1
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Antolínez-Fernández Á, Esteban-Ramos P, Fernández-Moreno MÁ, Clemente P. Molecular pathways in mitochondrial disorders due to a defective mitochondrial protein synthesis. Front Cell Dev Biol 2024; 12:1410245. [PMID: 38855161 PMCID: PMC11157125 DOI: 10.3389/fcell.2024.1410245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Accepted: 05/09/2024] [Indexed: 06/11/2024] Open
Abstract
Mitochondria play a central role in cellular metabolism producing the necessary ATP through oxidative phosphorylation. As a remnant of their prokaryotic past, mitochondria contain their own genome, which encodes 13 subunits of the oxidative phosphorylation system, as well as the tRNAs and rRNAs necessary for their translation in the organelle. Mitochondrial protein synthesis depends on the import of a vast array of nuclear-encoded proteins including the mitochondrial ribosome protein components, translation factors, aminoacyl-tRNA synthetases or assembly factors among others. Cryo-EM studies have improved our understanding of the composition of the mitochondrial ribosome and the factors required for mitochondrial protein synthesis and the advances in next-generation sequencing techniques have allowed for the identification of a growing number of genes involved in mitochondrial pathologies with a defective translation. These disorders are often multisystemic, affecting those tissues with a higher energy demand, and often present with neurodegenerative phenotypes. In this article, we review the known proteins required for mitochondrial translation, the disorders that derive from a defective mitochondrial protein synthesis and the animal models that have been established for their study.
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Affiliation(s)
- Álvaro Antolínez-Fernández
- Instituto de Investigaciones Biomédicas Sols-Morreale (IIBM), Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Departamento de Bioquímica, Universidad Autónoma de Madrid, Madrid, Spain
| | - Paula Esteban-Ramos
- Instituto de Investigaciones Biomédicas Sols-Morreale (IIBM), Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Departamento de Bioquímica, Universidad Autónoma de Madrid, Madrid, Spain
| | - Miguel Ángel Fernández-Moreno
- Instituto de Investigaciones Biomédicas Sols-Morreale (IIBM), Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Departamento de Bioquímica, Universidad Autónoma de Madrid, Madrid, Spain
| | - Paula Clemente
- Instituto de Investigaciones Biomédicas Sols-Morreale (IIBM), Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Departamento de Bioquímica, Universidad Autónoma de Madrid, Madrid, Spain
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2
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Krüger A, Remes C, Shiriaev DI, Liu Y, Spåhr H, Wibom R, Atanassov I, Nguyen MD, Cooperman BS, Rorbach J. Human mitochondria require mtRF1 for translation termination at non-canonical stop codons. Nat Commun 2023; 14:30. [PMID: 36596788 PMCID: PMC9810596 DOI: 10.1038/s41467-022-35684-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 12/19/2022] [Indexed: 01/04/2023] Open
Abstract
The mitochondrial translation machinery highly diverged from its bacterial counterpart. This includes deviation from the universal genetic code, with AGA and AGG codons lacking cognate tRNAs in human mitochondria. The locations of these codons at the end of COX1 and ND6 open reading frames, respectively, suggest they might function as stop codons. However, while the canonical stop codons UAA and UAG are known to be recognized by mtRF1a, the release mechanism at AGA and AGG codons remains a debated issue. Here, we show that upon the loss of another member of the mitochondrial release factor family, mtRF1, mitoribosomes accumulate specifically at AGA and AGG codons. Stalling of mitoribosomes alters COX1 transcript and protein levels, but not ND6 synthesis. In addition, using an in vitro reconstituted mitochondrial translation system, we demonstrate the specific peptide release activity of mtRF1 at the AGA and AGG codons. Together, our results reveal the role of mtRF1 in translation termination at non-canonical stop codons in mitochondria.
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Affiliation(s)
- Annika Krüger
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Biomedicum, 171 65, Solna, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Cristina Remes
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Dmitrii Igorevich Shiriaev
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Biomedicum, 171 65, Solna, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Yong Liu
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Biomedicum, 171 65, Solna, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Henrik Spåhr
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Biomedicum, 171 65, Solna, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Rolf Wibom
- Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Ilian Atanassov
- Proteomics Core Facility, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931, Cologne, Germany
| | - Minh Duc Nguyen
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Biomedicum, 171 65, Solna, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Barry S Cooperman
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Joanna Rorbach
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Biomedicum, 171 65, Solna, Sweden. .,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden. .,S.T.I.A.S: Stellenbosch Institute for Advanced Study, Marais Rd, Mostertsdrift, Stellenbosch, 7600, South Africa.
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3
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Molina‐Berenguer M, Vila‐Julià F, Pérez‐Ramos S, Salcedo‐Allende MT, Cámara Y, Torres‐Torronteras J, Martí R. Dysfunctional mitochondrial translation and combined oxidative phosphorylation deficiency in a mouse model of hepatoencephalopathy due to
Gfm1
mutations. FASEB J 2021; 36:e22091. [DOI: 10.1096/fj.202100819rrr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 11/19/2021] [Accepted: 11/23/2021] [Indexed: 11/11/2022]
Affiliation(s)
- Miguel Molina‐Berenguer
- Research Group on Neuromuscular and Mitochondrial Diseases Vall d'Hebron Research Institute Universitat Autònoma de Barcelona Barcelona Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER) Instituto de Salud Carlos III Madrid Spain
| | - Ferran Vila‐Julià
- Research Group on Neuromuscular and Mitochondrial Diseases Vall d'Hebron Research Institute Universitat Autònoma de Barcelona Barcelona Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER) Instituto de Salud Carlos III Madrid Spain
| | - Sandra Pérez‐Ramos
- Research Group on Neuromuscular and Mitochondrial Diseases Vall d'Hebron Research Institute Universitat Autònoma de Barcelona Barcelona Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER) Instituto de Salud Carlos III Madrid Spain
| | - Maria Teresa Salcedo‐Allende
- Pathology Department Vall d'Hebron Research Institute Hospital Universitari Vall d'Hebron Universitat Autònoma de Barcelona Barcelona Spain
| | - Yolanda Cámara
- Research Group on Neuromuscular and Mitochondrial Diseases Vall d'Hebron Research Institute Universitat Autònoma de Barcelona Barcelona Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER) Instituto de Salud Carlos III Madrid Spain
| | - Javier Torres‐Torronteras
- Research Group on Neuromuscular and Mitochondrial Diseases Vall d'Hebron Research Institute Universitat Autònoma de Barcelona Barcelona Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER) Instituto de Salud Carlos III Madrid Spain
| | - Ramon Martí
- Research Group on Neuromuscular and Mitochondrial Diseases Vall d'Hebron Research Institute Universitat Autònoma de Barcelona Barcelona Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER) Instituto de Salud Carlos III Madrid Spain
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4
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Criscuolo D, Avolio R, Matassa DS, Esposito F. Targeting Mitochondrial Protein Expression as a Future Approach for Cancer Therapy. Front Oncol 2021; 11:797265. [PMID: 34888254 PMCID: PMC8650000 DOI: 10.3389/fonc.2021.797265] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 11/03/2021] [Indexed: 12/20/2022] Open
Abstract
Extensive metabolic remodeling is a fundamental feature of cancer cells. Although early reports attributed such remodeling to a loss of mitochondrial functions, it is now clear that mitochondria play central roles in cancer development and progression, from energy production to synthesis of macromolecules, from redox modulation to regulation of cell death. Biosynthetic pathways are also heavily affected by the metabolic rewiring, with protein synthesis dysregulation at the hearth of cellular transformation. Accumulating evidence in multiple organisms shows that the metabolic functions of mitochondria are tightly connected to protein synthesis, being assembly and activity of respiratory complexes highly dependent on de novo synthesis of their components. In turn, protein synthesis within the organelle is tightly connected with the cytosolic process. This implies an entire network of interactions and fine-tuned regulations that build up a completely under-estimated level of complexity. We are now only preliminarily beginning to reconstitute such regulatory level in human cells, and to perceive its role in diseases. Indeed, disruption or alterations of these connections trigger conditions of proteotoxic and energetic stress that could be potentially exploited for therapeutic purposes. In this review, we summarize the available literature on the coordinated regulation of mitochondrial and cytosolic mRNA translation, and their effects on the integrity of the mitochondrial proteome and functions. Finally, we highlight the potential held by this topic for future research directions and for the development of innovative therapeutic approaches.
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Affiliation(s)
- Daniela Criscuolo
- Department of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy
| | - Rosario Avolio
- Department of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy
| | - Danilo Swann Matassa
- Department of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy
| | - Franca Esposito
- Department of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy
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5
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Cao Y, Chen Z, Huang J, Wu H, Zou J, Feng H. Black carp TUFM collaborates with NLRX1 to inhibit MAVS-mediated antiviral signaling pathway. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2021; 122:104134. [PMID: 34000319 DOI: 10.1016/j.dci.2021.104134] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 04/27/2021] [Accepted: 05/11/2021] [Indexed: 06/12/2023]
Abstract
TUFM is a mitochondrial protein and serves as a regulator of antiviral signaling; nevertheless, the character of TUFM in teleosts remains unidentified. In this study, TUFM homologue of black carp (Mylopharyngodon piceus) has been characterized and its role in innate immunity has been explored. Black carp TUFM (bcTUFM) comprises 447 amino acids and shows the high similarity to human TUFM. bcTUFM was about 50 kDa in the Western blot assay and was determined as a cytosolic protein by immunofluorescent microscopy. Knockdown of bcTUFM by shRNA enhanced the antiviral ability of the host cells. The induction fold of interferon promoter transcription in the cells co-expressing bcTUFM and bcMAVS was much lower than that of the cells expressing bcMAVS alone. Our previous study has identified that bcNLRX1 interacted with bcMAVS and functioned as an inhibitor of bcMAVS. The interaction between bcTUFM and bcNLRX1, but not bcTUFM and bcMAVS, was detected through co-immunoprecipitation. The subsequent reporter assay and plaque assay demonstrated that the inhibition of bcMAVS-mediated interferon production and antiviral activity by bcNLRX1 was enhanced by co-expressed bcTUFM. Thus, our data suggests that bcTUFM cooperates with bcNLRX1 to inhibit bcMAVS-mediated antiviral signaling during host antiviral innate immune response against SVCV.
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Affiliation(s)
- Yingyi Cao
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, China
| | - Zhaoyuan Chen
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, China
| | - Jiayi Huang
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, China
| | - Hui Wu
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, China.
| | - Jun Zou
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai, 201306, China
| | - Hao Feng
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, China.
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6
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Wang F, Zhang D, Zhang D, Li P, Gao Y. Mitochondrial Protein Translation: Emerging Roles and Clinical Significance in Disease. Front Cell Dev Biol 2021; 9:675465. [PMID: 34277617 PMCID: PMC8280776 DOI: 10.3389/fcell.2021.675465] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 06/09/2021] [Indexed: 12/28/2022] Open
Abstract
Mitochondria are one of the most important organelles in cells. Mitochondria are semi-autonomous organelles with their own genetic system, and can independently replicate, transcribe, and translate mitochondrial DNA. Translation initiation, elongation, termination, and recycling of the ribosome are four stages in the process of mitochondrial protein translation. In this process, mitochondrial protein translation factors and translation activators, mitochondrial RNA, and other regulatory factors regulate mitochondrial protein translation. Mitochondrial protein translation abnormalities are associated with a variety of diseases, including cancer, cardiovascular diseases, and nervous system diseases. Mutation or deletion of various mitochondrial protein translation factors and translation activators leads to abnormal mitochondrial protein translation. Mitochondrial tRNAs and mitochondrial ribosomal proteins are essential players during translation and mutations in genes encoding them represent a large fraction of mitochondrial diseases. Moreover, there is crosstalk between mitochondrial protein translation and cytoplasmic translation, and the imbalance between mitochondrial protein translation and cytoplasmic translation can affect some physiological and pathological processes. This review summarizes the regulation of mitochondrial protein translation factors, mitochondrial ribosomal proteins, mitochondrial tRNAs, and mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs) in the mitochondrial protein translation process and its relationship with diseases. The regulation of mitochondrial protein translation and cytoplasmic translation in multiple diseases is also summarized.
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Affiliation(s)
- Fei Wang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Deyu Zhang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Dejiu Zhang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Peifeng Li
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Yanyan Gao
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China.,Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, China
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7
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Koripella RK, Deep A, Agrawal EK, Keshavan P, Banavali NK, Agrawal RK. Distinct mechanisms of the human mitoribosome recycling and antibiotic resistance. Nat Commun 2021; 12:3607. [PMID: 34127662 PMCID: PMC8203779 DOI: 10.1038/s41467-021-23726-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 05/14/2021] [Indexed: 11/16/2022] Open
Abstract
Ribosomes are recycled for a new round of translation initiation by dissociation of ribosomal subunits, messenger RNA and transfer RNA from their translational post-termination complex. Here we present cryo-EM structures of the human 55S mitochondrial ribosome (mitoribosome) and the mitoribosomal large 39S subunit in complex with mitoribosome recycling factor (RRFmt) and a recycling-specific homolog of elongation factor G (EF-G2mt). These structures clarify an unusual role of a mitochondria-specific segment of RRFmt, identify the structural distinctions that confer functional specificity to EF-G2mt, and show that the deacylated tRNA remains with the dissociated 39S subunit, suggesting a distinct sequence of events in mitoribosome recycling. Furthermore, biochemical and structural analyses reveal that the molecular mechanism of antibiotic fusidic acid resistance for EF-G2mt is markedly different from that of mitochondrial elongation factor EF-G1mt, suggesting that the two human EF-Gmts have evolved diversely to negate the effect of a bacterial antibiotic. High-resolution cryo-EM structures and biochemical analyses of the human mitoribosome, in complex with mitochondria-specific factors mediating mitoribosome recycling, RRFmt and EF-G2mt, offer insight into mechanisms of mitoribosome recycling and resistance to antibiotic fusidic acid.
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Affiliation(s)
- Ravi Kiran Koripella
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA
| | - Ayush Deep
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA
| | - Ekansh K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA
| | - Pooja Keshavan
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA
| | - Nilesh K Banavali
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA.,Department of Biomedical Sciences, University at Albany, Albany, NY, USA
| | - Rajendra K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, USA. .,Department of Biomedical Sciences, University at Albany, Albany, NY, USA.
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8
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Mechanisms and regulation of protein synthesis in mitochondria. Nat Rev Mol Cell Biol 2021; 22:307-325. [PMID: 33594280 DOI: 10.1038/s41580-021-00332-2] [Citation(s) in RCA: 140] [Impact Index Per Article: 46.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2021] [Indexed: 02/06/2023]
Abstract
Mitochondria are cellular organelles responsible for generation of chemical energy in the process called oxidative phosphorylation. They originate from a bacterial ancestor and maintain their own genome, which is expressed by designated, mitochondrial transcription and translation machineries that differ from those operating for nuclear gene expression. In particular, the mitochondrial protein synthesis machinery is structurally and functionally very different from that governing eukaryotic, cytosolic translation. Despite harbouring their own genetic information, mitochondria are far from being independent of the rest of the cell and, conversely, cellular fitness is closely linked to mitochondrial function. Mitochondria depend heavily on the import of nuclear-encoded proteins for gene expression and function, and hence engage in extensive inter-compartmental crosstalk to regulate their proteome. This connectivity allows mitochondria to adapt to changes in cellular conditions and also mediates responses to stress and mitochondrial dysfunction. With a focus on mammals and yeast, we review fundamental insights that have been made into the biogenesis, architecture and mechanisms of the mitochondrial translation apparatus in the past years owing to the emergence of numerous near-atomic structures and a considerable amount of biochemical work. Moreover, we discuss how cellular mitochondrial protein expression is regulated, including aspects of mRNA and tRNA maturation and stability, roles of auxiliary factors, such as translation regulators, that adapt mitochondrial translation rates, and the importance of inter-compartmental crosstalk with nuclear gene expression and cytosolic translation and how it enables integration of mitochondrial translation into the cellular context.
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9
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Lee M, Matsunaga N, Akabane S, Yasuda I, Ueda T, Takeuchi-Tomita N. Reconstitution of mammalian mitochondrial translation system capable of correct initiation and long polypeptide synthesis from leaderless mRNA. Nucleic Acids Res 2021; 49:371-382. [PMID: 33300043 PMCID: PMC7797035 DOI: 10.1093/nar/gkaa1165] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 11/12/2020] [Accepted: 11/16/2020] [Indexed: 12/31/2022] Open
Abstract
Mammalian mitochondria have their own dedicated protein synthesis system, which produces 13 essential subunits of the oxidative phosphorylation complexes. We have reconstituted an in vitro translation system from mammalian mitochondria, utilizing purified recombinant mitochondrial translation factors, 55S ribosomes from pig liver mitochondria, and a tRNA mixture from either Escherichia coli or yeast. The system is capable of translating leaderless mRNAs encoding model proteins (DHFR and nanoLuciferase) or some mtDNA-encoded proteins. We show that a leaderless mRNA, encoding nanoLuciferase, is faithfully initiated without the need for any auxiliary factors other than IF-2mt and IF-3mt. We found that the ribosome-dependent GTPase activities of both the translocase EF-G1mt and the recycling factor EF-G2mt are insensitive to fusidic acid (FA), the translation inhibitor that targets bacterial EF-G homologs, and consequently the system is resistant to FA. Moreover, we demonstrate that a polyproline sequence in the protein causes 55S mitochondrial ribosome stalling, yielding ribosome nascent chain complexes. Analyses of the effects of the Mg concentration on the polyproline-mediated ribosome stalling suggested the unique regulation of peptide elongation by the mitoribosome. This system will be useful for analyzing the mechanism of translation initiation, and the interactions between the nascent peptide chain and the mitochondrial ribosome.
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Affiliation(s)
- Muhoon Lee
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Noriko Matsunaga
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Shiori Akabane
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan.,Department of Life Science, Rikkyo University, Tokyo, 171-8501, Japan
| | - Ippei Yasuda
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Takuya Ueda
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan.,Department of Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, Tokyo, Shinjuku 162-8480, Japan
| | - Nono Takeuchi-Tomita
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
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10
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Almeida L, Dhillon-LaBrooy A, Castro CN, Adossa N, Carriche GM, Guderian M, Lippens S, Dennerlein S, Hesse C, Lambrecht BN, Berod L, Schauser L, Blazar BR, Kalesse M, Müller R, Moita LF, Sparwasser T. Ribosome-Targeting Antibiotics Impair T Cell Effector Function and Ameliorate Autoimmunity by Blocking Mitochondrial Protein Synthesis. Immunity 2020; 54:68-83.e6. [PMID: 33238133 PMCID: PMC7837214 DOI: 10.1016/j.immuni.2020.11.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 09/16/2020] [Accepted: 11/03/2020] [Indexed: 02/08/2023]
Abstract
While antibiotics are intended to specifically target bacteria, most are known to affect host cell physiology. In addition, some antibiotic classes are reported as immunosuppressive for reasons that remain unclear. Here, we show that Linezolid, a ribosomal-targeting antibiotic (RAbo), effectively blocked the course of a T cell-mediated autoimmune disease. Linezolid and other RAbos were strong inhibitors of T helper-17 cell effector function in vitro, showing that this effect was independent of their antibiotic activity. Perturbing mitochondrial translation in differentiating T cells, either with RAbos or through the inhibition of mitochondrial elongation factor G1 (mEF-G1) progressively compromised the integrity of the electron transport chain. Ultimately, this led to deficient oxidative phosphorylation, diminishing nicotinamide adenine dinucleotide concentrations and impairing cytokine production in differentiating T cells. In accordance, mice lacking mEF-G1 in T cells were protected from experimental autoimmune encephalomyelitis, demonstrating that this pathway is crucial in maintaining T cell function and pathogenicity.
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Affiliation(s)
- Luís Almeida
- Institute of Infection Immunology, TWINCORE, Center for Experimental and Clinical Infection Research, Hannover Medical School and the Helmholtz Center for Infection Research, Hannover 30625, Germany; Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University, Mainz 55131, Germany
| | - Ayesha Dhillon-LaBrooy
- Institute of Infection Immunology, TWINCORE, Center for Experimental and Clinical Infection Research, Hannover Medical School and the Helmholtz Center for Infection Research, Hannover 30625, Germany; Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University, Mainz 55131, Germany
| | - Carla N Castro
- Institute of Infection Immunology, TWINCORE, Center for Experimental and Clinical Infection Research, Hannover Medical School and the Helmholtz Center for Infection Research, Hannover 30625, Germany
| | - Nigatu Adossa
- QIAGEN, Aarhus C 8000, Denmark; University of Turku, Computational Biomedicine, Turku Center for Biotechnology, Turku 20520, Finland
| | - Guilhermina M Carriche
- Institute of Infection Immunology, TWINCORE, Center for Experimental and Clinical Infection Research, Hannover Medical School and the Helmholtz Center for Infection Research, Hannover 30625, Germany; Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University, Mainz 55131, Germany
| | - Melanie Guderian
- Institute of Infection Immunology, TWINCORE, Center for Experimental and Clinical Infection Research, Hannover Medical School and the Helmholtz Center for Infection Research, Hannover 30625, Germany
| | | | - Sven Dennerlein
- Department of Cellular Biochemistry, University Medical Center, Göttingen 37073, Germany
| | - Christina Hesse
- Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM), Hannover 30625, Germany
| | | | - Luciana Berod
- Institute of Infection Immunology, TWINCORE, Center for Experimental and Clinical Infection Research, Hannover Medical School and the Helmholtz Center for Infection Research, Hannover 30625, Germany; Institute of Molecular Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | | | - Bruce R Blazar
- Department of Pediatrics, Division of Blood and Marrow Transplantation, University of Minnesota, Minneapolis, MN 55454, USA
| | - Markus Kalesse
- Institute for Organic Chemistry, Leibniz University Hannover, Hannover, Germany; Helmholtz Center for Infection Research (HZI), Braunschweig 38124, Germany
| | - Rolf Müller
- Helmholtz Institute for Pharmaceutical Research, Helmholtz Center for Infection Research and Department of Pharmaceutical Biotechnology, Saarland University, Saarbrücken 66123, Germany
| | - Luís F Moita
- Innate Immunity and Inflammation Laboratory, Instituto Gulbenkian de Ciência, Oeiras, Portugal
| | - Tim Sparwasser
- Institute of Infection Immunology, TWINCORE, Center for Experimental and Clinical Infection Research, Hannover Medical School and the Helmholtz Center for Infection Research, Hannover 30625, Germany; Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University, Mainz 55131, Germany.
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11
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Kummer E, Ban N. Structural insights into mammalian mitochondrial translation elongation catalyzed by mtEFG1. EMBO J 2020; 39:e104820. [PMID: 32602580 PMCID: PMC7396830 DOI: 10.15252/embj.2020104820] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/08/2020] [Accepted: 05/11/2020] [Indexed: 01/08/2023] Open
Abstract
Mitochondria are eukaryotic organelles of bacterial origin where respiration takes place to produce cellular chemical energy. These reactions are catalyzed by the respiratory chain complexes located in the inner mitochondrial membrane. Notably, key components of the respiratory chain complexes are encoded on the mitochondrial chromosome and their expression relies on a dedicated mitochondrial translation machinery. Defects in the mitochondrial gene expression machinery lead to a variety of diseases in humans mostly affecting tissues with high energy demand such as the nervous system, the heart, or the muscles. The mitochondrial translation system has substantially diverged from its bacterial ancestor, including alterations in the mitoribosomal architecture, multiple changes to the set of translation factors and striking reductions in otherwise conserved tRNA elements. Although a number of structures of mitochondrial ribosomes from different species have been determined, our mechanistic understanding of the mitochondrial translation cycle remains largely unexplored. Here, we present two cryo-EM reconstructions of human mitochondrial elongation factor G1 bound to the mammalian mitochondrial ribosome at two different steps of the tRNA translocation reaction during translation elongation. Our structures explain the mechanism of tRNA and mRNA translocation on the mitoribosome, the regulation of mtEFG1 activity by the ribosomal GTPase-associated center, and the basis of decreased susceptibility of mtEFG1 to the commonly used antibiotic fusidic acid.
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Affiliation(s)
- Eva Kummer
- Department of BiologyInstitute of Molecular Biology and BiophysicsSwiss Federal Institute of Technology ZurichZurichSwitzerland
| | - Nenad Ban
- Department of BiologyInstitute of Molecular Biology and BiophysicsSwiss Federal Institute of Technology ZurichZurichSwitzerland
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12
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Koripella RK, Sharma MR, Bhargava K, Datta PP, Kaushal PS, Keshavan P, Spremulli LL, Banavali NK, Agrawal RK. Structures of the human mitochondrial ribosome bound to EF-G1 reveal distinct features of mitochondrial translation elongation. Nat Commun 2020; 11:3830. [PMID: 32737313 PMCID: PMC7395135 DOI: 10.1038/s41467-020-17715-2] [Citation(s) in RCA: 22] [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: 04/13/2020] [Accepted: 07/15/2020] [Indexed: 02/06/2023] Open
Abstract
The mammalian mitochondrial ribosome (mitoribosome) and its associated translational factors have evolved to accommodate greater participation of proteins in mitochondrial translation. Here we present the 2.68-3.96 Å cryo-EM structures of the human 55S mitoribosome in complex with the human mitochondrial elongation factor G1 (EF-G1mt) in three distinct conformational states, including an intermediate state and a post-translocational state. These structures reveal the role of several mitochondria-specific (mito-specific) mitoribosomal proteins (MRPs) and a mito-specific segment of EF-G1mt in mitochondrial tRNA (tRNAmt) translocation. In particular, the mito-specific C-terminal extension in EF-G1mt is directly involved in translocation of the acceptor arm of the A-site tRNAmt. In addition to the ratchet-like and independent head-swiveling motions exhibited by the small mitoribosomal subunit, we discover significant conformational changes in MRP mL45 at the nascent polypeptide-exit site within the large mitoribosomal subunit that could be critical for tethering of the elongating mitoribosome onto the inner-mitochondrial membrane.
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MESH Headings
- Amino Acid Sequence
- Binding Sites
- Cryoelectron Microscopy
- HEK293 Cells
- Humans
- Mitochondria/metabolism
- Mitochondria/ultrastructure
- Mitochondrial Membranes/metabolism
- Mitochondrial Membranes/ultrastructure
- Mitochondrial Proteins/chemistry
- Mitochondrial Proteins/genetics
- Mitochondrial Proteins/metabolism
- Models, Molecular
- Nucleic Acid Conformation
- Peptide Chain Elongation, Translational
- Peptide Elongation Factor G/chemistry
- Peptide Elongation Factor G/genetics
- Peptide Elongation Factor G/metabolism
- Protein Binding
- Protein Conformation, alpha-Helical
- Protein Conformation, beta-Strand
- Protein Interaction Domains and Motifs
- RNA, Mitochondrial/chemistry
- RNA, Mitochondrial/genetics
- RNA, Mitochondrial/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Ribosomal Proteins/chemistry
- Ribosomal Proteins/genetics
- Ribosomal Proteins/metabolism
- Ribosomes/metabolism
- Ribosomes/ultrastructure
- Sequence Alignment
- Sequence Homology, Amino Acid
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Affiliation(s)
- Ravi Kiran Koripella
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA
| | - Manjuli R Sharma
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA
| | - Kalpana Bhargava
- Department of Chemistry, Campus Box 3290, University of North Carolina, Chapel Hill, NC, USA
- High Energy Material Research Lab, Defense Research and Development Organization, Sutarwadi, Pashan, Pune, Maharashtra, 411021, India
| | - Partha P Datta
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
| | - Prem S Kaushal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, PO Box # 3, Faridabad, Haryana, 121001, India
| | - Pooja Keshavan
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA
| | - Linda L Spremulli
- Department of Chemistry, Campus Box 3290, University of North Carolina, Chapel Hill, NC, USA
| | - Nilesh K Banavali
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA
- Department of Biomedical Sciences, University at Albany, SUNY, Albany, NY, 12201-0509, USA
| | - Rajendra K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA.
- Department of Biomedical Sciences, University at Albany, SUNY, Albany, NY, 12201-0509, USA.
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13
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Wang R, Zhu Y, Ren C, Yang S, Tian S, Chen H, Jin M, Zhou H. Influenza A virus protein PB1-F2 impairs innate immunity by inducing mitophagy. Autophagy 2020; 17:496-511. [PMID: 32013669 DOI: 10.1080/15548627.2020.1725375] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Influenza A virus (IAV) infection induces mitophagy, which is essential for the clearance of damaged mitochondria. Dysfunctional mitochondria can be selectively targeted by PINK1, which recruits PRKN/PARK2 and leads to subsequent mitochondrial sequestration within autophagosomes. The IAV PB1-F2 protein translocates to mitochondria, accelerates the mitochondrial fragmentation and impairs the innate immunity. However, whether PB1-F2 mediates IAV-induced mitophagy and the relation between mitophagy and PB1-F2-attenuated innate immunity remain obscure. Here, we showed that PB1-F2 translocated to mitochondria by interacting and colocalizing with TUFM (Tu translation elongation factor, mitochondrial). Further studies revealed that PB1-F2 induced complete mitophagy, which required the interactions of PB1-F2 with both TUFM and MAP1LC3B/LC3B that mediated the autophagosome formation. PB1-F2-induced mitophagy was critical for the MAVS (mitochondrial antiviral signaling protein) degradation and led to its suppression of the type I IFN production. Importantly, the C-terminal LIR motif of PB1-F2 protein was demonstrated to be essential for its mitophagy induction and attenuated innate immunity. In conclusion, PB1-F2-induced mitophagy strongly correlates with impaired cellular innate immunity, revealing it is a potential therapeutic target.Abbreviations: BCL2L13: BCL2 like 13; BECN1: beclin 1; BNIP3L/Nix: BCL2 interacting protein 3 like; CQ: chloroquine; DDX58: DExD/H-box helicase 58; eGFP: enhanced green fluorescent protein; hpi: hours post infection; IAV: influenza A virus; IFN: interferon; IP: immunoprecipitation; LIR: LC3-interacting region; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAVS: mitochondrial antiviral signaling protein; MMP: mitochondrial membrane potential; MOI, multiplicity of infection; mRFP: monomeric red fluorescent protein; NBR1: NBR1 autophagy cargo receptor; NC: negative control; NLRP3: NLR family pyrin domain containing 3; PINK1: PTEN induced kinase 1; PRKN/PARK2: parkin RBR E3 ubiquitin protein ligase; RLR: RIG-I-like-receptor; ROS: reactive oxygen species; SEV: sendai virus; SQSTM1/p62: sequestosome 1; TAX1BP1: Tax1 binding protein 1; TM: transmembrane; TOMM20/40: translocase of outer mitochondrial membrane 20/40; TUFM: Tu translation elongation factor, mitochondrial.
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Affiliation(s)
- Ruifang Wang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Yinxing Zhu
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Chenwei Ren
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Shuaike Yang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Shan Tian
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Huanchun Chen
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Meilin Jin
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Hongbo Zhou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
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14
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Structural insights into unique features of the human mitochondrial ribosome recycling. Proc Natl Acad Sci U S A 2019; 116:8283-8288. [PMID: 30962385 PMCID: PMC6486771 DOI: 10.1073/pnas.1815675116] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Mammalian mitochondrial ribosomes (mitoribosomes) are responsible for synthesizing proteins that are essential for oxidative phosphorylation (ATP generation). Despite their common ancestry with bacteria, the composition and structure of the human mitoribosome and its translational factors are significantly different from those of their bacterial counterparts. The mammalian mitoribosome recycling factor (RRFmt) carries a mito-specific N terminus extension (NTE), which is necessary for the function of RRFmt Here we present a 3.9-Å resolution cryo-electron microscopic (cryo-EM) structure of the human 55S mitoribosome-RRFmt complex, which reveals α-helix and loop structures for the NTE that makes multiple mito-specific interactions with functionally critical regions of the mitoribosome. These include ribosomal RNA segments that constitute the peptidyl transferase center (PTC) and those that connect PTC with the GTPase-associated center and with mitoribosomal proteins L16 and L27. Our structure reveals the presence of a tRNA in the pe/E position and a rotation of the small mitoribosomal subunit on RRFmt binding. In addition, we observe an interaction between the pe/E tRNA and a mito-specific protein, mL64. These findings help understand the unique features of mitoribosome recycling.
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15
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Affiliation(s)
- Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden;
| | - Alexey Amunts
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden;
- Science for Life Laboratory, Stockholm University, SE-171 21 Solna, Sweden;
| | - Alan Brown
- Laboratory of Molecular Biology, Medical Research Council, Cambridge CB2 0QH, United Kingdom;
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16
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Suematsu T, Watanabe O, Kita K, Yokobori SI, Watanabe YI. Arabidopsis thaliana mitochondrial EF-G1 functions in two different translation steps. J Biochem 2013; 155:107-14. [PMID: 24272752 DOI: 10.1093/jb/mvt105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Translation elongation factor G (EF-G) in bacteria catalyses the translocation of transfer RNA on ribosomes in the elongation step as well as dissociation of post-termination state ribosomes into two subunits in the recycling step. In contrast, the dual functions of EF-G are exclusively divided into two different paralogues in human mitochondria, named EF-G1mt for translocation and EF-G2mt for ribosomal dissociation. Many of the two eukaryotic EF-G paralogues are phylogenetically associated with EF-G1mt and EF-G2mt groups. However, plant paralogues are associated with EF-G1mt and plastid EF-G, not with EF-G2mt. In this study, we phylogenetically and biochemically characterized Arabidopsis thaliana EF-G1mt (AtEF-G1mt) to clarify the factor responsible for the dissociation of ribosomes in plant mitochondria. We showed that eukaryotic EF-G1mts form one monophyletic group separated from bacterial EF-G and are classified into five sister groups. AtEF-G1mt is classified into a different group from its human counterpart. We also demonstrated that AtEF-G1mt catalyses both translocation and ribosomal dissociation, unlike in humans. Meanwhile, AtEF-G1mt is resistant to fusidic acid, an inhibitor of bacterial EF-G. Here, we propose that the functional division is not necessarily conserved among mitochondriate eukaryotes and also that EF-G1mt in organisms lacking EF-G2mt functions in two steps, similar to conventional bacterial EF-G.
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Affiliation(s)
- Takuma Suematsu
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, and Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji-shi, Tokyo 192-0392, Japan
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17
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Palmer SO, Rangel EY, Hu Y, Tran AT, Bullard JM. Two homologous EF-G proteins from Pseudomonas aeruginosa exhibit distinct functions. PLoS One 2013; 8:e80252. [PMID: 24260360 PMCID: PMC3832671 DOI: 10.1371/journal.pone.0080252] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 10/11/2013] [Indexed: 11/28/2022] Open
Abstract
Genes encoding two proteins corresponding to elongation factor G (EF-G) were cloned from Pseudomonas aeruginosa. The proteins encoded by these genes are both members of the EFG I subfamily. The gene encoding one of the forms of EF-G is located in the str operon and the resulting protein is referred to as EF-G1A while the gene encoding the other form of EF-G is located in another part of the genome and the resulting protein is referred to as EF-G1B. These proteins were expressed and purified to 98% homogeneity. Sequence analysis indicated the two proteins are 90/84% similar/identical. In other organisms containing multiple forms of EF-G a lower degree of similarity is seen. When assayed in a poly(U)-directed poly-phenylalanine translation system, EF-G1B was 75-fold more active than EF-G1A. EF-G1A pre-incubate with ribosomes in the presence of the ribosome recycling factor (RRF) decreased polymerization of poly-phenylalanine upon addition of EF-G1B in poly(U)-directed translation suggesting a role for EF-G1A in uncoupling of the ribosome into its constituent subunits. Both forms of P. aeruginosa EF-G were active in ribosome dependent GTPase activity. The kinetic parameters (KM) for the interaction of EF-G1A and EF-G1B with GTP were 85 and 70 μM, respectively. However, EF-G1B exhibited a 5-fold greater turnover number (observed kcat) for the hydrolysis of GTP than EF-G1A; 0.2 s-1 vs. 0.04 s-1. These values resulted in specificity constants (kcatobs/KM) for EF-G1A and EF-G1B of 0.5 x 103 s-1 M-1 and 3.0 x 103 s-1 M-1, respectively. The antibiotic fusidic acid (FA) completely inhibited poly(U)-dependent protein synthesis containing P. aeruginosa EF-G1B, but the same protein synthesis system containing EF-G1A was not affected. Likewise, the activity of EF-G1B in ribosome dependent GTPase assays was completely inhibited by FA, while the activity of EF-G1A was not affected.
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Affiliation(s)
- Stephanie O. Palmer
- The University of Texas-Pan American, Edinburg, Texas, United States of America
| | - Edna Y. Rangel
- The University of Texas-Pan American, Edinburg, Texas, United States of America
| | - Yanmei Hu
- The University of Texas-Pan American, Edinburg, Texas, United States of America
| | - Alexis T. Tran
- The University of Texas-Pan American, Edinburg, Texas, United States of America
| | - James M. Bullard
- The University of Texas-Pan American, Edinburg, Texas, United States of America
- * E-mail:
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18
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Gupta A, Mir SS, Saqib U, Biswas S, Vaishya S, Srivastava K, Siddiqi MI, Habib S. The effect of fusidic acid on Plasmodium falciparum elongation factor G (EF-G). Mol Biochem Parasitol 2013; 192:39-48. [PMID: 24211494 DOI: 10.1016/j.molbiopara.2013.10.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 10/29/2013] [Accepted: 10/29/2013] [Indexed: 11/30/2022]
Abstract
Inhibition of growth of the malaria parasite Plasmodium falciparum by known translation-inhibitory antibiotics has generated interest in understanding their action on the translation apparatus of the two genome containing organelles of the malaria parasite: the mitochondrion and the relic plastid (apicoplast). We report GTPase activity of recombinant EF-G proteins that are targeted to the organelles and further use these to test the effect of the EF-G inhibitor fusidic acid (FA) on the factor-ribosome interface. Our results monitoring locking of EF-G·GDP onto surrogate Escherichia coli ribosomes as well as multi-turnover GTP hydrolysis by the factor indicate that FA has a greater effect on apicoplast EF-G compared to the mitochondrial counterpart. Deletion of a three amino acid (GVG) sequence in the switch I loop that is conserved in proteins of the mitochondrial EF-G1 family and the Plasmodium mitochondrial factor, but is absent in apicoplast EF-G, demonstrated that this motif contributes to differential inhibition of the two EF-Gs by FA. Additionally, the drug thiostrepton, that is known to target the apicoplast and proteasome, enhanced retention of only mitochondrial EF-G on ribosomes providing support for the reported effect of the drug on parasite mitochondrial translation.
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Affiliation(s)
- Ankit Gupta
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Snober S Mir
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Uzma Saqib
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Subir Biswas
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Suniti Vaishya
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Kumkum Srivastava
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Mohammad Imran Siddiqi
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India
| | - Saman Habib
- Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India.
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19
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Abstract
Mitochondrial genome contains 13 protein coding genes, all being part of the oxidative phosphorylation complexes. The process of translation of these protein coding mRNAs in mitochondrial matrix is a good miniature model of translation in cytoplasm. In this work, we have simulated three phases of mitochondrial translation viz. initiation, elongation and termination (including ribosome recycling). The kinetic equations for these phases have been deduced based on the information available in literature. Various factors involved in the process have been included explicitly. Kinetic simulation was done using Octave, open source software. Scripts were written individually for each phase. Initiation begins with mitoribosome, mRNA, fMet-tRNA and initiation factors. The final product of the initiation script, the initiation complex, was introduced as the start point in the successive step, i.e. elongation. Elongation is a particular extensive process where the various aminoacyl-tRNAs already present in the matrix check for matching with the triplet codon in A-site of mitoribosome. This script consists of two parts: one with the time behaviour of the factors involved in the molecular process (using ordinary differential equation solver) and the other including the reading of triplet codon on the mRNA and incorporating the corresponding aminoacyl-tRNA, and then at each step elongating the peptide chain (using loops and conditions). The peptide chain thus formed in the elongation step (in the loops and conditions segment) was released in the termination step. This was followed by mitoribosome recycling where the mitoribosome reached the native state and was ready for the next cycle of translation.
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Affiliation(s)
- Kalyani Korla
- a Department of Biochemistry, School of Life Sciences, University of Hyderabad , Hyderabad , 500046 , India
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20
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Lei Y, Wen H, Yu Y, Taxman DJ, Zhang L, Widman DG, Swanson KV, Wen KW, Damania B, Moore CB, Giguère PM, Siderovski DP, Hiscott J, Razani B, Semenkovich CF, Chen X, Ting JPY. The mitochondrial proteins NLRX1 and TUFM form a complex that regulates type I interferon and autophagy. Immunity 2012; 36:933-46. [PMID: 22749352 DOI: 10.1016/j.immuni.2012.03.025] [Citation(s) in RCA: 229] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 02/17/2012] [Accepted: 03/31/2012] [Indexed: 12/16/2022]
Abstract
The mitochondrial protein MAVS (also known as IPS-1, VISA, and CARDIF) interacts with RIG-I-like receptors (RLRs) to induce type I interferon (IFN-I). NLRX1 is a mitochondrial nucleotide-binding, leucine-rich repeats (NLR)-containing protein that attenuates MAVS-RLR signaling. Using Nlrx1(-/-) cells, we confirmed that NLRX1 attenuated IFN-I production, but additionally promoted autophagy during viral infection. This dual function of NLRX1 paralleled the previously described functions of the autophagy-related proteins Atg5-Atg12, but NLRX1 did not associate with Atg5-Atg12. High-throughput quantitative mass spectrometry and endogenous protein-protein interaction revealed an NLRX1-interacting partner, mitochondrial Tu translation elongation factor (TUFM). TUFM interacted with Atg5-Atg12 and Atg16L1 and has similar functions as NLRX1 by inhibiting RLR-induced IFN-I but promoting autophagy. In the absence of NLRX1, increased IFN-I and decreased autophagy provide an advantage for host defense against vesicular stomatitis virus. This study establishes a link between an NLR protein and the viral-induced autophagic machinery via an intermediary partner, TUFM.
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Affiliation(s)
- Yu Lei
- The Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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21
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Christian BE, Spremulli LL. Mechanism of protein biosynthesis in mammalian mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:1035-54. [PMID: 22172991 DOI: 10.1016/j.bbagrm.2011.11.009] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/03/2011] [Accepted: 11/08/2011] [Indexed: 01/25/2023]
Abstract
Protein synthesis in mammalian mitochondria produces 13 proteins that are essential subunits of the oxidative phosphorylation complexes. This review provides a detailed outline of each phase of mitochondrial translation including initiation, elongation, termination, and ribosome recycling. The roles of essential proteins involved in each phase are described. All of the products of mitochondrial protein synthesis in mammals are inserted into the inner membrane. Several proteins that may help bind ribosomes to the membrane during translation are described, although much remains to be learned about this process. Mutations in mitochondrial or nuclear genes encoding components of the translation system often lead to severe deficiencies in oxidative phosphorylation, and a summary of these mutations is provided. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Brooke E Christian
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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22
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Han MJ, Cimen H, Miller-Lee JL, Koc H, Koc EC. Purification of human mitochondrial ribosomal L7/L12 stalk proteins and reconstitution of functional hybrid ribosomes in Escherichia coli. Protein Expr Purif 2011; 78:48-54. [PMID: 21453772 DOI: 10.1016/j.pep.2011.03.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Revised: 03/04/2011] [Accepted: 03/07/2011] [Indexed: 01/09/2023]
Abstract
Bacterial ribosomal L7/L12 stalk is formed by L10, L11, and multiple copies of L7/L12, which plays an essential role in recruiting initiation and elongation factors during translation. The homologs of these proteins, MRPL10, MRPL11, and MRPL12, are present in human mitochondrial ribosomes. To evaluate the role of MRPL10, MRPL11, and MRPL12 in translation, we over-expressed and purified components of the human mitochondrial L7/L12 stalk proteins in Escherichia coli. Here, we designed a construct to co-express MRPL10 and MRPL12 using a duet expression system to form a functional MRPL10-MRPL12 complex. The goal is to demonstrate the homology between the mitochondrial and bacterial L7/L12 stalk proteins and to reconstitute a hybrid ribosome to be used in structural and functional studies of the mitochondrial stalk.
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Affiliation(s)
- Min-Joon Han
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
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23
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Abstract
Mitochondria are ubiquitous and essential organelles for all nucleated cells of higher eukaryotes. They contain their own genome [mtDNA (mitochondrial DNA)], and this autosomally replicating extranuclear DNA encodes a complement of genes whose products are required to couple oxidative phosphorylation. Sequencing of this human mtDNA more than 20 years ago revealed unusual features that included a modified codon usage. Specific deviations from the standard genetic code include recoding of the conventional UGA stop to tryptophan, and, strikingly, the apparent recoding of two arginine triplets (AGA and AGG) to termination signals. This latter reassignment was made because of the absence of cognate mtDNA-encoded tRNAs, and a lack of tRNAs imported from the cytosol. Each of these codons only occurs once and, in both cases, at the very end of an open reading frame. The presence of both AGA and AGG is rarely found in other mammals, and the molecular mechanism that has driven the change from encoding arginine to dictating a translational stop has posed a challenging conundrum. Mitochondria from the majority of other organisms studied use only UAA and UAG, leaving the intriguing question of why human organelles appear to have added the complication of a further two stop codons, AGA and AGG, or have they? In the present review, we report recent data to show that mammalian mitochondria can utilize a -1 frameshift such that only the standard UAA and UAG stop codons are required to terminate the synthesis of all 13 polypeptides.
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Atkinson GC, Baldauf SL. Evolution of elongation factor G and the origins of mitochondrial and chloroplast forms. Mol Biol Evol 2010; 28:1281-92. [PMID: 21097998 DOI: 10.1093/molbev/msq316] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Protein synthesis elongation factor G (EF-G) is an essential protein with central roles in both the elongation and ribosome recycling phases of protein synthesis. Although EF-G evolution is predicted to be conservative, recent reports suggest otherwise. We have characterized EF-G in terms of its molecular phylogeny, genomic context, and patterns of amino acid substitution. We find that most bacteria carry a single "canonical" EF-G, which is phylogenetically conservative and encoded in an str operon. However, we also find a number of EF-G paralogs. These include a pair of EF-Gs that are mostly found together and in an eclectic subset of bacteria, specifically δ-proteobacteria, spirochaetes, and planctomycetes (the "spd" bacteria). These spdEFGs have also given rise to the mitochondrial factors mtEFG1 and mtEFG2, which probably arrived in eukaryotes before the eukaryotic last common ancestor. Meanwhile, chloroplasts apparently use an α-proteobacterial-derived EF-G rather than the expected cyanobacterial form. The long-term comaintenance of the spd/mtEFGs may be related to their subfunctionalization for translocation and ribosome recycling. Consistent with this, patterns of sequence conservation and site-specific evolutionary rate shifts suggest that the faster evolving spd/mtEFG2 has lost translocation function, but surprisingly, the protein also shows little conservation of sites related to recycling activity. On the other hand, spd/mtEFG1, although more slowly evolving, shows signs of substantial remodeling. This is particularly extensive in the GTPase domain, including a highly conserved three amino acid insertion in switch I. We suggest that subfunctionalization of the spd/mtEFGs is not a simple case of specialization for subsets of original activities. Rather, the duplication allows the release of one paralog from the selective constraints imposed by dual functionality, thus allowing it to become more highly specialized. Thus, the potential for fine tuning afforded by subfunctionalization may explain the maintenance of EF-G paralogs.
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Affiliation(s)
- Gemma C Atkinson
- Department of Systematic Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
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25
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Koc E, Haque M, Spremulli L. Current Views of the Structure of the Mammalian Mitochondrial Ribosome. Isr J Chem 2010. [DOI: 10.1002/ijch.201000002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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26
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Mitochondrial translation and beyond: processes implicated in combined oxidative phosphorylation deficiencies. J Biomed Biotechnol 2010; 2010:737385. [PMID: 20396601 PMCID: PMC2854570 DOI: 10.1155/2010/737385] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Accepted: 01/29/2010] [Indexed: 12/22/2022] Open
Abstract
Mitochondrial disorders are a heterogeneous group of often multisystemic and early fatal diseases, which are amongst the most common inherited human diseases. These disorders are caused by defects in the oxidative phosphorylation (OXPHOS) system, which comprises five multisubunit enzyme complexes encoded by both the nuclear and the mitochondrial genomes. Due to the multitude of proteins and intricacy of the processes required for a properly functioning OXPHOS system, identifying the genetic defect that underlies an OXPHOS deficiency is not an easy task, especially in the case of combined OXPHOS defects. In the present communication we give an extensive overview of the proteins and processes (in)directly involved in mitochondrial translation and the biogenesis of the OXPHOS system and their roles in combined OXPHOS deficiencies. This knowledge is important for further research into the genetic causes, with the ultimate goal to effectively prevent and cure these complex and often devastating disorders.
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27
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Suematsu T, Yokobori SI, Morita H, Yoshinari S, Ueda T, Kita K, Takeuchi N, Watanabe YI. A bacterial elongation factor G homologue exclusively functions in ribosome recycling in the spirochaete Borrelia burgdorferi. Mol Microbiol 2010; 75:1445-54. [PMID: 20132446 DOI: 10.1111/j.1365-2958.2010.07067.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Translation elongation factor G (EF-G) in bacteria plays two distinct roles in different phases of the translation system. EF-G catalyses the translocation of tRNAs on the ribosome in the elongation step, as well as the dissociation of the post-termination state ribosome into two subunits in the recycling step. In contrast to this conventional view, it has very recently been demonstrated that the dual functions of bacterial EF-G are distributed over two different EF-G paralogues in human mitochondria. In the present study, we show that the same division of roles of EF-G is also found in bacteria. Two EF-G paralogues are found in the spirochaete Borrelia burgdorferi, EF-G1 and EF-G2. We demonstrate that EF-G1 is a translocase, while EF-G2 is an exclusive recycling factor. We further demonstrate that B. burgdorferi EF-G2 does not require GTP hydrolysis for ribosome disassembly, provided that translation initiation factor 3 (IF-3) is present in the reaction. These results indicate that two B. burgdorferi EF-G paralogues are close relatives to mitochondrial EF-G paralogues rather than the conventional bacterial EF-G, in both their phylogenetic and biochemical features.
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Affiliation(s)
- Takuma Suematsu
- Department of Biomedical Chemistry, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan
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28
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Miller JL, Cimen H, Koc H, Koc EC. Phosphorylated proteins of the mammalian mitochondrial ribosome: implications in protein synthesis. J Proteome Res 2010; 8:4789-98. [PMID: 19702336 DOI: 10.1021/pr9004844] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mitochondria, the powerhouse of eukaryotic cells, have their own translation machinery that is solely responsible for synthesis of 13 mitochondrially encoded protein subunits of oxidative phosphorylation complexes. Phosphorylation is a well-known post-translational modification in regulation of many processes in mammalian mitochondria including oxidative phosphorylation. However, there is still very limited knowledge on phosphorylation of mitochondrial ribosomal proteins and their role(s) in ribosome function. In this study, we have identified the mitochondrial ribosomal proteins that are phosphorylated at serine, threonine or tyrosine residues. Twenty-four phosphorylated proteins were visualized by phosphorylation-specific techniques including in vitro radiolabeling, residue specific antibodies for phosphorylated residues, or ProQ phospho dye and identified by tandem mass spectrometry. Translation assays with isolated ribosomes that were phosphorylated in vitro by kinases PKA, PKCdelta, or Abl Tyr showed up to 30% inhibition due to phosphorylation. Findings from this study should serve as the framework for future studies addressing the regulation mechanisms of mitochondrial translation machinery by phosphorylation and other post-translational modifications.
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Affiliation(s)
- Jennifer L Miller
- Department of Biochemistry & Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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29
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Tsuboi M, Morita H, Nozaki Y, Akama K, Ueda T, Ito K, Nierhaus KH, Takeuchi N. EF-G2mt is an exclusive recycling factor in mammalian mitochondrial protein synthesis. Mol Cell 2009; 35:502-10. [PMID: 19716793 DOI: 10.1016/j.molcel.2009.06.028] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 05/04/2009] [Accepted: 06/18/2009] [Indexed: 11/30/2022]
Abstract
Bacterial translation elongation factor G (EF-G) catalyzes translocation during peptide elongation and mediates ribosomal disassembly during ribosome recycling in concert with the ribosomal recycling factor (RRF). Two homologs of EF-G have been identified in mitochondria from yeast to man, EF-G1mt and EF-G2mt. Here, we demonstrate that the dual function of bacterial EF-G is divided between EF-G1mt and EF-G2mt in human mitochondria (RRFmt). EF-G1mt specifically catalyzes translocation, whereas EF-G2mt mediates ribosome recycling with human mitochondrial RRF but lacks translocation activity. Domain swapping experiments suggest that the functional specificity for EF-G2mt resides in domains III and IV. Furthermore, GTP hydrolysis by EF-G2mt is not necessary for ribosomal splitting, in contrast to the bacterial-recycling mode. Because EF-G2mt represents a class of translational GTPase that is involved in ribosome recycling, we propose to rename this factor mitochondrial ribosome recycling factor 2 (RRF2mt).
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Affiliation(s)
- Masafumi Tsuboi
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
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30
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Antibiotic effects on mitochondrial translation and in patients with mitochondrial translational defects. Mitochondrion 2009; 9:429-37. [PMID: 19671450 DOI: 10.1016/j.mito.2009.08.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 07/08/2009] [Accepted: 08/04/2009] [Indexed: 11/20/2022]
Abstract
The infantile presentation of mitochondrial respiratory chain defects frequently simulates acute bacterial infection and sepsis. Consequently, broad spectrum antibiotic therapy is often initiated before definitive diagnosis is reached and without taking into consideration the potential harm of antibiotics affecting mitochondrial translation. Here, we demonstrate that some commonly used translation-targeted antibiotics adversely affect the growth of fibroblasts from patients with defective mitochondrial translation systems. In addition, we show that these antibiotics inhibit mitochondrial translation in vitro. Our results suggest that patients with mitochondrial translation defects may be more vulnerable to toxic-side-effects following the administration of certain translation-targeted antibiotics.
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31
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Sissler M, Lorber B, Messmer M, Schaller A, Pütz J, Florentz C. Handling mammalian mitochondrial tRNAs and aminoacyl-tRNA synthetases for functional and structural characterization. Methods 2008; 44:176-89. [PMID: 18241799 DOI: 10.1016/j.ymeth.2007.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 11/07/2007] [Accepted: 11/07/2007] [Indexed: 10/22/2022] Open
Abstract
The mammalian mitochondrial (mt) genome codes for only 13 proteins, which are essential components in the process of oxidative phosphorylation of ADP into ATP. Synthesis of these proteins relies on a proper mt translation machinery. While 22 tRNAs and 2 rRNAs are also coded by the mt genome, all other factors including the set of aminoacyl-tRNA synthetases (aaRSs) are encoded in the nucleus and imported. Investigation of mammalian mt aminoacylation systems (and mt translation in general) gains more and more interest not only in regard of evolutionary considerations but also with respect to the growing number of diseases linked to mutations in the genes of either mt-tRNAs, synthetases or other factors. Here we report on methodological approaches for biochemical, functional, and structural characterization of human/mammalian mt-tRNAs and aaRSs. Procedures for preparation of native and in vitro transcribed tRNAs are accompanied by recommendations for specific handling of tRNAs incline to structural instability and chemical fragility. Large-scale preparation of mg amounts of highly soluble recombinant synthetases is a prerequisite for structural investigations that requires particular optimizations. Successful examples leading to crystallization of four mt-aaRSs and high-resolution structures are recalled and limitations discussed. Finally, the need for and the state-of-the-art in setting up an in vitro mt translation system are emphasized. Biochemical characterization of a subset of mammalian aminoacylation systems has already revealed a number of unprecedented peculiarities of interest for the study of evolution and forensic research. Further efforts in this field will certainly be rewarded by many exciting discoveries.
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Affiliation(s)
- Marie Sissler
- Architecture et Réactivité de l'ARN, Université Louis Pasteur de Strasbourg, CNRS, IBMC, 15 rue René Descartes, 67084 Strasbourg, France.
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32
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Ruggiero I, Raimo G, Palma M, Arcari P, Masullo M. Molecular and functional properties of the psychrophilic elongation factor G from the Antarctic Eubacterium Pseudoalteromonas haloplanktis TAC 125. Extremophiles 2007; 11:699-709. [PMID: 17541754 DOI: 10.1007/s00792-007-0088-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Accepted: 04/17/2007] [Indexed: 11/25/2022]
Abstract
The molecular and functional properties of the elongation factor (EF) G from the psychrophilic Antarctic eubacterium Pseudoalteromonas haloplanktis (Ph) were studied. PhEF-G catalyzed protein synthesis in vitro that was inhibited by fusidic acid, an antibiotic specifically acting on EF-G. The EF interacted with GDP only in the presence of P. haloplanktis ribosome and fusidic acid with an affinity similar to that displayed by Escherichia coli EF-G. The psychrophilic translocase elicited a ribosome-dependent GTPase that was competitively inhibited by GDP, the slowly hydrolyzable GTP analog GppNHp, and the protein synthesis inhibitor ppGDP. The temperature dependence of the activity of PhEF-G reached its maximum at least 26 degrees C beyond the growth temperature of P. haloplanktis (4-20 degrees C). The heat inactivation profile of the ribosome-dependent GTPase of PhEF-G gave a temperature for half inactivation (46 degrees C), significantly lower than that for half denaturation measured by either UV- (57 degrees C) or fluorescence-melting (62 degrees C). This finding was attributed to a different effect of the temperature on the catalytic domain with respect to that elicited on the other domains constituting the EF, thus confirming the differential molecular flexibility present in psychrophilic enzymes. A molecular model, based on the 3D coordinates of a thermophilic EF-G, showed differences only in connecting loops.
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Affiliation(s)
- Immacolata Ruggiero
- Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli Federico II, Via S. Pansini 5, 80131, Naples, Italy
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33
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Grasso DG, Christian BE, Spencer A, Spremulli LL. Overexpression and purification of mammalian mitochondrial translational initiation factor 2 and initiation factor 3. Methods Enzymol 2007; 430:59-78. [PMID: 17913635 DOI: 10.1016/s0076-6879(07)30004-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Two mammalian mitochondrial initiation factors have been identified. Initiation factor 2 (IF2(mt)) selects the initiator tRNA (fMet-tRNA) and promotes its binding to the ribosome. Initiation factor 3 (IF3(mt)) promotes the dissociation of the 55S mitochondrial ribosome into subunits and may play additional, less-well-understood, roles in initiation complex formation. Native bovine IF2(mt) was purified from liver a number of years ago. The yield of this factor is very low making biochemical studies difficult. The cDNA for bovine IF2(mt) was expressed in Escherichia coli under the control of the T7 polymerase promoter in a vector that provides a His(6)-tag at the C-terminus of the expressed protein. This factor was expressed in E. coli and purified by chromatography on Ni-NTA resins. The expressed protein has a number of degradation products in partially purified preparations and this factor is then further purified by high-performance liquid chromatography or gravity chromatography on anion exchange resins. IF3(mt) has never been purified from any mammalian system. However, the cDNA for this protein can be identified in the expressed sequence tag (EST) libraries. The portion of the sequence encoding the region of human IF3(mt) predicted to be present in the mitochondrially imported form of this factor was cloned and expressed in E. coli using a vector that provides a C-terminal His(6)-tag. The tagged factor is partially purified on Ni-NTA resins. However, a major proteolytic fragment arising from a defined cleavage of this protein is present in these preparations. This contaminant can be removed by a single step of high-performance liquid chromatography on a cation exchange resin. Alternatively, the mature form of IF3(mt) can be purified by two sequential passes through a gravity S-Sepharose column.
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Affiliation(s)
- Domenick G Grasso
- Department of Chemistry, University of North Carolina at Chapel Hill, USA
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