neurospora crassa TOB complex: analysis of the topology and function of Tob38 and Tob37. PLoS One 2011; 6:e25650. [PMID: 21980517 PMCID: PMC3182244 DOI: 10.1371/journal.pone.0025650] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 09/07/2011] [Indexed: 11/18/2022] Open
Abstract
The TOB or SAM complex is responsible for assembling several proteins into the mitochondrial outer membrane, including all β-barrel proteins. We have identified several forms of the complex in Neurospora crassa. One form contains Tob55, Tob38, and Tob37; another contains these three subunits plus the Mdm10 protein; while additional complexes contain only Tob55. As previously shown for Tob55, both Tob37 and Tob38 are essential for viability of the organism. Mitochondria deficient in Tob37 or Tob38 have reduced ability to assemble β-barrel proteins. The function of two hydrophobic domains in the C-terminal region of the Tob37 protein was investigated. Mutant Tob37 proteins lacking either or both of these regions are able to restore viability to cells lacking the protein. One of the domains was found to anchor the protein to the outer mitochondrial membrane but was not necessary for targeting or association of the protein with mitochondria. Examination of the import properties of mitochondria containing Tob37 with deletions of the hydrophobic domains reveals that the topology of Tob37 may be important for interactions between specific classes of β-barrel precursors and the TOB complex.
Collapse
Affiliation(s)
| | - Jeremy G. Wideman
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Erin K. Kennedy
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Nancy E. Go
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Frank E. Nargang
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
| |
Collapse
|
77
|
Stroud DA, Oeljeklaus S, Wiese S, Bohnert M, Lewandrowski U, Sickmann A, Guiard B, van der Laan M, Warscheid B, Wiedemann N. Composition and topology of the endoplasmic reticulum-mitochondria encounter structure. J Mol Biol 2011; 413:743-50. [PMID: 21945531 DOI: 10.1016/j.jmb.2011.09.012] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 09/05/2011] [Accepted: 09/07/2011] [Indexed: 11/17/2022]
Abstract
Eukaryotic cells contain multiple organelles, which are functionally and structurally interconnected. The endoplasmic reticulum-mitochondria encounter structure (ERMES) forms a junction between mitochondria and the endoplasmic reticulum (ER). Four ERMES proteins are known in yeast, the ER-anchored protein Mmm1 and three mitochondria-associated proteins, Mdm10, Mdm12 and Mdm34, with functions related to mitochondrial morphology and protein biogenesis. We mapped the glycosylation sites of ERMES and demonstrate that three asparagine residues in the N‑terminal domain of Mmm1 are glycosylated. While the glycosylation is dispensable, the cytosolic C‑terminal domain of Mmm1 that connects to the Mdm proteins is required for Mmm1 function. To analyze the composition of ERMES, we determined the subunits by quantitative mass spectrometry. We identified the calcium-binding GTPase Gem1 as a new ERMES subunit, revealing that ERMES is composed of five genuine subunits. Taken together, ERMES represents a platform that integrates components with functions in formation of ER-mitochondria junctions, maintenance of mitochondrial morphology, protein biogenesis and calcium binding.
Collapse
Affiliation(s)
- David A Stroud
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
78
|
Dukanovic J, Rapaport D. Multiple pathways in the integration of proteins into the mitochondrial outer membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:971-80. [DOI: 10.1016/j.bbamem.2010.06.021] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 06/22/2010] [Accepted: 06/23/2010] [Indexed: 11/25/2022]
|
79
|
Gebert N, Ryan MT, Pfanner N, Wiedemann N, Stojanovski D. Mitochondrial protein import machineries and lipids: A functional connection. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1002-11. [DOI: 10.1016/j.bbamem.2010.08.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 08/02/2010] [Accepted: 08/02/2010] [Indexed: 01/01/2023]
|
80
|
Biogenesis of Mitochondria: Dual Role of Tom7 in Modulating Assembly of the Preprotein Translocase of the Outer Membrane. J Mol Biol 2011; 405:113-24. [DOI: 10.1016/j.jmb.2010.11.002] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2010] [Revised: 10/25/2010] [Accepted: 11/02/2010] [Indexed: 11/21/2022]
|
81
|
Dagley MJ, Gentle IE, Beilharz TH, Pettolino FA, Djordjevic JT, Lo TL, Uwamahoro N, Rupasinghe T, Tull DL, McConville M, Beaurepaire C, Nantel A, Lithgow T, Mitchell AP, Traven A. Cell wall integrity is linked to mitochondria and phospholipid homeostasis in Candida albicans through the activity of the post-transcriptional regulator Ccr4-Pop2. Mol Microbiol 2010; 79:968-89. [PMID: 21299651 DOI: 10.1111/j.1365-2958.2010.07503.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cell wall is essential for viability of fungi and is an effective drug target in pathogens such as Candida albicans. The contribution of post-transcriptional gene regulators to cell wall integrity in C. albicans is unknown. We show that the C. albicans Ccr4-Pop2 mRNA deadenylase, a regulator of mRNA stability and translation, is required for cell wall integrity. The ccr4/pop2 mutants display reduced wall β-glucans and sensitivity to the echinocandin caspofungin. Moreover, the deadenylase mutants are compromised for filamentation and virulence. We demonstrate that defective cell walls in the ccr4/pop2 mutants are linked to dysfunctional mitochondria and phospholipid imbalance. To further understand mitochondrial function in cell wall integrity, we screened a Saccharomyces cerevisiae collection of mitochondrial mutants. We identify several mitochondrial proteins required for caspofungin tolerance and find a connection between mitochondrial phospholipid homeostasis and caspofungin sensitivity. We focus on the mitochondrial outer membrane SAM complex subunit Sam37, demonstrating that it is required for both trafficking of phospholipids between the ER and mitochondria and cell wall integrity. Moreover, in C. albicans also Sam37 is essential for caspofungin tolerance. Our study provides the basis for an integrative view of mitochondrial function in fungal cell wall biogenesis and resistance to echinocandin antifungal drugs.
Collapse
Affiliation(s)
- Michael J Dagley
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
82
|
Harsman A, Krüger V, Bartsch P, Honigmann A, Schmidt O, Rao S, Meisinger C, Wagner R. Protein conducting nanopores. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:454102. [PMID: 21339590 DOI: 10.1088/0953-8984/22/45/454102] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
About 50% of the cellular proteins have to be transported into or across cellular membranes. This transport is an essential step in the protein biosynthesis. In eukaryotic cells secretory proteins are transported into the endoplasmic reticulum before they are transported in vesicles to the plasma membrane. Almost all proteins of the endosymbiotic organelles chloroplasts and mitochondria are synthesized on cytosolic ribosomes and posttranslationally imported. Genetic, biochemical and biophysical approaches led to rather detailed knowledge on the composition of the translocon-complexes which catalyze the membrane transport of the preproteins. Comprehensive concepts on the targeting and membrane transport of polypeptides emerged, however little detail on the molecular nature and mechanisms of the protein translocation channels comprising nanopores has been achieved. In this paper we will highlight recent developments of the diverse protein translocation systems and focus particularly on the common biophysical properties and functions of the protein conducting nanopores. We also provide a first analysis of the interaction between the genuine protein conducting nanopore Tom40(SC) as well as a mutant Tom40(SC) (S(54 --> E) containing an additional negative charge at the channel vestibule and one of its native substrates, CoxIV, a mitochondrial targeting peptide. The polypeptide induced a voltage-dependent increase in the frequency of channel closure of Tom40(SC) corresponding to a voltage-dependent association rate, which was even more pronounced for the Tom40(SC) S54E mutant. The corresponding dwelltime reflecting association/transport of the peptide could be determined with t(off) approximately = 1.1 ms for the wildtype, whereas the mutant Tom40(SC) S54E displayed a biphasic dwelltime distribution (t(off)(-1) approximately = 0.4 ms; t(off)(-2) approximately = 4.6 ms).
Collapse
Affiliation(s)
- Anke Harsman
- Biophysics, Department of Biology/Chemistry, University of Osnabrueck, Germany
| | | | | | | | | | | | | | | |
Collapse
|
83
|
Peraza-Reyes L, Crider DG, Pon LA. Mitochondrial manoeuvres: latest insights and hypotheses on mitochondrial partitioning during mitosis in Saccharomyces cerevisiae. Bioessays 2010; 32:1040-9. [PMID: 20886527 DOI: 10.1002/bies.201000083] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 08/19/2010] [Accepted: 08/24/2010] [Indexed: 12/22/2022]
Abstract
Movement and positional control of mitochondria and other organelles are coordinated with cell cycle progression in the budding yeast, Saccharomyces cerevisiae. Recent studies have revealed a checkpoint that inhibits cytokinesis when there are severe defects in mitochondrial inheritance. An established checkpoint signaling pathway, the mitotic exit network (MEN), participates in this process. Here, we describe mitochondrial motility during inheritance in budding yeast, emerging evidence for mitochondrial quality control during inheritance, and organelle inheritance checkpoints for mitochondria and other organelles.
Collapse
Affiliation(s)
- Leonardo Peraza-Reyes
- Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | | | | |
Collapse
|
84
|
Mitochondrial protein import: from proteomics to functional mechanisms. Nat Rev Mol Cell Biol 2010; 11:655-67. [PMID: 20729931 DOI: 10.1038/nrm2959] [Citation(s) in RCA: 500] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
85
|
Becker T, Guiard B, Thornton N, Zufall N, Stroud DA, Wiedemann N, Pfanner N. Assembly of the mitochondrial protein import channel: role of Tom5 in two-stage interaction of Tom40 with the SAM complex. Mol Biol Cell 2010; 21:3106-13. [PMID: 20668160 PMCID: PMC2938377 DOI: 10.1091/mbc.e10-06-0518] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Tom40 forms the channel of the mitochondrial preprotein translocase. This beta-barrel protein assembles with alpha-helical proteins, however little is known about the mechanism of assembly. Becker et al identified a new intermediate in Tom40 assembly and show that small alpha-helical Tom proteins associate with Tom40 directly at the SAM complex. The preprotein translocase of the outer mitochondrial membrane (TOM) consists of a central β-barrel channel, Tom40, and six proteins with α-helical transmembrane segments. The precursor of Tom40 is imported from the cytosol by a pre-existing TOM complex and inserted into the outer membrane by the sorting and assembly machinery (SAM). Tom40 then assembles with α-helical Tom proteins to the mature TOM complex. The outer membrane protein Mim1 promotes membrane insertion of several α-helical Tom proteins but also affects the biogenesis of Tom40 by an unknown mechanism. We have identified a novel intermediate in the assembly pathway of Tom40, revealing a two-stage interaction of the precursor with the SAM complex. The second SAM stage represents assembly of Tom5 with the precursor of Tom40. Mim1-deficient mitochondria accumulate Tom40 at the first SAM stage like Tom5-deficient mitochondria. Tom5 promotes formation of the second SAM stage and thus suppresses the Tom40 assembly defect of mim1Δ mitochondria. We conclude that the assembly of newly imported Tom40 is directly initiated at the SAM complex by its association with Tom5. The involvement of Mim1 in Tom40 biogenesis can be largely attributed to its role in import of Tom5.
Collapse
Affiliation(s)
- Thomas Becker
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, Freiburg, Germany
| | | | | | | | | | | | | |
Collapse
|
86
|
Minor modifications and major adaptations: the evolution of molecular machines driving mitochondrial protein import. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:947-54. [PMID: 20659421 DOI: 10.1016/j.bbamem.2010.07.019] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 07/17/2010] [Accepted: 07/20/2010] [Indexed: 11/23/2022]
Abstract
Bacterial endosymbionts gave rise to mitochondria in a process that depended on the acquisition of protein import pathways. Modification and in some cases major re-tooling of the endosymbiont's cellular machinery produced these pathways, establishing mitochondria as organelles common to all eukaryotic cells. The legacy of this evolutionary tinkering can be seen in the homologies and structural similarities between mitochondrial protein import machinery and modern day bacterial proteins. Comparative analysis of these systems is revealing both possible routes for the evolution of the mitochondrial membrane translocases and a greater understanding of the mechanisms behind mitochondrial protein import. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
Collapse
|
87
|
Sukhorukov VM, Dikov D, Busch K, Strecker V, Wittig I, Bereiter-Hahn J. Determination of protein mobility in mitochondrial membranes of living cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:2022-32. [PMID: 20655870 DOI: 10.1016/j.bbamem.2010.07.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 07/15/2010] [Accepted: 07/16/2010] [Indexed: 12/21/2022]
Abstract
Molecular mobility in membranes of intracellular organelles is poorly understood, due to the lack of experimental tools applicable for a great diversity of shapes and sizes such organelles can acquire. Determinations of diffusion within the plasma membrane or cytosol are based mostly on the assumption of an infinite flat space, not valid for curved membranes of smaller organelles. Here we extend the application of FRAP to mitochondria of living cells by application of numerical analysis to data collected from a small region inside a single organelle. The spatiotemporal pattern of light pulses generated by the laser scanning microscope during the measurement is reconstructed in silico and consequently the values of diffusion parameters best suited to the particular organelle are found. The mobility of the outer membrane proteins hFis and Tom7, as well as oxidative phosphorylation complexes COX and F(1)F(0) ATPase located in the inner membrane is analyzed in detail. Several alternative models of diffusivity applied to these proteins provide insight into the mechanisms determining the rate of motion in each of the membranes. Tom7 and hFis move along the mitochondrial axis in the outer membrane with similar diffusion coefficients (D=0.7μm(2)/s and 0.6μm(2)/s respectively) and equal immobile fraction (7%). The notably slower motion of the inner membrane proteins is best represented by a dual-component model with approximately equal partitioning of the fractions (F(1)F(0) ATPase: 0.4μm(2)/s and 0.0005μm(2)/s; COX: 0.3μm(2)/s and 0.007μm(2)/s). The mobility patterns specific for the membranes of this organelle are unambiguously distinguishable from those of the plasma membrane or artificial lipid environments: The parameters of mitochondrial proteins indicate a distinct set of factors responsible for their diffusion characteristics.
Collapse
Affiliation(s)
- Valerii M Sukhorukov
- Kinematic Cell Research Group, Institute for Cell Biology and Neurosciences, Goethe University, 60438 Frankfurt am Main, Germany.
| | | | | | | | | | | |
Collapse
|
88
|
Kornmann B, Walter P. ERMES-mediated ER-mitochondria contacts: molecular hubs for the regulation of mitochondrial biology. J Cell Sci 2010; 123:1389-93. [PMID: 20410371 DOI: 10.1242/jcs.058636] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Organelles are separate yet interdependent units of eukaryotic cells. They provide an appropriate milieu for the catalysis of many biochemical reactions, and they must establish physical links to communicate and exchange metabolites throughout the cell. Interorganelle communication is an important, yet still poorly understood, aspect of cell biology. We recently identified a protein complex that we refer to as ERMES [endoplasmic reticulum (ER)-mitochondria encounter structure], the main function of which is to provide a tethering force between the ER and the mitochondria. This complex, composed of both ER and mitochondrial transmembrane proteins, is located at the interface of the two organelles and serves to zipper them together. Previous work had implicated several ERMES components in many different physiological processes. The identification of ERMES as an interorganelle tether allows us to re-examine the amply documented phenotypic consequences of the loss of this complex in the light of this new function, thus providing a unique opportunity to assess the physiological relevance of ER-mitochondria junctions. These phenotypes hint at a broad role for ER-mitochondria connections in regulating mitochondrial and cell physiology. In this Hypothesis, we speculate on the potential role of ER-mitochondria connections as hubs in regulating several aspects of mitochondrial biology, including the regulation of mitochondrial membrane biosynthesis, genome replication, Ca(2+) signaling and protein import. Finally, we discuss how cells might use ER-mitochondria communication to fine-tune these processes according to their metabolic needs.
Collapse
Affiliation(s)
- Benoît Kornmann
- Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California at San Francisco, CA 94158, USA.
| | | |
Collapse
|
89
|
Endo T, Yamano K. Transport of proteins across or into the mitochondrial outer membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:706-14. [DOI: 10.1016/j.bbamcr.2009.11.007] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2009] [Revised: 11/11/2009] [Accepted: 11/17/2009] [Indexed: 11/30/2022]
|
90
|
Structure and evolution of mitochondrial outer membrane proteins of beta-barrel topology. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1292-9. [PMID: 20450883 DOI: 10.1016/j.bbabio.2010.04.019] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 04/25/2010] [Accepted: 04/27/2010] [Indexed: 11/22/2022]
Abstract
Gram-negative bacteria are the ancestors of mitochondrial organelles. Consequently, both entities contain two surrounding lipid bilayers known as the inner and outer membranes. While protein synthesis in bacteria is accomplished in the cytoplasm, mitochondria import 90-99% of their protein ensemble from the cytosol in the opposite direction. Three protein families including Sam50, VDAC and Tom40 together with Mdm10 compose the set of integral beta-barrel proteins embedded in the mitochondrial outer membrane in S. cerevisiae (MOM). The 16-stranded Sam50 protein forms part of the sorting and assembly machinery (SAM) and shows a clear evolutionary relationship to members of the bacterial Omp85 family. By contrast, the evolution of VDAC and Tom40, both adopting the same fold cannot be traced to any bacterial precursor. This finding is in agreement with the specific function of Tom40 in the TOM complex not existent in the enslaved bacterial precursor cell. Models of Tom40 and Sam50 have been developed using X-ray structures of related proteins. These models are analyzed with respect to properties such as conservation and charge distribution yielding features related to their individual functions.
Collapse
|
91
|
Spelbrink JN. Functional organization of mammalian mitochondrial DNA in nucleoids: history, recent developments, and future challenges. IUBMB Life 2010; 62:19-32. [PMID: 20014006 DOI: 10.1002/iub.282] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Various proteins involved in replication, repair, and the structural organization of mitochondrial DNA (mtDNA) have been characterized in detail over the past 25 or so years. In addition, in recent years, many proteins were identified with a role in the dynamics of the mitochondrial network. Using advanced imaging and an increasing number of cytological techniques, we have begun to realize that an important aspect to mtDNA maintenance, in both health and disease, is its organization within the dynamic mitochondrial network in discrete protein-DNA complexes usually termed nucleoids. Here, I review recent developments in the study of nucleoid dynamics and proteins. I will discuss the implications of the organization of mtDNA in nucleoids in light of DNA replication, repair, gene expression, segregation, and inheritance.
Collapse
Affiliation(s)
- Johannes N Spelbrink
- FinMIT Centre of Excellence, Institute of Medical Technology and Tampere University Hospital, University of Tampere, Tampere 33014 TAY, Finland.
| |
Collapse
|
92
|
Wideman JG, Go NE, Klein A, Redmond E, Lackey SWK, Tao T, Kalbacher H, Rapaport D, Neupert W, Nargang FE. Roles of the Mdm10, Tom7, Mdm12, and Mmm1 proteins in the assembly of mitochondrial outer membrane proteins in Neurospora crassa. Mol Biol Cell 2010; 21:1725-36. [PMID: 20335503 PMCID: PMC2869378 DOI: 10.1091/mbc.e09-10-0844] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Mdm10, Mdm12, and Mmm1 are implicated in several mitochondrial functions. We show that loss of any of these proteins in Neurospora crassa results in the formation of large mitochondrial tubules and reduces assembly of porin and Tom40. The effects of mutations affecting Tom7 and Mdm10 are additive with respect to the assembly of Tom40 and porin. The Mdm10, Mdm12, and Mmm1 proteins have been implicated in several mitochondrial functions including mitochondrial distribution and morphology, assembly of β-barrel proteins such as Tom40 and porin, association of mitochondria and endoplasmic reticulum, and maintaining lipid composition of mitochondrial membranes. Here we show that loss of any of these three proteins in Neurospora crassa results in the formation of large mitochondrial tubules and reduces the assembly of porin and Tom40 into the outer membrane. We have also investigated the relationship of Mdm10 and Tom7 in the biogenesis of β-barrel proteins. Previous work showed that mitochondria lacking Tom7 assemble Tom40 more efficiently, and porin less efficiently, than wild-type mitochondria. Analysis of mdm10 and tom7 single and double mutants, has demonstrated that the effects of the two mutations are additive. Loss of Tom7 partially compensates for the decrease in Tom40 assembly resulting from loss of Mdm10, whereas porin assembly is more severely reduced in the double mutant than in either single mutant. The additive effects observed in the double mutant suggest that different steps in β-barrel assembly are affected in the individual mutants. Many aspects of Tom7 and Mdm10 function in N. crassa are different from those of their homologues in Saccharomyces cerevisiae.
Collapse
Affiliation(s)
- Jeremy G Wideman
- Department of Biological Sciences, University of Alberta, Alberta, Canada
| | | | | | | | | | | | | | | | | | | |
Collapse
|
93
|
|
94
|
Two Modular Forms of the Mitochondrial Sorting and Assembly Machinery Are Involved in Biogenesis of α-Helical Outer Membrane Proteins. J Mol Biol 2010; 396:540-9. [DOI: 10.1016/j.jmb.2009.12.026] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 12/11/2009] [Accepted: 12/13/2009] [Indexed: 11/19/2022]
|
95
|
Mdm10 as a dynamic constituent of the TOB/SAM complex directs coordinated assembly of Tom40. EMBO Rep 2010; 11:187-93. [PMID: 20111053 DOI: 10.1038/embor.2009.283] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 12/03/2009] [Accepted: 12/14/2009] [Indexed: 11/08/2022] Open
Abstract
The mitochondrial outer membrane contains two protein translocators: the TOM40 and TOB/SAM complexes. Mdm10 is distributed in the TOB complex for beta-barrel protein assembly and in the MMM1 complex for tethering of the endoplasmic reticulum and mitochondria. Here, we establish a system in which the Mdm10 level in the TOB complex--but not in the MMM1 complex--is altered to analyse its part in beta-barrel protein assembly. A decrease in the Mdm10 level results in accumulation of in vitro imported Tom40, which is a beta-barrel protein, at the level of the TOB complex. An increase in the Mdm10 level inhibits association not only of Tom40 but also of other beta-barrel proteins with the TOB complex. These results show that Mdm10 regulates the timing of release of unassembled Tom40 from the TOB complex, to facilitate its coordinated assembly into the TOM40 complex.
Collapse
|
96
|
Abstract
The translocase of the outer mitochondrial membrane (TOM complex) is a multi-subunit complex that serves as the general entry site for newly synthesized proteins into the organelle. The assembly of this complex is a multi-step process that requires the coordinated action of several proteins. A central, but rather undefined role in this process is played by Mim1, a mitochondrial outer membrane protein. The deletion of MIM1 leads to severe defects in the biogenesis of TOM complex subunits and to altered mitochondrial morphology. The protein is built from an N-terminal cytosolic domain, a central transmembrane segment, and a C-terminal domain facing the intermembrane space. In this review we summarize our current knowledge on the structure-function relationship of Mim1 and discuss some possibilities for its molecular function.
Collapse
|
97
|
Shibata Y, Hu J, Kozlov MM, Rapoport TA. Mechanisms Shaping the Membranes of Cellular Organelles. Annu Rev Cell Dev Biol 2009; 25:329-54. [DOI: 10.1146/annurev.cellbio.042308.113324] [Citation(s) in RCA: 328] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yoko Shibata
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115; ,
| | - Junjie Hu
- College of Life Sciences, Nankai University, 300071 Tianjin, China;
| | - Michael M. Kozlov
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel;
| | - Tom A. Rapoport
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115; ,
| |
Collapse
|
98
|
Chacinska A, Koehler CM, Milenkovic D, Lithgow T, Pfanner N. Importing mitochondrial proteins: machineries and mechanisms. Cell 2009; 138:628-44. [PMID: 19703392 DOI: 10.1016/j.cell.2009.08.005] [Citation(s) in RCA: 1039] [Impact Index Per Article: 69.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Most mitochondrial proteins are synthesized on cytosolic ribosomes and must be imported across one or both mitochondrial membranes. There is an amazingly versatile set of machineries and mechanisms, and at least four different pathways, for the importing and sorting of mitochondrial precursor proteins. The translocases that catalyze these processes are highly dynamic machines driven by the membrane potential, ATP, or redox reactions, and they cooperate with molecular chaperones and assembly complexes to direct mitochondrial proteins to their correct destinations. Here, we discuss recent insights into the importing and sorting of mitochondrial proteins and their contributions to mitochondrial biogenesis.
Collapse
Affiliation(s)
- Agnieszka Chacinska
- Institut für Biochemie und Molekularbiologie, ZBMZ, Universität Freiburg, 79104 Freiburg, Germany
| | | | | | | | | |
Collapse
|
99
|
Genetic and functional interactions between the mitochondrial outer membrane proteins Tom6 and Sam37. Mol Cell Biol 2009; 29:5975-88. [PMID: 19797086 DOI: 10.1128/mcb.00069-09] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The TOM complex is the general mitochondrial entry site for newly synthesized proteins. Precursors of beta-barrel proteins initially follow this common pathway and are then relayed to the SAM/TOB complex, which mediates their integration into the outer membrane. Three proteins, Sam50 (Tob55), Sam35 (Tob38/Tom38), and Sam37 (Mas37), have been identified as the core constituents of the latter complex. Sam37 is essential for growth at elevated temperatures, but the function of the protein is currently unresolved. To identify interacting partners of Sam37 and thus shed light on its function, we screened for multicopy suppressors of sam37Delta. We identified the small subunit of the TOM complex, Tom6, as such a suppressor and found a tight genetic interaction between the two proteins. Overexpression of SAM37 suppresses the growth phenotype of tom6Delta, and cells lacking both genes are not viable. The ability of large amounts of Tom6 to suppress the sam37Delta phenotype can be linked to the capacity of Tom6 to stabilize Tom40, an essential beta-barrel protein which is the central component of the TOM complex. Our results suggest that Sam37 is required for growth at higher temperatures, since it enhances the biogenesis of Tom40, and this requirement can be overruled by improved stability of newly synthesized Tom40 molecules.
Collapse
|
100
|
Walther DM, Rapaport D, Tommassen J. Biogenesis of beta-barrel membrane proteins in bacteria and eukaryotes: evolutionary conservation and divergence. Cell Mol Life Sci 2009; 66:2789-804. [PMID: 19399587 PMCID: PMC2724633 DOI: 10.1007/s00018-009-0029-z] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 03/26/2009] [Accepted: 04/01/2009] [Indexed: 01/01/2023]
Abstract
Membrane-embedded beta-barrel proteins span the membrane via multiple amphipathic beta-strands arranged in a cylindrical shape. These proteins are found in the outer membranes of Gram-negative bacteria, mitochondria and chloroplasts. This situation is thought to reflect the evolutionary origin of mitochondria and chloroplasts from Gram-negative bacterial endosymbionts. beta-barrel proteins fulfil a variety of functions; among them are pore-forming proteins that allow the flux of metabolites across the membrane by passive diffusion, active transporters of siderophores, enzymes, structural proteins, and proteins that mediate protein translocation across or insertion into membranes. The biogenesis process of these proteins combines evolutionary conservation of the central elements with some noticeable differences in signals and machineries. This review summarizes our current knowledge of the functions and biogenesis of this special family of proteins.
Collapse
Affiliation(s)
- Dirk M. Walther
- Interfaculty Institute for Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany
- Department of Proteomics and Signal Transduction, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Doron Rapaport
- Interfaculty Institute for Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany
| | - Jan Tommassen
- Department of Molecular Microbiology, Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands
| |
Collapse
|