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Box JM, Higgins ME, Stuart RA. Importance of conserved hydrophobic pocket region in yeast mitoribosomal mL44 protein for mitotranslation and transcript preference. J Biol Chem 2024; 300:107519. [PMID: 38950860 PMCID: PMC11345376 DOI: 10.1016/j.jbc.2024.107519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 06/14/2024] [Accepted: 06/19/2024] [Indexed: 07/03/2024] Open
Abstract
The mitochondrial ribosome (mitoribosome) is responsible for the synthesis of key oxidative phosphorylation subunits encoded by the mitochondrial genome. Defects in mitoribosomal function therefore can have serious consequences for the bioenergetic capacity of the cell. Mutation of the conserved mitoribosomal mL44 protein has been directly linked to childhood cardiomyopathy and progressive neurophysiology issues. To further explore the functional significance of the mL44 protein in supporting mitochondrial protein synthesis, we have performed a mutagenesis study of the yeast mL44 homolog, the MrpL3/mL44 protein. We specifically investigated the conserved hydrophobic pocket region of the MrpL3/mL44 protein, where the known disease-related residue in the human mL44 protein (L156R) is located. While our findings identify a number of residues in this region critical for MrpL3/mL44's ability to support the assembly of translationally active mitoribosomes, the introduction of the disease-related mutation into the equivalent position in the yeast protein (residue A186) was found to not have a major impact on function. The human and yeast mL44 proteins share many similarities in sequence and structure; however results presented here indicate that these two proteins have diverged somewhat in evolution. Finally, we observed that mutation of the MrpL3/mL44 does not impact the translation of all mitochondrial encoded proteins equally, suggesting the mitochondrial translation system may exhibit a transcript hierarchy and prioritization.
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Affiliation(s)
- Jodie M Box
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - Margo E Higgins
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, USA
| | - Rosemary A Stuart
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, USA.
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2
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Kohler A, Carlström A, Nolte H, Kohler V, Jung SJ, Sridhara S, Tatsuta T, Berndtsson J, Langer T, Ott M. Early fate decision for mitochondrially encoded proteins by a molecular triage. Mol Cell 2023; 83:3470-3484.e8. [PMID: 37751741 DOI: 10.1016/j.molcel.2023.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 07/12/2023] [Accepted: 09/05/2023] [Indexed: 09/28/2023]
Abstract
Folding of newly synthesized proteins poses challenges for a functional proteome. Dedicated protein quality control (PQC) systems either promote the folding of nascent polypeptides at ribosomes or, if this fails, ensure their degradation. Although well studied for cytosolic protein biogenesis, it is not understood how these processes work for mitochondrially encoded proteins, key subunits of the oxidative phosphorylation (OXPHOS) system. Here, we identify dedicated hubs in proximity to mitoribosomal tunnel exits coordinating mitochondrial protein biogenesis and quality control. Conserved prohibitin (PHB)/m-AAA protease supercomplexes and the availability of assembly chaperones determine the fate of newly synthesized proteins by molecular triaging. The localization of these competing activities in the vicinity of the mitoribosomal tunnel exit allows for a prompt decision on whether newly synthesized proteins are fed into OXPHOS assembly or are degraded.
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Affiliation(s)
- Andreas Kohler
- Department of Biochemistry and Biophysics, Stockholm University, 106 91 Stockholm, Sweden; Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Andreas Carlström
- Department of Biochemistry and Biophysics, Stockholm University, 106 91 Stockholm, Sweden
| | - Hendrik Nolte
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Verena Kohler
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria; Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden
| | - Sung-Jun Jung
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 405 30 Gothenburg, Sweden
| | - Sagar Sridhara
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 405 30 Gothenburg, Sweden
| | - Takashi Tatsuta
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Jens Berndtsson
- Department of Biochemistry and Biophysics, Stockholm University, 106 91 Stockholm, Sweden
| | - Thomas Langer
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany.
| | - Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, 106 91 Stockholm, Sweden; Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 405 30 Gothenburg, Sweden.
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3
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Dickinson Q, Aufschnaiter A, Ott M, Meyer JG. Multi-omic integration by machine learning (MIMaL). Bioinformatics 2022; 38:4908-4918. [PMID: 36106996 PMCID: PMC9801967 DOI: 10.1093/bioinformatics/btac631] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 08/17/2022] [Accepted: 09/14/2022] [Indexed: 01/05/2023] Open
Abstract
MOTIVATION Cells respond to environments by regulating gene expression to exploit resources optimally. Recent advances in technologies allow for measuring the abundances of RNA, proteins, lipids and metabolites. These highly complex datasets reflect the states of the different layers in a biological system. Multi-omics is the integration of these disparate methods and data to gain a clearer picture of the biological state. Multi-omic studies of the proteome and metabolome are becoming more common as mass spectrometry technology continues to be democratized. However, knowledge extraction through the integration of these data remains challenging. RESULTS Connections between molecules in different omic layers were discovered through a combination of machine learning and model interpretation. Discovered connections reflected protein control (ProC) over metabolites. Proteins discovered to control citrate were mapped onto known genetic and metabolic networks, revealing that these protein regulators are novel. Further, clustering the magnitudes of ProC over all metabolites enabled the prediction of five gene functions, each of which was validated experimentally. Two uncharacterized genes, YJR120W and YDL157C, were accurately predicted to modulate mitochondrial translation. Functions for three incompletely characterized genes were also predicted and validated, including SDH9, ISC1 and FMP52. A website enables results exploration and also MIMaL analysis of user-supplied multi-omic data. AVAILABILITY AND IMPLEMENTATION The website for MIMaL is at https://mimal.app. Code for the website is at https://github.com/qdickinson/mimal-website. Code to implement MIMaL is at https://github.com/jessegmeyerlab/MIMaL. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Quinn Dickinson
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Computational Biomedicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Andreas Aufschnaiter
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Jesse G Meyer
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Computational Biomedicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
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4
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Zhang M, Guo Y, Su R, Corazzin M, Li J, Huang H, Zhang Y, Yao D, Su L, Zhao L, Jin Y. Effects of physical exercise on muscle metabolism and meat quality characteristics of Mongolian sheep. Food Sci Nutr 2022; 10:1494-1509. [PMID: 35592278 PMCID: PMC9094461 DOI: 10.1002/fsn3.2768] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The objective of this study was to investigate the effects of exercise training on muscle metabolism, fatty acid composition, carcass traits, and meat quality characteristics of Mongolian sheep. Fourteen Mongolian sheep were randomly divided into two groups (7 sheep in each) and placed in two adjacent livestock pens. One group of sheep was kept in the pen (Control [C] group) and the other group of sheep (Training [T] group) were driven away in a field to walk twice a day. The results showed a reduction in pH measured 45 min post mortem, L*, a*, and b* value, intramuscular fat, and carcass length, and an increase in the ultimate pH value and shear force in the meat of T group in comparison with that of C group (p < .050). Also, exercise training moderately affected the fatty acid composition of LT muscle. Compared with C group, the concentrations of myristoleic acid (C14:1) and stearic acid (C18:0) were increased (p < .050), while the concentrations of C20:3 n‐6, neurolic acid (C24:1), and n‐3 polyunsaturated fatty acid (PUFA) were decreased in T group (p < .050). Transcriptome analysis highlighted 621 genes differentially expressed in two groups, including 385 were up‐regulated (e.g., GLUT4 and PGC‐1α) and 236 were down‐regulated (e.g., PLIN1 and ACSL3) in T with respect to C group. Besides, considering these genes, a number of enrichment pathways related to muscle metabolic processes, involving carbohydrate metabolism, lipid metabolism, oxidation reduction process, and muscle tissue development, were highlighted. In conclusion, these results contributed to a better understanding of the possible biological and molecular processes underlying the effects of exercise training on muscle metabolism and meat quality in Mongolian sheep, and provide useful information for contributing to understand the phenotypic and functional differences in meat quality of sheep.
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Affiliation(s)
- Min Zhang
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
| | - Yueying Guo
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
| | - Rina Su
- Inner Mongolia Vocational College of Chemical Engineering Hohhot China
| | - Mirco Corazzin
- Dipartimento di Scienze Animali Università di Udine Italy
| | - Jiale Li
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
| | - Huan Huang
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
| | - Yue Zhang
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
| | - Duo Yao
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
| | - Lin Su
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
| | - Lihua Zhao
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
| | - Ye Jin
- College of Food Science and Engineering Inner Mongolia Agriculture University Hohhot China
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Santos B, Zeng R, Jorge SF, Ferreira-Junior JR, Barrientos A, Barros MH. Functional analyses of mitoribosome 54S subunit devoid of mitochondria-specific protein sequences. Yeast 2022; 39:208-229. [PMID: 34713496 PMCID: PMC8969203 DOI: 10.1002/yea.3678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 10/19/2021] [Accepted: 10/21/2021] [Indexed: 12/17/2022] Open
Abstract
In Saccharomyces cerevisiae, mitoribosomes are composed of a 54S large subunit (mtLSU) and a 37S small subunit (mtSSU). The two subunits altogether contain 73 mitoribosome proteins (MRPs) and two ribosomal RNAs (rRNAs). Although mitoribosomes preserve some similarities with their bacterial counterparts, they have significantly diverged by acquiring new proteins, protein extensions, and new RNA segments, adapting the mitoribosome to the synthesis of highly hydrophobic membrane proteins. In this study, we investigated the functional relevance of mitochondria-specific protein extensions at the C-terminus (C) or N-terminus (N) present in 19 proteins of the mtLSU. The studied mitochondria-specific extensions consist of long tails and loops extending from globular domains that mainly interact with mitochondria-specific proteins and 21S rRNA moieties extensions. The expression of variants devoid of extensions in uL4 (C), uL5 (N), uL13 (N), uL13 (C), uL16 (C), bL17 (N), bL17 (C), bL21 (24), uL22 (N), uL23 (N), uL23 (C), uL24 (C), bL27 (C), bL28 (N), bL28 (C), uL29 (N), uL29 (C), uL30 (C), bL31 (C), and bL32 (C) did not rescue the mitochondrial protein synthesis capacities and respiratory growth of the respective null mutants. On the contrary, the truncated form of the mitoribosome exit tunnel protein uL24 (N) yields a partially functional mitoribosome. Also, the removal of mitochondria-specific sequences from uL1 (N), uL3 (N), uL16 (N), bL9 (N), bL19 (C), uL29 (C), and bL31 (N) did not affect the mitoribosome function and respiratory growth. The collection of mutants described here provides new means to study and evaluate defective assembly modules in the mitoribosome biogenesis process.
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Affiliation(s)
- Barbara Santos
- Departamento de Microbiologia, Universidade de São Paulo, São Paulo, Brazil
| | - Rui Zeng
- Department of Neurology University of Miami Miller School of Medicine, Miami, USA
| | - Sasa F. Jorge
- Departamento de Microbiologia, Universidade de São Paulo, São Paulo, Brazil
| | | | - Antoni Barrientos
- Department of Neurology University of Miami Miller School of Medicine, Miami, USA
| | - Mario H. Barros
- Departamento de Microbiologia, Universidade de São Paulo, São Paulo, Brazil
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6
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Anderson JM, Box JM, Stuart RA. The mitospecific domain of Mrp7 (bL27) supports mitochondrial translation during fermentation and is required for effective adaptation to respiration. Mol Biol Cell 2021; 33:ar7. [PMID: 34731012 PMCID: PMC8886811 DOI: 10.1091/mbc.e21-07-0370] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
We demonstrate here that mitoribosomal protein synthesis, responsible for the synthesis of oxidative phosphorylation (OXPHOS) subunits encoded by mitochondrial genome, occurs at high levels during glycolysis fermentation and in a manner uncoupled from OXPHOS complex assembly regulation. Furthermore, we provide evidence that the mitospecific domain of Mrp7 (bL27), a mitoribosomal component, is required to maintain mitochondrial protein synthesis during fermentation, but is not required under respiration growth conditions. Maintaining mitotranslation under high glucose fermentation conditions also involves Mam33 (p32/gC1qR homolog), a binding partner of Mrp7's mitospecific domain, and together they confer a competitive advantage for a cell's ability to adapt to respiration-based metabolism when glucose becomes limiting. Furthermore, our findings support that the mitoribosome, and specifically the central protuberance (CP) region, may be differentially regulated and/or assembled, under the different metabolic conditions of fermentation and respiration. Based on our findings, we propose the purpose of mitotranslation is not limited to the assembly of OXPHOS complexes, but also plays a role in mitochondrial signaling critical for switching cellular metabolism from a glycolysis- to a respiratory-based state.
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Affiliation(s)
| | - Jodie M Box
- Dept. of Biological Sciences, Marquette University, Milwaukee, WI, USA
| | - Rosemary A Stuart
- Dept. of Biological Sciences, Marquette University, Milwaukee, WI, USA
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7
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Singh AP, Salvatori R, Aftab W, Kohler A, Carlström A, Forne I, Imhof A, Ott M. Molecular Connectivity of Mitochondrial Gene Expression and OXPHOS Biogenesis. Mol Cell 2020; 79:1051-1065.e10. [PMID: 32877643 DOI: 10.1016/j.molcel.2020.07.024] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 07/20/2020] [Accepted: 07/21/2020] [Indexed: 01/05/2023]
Abstract
Mitochondria contain their own gene expression systems, including membrane-bound ribosomes dedicated to synthesizing a few hydrophobic subunits of the oxidative phosphorylation (OXPHOS) complexes. We used a proximity-dependent biotinylation technique, BioID, coupled with mass spectrometry to delineate in baker's yeast a comprehensive network of factors involved in biogenesis of mitochondrial encoded proteins. This mitochondrial gene expression network (MiGENet) encompasses proteins involved in transcription, RNA processing, translation, or protein biogenesis. Our analyses indicate the spatial organization of these processes, thereby revealing basic mechanistic principles and the proteins populating strategically important sites. For example, newly synthesized proteins are directly handed over to ribosomal tunnel exit-bound factors that mediate membrane insertion, co-factor acquisition, or their mounting into OXPHOS complexes in a special early assembly hub. Collectively, the data reveal the connectivity of mitochondrial gene expression, reflecting a unique tailoring of the mitochondrial gene expression system.
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Affiliation(s)
- Abeer Prakash Singh
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden; Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 40530 Gothenburg, Sweden
| | - Roger Salvatori
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden; Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 40530 Gothenburg, Sweden
| | - Wasim Aftab
- BioMedical Center, Faculty of Medicine, Ludwig Maximilians University of Munich, 82152 Planegg-Martinsried, Germany; Graduate School for Quantitative Biosciences (QBM), Ludwig Maximilians University of Munich, 81377 Munich, Germany
| | - Andreas Kohler
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden
| | - Andreas Carlström
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden
| | - Ignasi Forne
- BioMedical Center, Faculty of Medicine, Ludwig Maximilians University of Munich, 82152 Planegg-Martinsried, Germany
| | - Axel Imhof
- BioMedical Center, Faculty of Medicine, Ludwig Maximilians University of Munich, 82152 Planegg-Martinsried, Germany
| | - Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, 10691 Stockholm, Sweden; Department of Medical Biochemistry and Cell Biology, University of Gothenburg, 40530 Gothenburg, Sweden.
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8
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Salvatori R, Kehrein K, Singh AP, Aftab W, Möller-Hergt BV, Forne I, Imhof A, Ott M. Molecular Wiring of a Mitochondrial Translational Feedback Loop. Mol Cell 2020; 77:887-900.e5. [DOI: 10.1016/j.molcel.2019.11.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 09/03/2019] [Accepted: 11/25/2019] [Indexed: 11/16/2022]
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9
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Hillman GA, Henry MF. The yeast protein Mam33 functions in the assembly of the mitochondrial ribosome. J Biol Chem 2019; 294:9813-9829. [PMID: 31053642 DOI: 10.1074/jbc.ra119.008476] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 04/24/2019] [Indexed: 02/04/2023] Open
Abstract
Mitochondrial ribosomes are functionally specialized for the synthesis of several essential inner membrane proteins of the respiratory chain. Although remarkable progress has been made toward understanding the structure of mitoribosomes, the pathways and factors that facilitate their biogenesis remain largely unknown. The long unstructured domains of unassembled ribosomal proteins are highly prone to misfolding and often require dedicated chaperones to prevent aggregation. To date, chaperones that ensure safe delivery to the assembling ribosome have not been identified in the mitochondrion. In this study, a respiratory synthetic lethality screen revealed a role for an evolutionarily conserved mitochondrial matrix protein called Mam33 in Saccharomyces cerevisiae mitoribosome biogenesis. We found that the absence of Mam33 results in misassembled, aggregated ribosomes and a respiratory lethal phenotype in combination with other ribosome-assembly mutants. Using sucrose gradient sedimentation, native affinity purifications, in vitro binding assays, and SILAC-based quantitative proteomics, we found that Mam33 does not associate with the mature mitoribosome, but directly binds a subset of unassembled large subunit proteins. Based on these data, we propose that Mam33 binds specific mitoribosomal proteins to ensure proper assembly.
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Affiliation(s)
- Gabrielle A Hillman
- From the Department of Molecular Biology, Rowan University School of Osteopathic Medicine, Stratford, New Jersey 08084 and.,the Graduate School of Biomedical Sciences, Rowan University, Stratford, New Jersey 08084
| | - Michael F Henry
- From the Department of Molecular Biology, Rowan University School of Osteopathic Medicine, Stratford, New Jersey 08084 and .,the Graduate School of Biomedical Sciences, Rowan University, Stratford, New Jersey 08084
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10
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Corrêa T, Feltes BC, Riegel M. Integrated analysis of the critical region 5p15.3-p15.2 associated with cri-du-chat syndrome. Genet Mol Biol 2019; 42:186-196. [PMID: 30985858 PMCID: PMC6687350 DOI: 10.1590/1678-4685-gmb-2018-0173] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 07/29/2018] [Indexed: 11/21/2022] Open
Abstract
Cri-du-chat syndrome (CdCs) is one of the most common contiguous gene syndromes, with an incidence of 1:15,000 to 1:50,000 live births. To better understand the etiology of CdCs at the molecular level, we investigated theprotein-protein interaction (PPI) network within the critical chromosomal region 5p15.3-p15.2 associated with CdCs using systemsbiology. Data were extracted from cytogenomic findings from patients with CdCs. Based on clinical findings, molecular characterization of chromosomal rearrangements, and systems biology data, we explored possible genotype-phenotype correlations involving biological processes connected with CdCs candidate genes. We identified biological processes involving genes previously found to be associated with CdCs, such as TERT, SLC6A3, and CTDNND2, as well as novel candidate proteins with potential contributions to CdCs phenotypes, including CCT5, TPPP, MED10, ADCY2, MTRR, CEP72, NDUFS6, and MRPL36. Although further functional analyses of these proteins are required, we identified candidate proteins for the development of new multi-target genetic editing tools to study CdCs. Further research may confirm those that are directly involved in the development of CdCs phenotypes and improve our understanding of CdCs-associated molecular mechanisms.
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Affiliation(s)
- Thiago Corrêa
- Post-Graduate Program in Genetics and Molecular Biology,
Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Bruno César Feltes
- Institute of Informatics, Universidade Federal do Rio Grande
do Sul, Porto Alegre, RS, Brazil
| | - Mariluce Riegel
- Post-Graduate Program in Genetics and Molecular Biology,
Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
- Medical Genetics Service, Hospital de Clínicas de Porto
Alegre, Porto Alegre, RS, Brazil
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11
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Möller-Hergt BV, Carlström A, Stephan K, Imhof A, Ott M. The ribosome receptors Mrx15 and Mba1 jointly organize cotranslational insertion and protein biogenesis in mitochondria. Mol Biol Cell 2018; 29:2386-2396. [PMID: 30091672 PMCID: PMC6233058 DOI: 10.1091/mbc.e18-04-0227] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mitochondrial gene expression in Saccharomyces cerevisiae is responsible for the production of highly hydrophobic subunits of the oxidative phosphorylation system. Membrane insertion occurs cotranslationally on membrane-bound mitochondrial ribosomes. Here, by employing a systematic mass spectrometry–based approach, we discovered the previously uncharacterized membrane protein Mrx15 that interacts via a soluble C-terminal domain with the large ribosomal subunit. Mrx15 contacts mitochondrial translation products during their synthesis and plays, together with the ribosome receptor Mba1, an overlapping role in cotranslational protein insertion. Taken together, our data reveal how these ribosome receptors organize membrane protein biogenesis in mitochondria.
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Affiliation(s)
| | - Andreas Carlström
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Katharina Stephan
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Axel Imhof
- Protein Analysis Unit, Biomedical Center, Faculty of Medicine, Ludwig Maximilian University of Munich, DE-82152 Planegg-Martinsried, Germany
| | - Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
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12
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Woogeng IN, Kitakawa M. The C-terminal extension domain of Saccharomyces cerevisiae MrpL32, a homolog of ribosomal protein L32, functions in trans to support mitochondrial translation. Genes Genet Syst 2018; 93:21-24. [PMID: 29343666 DOI: 10.1266/ggs.17-00023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Mitochondrial ribosomal protein L32 (MrpL32) of Saccharomyces cerevisiae is homologous to the bacterial L32 ribosomal protein. MrpL32 carries an N-terminal mitochondrion-targeting sequence (MTS) and is about 60 amino acid residues longer at the C-terminus. Adding to its function as a leader sequence, the MTS of MrpL32 has been reported to regulate ribosome biogenesis through its processing by m-AAA protease. However, the function of the C-terminal extension (CE) remains totally unknown. Therefore, we constructed a series of C-terminally truncated mrpl32 (mrpl32ΔC) genes and expressed them in a Δmrpl32 mutant to examine their function. Interestingly, some MrpL32ΔC derivatives exhibited temperature-sensitive (ts) growth on medium with non-fermentable carbon sources. Furthermore, the CE domain of MrpL32, expressed separately from MrpL32ΔC, could rescue the ts phenotype of mutants by improving mitochondrial protein synthesis.
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13
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Suhm T, Kaimal JM, Dawitz H, Peselj C, Masser AE, Hanzén S, Ambrožič M, Smialowska A, Björck ML, Brzezinski P, Nyström T, Büttner S, Andréasson C, Ott M. Mitochondrial Translation Efficiency Controls Cytoplasmic Protein Homeostasis. Cell Metab 2018; 27:1309-1322.e6. [PMID: 29754951 DOI: 10.1016/j.cmet.2018.04.011] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 02/02/2018] [Accepted: 04/12/2018] [Indexed: 01/02/2023]
Abstract
Cellular proteostasis is maintained via the coordinated synthesis, maintenance, and breakdown of proteins in the cytosol and organelles. While biogenesis of the mitochondrial membrane complexes that execute oxidative phosphorylation depends on cytoplasmic translation, it is unknown how translation within mitochondria impacts cytoplasmic proteostasis and nuclear gene expression. Here we have analyzed the effects of mutations in the highly conserved accuracy center of the yeast mitoribosome. Decreased accuracy of mitochondrial translation shortened chronological lifespan, impaired management of cytosolic protein aggregates, and elicited a general transcriptional stress response. In striking contrast, increased accuracy extended lifespan, improved cytosolic aggregate clearance, and suppressed a normally stress-induced, Msn2/4-dependent interorganellar proteostasis transcription program (IPTP) that regulates genes important for mitochondrial proteostasis. Collectively, the data demonstrate that cytosolic protein homeostasis and nuclear stress signaling are controlled by mitochondrial translation efficiency in an inter-connected organelle quality control network that determines cellular lifespan.
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Affiliation(s)
- Tamara Suhm
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | | | - Hannah Dawitz
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Carlotta Peselj
- Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, SE-10691 Stockholm, Sweden
| | - Anna E Masser
- Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, SE-10691 Stockholm, Sweden
| | - Sarah Hanzén
- Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-413 90 Göteborg, Sweden
| | - Matevž Ambrožič
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Agata Smialowska
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden; National Bioinformatics Infrastructure Sweden (NBIS), Science for Life Laboratory, SE-17165 Solna, Sweden
| | - Markus L Björck
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Peter Brzezinski
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Thomas Nyström
- Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-413 90 Göteborg, Sweden
| | - Sabrina Büttner
- Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, SE-10691 Stockholm, Sweden; Institute of Molecular Biosciences, NAWI Graz, University of Graz, A-8010 Graz, Austria
| | - Claes Andréasson
- Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, SE-10691 Stockholm, Sweden.
| | - Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden.
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14
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Stoldt S, Wenzel D, Kehrein K, Riedel D, Ott M, Jakobs S. Spatial orchestration of mitochondrial translation and OXPHOS complex assembly. Nat Cell Biol 2018; 20:528-534. [PMID: 29662179 DOI: 10.1038/s41556-018-0090-7] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 03/20/2018] [Indexed: 12/11/2022]
Abstract
Oxidative phosphorylation (OXPHOS) is vital for the regeneration of the vast majority of ATP in eukaryotic cells 1 . OXPHOS is carried out by large multi-subunit protein complexes in the cristae membranes, which are invaginations of the mitochondrial inner membrane. The OXPHOS complexes are a mix of subunits encoded in the nuclear and mitochondrial genomes. Thus, the assembly of these dual-origin complexes is an enormous logistical challenge for the cell. Using super-resolution microscopy (nanoscopy) and quantitative cryo-immunogold electron microscopy, we determined where specific transcripts are translated and where distinct assembly steps of the dual-origin complexes in the yeast Saccharomyces cerevisiae occur. Our data indicate that the mitochondrially encoded proteins of complex III and complex IV are preferentially inserted in different sites of the inner membrane than those of complex V. We further demonstrate that the early, but not the late, assembly steps of complex III and complex IV occur preferentially in the inner boundary membrane. By contrast, all steps of complex V assembly occur mainly in the cristae membranes. Thus, OXPHOS complex assembly is spatially well orchestrated, probably representing an unappreciated regulatory layer in mitochondrial biogenesis.
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Affiliation(s)
- Stefan Stoldt
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Dirk Wenzel
- Laboratory of Electron Microscopy, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Kirsten Kehrein
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Dietmar Riedel
- Laboratory of Electron Microscopy, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Stefan Jakobs
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany. .,Department of Neurology, University Medical Center Göttingen, Göttingen, Germany.
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15
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Zeng R, Smith E, Barrientos A. Yeast Mitoribosome Large Subunit Assembly Proceeds by Hierarchical Incorporation of Protein Clusters and Modules on the Inner Membrane. Cell Metab 2018. [PMID: 29514071 PMCID: PMC5951612 DOI: 10.1016/j.cmet.2018.01.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Mitoribosomes are specialized for the synthesis of hydrophobic membrane proteins encoded by mtDNA, all essential for oxidative phosphorylation. Despite their linkage to human mitochondrial diseases and the recent cryoelectron microscopy reconstruction of yeast and mammalian mitoribosomes, how they are assembled remains obscure. Here, we dissected the yeast mitoribosome large subunit (mtLSU) assembly process by systematic genomic deletion of 44 mtLSU proteins (MRPs). Analysis of the strain collection unveiled 37 proteins essential for functional mtLSU assembly, three of which are critical for mtLSU 21S rRNA stability. Hierarchical cluster analysis of mtLSU subassemblies accumulated in mutant strains revealed co-operative assembly of protein sets forming structural clusters and preassembled modules. It also indicated crucial roles for mitochondrion-specific membrane-binding MRPs in anchoring newly transcribed 21S rRNA to the inner membrane, where assembly proceeds. Our results define the yeast mtLSU assembly landscape in vivo and provide a foundation for studies of mitoribosome assembly across evolution.
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Affiliation(s)
- Rui Zeng
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, 1420 NW 9th Ave, Miami, FL 33136, USA
| | - Erin Smith
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, 1420 NW 9th Ave, Miami, FL 33136, USA
| | - Antoni Barrientos
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, 1420 NW 9th Ave, Miami, FL 33136, USA; Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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16
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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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17
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Alfaiz AA, Müller V, Boutry-Kryza N, Ville D, Guex N, de Bellescize J, Rivier C, Labalme A, des Portes V, Edery P, Till M, Xenarios I, Sanlaville D, Herrmann JM, Lesca G, Reymond A. West syndrome caused by homozygous variant in the evolutionary conserved gene encoding the mitochondrial elongation factor GUF1. Eur J Hum Genet 2015; 24:1001-8. [PMID: 26486472 DOI: 10.1038/ejhg.2015.227] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 09/12/2015] [Accepted: 09/18/2015] [Indexed: 12/15/2022] Open
Abstract
West syndrome (WS), defined by the triad of infantile spasms, pathognomonic hypsarrhythmia and developmental regression, is a rare epileptic disease affecting about 1:3500 live births. To get better insights on the genetic of this pathology, we exome-sequenced the members of a consanguineous family affected with isolated WS. We identified a homozygous variant (c.1825G>T/p.(Ala609Ser)) in the GUF1 gene in the three affected siblings. GUF1 encodes a protein essential in conditions that counteract faithful protein synthesis: it is able to remobilize stuck ribosomes and transiently inhibit the elongation process to optimize protein synthesis. The variant identified in the WS family changes an alanine residue conserved in all eukaryotic organisms and positioned within the tRNA-binding moiety of this nuclear genome-encoded mitochondrial translational elongation factor. Yeast complementation assays show that the activity of GUF1(A609S) is modified in suboptimal environments. We suggest a new link between improper assembly of respiratory chain complexes and WS.
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Affiliation(s)
- Ali Abdullah Alfaiz
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, Switzerland.,King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences (KSAU-HS), Riyadh, Saudi Arabia
| | - Verena Müller
- Division of Cell Biology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Nadia Boutry-Kryza
- Department of Constitutional Cytogenetics, Lyon Hospices Civils, Lyon, France.,Claude Bernard Lyon I University, Lyon, France.,CRNL, CNRS UMR 5292, INSERM U1028, Lyon, France
| | - Dorothée Ville
- Center of Reference for Tuberous Sclerosis and Rare Epileptic Disorders, Hospices Civils de Lyon, Lyon, France
| | - Nicolas Guex
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, Switzerland
| | | | - Clotilde Rivier
- Department of Pediatrics, Hopital Nord-Ouest, Villefranche-sur-Saône, France
| | - Audrey Labalme
- Department of Constitutional Cytogenetics, Lyon Hospices Civils, Lyon, France
| | - Vincent des Portes
- Claude Bernard Lyon I University, Lyon, France.,Center of Reference for Tuberous Sclerosis and Rare Epileptic Disorders, Hospices Civils de Lyon, Lyon, France
| | - Patrick Edery
- Department of Constitutional Cytogenetics, Lyon Hospices Civils, Lyon, France.,Claude Bernard Lyon I University, Lyon, France.,CRNL, CNRS UMR 5292, INSERM U1028, Lyon, France
| | - Marianne Till
- Department of Constitutional Cytogenetics, Lyon Hospices Civils, Lyon, France
| | - Ioannis Xenarios
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.,Swiss Institute of Bioinformatics (SIB), Lausanne, Switzerland
| | - Damien Sanlaville
- Department of Constitutional Cytogenetics, Lyon Hospices Civils, Lyon, France.,Claude Bernard Lyon I University, Lyon, France.,CRNL, CNRS UMR 5292, INSERM U1028, Lyon, France
| | - Johannes M Herrmann
- Division of Cell Biology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Gaétan Lesca
- Department of Constitutional Cytogenetics, Lyon Hospices Civils, Lyon, France.,Claude Bernard Lyon I University, Lyon, France.,CRNL, CNRS UMR 5292, INSERM U1028, Lyon, France
| | - Alexandre Reymond
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
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18
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Balakrishnan R, Oman K, Shoji S, Bundschuh R, Fredrick K. The conserved GTPase LepA contributes mainly to translation initiation in Escherichia coli. Nucleic Acids Res 2014; 42:13370-83. [PMID: 25378333 PMCID: PMC4245954 DOI: 10.1093/nar/gku1098] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
LepA is a paralog of EF-G found in all bacteria. Deletion of lepA confers no obvious growth defect in Escherichia coli, and the physiological role of LepA remains unknown. Here, we identify nine strains (ΔdksA, ΔmolR1, ΔrsgA, ΔtatB, ΔtonB, ΔtolR, ΔubiF, ΔubiG or ΔubiH) in which ΔlepA confers a synthetic growth phenotype. These strains are compromised for gene regulation, ribosome assembly, transport and/or respiration, indicating that LepA contributes to these functions in some way. We also use ribosome profiling to deduce the effects of LepA on translation. We find that loss of LepA alters the average ribosome density (ARD) for hundreds of mRNA coding regions in the cell, substantially reducing ARD in many cases. By contrast, only subtle and codon-specific changes in ribosome distribution along mRNA are seen. These data suggest that LepA contributes mainly to the initiation phase of translation. Consistent with this interpretation, the effect of LepA on ARD is related to the sequence of the Shine–Dalgarno region. Global perturbation of gene expression in the ΔlepA mutant likely explains most of its phenotypes.
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Affiliation(s)
- Rohan Balakrishnan
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Kenji Oman
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA Department of Physics, The Ohio State University, Columbus, OH 43210, USA
| | - Shinichiro Shoji
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Ralf Bundschuh
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA Department of Physics, The Ohio State University, Columbus, OH 43210, USA
| | - Kurt Fredrick
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
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19
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Woellhaf MW, Hansen KG, Garth C, Herrmann JM. Import of ribosomal proteins into yeast mitochondria. Biochem Cell Biol 2014; 92:489-98. [PMID: 24943357 DOI: 10.1139/bcb-2014-0029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Mitochondrial ribosomes of baker's yeast contain at least 78 protein subunits. All but one of these proteins are nuclear-encoded, synthesized on cytosolic ribosomes, and imported into the matrix for biogenesis. The import of matrix proteins typically relies on N-terminal mitochondrial targeting sequences that form positively charged amphipathic helices. Interestingly, the N-terminal regions of many ribosomal proteins do not closely match the characteristics of matrix targeting sequences, suggesting that the import processes of these proteins might deviate to some extent from the general import route. So far, the biogenesis of only two ribosomal proteins, Mrpl32 and Mrp10, was studied experimentally and indeed showed surprising differences to the import of other preproteins. In this review article we summarize the current knowledge on the transport of proteins into the mitochondrial matrix, and thereby specifically focus on proteins of the mitochondrial ribosome.
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Affiliation(s)
- Michael W Woellhaf
- a Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse 13, 67663 Kaiserslautern, Germany
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20
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Hildenbeutel M, Hegg EL, Stephan K, Gruschke S, Meunier B, Ott M. Assembly factors monitor sequential hemylation of cytochrome b to regulate mitochondrial translation. ACTA ACUST UNITED AC 2014; 205:511-24. [PMID: 24841564 PMCID: PMC4033779 DOI: 10.1083/jcb.201401009] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mitochondrial respiratory chain complexes convert chemical energy into a membrane potential by connecting electron transport with charge separation. Electron transport relies on redox cofactors that occupy strategic positions in the complexes. How these redox cofactors are assembled into the complexes is not known. Cytochrome b, a central catalytic subunit of complex III, contains two heme bs. Here, we unravel the sequence of events in the mitochondrial inner membrane by which cytochrome b is hemylated. Heme incorporation occurs in a strict sequential process that involves interactions of the newly synthesized cytochrome b with assembly factors and structural complex III subunits. These interactions are functionally connected to cofactor acquisition that triggers the progression of cytochrome b through successive assembly intermediates. Failure to hemylate cytochrome b sequesters the Cbp3-Cbp6 complex in early assembly intermediates, thereby causing a reduction in cytochrome b synthesis via a feedback loop that senses hemylation of cytochrome b.
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Affiliation(s)
- Markus Hildenbeutel
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Eric L Hegg
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Katharina Stephan
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Steffi Gruschke
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Brigitte Meunier
- Centre de Génétique Moléculaire du Centre National de la Recherche Scientifique (CNRS), 91198 Gif-sur-Yvette, France
| | - Martin Ott
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
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21
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Amunts A, Brown A, Bai XC, Llácer JL, Hussain T, Emsley P, Long F, Murshudov G, Scheres SH, Ramakrishnan V. Structure of the yeast mitochondrial large ribosomal subunit. Science 2014; 343:1485-1489. [PMID: 24675956 PMCID: PMC4046073 DOI: 10.1126/science.1249410] [Citation(s) in RCA: 447] [Impact Index Per Article: 44.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Mitochondria have specialized ribosomes that have diverged from their bacterial and cytoplasmic counterparts. We have solved the structure of the yeast mitoribosomal large subunit using single-particle cryo-electron microscopy. The resolution of 3.2 angstroms enabled a nearly complete atomic model to be built de novo and refined, including 39 proteins, 13 of which are unique to mitochondria, as well as expansion segments of mitoribosomal RNA. The structure reveals a new exit tunnel path and architecture, unique elements of the E site, and a putative membrane docking site.
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Affiliation(s)
- Alexey Amunts
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Alan Brown
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Xiao-chen Bai
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Jose L. Llácer
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Tanweer Hussain
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Paul Emsley
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Fei Long
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Garib Murshudov
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Sjors H.W. Scheres
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - V. Ramakrishnan
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
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22
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Janska H, Kwasniak M. Mitoribosomal regulation of OXPHOS biogenesis in plants. FRONTIERS IN PLANT SCIENCE 2014; 5:79. [PMID: 24634672 PMCID: PMC3942809 DOI: 10.3389/fpls.2014.00079] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 02/19/2014] [Indexed: 05/20/2023]
Abstract
The ribosome filter hypothesis posits that ribosomes are not simple non-selective translation machines but may also function as regulatory elements in protein synthesis. Recent data supporting ribosomal filtering come from plant mitochondria where it has been shown that translation of mitochondrial transcripts encoding components of oxidative phosphorylation complexes (OXPHOS) and of mitoribosomes can be differentially affected by alterations in mitoribosomes. The biogenesis of mitoribosome was perturbed by silencing of a gene encoding a small-subunit protein of the mitoribosome in Arabidopsis thaliana. As a consequence, the mitochondrial OXPHOS and ribosomal transcripts were both upregulated, but only the ribosomal proteins were oversynthesized, while the OXPHOS subunits were actually depleted. This finding implies that the heterogeneity of plant mitoribosomes found in vivo could contribute to the functional selectivity of translation under distinct conditions. Furthermore, global analysis indicates that biogenesis of OXPHOS complexes in plants can be regulated at different levels of mitochondrial and nuclear gene expression, however, the ultimate coordination of genome expression occurs at the complex assembly level.
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Affiliation(s)
- Hanna Janska
- *Correspondence: Hanna Janska, Molecular Biology of the Cell Department, Faculty of Biotechnology, University of Wroclaw, F. Joliot-Curie 14A, 50-383 Wroclaw, Poland e-mail:
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23
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Toepel J, Illmer-Kephalides M, Jaenicke S, Straube J, May P, Goesmann A, Kruse O. New insights into Chlamydomonas reinhardtii hydrogen production processes by combined microarray/RNA-seq transcriptomics. PLANT BIOTECHNOLOGY JOURNAL 2013; 11:717-33. [PMID: 23551401 DOI: 10.1111/pbi.12062] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 01/07/2013] [Accepted: 02/09/2013] [Indexed: 05/06/2023]
Abstract
Hydrogen production with Chlamydomonas reinhardtii induced by sulphur starvation is a multiphase process while the cell internal metabolism is completely remodelled. The first cellular response is characterized by induction of genes with regulatory functions, followed by a total remodelling of the metabolism to provide reduction equivalents for cellular processes. We were able to characterize all major processes that provide energy and reduction equivalents during hydrogen production. Furthermore, C. reinhardtii showed a strong transcript increase for gene models responsible for stress response and detoxification of oxygen radicals. Finally, we were able to determine potential bottlenecks and target genes for manipulation to increase hydrogen production or to prolong the hydrogen production phase. The investigation of transcriptomic changes during the time course of hydrogen production in C. reinhardtii with microarrays and RNA-seq revealed new insights into the regulation and remodelling of the cell internal metabolism. Both methods showed a good correlation. The microarray platform can be used as a reliable standard tool for routine gene expression analysis. RNA-seq additionally allowed a detailed time-dependent study of gene expression and determination of new genes involved in the hydrogen production process.
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Affiliation(s)
- Jörg Toepel
- Algae Biotechnology & Bioenergy Group, Department of Biology/Center for Biotechnology, Bielefeld University, Bielefeld, Germany
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24
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Abstract
The mitochondrion is arguably the most complex organelle in the budding yeast cell cytoplasm. It is essential for viability as well as respiratory growth. Its innermost aqueous compartment, the matrix, is bounded by the highly structured inner membrane, which in turn is bounded by the intermembrane space and the outer membrane. Approximately 1000 proteins are present in these organelles, of which eight major constituents are coded and synthesized in the matrix. The import of mitochondrial proteins synthesized in the cytoplasm, and their direction to the correct soluble compartments, correct membranes, and correct membrane surfaces/topologies, involves multiple pathways and macromolecular machines. The targeting of some, but not all, cytoplasmically synthesized mitochondrial proteins begins with translation of messenger RNAs localized to the organelle. Most proteins then pass through the translocase of the outer membrane to the intermembrane space, where divergent pathways sort them to the outer membrane, inner membrane, and matrix or trap them in the intermembrane space. Roughly 25% of mitochondrial proteins participate in maintenance or expression of the organellar genome at the inner surface of the inner membrane, providing 7 membrane proteins whose synthesis nucleates the assembly of three respiratory complexes.
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25
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Kumar K, Wigfield S, Gee HE, Devlin CM, Singleton D, Li JL, Buffa F, Huffman M, Sinn AL, Silver J, Turley H, Leek R, Harris AL, Ivan M. Dichloroacetate reverses the hypoxic adaptation to bevacizumab and enhances its antitumor effects in mouse xenografts. J Mol Med (Berl) 2013; 91:749-58. [PMID: 23361368 DOI: 10.1007/s00109-013-0996-2] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 12/20/2012] [Accepted: 01/02/2013] [Indexed: 11/30/2022]
Abstract
Inhibition of vascular endothelial growth factor increases response rates to chemotherapy and progression-free survival in glioblastoma. However, resistance invariably occurs, prompting the urgent need for identification of synergizing agents. One possible strategy is to understand tumor adaptation to microenvironmental changes induced by antiangiogenic drugs and test agents that exploit this process. We used an in vivo glioblastoma-derived xenograft model of tumor escape in presence of continuous treatment with bevacizumab. U87-MG or U118-MG cells were subcutaneously implanted into either BALB/c SCID or athymic nude mice. Bevacizumab was given by intraperitoneal injection every 3 days (2.5 mg/kg/dose) and/or dichloroacetate (DCA) was administered by oral gavage twice daily (50 mg/kg/dose) when tumor volumes reached 0.3 cm(3) and continued until tumors reached approximately 1.5-2.0 cm(3). Microarray analysis of resistant U87 tumors revealed coordinated changes at the level of metabolic genes, in particular, a widening gap between glycolysis and mitochondrial respiration. There was a highly significant difference between U87-MG-implanted athymic nude mice 1 week after drug treatment. By 2 weeks of treatment, bevacizumab and DCA together dramatically blocked tumor growth compared to either drug alone. Similar results were seen in athymic nude mice implanted with U118-MG cells. We demonstrate for the first time that reversal of the bevacizumab-induced shift in metabolism using DCA is detrimental to neoplastic growth in vivo. As DCA is viewed as a promising agent targeting tumor metabolism, our data establish the timely proof of concept that combining it with antiangiogenic therapy represents a potent antineoplastic strategy.
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Affiliation(s)
- Krishan Kumar
- Department of Medicine, Indiana University, Indianapolis, IN 46202, USA
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26
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Funes S, Westerburg H, Jaimes-Miranda F, Woellhaf MW, Aguilar-Lopez JL, Janßen L, Bonnefoy N, Kauff F, Herrmann JM. Partial suppression of Oxa1 mutants by mitochondria-targeted signal recognition particle provides insights into the evolution of the cotranslational insertion systems. FEBS J 2013. [PMID: 23198851 DOI: 10.1111/febs.12082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The biogenesis of hydrophobic membrane proteins involves their cotranslational membrane integration in order to prevent their unproductive aggregation. In the cytosol of bacteria and eukaryotes, membrane targeting of ribosomes that synthesize membrane proteins is achieved by signal recognition particles (SRPs) and their cognate membrane-bound receptors. As is evident from the genomes of fully sequenced eukaryotes, mitochondria generally lack an SRP system. Instead, mitochondrial ribosomes are physically associated with the protein insertion machinery in the inner membrane. Accordingly, deletion of ribosome-binding sites on the Oxa1 insertase and the Mba1 ribosome receptor in yeast leads to severe defects in cotranslational protein insertion and results in respiration-deficient mutants. In this study, we expressed mitochondria-targeted versions of the bacterial SRP protein Ffh and its receptor FtsY in these yeast mutants. Interestingly, Ffh was found to bind to the large subunit of mitochondrial ribosomes, and could relieve, to some degree, the defect of these insertion mutants. Although FtsY could also bind to mitochondrial membranes, it did not improve membrane protein biogenesis in this strain, presumably because of its inability to interact with Ffh. Hence, mitochondrial ribosomes are still able to interact physically and functionally with the bacterial SRP system. Our observations are consistent with a model according to which the protein insertion system in mitochondria evolved in three steps. The loss of genes for hydrophilic polypeptides (step 1) allowed the development of ribosome-binding sites on membrane proteins (step 2), which finally made the existence of an SRP-mediated system dispensable (step 3).
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Affiliation(s)
- Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Ciudad Universitaria, Universidad Nacional Autónoma de México, Distrito Federal, Mexico.
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27
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Characterization of TsMRP-L28, a mitochondrial ribosomal protein L28 from the parasitic nematode Trichinella spiralis. Gene 2013; 512:496-504. [DOI: 10.1016/j.gene.2012.10.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 06/06/2012] [Accepted: 10/10/2012] [Indexed: 11/20/2022]
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28
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Gruschke S, Römpler K, Hildenbeutel M, Kehrein K, Kühl I, Bonnefoy N, Ott M. The Cbp3-Cbp6 complex coordinates cytochrome b synthesis with bc(1) complex assembly in yeast mitochondria. ACTA ACUST UNITED AC 2012; 199:137-50. [PMID: 23007649 PMCID: PMC3461508 DOI: 10.1083/jcb.201206040] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Cbp3–Cbp6 complex, which has been shown previously to promote cytochrome b synthesis and assembly, plays a key role in adjusting cytochrome b expression to the efficiency of assembly of the respiratory chain bc1 complex. Respiratory chain complexes in mitochondria are assembled from subunits derived from two genetic systems. For example, the bc1 complex consists of nine nuclear encoded subunits and the mitochondrially encoded subunit cytochrome b. We recently showed that the Cbp3–Cbp6 complex has a dual function for biogenesis of cytochrome b: it is both required for efficient synthesis of cytochrome b and for protection of the newly synthesized protein from proteolysis. Here, we report that Cbp3–Cbp6 also coordinates cytochrome b synthesis with bc1 complex assembly. We show that newly synthesized cytochrome b assembled through a series of four assembly intermediates. Blocking assembly at early and intermediate steps resulted in sequestration of Cbp3–Cbp6 in a cytochrome b–containing complex, thereby making Cbp3–Cbp6 unavailable for cytochrome b synthesis and thus reducing overall cytochrome b levels. This feedback loop regulates protein synthesis at the inner mitochondrial membrane by directly monitoring the efficiency of bc1 complex assembly.
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Affiliation(s)
- Steffi Gruschke
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
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Herrmann JM, Woellhaf MW, Bonnefoy N. Control of protein synthesis in yeast mitochondria: the concept of translational activators. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:286-94. [PMID: 22450032 DOI: 10.1016/j.bbamcr.2012.03.007] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 03/01/2012] [Accepted: 03/08/2012] [Indexed: 12/18/2022]
Abstract
Mitochondria contain their own genome which codes for a small number of proteins. Most mitochondrial translation products are part of the membrane-embedded reaction centers of the respiratory chain complexes. In the yeast Saccharomyces cerevisiae, the expression of these proteins is regulated by translational activators that bind mitochondrial mRNAs, in most cases to their 5'-untranslated regions, and each mitochondrial mRNA appears to have its own translational activator(s). Recent studies showed that these translational activators can be part of feedback control loops which only permit translation if the downstream assembly of nascent translation products can occur. In several cases, the accumulation of a non-assembled protein prevents further synthesis of this protein but not translation in general. These control loops prevent the synthesis of potentially harmful assembly intermediates of the reaction centers of mitochondrial enzymes. Since such regulatory feedback loops only work if translation occurs in the compartment in which the complexes of the respiratory chain are assembled, these control mechanisms require the presence of a translation machinery in mitochondria. This might explain why eukaryotic cells maintained DNA in mitochondria during the last two billion years of evolution. This review gives an overview of the mitochondrial translation system and summarizes the current knowledge on translational activators and their role in the regulation of mitochondrial protein synthesis. This article is part of a Special Issue entitled: Protein import and quality control in mitochondria and plastids.
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Affiliation(s)
- Johannes M Herrmann
- Cell Biology, Erwin-Schrödinger-Strasse 13, University of Kaiserslautern, 67663 Kaiserslautern, Germany.
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Gruschke S, Kehrein K, Römpler K, Gröne K, Israel L, Imhof A, Herrmann JM, Ott M. Cbp3-Cbp6 interacts with the yeast mitochondrial ribosomal tunnel exit and promotes cytochrome b synthesis and assembly. ACTA ACUST UNITED AC 2011; 193:1101-14. [PMID: 21670217 PMCID: PMC3115798 DOI: 10.1083/jcb.201103132] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
A complex specifically required for the biogenesis of the respiratory chain component cytochrome b binds to the tunnel exit of yeast mitochondrial ribosomes to coordinate protein synthesis and assembly. Mitochondria contain their own genetic system to express a small number of hydrophobic polypeptides, including cytochrome b, an essential subunit of the bc1 complex of the respiratory chain. In this paper, we show in yeast that Cbp3, a bc1 complex assembly factor, and Cbp6, a regulator of cytochrome b translation, form a complex that associates with the polypeptide tunnel exit of mitochondrial ribosomes and that exhibits two important functions in the biogenesis of cytochrome b. On the one hand, the interaction of Cbp3 and Cbp6 with mitochondrial ribosomes is necessary for efficient translation of cytochrome b transcript. On the other hand, the Cbp3–Cbp6 complex interacts directly with newly synthesized cytochrome b in an assembly intermediate that is not ribosome bound and that contains the assembly factor Cbp4. Our results suggest that synthesis of cytochrome b occurs preferentially on those ribosomes that have the Cbp3–Cbp6 complex bound to their tunnel exit, an arrangement that may ensure tight coordination of cytochrome b synthesis and assembly.
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Affiliation(s)
- Steffi Gruschke
- Abteilung Membranbiogenese and 2 Abteilung Membranbiogenese Zellbiologie, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
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Kaur J, Stuart RA. Truncation of the Mrp20 protein reveals new ribosome-assembly subcomplex in mitochondria. EMBO Rep 2011; 12:950-5. [PMID: 21779004 DOI: 10.1038/embor.2011.133] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 06/08/2011] [Accepted: 06/09/2011] [Indexed: 12/30/2022] Open
Abstract
Mitochondrial ribosomal protein 20 (Mrp20) is a component of the yeast mitochondrial large (54S) ribosomal subunit and is homologous to the bacterial L23 protein, located at the ribosomal tunnel exit site. The carboxy-terminal mitochondrial-specific domain of Mrp20 was found to have a crucial role in the assembly of the ribosomes. A new, membrane-bound, ribosomal-assembly subcomplex composed of known tunnel-exit-site proteins, an uncharacterized ribosomal protein, MrpL25, and the mitochondrial peroxiredoxin (Prx), Prx1, accumulates in an mrp20ΔC yeast mutant. Finally, data supporting the idea that the inner mitochondrial membrane acts as a platform for the ribosome assembly process are discussed.
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Affiliation(s)
- Jasvinder Kaur
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53233, USA
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Reinhold R, Bareth B, Balleininger M, Wissel M, Rehling P, Mick DU. Mimicking a SURF1 allele reveals uncoupling of cytochrome c oxidase assembly from translational regulation in yeast. Hum Mol Genet 2011; 20:2379-93. [PMID: 21470975 DOI: 10.1093/hmg/ddr145] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Defects in mitochondrial energy metabolism lead to severe human disorders, mainly affecting tissues especially dependent on oxidative phosphorylation, such as muscle and brain. Leigh Syndrome describes a severe encephalomyopathy in infancy, frequently caused by mutations in SURF1. SURF1, termed Shy1 in Saccharomyces cerevisiae, is a conserved assembly factor for the terminal enzyme of the respiratory chain, cytochrome c oxidase. Although the molecular function of SURF1/Shy1 is still enigmatic, loss of function leads to cytochrome c oxidase deficiency and reduced expression of the central subunit Cox1 in yeast. Here, we provide insights into the molecular mechanisms leading to disease through missense mutations in codons of the most conserved amino acids in SURF1. Mutations affecting G(124) do not compromise import of the SURF1 precursor protein but lead to fast turnover of the mature protein within the mitochondria. Interestingly, an Y(274)D exchange neither affects stability nor localization of the protein. Instead, SURF1(Y274D) accumulates in a 200 kDa cytochrome c oxidase assembly intermediate. Using yeast as a model, we demonstrate that the corresponding Shy1(Y344D) is able to overcome the stage where cytochrome c oxidase assembly links to the feedback regulation of mitochondrial Cox1 expression. However, Shy1(Y344D) impairs the assembly at later steps, most apparent at low temperature and exhibits a dominant-negative phenotype upon overexpression. Thus, exchanging the conserved tyrosine (Y(344)) with aspartate in yeast uncouples translational regulation of Cox1 from cytochrome c oxidase assembly and provides evidence for the dual functionality of Shy1.
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Affiliation(s)
- Robert Reinhold
- Abteilung für Biochemie II, Universität Göttingen, D-37073 Göttingen, Germany
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Gruschke S, Ott M. The polypeptide tunnel exit of the mitochondrial ribosome is tailored to meet the specific requirements of the organelle. Bioessays 2010; 32:1050-7. [PMID: 20967780 DOI: 10.1002/bies.201000081] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The ribosomal polypeptide tunnel exit is the site where a variety of factors interact with newly synthesized proteins to guide them through the early steps of their biogenesis. In mitochondrial ribosomes, this site has been considerably modified in the course of evolution. In contrast to all other translation systems, mitochondrial ribosomes are responsible for the synthesis of only a few hydrophobic membrane proteins that are essential subunits of the mitochondrial respiratory chain. Membrane insertion of these proteins occurs co-translationally and is connected to a sophisticated assembly process that not only includes the assembly of the different subunits but also the acquisition of redox co-factors. Here, we describe how mitochondrial translation is organized in the context of respiratory chain assembly and speculate how alteration of the ribosomal tunnel exit might allow the establishment of a subset of specialized ribosomes that individually organize the early steps in the biogenesis of distinct mitochondrially-encoded proteins.
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Affiliation(s)
- Steffi Gruschke
- Research Group Membrane Biogenesis, University of Kaiserslautern, Kaiserslautern, Germany
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Bauerschmitt H, Mick DU, Deckers M, Vollmer C, Funes S, Kehrein K, Ott M, Rehling P, Herrmann JM. Ribosome-binding proteins Mdm38 and Mba1 display overlapping functions for regulation of mitochondrial translation. Mol Biol Cell 2010; 21:1937-44. [PMID: 20427570 PMCID: PMC2883938 DOI: 10.1091/mbc.e10-02-0101] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Biogenesis of respiratory chain complexes depends on the expression of mitochondrial-encoded subunits. Their synthesis occurs on membrane-associated ribosomes and is probably coupled to their membrane insertion. Defects in expression of mitochondrial translation products are among the major causes of mitochondrial disorders. Mdm38 is related to Letm1, a protein affected in Wolf-Hirschhorn syndrome patients. Like Mba1 and Oxa1, Mdm38 is an inner membrane protein that interacts with ribosomes and is involved in respiratory chain biogenesis. We find that simultaneous loss of Mba1 and Mdm38 causes severe synthetic defects in the biogenesis of cytochrome reductase and cytochrome oxidase. These defects are not due to a compromised membrane binding of ribosomes but the consequence of a mis-regulation in the synthesis of Cox1 and cytochrome b. Cox1 expression is restored by replacing Cox1-specific regulatory regions in the mRNA. We conclude, that Mdm38 and Mba1 exhibit overlapping regulatory functions in translation of selected mitochondrial mRNAs.
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Gruschke S, Gröne K, Heublein M, Hölz S, Israel L, Imhof A, Herrmann JM, Ott M. Proteins at the polypeptide tunnel exit of the yeast mitochondrial ribosome. J Biol Chem 2010; 285:19022-8. [PMID: 20404317 DOI: 10.1074/jbc.m110.113837] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Oxidative phosphorylation in mitochondria requires the synthesis of proteins encoded in the mitochondrial DNA. The mitochondrial translation machinery differs significantly from that of the bacterial ancestor of the organelle. This is especially evident from many mitochondria-specific ribosomal proteins. An important site of the ribosome is the polypeptide tunnel exit. Here, nascent chains are exposed to an aqueous environment for the first time. Many biogenesis factors interact with the tunnel exit of pro- and eukaryotic ribosomes to help the newly synthesized proteins to mature. To date, nothing is known about the organization of the tunnel exit of mitochondrial ribosomes. We therefore undertook a comprehensive approach to determine the composition of the yeast mitochondrial ribosomal tunnel exit. Mitochondria contain homologues of the ribosomal proteins located at this site in bacterial ribosomes. Here, we identified proteins located in their proximity by chemical cross-linking and mass spectrometry. Our analysis revealed a complex network of interacting proteins including proteins and protein domains specific to mitochondrial ribosomes. This network includes Mba1, the membrane-bound ribosome receptor of the inner membrane, as well as Mrpl3, Mrpl13, and Mrpl27, which constitute ribosomal proteins exclusively found in mitochondria. This unique architecture of the tunnel exit is presumably an adaptation of the translation system to the specific requirements of the organelle.
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Affiliation(s)
- Steffi Gruschke
- Abteilung Zellbiologie, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
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Ott M, Herrmann JM. Co-translational membrane insertion of mitochondrially encoded proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1803:767-75. [PMID: 19962410 DOI: 10.1016/j.bbamcr.2009.11.010] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Revised: 11/18/2009] [Accepted: 11/25/2009] [Indexed: 11/29/2022]
Abstract
The components of the mitochondrial proteome represent a mosaic of dual genetic origin: while most mitochondrial proteins are encoded by nuclear genes and imported into the organelle following synthesis in the cytosol, a small number of proteins is encoded by the mitochondrial genome. Though small in number, mitochondrial translation products are vital for cellular functionality as these proteins represent the core subunits of the respiratory chain and the ATPase which produce the vast majority of the cellular ATP. Mitochondrial translation products are almost exclusively highly hydrophobic polypeptides which are inserted into the inner membrane in the course of their synthesis. The machinery that mediates membrane insertion in mitochondria is deduced from that of their bacterial ancestors and hence shows profound similarities to the insertion machinery of prokaryotes. However, the specialization on the production of a very small set of translation products drove a severe reduction in the complexity of this system. The insertase Oxa1 forms the central component of the insertion machinery. Oxa1 directly binds to mitochondrial ribosomes and, together with the inner membrane protein Mba1, aligns the polypeptide exit tunnel of the ribosome with the insertion site at the inner membrane. The specific hallmarks and the critical components of this machinery are discussed in this review article.
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Affiliation(s)
- Martin Ott
- Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
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Systematic Analysis of the Twin Cx9C Protein Family. J Mol Biol 2009; 393:356-68. [DOI: 10.1016/j.jmb.2009.08.041] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Revised: 08/14/2009] [Accepted: 08/17/2009] [Indexed: 11/20/2022]
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Mapping of the Saccharomyces cerevisiae Oxa1-mitochondrial ribosome interface and identification of MrpL40, a ribosomal protein in close proximity to Oxa1 and critical for oxidative phosphorylation complex assembly. EUKARYOTIC CELL 2009; 8:1792-802. [PMID: 19783770 DOI: 10.1128/ec.00219-09] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Oxa1 protein plays a central role in facilitating the cotranslational insertion of the nascent polypeptide chains into the mitochondrial inner membrane. Mitochondrially encoded proteins are synthesized on matrix-localized ribosomes which are tethered to the inner membrane and in physical association with the Oxa1 protein. In the present study we used a chemical cross-linking approach to map the Saccharomyces cerevisiae Oxa1-ribosome interface, and we demonstrate here a close association of Oxa1 and the large ribosomal subunit protein, MrpL40. Evidence to indicate that a close physical and functional relationship exists between MrpL40 and another large ribosomal protein, the Mrp20/L23 protein, is also provided. MrpL40 shares sequence features with the bacterial ribosomal protein L24, which like Mrp20/L23 is known to be located adjacent to the ribosomal polypeptide exit site. We propose therefore that MrpL40 represents the Saccharomyces cerevisiae L24 homolog. MrpL40, like many mitochondrial ribosomal proteins, contains a C-terminal extension region that bears no similarity to the bacterial counterpart. We show that this C-terminal mitochondria-specific region is important for MrpL40's ability to support the synthesis of the correct complement of mitochondrially encoded proteins and their subsequent assembly into oxidative phosphorylation complexes.
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