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Ghifari AS, Saha S, Murcha MW. The biogenesis and regulation of the plant oxidative phosphorylation system. PLANT PHYSIOLOGY 2023; 192:728-747. [PMID: 36806687 DOI: 10.1093/plphys/kiad108] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 01/19/2023] [Accepted: 01/22/2023] [Indexed: 06/01/2023]
Abstract
Mitochondria are central organelles for respiration in plants. At the heart of this process is oxidative phosphorylation (OXPHOS) system, which generates ATP required for cellular energetic needs. OXPHOS complexes comprise of multiple subunits that originated from both mitochondrial and nuclear genome, which requires careful orchestration of expression, translation, import, and assembly. Constant exposure to reactive oxygen species due to redox activity also renders OXPHOS subunits to be more prone to oxidative damage, which requires coordination of disassembly and degradation. In this review, we highlight the composition, assembly, and activity of OXPHOS complexes in plants based on recent biochemical and structural studies. We also discuss how plants regulate the biogenesis and turnover of OXPHOS subunits and the importance of OXPHOS in overall plant respiration. Further studies in determining the regulation of biogenesis and activity of OXPHOS will advances the field, especially in understanding plant respiration and its role to plant growth and development.
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Affiliation(s)
- Abi S Ghifari
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009, Australia
| | - Saurabh Saha
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009, Australia
| | - Monika W Murcha
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009, Australia
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2
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Moloi SJ, Ngara R. The roles of plant proteases and protease inhibitors in drought response: a review. FRONTIERS IN PLANT SCIENCE 2023; 14:1165845. [PMID: 37143877 PMCID: PMC10151539 DOI: 10.3389/fpls.2023.1165845] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 03/30/2023] [Indexed: 05/06/2023]
Abstract
Upon exposure to drought, plants undergo complex signal transduction events with concomitant changes in the expression of genes, proteins and metabolites. For example, proteomics studies continue to identify multitudes of drought-responsive proteins with diverse roles in drought adaptation. Among these are protein degradation processes that activate enzymes and signalling peptides, recycle nitrogen sources, and maintain protein turnover and homeostasis under stressful environments. Here, we review the differential expression and functional activities of plant protease and protease inhibitor proteins under drought stress, mainly focusing on comparative studies involving genotypes of contrasting drought phenotypes. We further explore studies of transgenic plants either overexpressing or repressing proteases or their inhibitors under drought conditions and discuss the potential roles of these transgenes in drought response. Overall, the review highlights the integral role of protein degradation during plant survival under water deficits, irrespective of the genotypes' level of drought resilience. However, drought-sensitive genotypes exhibit higher proteolytic activities, while drought-tolerant genotypes tend to protect proteins from degradation by expressing more protease inhibitors. In addition, transgenic plant biology studies implicate proteases and protease inhibitors in various other physiological functions under drought stress. These include the regulation of stomatal closure, maintenance of relative water content, phytohormonal signalling systems including abscisic acid (ABA) signalling, and the induction of ABA-related stress genes, all of which are essential for maintaining cellular homeostasis under water deficits. Therefore, more validation studies are required to explore the various functions of proteases and their inhibitors under water limitation and their contributions towards drought adaptation.
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3
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Heidorn-Czarna M, Maziak A, Janska H. Protein Processing in Plant Mitochondria Compared to Yeast and Mammals. FRONTIERS IN PLANT SCIENCE 2022; 13:824080. [PMID: 35185991 PMCID: PMC8847149 DOI: 10.3389/fpls.2022.824080] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 01/12/2022] [Indexed: 05/02/2023]
Abstract
Limited proteolysis, called protein processing, is an essential post-translational mechanism that controls protein localization, activity, and in consequence, function. This process is prevalent for mitochondrial proteins, mainly synthesized as precursor proteins with N-terminal sequences (presequences) that act as targeting signals and are removed upon import into the organelle. Mitochondria have a distinct and highly conserved proteolytic system that includes proteases with sole function in presequence processing and proteases, which show diverse mitochondrial functions with limited proteolysis as an additional one. In virtually all mitochondria, the primary processing of N-terminal signals is catalyzed by the well-characterized mitochondrial processing peptidase (MPP). Subsequently, a second proteolytic cleavage occurs, leading to more stabilized residues at the newly formed N-terminus. Lately, mitochondrial proteases, intermediate cleavage peptidase 55 (ICP55) and octapeptidyl protease 1 (OCT1), involved in proteolytic cleavage after MPP and their substrates have been described in the plant, yeast, and mammalian mitochondria. Mitochondrial proteins can also be processed by removing a peptide from their N- or C-terminus as a maturation step during insertion into the membrane or as a regulatory mechanism in maintaining their function. This type of limited proteolysis is characteristic for processing proteases, such as IMP and rhomboid proteases, or the general mitochondrial quality control proteases ATP23, m-AAA, i-AAA, and OMA1. Identification of processing protease substrates and defining their consensus cleavage motifs is now possible with the help of large-scale quantitative mass spectrometry-based N-terminomics, such as combined fractional diagonal chromatography (COFRADIC), charge-based fractional diagonal chromatography (ChaFRADIC), or terminal amine isotopic labeling of substrates (TAILS). This review summarizes the current knowledge on the characterization of mitochondrial processing peptidases and selected N-terminomics techniques used to uncover protease substrates in the plant, yeast, and mammalian mitochondria.
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Heinemann B, Künzler P, Eubel H, Braun HP, Hildebrandt TM. Estimating the number of protein molecules in a plant cell: protein and amino acid homeostasis during drought. PLANT PHYSIOLOGY 2021; 185:385-404. [PMID: 33721903 PMCID: PMC8133651 DOI: 10.1093/plphys/kiaa050] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 11/17/2020] [Indexed: 05/21/2023]
Abstract
During drought stress, cellular proteostasis on the one hand and amino acid homeostasis on the other hand are severely challenged, because the decrease in photosynthesis induces massive proteolysis, leading to drastic changes in both the proteome and the free amino acid pool. Thus, we selected progressive drought stress in Arabidopsis (Arabidopsis thaliana) as a model to investigate on a quantitative level the balance between protein and free amino acid homeostasis. We analyzed the mass composition of the leaf proteome based on proteomics datasets, and estimated how many protein molecules are present in a plant cell and its subcellular compartments. In addition, we calculated stress-induced changes in the distribution of individual amino acids between the free and protein-bound pools. Under control conditions, an average Arabidopsis mesophyll cell contains about 25 billion protein molecules, of which 80% are localized in chloroplasts. Severe water deficiency leads to degradation of more than 40% of the leaf protein mass, and thus causes a drastic shift in distribution toward the free amino acid pool. Stress-induced proteolysis of just half of the 340 million RubisCO hexadecamers present in the chloroplasts of a single mesophyll cell doubles the cellular content of free amino acids. A major fraction of the amino acids released from proteins is channeled into synthesis of proline, which is a compatible osmolyte. Complete oxidation of the remaining fraction as an alternative respiratory substrate can fully compensate for the lack of photosynthesis-derived carbohydrates for several hours.
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Affiliation(s)
- Björn Heinemann
- Department of Plant Proteomics, Institute of Plant Genetics, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Patrick Künzler
- Department of Plant Proteomics, Institute of Plant Genetics, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Holger Eubel
- Department of Plant Proteomics, Institute of Plant Genetics, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Hans-Peter Braun
- Department of Plant Proteomics, Institute of Plant Genetics, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Tatjana M Hildebrandt
- Department of Plant Proteomics, Institute of Plant Genetics, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
- Address for communication:
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5
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Degradation of mitochondrial alternative oxidase in the appendices of Arum maculatum. Biochem J 2021; 477:3417-3431. [PMID: 32856714 PMCID: PMC7505559 DOI: 10.1042/bcj20200515] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 08/25/2020] [Accepted: 08/27/2020] [Indexed: 01/09/2023]
Abstract
Cyanide-resistant alternative oxidase (AOX) is a nuclear-encoded quinol oxidase located in the inner mitochondrial membrane. Although the quality control of AOX proteins is expected to have a role in elevated respiration in mitochondria, it remains unclear whether thermogenic plants possess molecular mechanisms for the mitochondrial degradation of AOX. To better understand the mechanism of AOX turnover in mitochondria, we performed a series of in organello AOX degradation assays using mitochondria from various stages of the appendices of Arum maculatum. Our analyses clearly indicated that AOX proteins at certain stages in the appendices are degraded at 30°C, which is close to the maximum appendix temperature observed during thermogenesis. Interestingly, such temperature-dependent protease activities were specifically inhibited by E-64, a cysteine protease inhibitor. Moreover, purification and subsequent nano LC–MS/MS analyses of E-64-sensitive and DCG-04-labeled active mitochondrial protease revealed an ∼30 kDa protein with an identical partial peptide sequence to the cysteine protease 1-like protein from Phoenix dactylifera. Our data collectively suggest that AOX is a potential target for temperature-dependent E-64-sensitive cysteine protease in the appendices of A. maculatum. A possible retrograde signalling cascade mediated by specific degradation of AOX proteins and its physiological significance are discussed.
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Huang S, Petereit J, Millar AH. Loss of conserved mitochondrial CLPP and its functions lead to different phenotypes in plants and other organisms. PLANT SIGNALING & BEHAVIOR 2020; 15:1831789. [PMID: 33073672 PMCID: PMC7671067 DOI: 10.1080/15592324.2020.1831789] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Caseinolytic protease (CLPP) is an energy-dependent serine-type protease that plays a role in protein quality control. The CLPP gene is highly conserved across kingdoms and the protein is present in both bacteria and eukaryote organelles like mitochondria across a wide phylogenetic range. This pedigree has all the hallmarks of CLPP being an essential gene. However, in plants, disruption of mitochondrial CLPP has no impact on its growth, reminiscent of its nonessential role in some model fungi. Deletion of mitochondrial CLPP improves health and increased life span in the filamentous fungus, Podospora anserina, while loss of human mitochondrial CLPP leads to infertility and hearing loss. Recently it was revealed that both plant and human CLPP share a similar role in maintenance of the N-module of respiratory complex I. In addition, plant mitochondrial CLPP also coordinates the homeostasis of other mitochondrial protein complexes encoded by genes across mitochondrial and nuclear genomes. Understanding the contextual role of mitochondrial CLPP across kingdoms may help to understand these diverse sets of clpp phenotypes and the widespread conservation of CLPP genes.
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Affiliation(s)
- Shaobai Huang
- ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Perth, Australia
| | - Jakob Petereit
- ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Perth, Australia
| | - A. Harvey Millar
- ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Perth, Australia
- CONTACT A. Harvey Millar ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, 35 Stirling Hwy, Crawley 6009, Perth, Western Australia
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Huang S, Li L, Petereit J, Millar AH. Protein turnover rates in plant mitochondria. Mitochondrion 2020; 53:57-65. [DOI: 10.1016/j.mito.2020.04.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 04/22/2020] [Accepted: 04/29/2020] [Indexed: 02/06/2023]
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Kolodziejczak M, Skibior-Blaszczyk R, Janska H. m-AAA Complexes Are Not Crucial for the Survival of Arabidopsis Under Optimal Growth Conditions Despite Their Importance for Mitochondrial Translation. PLANT & CELL PHYSIOLOGY 2018; 59:1006-1016. [PMID: 29462458 DOI: 10.1093/pcp/pcy041] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 02/09/2018] [Indexed: 05/17/2023]
Abstract
For optimal mitochondrial activity, the mitochondrial proteome must be properly maintained or altered in response to developmental and environmental stimuli. Based on studies of yeast and humans, one of the key players in this control are m-AAA proteases, mitochondrial inner membrane-bound ATP-dependent metalloenzymes. This study focuses on the importance of m-AAA proteases in plant mitochondria, providing their first experimentally proven physiological substrate. We found that the Arabidopsis m- AAA complexes composed of AtFTSH3 and/or AtFTSH10 are involved in the proteolytic maturation of ribosomal subunit L32. Consequently, in the double Arabidopsis ftsh3/10 mutant, mitoribosome biogenesis, mitochondrial translation and functionality of OXPHOS (oxidative phosphorylation) complexes are impaired. However, in contrast to their mammalian or yeast counterparts, plant m-AAA complexes are not critical for the survival of Arabidopsis under optimal conditions; ftsh3/10 plants are only slightly smaller in size at the early developmental stage compared with plants containing m-AAA complexes. Our data suggest that a lack of significant visible morphological alterations under optimal growth conditions involves mechanisms which rely on existing functional redundancy and induced functional compensation in Arabidopsis mitochondria.
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Affiliation(s)
- Marta Kolodziejczak
- Department of Cellular Molecular Biology, Faculty of Biotechnology, University of Wroclaw, Wroclaw 50-383, Poland
| | - Renata Skibior-Blaszczyk
- Department of Cellular Molecular Biology, Faculty of Biotechnology, University of Wroclaw, Wroclaw 50-383, Poland
| | - Hanna Janska
- Department of Cellular Molecular Biology, Faculty of Biotechnology, University of Wroclaw, Wroclaw 50-383, Poland
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Li L, Millar AH, Huang S. Mitochondrial Lon1 has a role in homeostasis of the mitochondrial ribosome and pentatricopeptide repeat proteins in plants. PLANT SIGNALING & BEHAVIOR 2017; 12:e1276686. [PMID: 28045582 PMCID: PMC5351720 DOI: 10.1080/15592324.2016.1276686] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 12/20/2016] [Indexed: 05/28/2023]
Abstract
Lon is a highly conserved protein family in eukaryotes and eubacteria and its members all contain both a chaperone and a proteolytic domain that are important for Lon function. Loss of mitochondrial Lon1 leads to deleterious phenotypes in yeast and plants, and causes developmental disorders and aging-related diseases in humans. In Arabidopsis, we have recently reported the multiple roles of Lon1 in mitochondrial protein homeostasis through an evaluation of changes in protein degradation rates in the absence of Lon1. 1 In this addendum, we extend our discussion to the roles of Lon1 in mitochondrial post-transcriptional regulation by considering the effects of its loss on ribosome proteins required for protein synthesis and mitochondrial PPR proteins required for RNA regulation.
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Affiliation(s)
- Lei Li
- ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, Crawley, WA, Australia
| | - A. Harvey Millar
- ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, Crawley, WA, Australia
| | - Shaobai Huang
- ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, Crawley, WA, Australia
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Li L, Nelson C, Fenske R, Trösch J, Pružinská A, Millar AH, Huang S. Changes in specific protein degradation rates in Arabidopsis thaliana reveal multiple roles of Lon1 in mitochondrial protein homeostasis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:458-471. [PMID: 27726214 DOI: 10.1111/tpj.13392] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 09/29/2016] [Accepted: 10/03/2016] [Indexed: 05/20/2023]
Abstract
Mitochondrial Lon1 loss impairs oxidative phosphorylation complexes and TCA enzymes and causes accumulation of specific mitochondrial proteins. Analysis of over 400 mitochondrial protein degradation rates using 15 N labelling showed that 205 were significantly different between wild type (WT) and lon1-1. Those proteins included ribosomal proteins, electron transport chain subunits and TCA enzymes. For respiratory complexes I and V, decreased protein abundance correlated with higher degradation rate of subunits in total mitochondrial extracts. After blue native separation, however, the assembled complexes had slow degradation, while smaller subcomplexes displayed rapid degradation in lon1-1. In insoluble fractions, a number of TCA enzymes were more abundant but the proteins degraded slowly in lon1-1. In soluble protein fractions, TCA enzymes were less abundant but degraded more rapidly. These observations are consistent with the reported roles of Lon1 as a chaperone aiding the proper folding of newly synthesized/imported proteins to stabilise them and as a protease to degrade mitochondrial protein aggregates. HSP70, prohibitin and enzymes of photorespiration accumulated in lon1-1 and degraded slowly in all fractions, indicating an important role of Lon1 in their clearance from the proteome.
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Affiliation(s)
- Lei Li
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Western Australia, Australia
| | - Clark Nelson
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Western Australia, Australia
| | - Ricarda Fenske
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Western Australia, Australia
| | - Josua Trösch
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Western Australia, Australia
| | - Adriana Pružinská
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Western Australia, Australia
| | - A Harvey Millar
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Western Australia, Australia
| | - Shaobai Huang
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Western Australia, Australia
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11
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Migdal I, Skibior-Blaszczyk R, Heidorn-Czarna M, Kolodziejczak M, Garbiec A, Janska H. AtOMA1 Affects the OXPHOS System and Plant Growth in Contrast to Other Newly Identified ATP-Independent Proteases in Arabidopsis Mitochondria. FRONTIERS IN PLANT SCIENCE 2017; 8:1543. [PMID: 28936218 PMCID: PMC5594102 DOI: 10.3389/fpls.2017.01543] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 08/23/2017] [Indexed: 05/17/2023]
Abstract
Compared with yeast, our knowledge on members of the ATP-independent plant mitochondrial proteolytic machinery is rather poor. In the present study, using confocal microscopy and immunoblotting, we proved that homologs of yeast Oma1, Atp23, Imp1, Imp2, and Oct1 proteases are localized in Arabidopsis mitochondria. We characterized these components of the ATP-independent proteolytic system as well as the earlier identified protease, AtICP55, with an emphasis on their significance in plant growth and functionality in the OXPHOS system. A functional complementation assay demonstrated that out of all the analyzed proteases, only AtOMA1 and AtICP55 could substitute for a lack of their yeast counterparts. We did not observe any significant developmental or morphological changes in plants lacking the studied proteases, either under optimal growth conditions or after exposure to stress, with the only exception being retarded root growth in oma1-1, thus implying that the absence of a single mitochondrial ATP-independent protease is not critical for Arabidopsis growth and development. We did not find any evidence indicating a clear functional complementation of the missing protease by any other protease at the transcript or protein level. Studies on the impact of the analyzed proteases on mitochondrial bioenergetic function revealed that out of all the studied mutants, only oma1-1 showed differences in activities and amounts of OXPHOS proteins. Among all the OXPHOS disorders found in oma1-1, the complex V deficiency is distinctive because it is mainly associated with decreased catalytic activity and not correlated with complex abundance, which has been observed in the case of supercomplex I + III2 and complex I deficiencies. Altogether, our study indicates that despite the presence of highly conservative homologs, the mitochondrial ATP-independent proteolytic system is not functionally conserved in plants as compared with yeast. Our findings also highlight the importance of AtOMA1 in maintenance of proper function of the OXPHOS system as well as in growth and development of Arabidopsis thaliana.
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Affiliation(s)
- Iwona Migdal
- Institute of Experimental Biology, Faculty of Biological Sciences, University of WroclawWroclaw, Poland
| | - Renata Skibior-Blaszczyk
- Department of Cellular Molecular Biology, Faculty of Biotechnology, University of WroclawWroclaw, Poland
| | - Malgorzata Heidorn-Czarna
- Department of Cellular Molecular Biology, Faculty of Biotechnology, University of WroclawWroclaw, Poland
| | - Marta Kolodziejczak
- Department of Cellular Molecular Biology, Faculty of Biotechnology, University of WroclawWroclaw, Poland
| | - Arnold Garbiec
- Institute of Experimental Biology, Faculty of Biological Sciences, University of WroclawWroclaw, Poland
| | - Hanna Janska
- Department of Cellular Molecular Biology, Faculty of Biotechnology, University of WroclawWroclaw, Poland
- *Correspondence: Hanna Janska,
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12
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Carrie C, Venne AS, Zahedi RP, Soll J. Identification of cleavage sites and substrate proteins for two mitochondrial intermediate peptidases in Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:2691-708. [PMID: 25732537 PMCID: PMC4986872 DOI: 10.1093/jxb/erv064] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Most mitochondrial proteins contain an N-terminal targeting signal that is removed by specific proteases following import. In plant mitochondria, only mitochondrial processing peptidase (MPP) has been characterized to date. Therefore, we sought to determine the substrates and cleavage sites of the Arabidopsis thaliana homologues to the yeast Icp55 and Oct1 proteins, using the newly developed ChaFRADIC method for N-terminal protein sequencing. We identified 88 and seven putative substrates for Arabidopsis ICP55 and OCT1, respectively. It was determined that the Arabidopsis ICP55 contains an almost identical cleavage site to that of Icp55 from yeast. However, it can also remove a far greater range of amino acids. The OCT1 substrates from Arabidopsis displayed no consensus cleavage motif, and do not contain the classical -10R motif identified in other eukaryotes. Arabidopsis OCT1 can also cleave presequences independently, without the prior cleavage of MPP. It was concluded that while both OCT1 and ICP55 were probably acquired early on in the evolution of mitochondria, their substrate profiles and cleavage sites have either remained very similar or diverged completely.
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Affiliation(s)
- Chris Carrie
- Department of Biology I, Botany, Ludwig-Maximilians Universität München, Großhaderner Strasse 2-4, D-82152 Planegg-Martinsried, Germany
| | - A Saskia Venne
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Otto-Hahn-Str. 11, D-44139 Dortmund, Germany
| | - René P Zahedi
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Otto-Hahn-Str. 11, D-44139 Dortmund, Germany
| | - Jürgen Soll
- Department of Biology I, Botany, Ludwig-Maximilians Universität München, Großhaderner Strasse 2-4, D-82152 Planegg-Martinsried, Germany Munich Centre for Integrated Protein Science, CiPSM, Ludwig-Maximilians Universität München, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany
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13
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Abstract
The protein content of plant cells is constantly being updated. This process is driven by the opposing actions of protein degradation, which defines the half-life of each polypeptide, and protein synthesis. Our understanding of the processes that regulate protein synthesis and degradation in plants has advanced significantly over the past decade. Post-transcriptional modifications that influence features of the mRNA populations, such as poly(A) tail length and secondary structure, contribute to the regulation of protein synthesis. Post-translational modifications such as phosphorylation, ubiquitination and non-enzymatic processes such as nitrosylation and carbonylation, govern the rate of degradation. Regulators such as the plant TOR kinase, and effectors such as the E3 ligases, allow plants to balance protein synthesis and degradation under developmental and environmental change. Establishing an integrated understanding of the processes that underpin changes in protein abundance under various physiological and developmental scenarios will accelerate our ability to model and rationally engineer plants.
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Affiliation(s)
- Clark J Nelson
- ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Hwy, Crawley 6009, Perth, Western Australia, Australia
| | - A Harvey Millar
- ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Hwy, Crawley 6009, Perth, Western Australia, Australia
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Köhler D, Montandon C, Hause G, Majovsky P, Kessler F, Baginsky S, Agne B. Characterization of chloroplast protein import without Tic56, a component of the 1-megadalton translocon at the inner envelope membrane of chloroplasts. PLANT PHYSIOLOGY 2015; 167:972-90. [PMID: 25588737 PMCID: PMC4348784 DOI: 10.1104/pp.114.255562] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 01/14/2015] [Indexed: 05/17/2023]
Abstract
We report on the characterization of Tic56, a unique component of the recently identified 1-MD translocon at the inner envelope membrane of chloroplasts (TIC) in Arabidopsis (Arabidopsis thaliana) comprising Tic20, Tic100, and Tic214. We isolated Tic56 by copurification with Tandem Affinity Purification-tagged Toc159 in the absence of precursor protein, indicating spontaneous and translocation-independent formation of the translocon at the outer envelope membrane of chloroplasts (TOC) and TIC supercomplexes. Tic56 mutant plants have an albino phenotype and are unable to grow without an external carbon source. Using specific enrichment of protein amino termini, we analyzed the tic56-1 and plastid protein import2 (toc159) mutants to assess the in vivo import capacity of plastids in mutants of an outer and inner envelope component of the anticipated TOC-TIC supercomplex. Inboth mutants, we observed processing of several import substrates belonging to various pathways. Our results suggest that despite the severe developmental defects, protein import into Tic56-deficient plastids is functional to a considerable degree, indicating the existence of alternative translocases at the inner envelope membrane.
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van Wijk KJ. Protein maturation and proteolysis in plant plastids, mitochondria, and peroxisomes. ANNUAL REVIEW OF PLANT BIOLOGY 2015; 66:75-111. [PMID: 25580835 DOI: 10.1146/annurev-arplant-043014-115547] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Plastids, mitochondria, and peroxisomes are key organelles with dynamic proteomes in photosynthetic eukaryotes. Their biogenesis and activity must be coordinated and require intraorganellar protein maturation, degradation, and recycling. The three organelles together are predicted to contain ∼200 presequence peptidases, proteases, aminopeptidases, and specific protease chaperones/adaptors, but the substrates and substrate selection mechanisms are poorly understood. Similarly, lifetime determinants of organellar proteins, such as N-end degrons and tagging systems, have not been identified, but the substrate recognition mechanisms likely share similarities between organelles. Novel degradomics tools for systematic analysis of protein lifetime and proteolysis could define such protease-substrate relationships, degrons, and protein lifetime. Intraorganellar proteolysis is complemented by autophagy of whole organelles or selected organellar content, as well as by cytosolic protein ubiquitination and degradation by the proteasome. This review summarizes (putative) plant organellar protease functions and substrate-protease relationships. Examples illustrate key proteolytic events.
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Affiliation(s)
- Klaas J van Wijk
- Department of Plant Biology, Cornell University, Ithaca, New York 14853;
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Kmiec B, Teixeira PF, Glaser E. Shredding the signal: targeting peptide degradation in mitochondria and chloroplasts. TRENDS IN PLANT SCIENCE 2014; 19:771-8. [PMID: 25305111 DOI: 10.1016/j.tplants.2014.09.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 09/05/2014] [Accepted: 09/11/2014] [Indexed: 05/25/2023]
Abstract
The biogenesis and functionality of mitochondria and chloroplasts depend on the constant turnover of their proteins. The majority of mitochondrial and chloroplastic proteins are imported as precursors via their N-terminal targeting peptides. After import, the targeting peptides are cleaved off and degraded. Recent work has elucidated a pathway involved in the degradation of targeting peptides in mitochondria and chloroplasts, with two proteolytic components: the presequence protease (PreP) and the organellar oligopeptidase (OOP). PreP and OOP are specialized in degrading peptides of different lengths, with the substrate restriction being dictated by the structure of their proteolytic cavities. The importance of the intraorganellar peptide degradation is highlighted by the fact that elimination of both oligopeptidases affects growth and development of Arabidopsis thaliana.
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Affiliation(s)
- Beata Kmiec
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-106 91 Stockholm, Sweden.
| | - Pedro F Teixeira
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-106 91 Stockholm, Sweden
| | - Elzbieta Glaser
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-106 91 Stockholm, Sweden.
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Murcha MW, Kmiec B, Kubiszewski-Jakubiak S, Teixeira PF, Glaser E, Whelan J. Protein import into plant mitochondria: signals, machinery, processing, and regulation. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:6301-35. [PMID: 25324401 DOI: 10.1093/jxb/eru399] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The majority of more than 1000 proteins present in mitochondria are imported from nuclear-encoded, cytosolically synthesized precursor proteins. This impressive feat of transport and sorting is achieved by the combined action of targeting signals on mitochondrial proteins and the mitochondrial protein import apparatus. The mitochondrial protein import apparatus is composed of a number of multi-subunit protein complexes that recognize, translocate, and assemble mitochondrial proteins into functional complexes. While the core subunits involved in mitochondrial protein import are well conserved across wide phylogenetic gaps, the accessory subunits of these complexes differ in identity and/or function when plants are compared with Saccharomyces cerevisiae (yeast), the model system for mitochondrial protein import. These differences include distinct protein import receptors in plants, different mechanistic operation of the intermembrane protein import system, the location and activity of peptidases, the function of inner-membrane translocases in linking the outer and inner membrane, and the association/regulation of mitochondrial protein import complexes with components of the respiratory chain. Additionally, plant mitochondria share proteins with plastids, i.e. dual-targeted proteins. Also, the developmental and cell-specific nature of mitochondrial biogenesis is an aspect not observed in single-celled systems that is readily apparent in studies in plants. This means that plants provide a valuable model system to study the various regulatory processes associated with protein import and mitochondrial biogenesis.
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Affiliation(s)
- Monika W Murcha
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Beata Kmiec
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-10691 Stockholm, Sweden
| | - Szymon Kubiszewski-Jakubiak
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Pedro F Teixeira
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-10691 Stockholm, Sweden
| | - Elzbieta Glaser
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-10691 Stockholm, Sweden
| | - James Whelan
- Australian Research Council Centre of Excellence in Plant Energy Biology, School of Life Science, La Trobe University, Bundoora, Victoria, 3086, Australia
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Smakowska E, Czarna M, Janska H. Mitochondrial ATP-dependent proteases in protection against accumulation of carbonylated proteins. Mitochondrion 2014; 19 Pt B:245-51. [PMID: 24662487 DOI: 10.1016/j.mito.2014.03.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/11/2014] [Accepted: 03/14/2014] [Indexed: 10/25/2022]
Abstract
Carbonylation is an irreversible oxidative modification of proteins induced by reactive oxygen species (ROS) and reactive nitrogen species (RNS) or by-products of oxidative stress. Carbonylation leads to the loss of protein function and is used as a marker of oxidative stress. Recent data indicate that carbonylation is not only an unfavorable chance process but may also play a significant role in the control of diverse physiological processes. In plants, carbonylated proteins have been found in all cellular compartments; however, mitochondria, one of the major sources of reactive species, show the highest levels of oxidatively modified proteins under normal or stress conditions. Carbonylated proteins tend to misfold and have to be removed to prevent the formation of harmful insoluble aggregates. Mitochondria have developed several pathways that continuously monitor and remove oxidatively damaged polypeptides, and the mitochondrial protein quality control (mtPQC) system, comprising chaperones and ATP-dependent proteases, is the first line of defense. The Lon protease has been recognized as a key protease involved in the removal of oxidized proteins in yeast and mammalian mitochondria, but not in plants. Recently, it has been reported that the inner-membrane human i-AAA and m-AAA and Arabidopsis i-AAA proteases are crucial components of the defense against accumulation of carbonylated proteins, but the molecular basis of their action is not yet clear. Altogether, the mitochondrial AAA proteases secure the mitochondrial proteome against accumulation of carbonylated proteins.
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Affiliation(s)
- Elwira Smakowska
- Faculty of Biotechnology, University of Wroclaw, F. Joliot-Curie 14A, 50-383 Wroclaw, Poland
| | - Malgorzata Czarna
- Faculty of Biotechnology, University of Wroclaw, F. Joliot-Curie 14A, 50-383 Wroclaw, Poland
| | - Hanna Janska
- Faculty of Biotechnology, University of Wroclaw, F. Joliot-Curie 14A, 50-383 Wroclaw, Poland.
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Braun HP, Binder S, Brennicke A, Eubel H, Fernie AR, Finkemeier I, Klodmann J, König AC, Kühn K, Meyer E, Obata T, Schwarzländer M, Takenaka M, Zehrmann A. The life of plant mitochondrial complex I. Mitochondrion 2014; 19 Pt B:295-313. [PMID: 24561573 DOI: 10.1016/j.mito.2014.02.006] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 01/28/2014] [Accepted: 02/12/2014] [Indexed: 12/29/2022]
Abstract
The mitochondrial NADH dehydrogenase complex (complex I) of the respiratory chain has several remarkable features in plants: (i) particularly many of its subunits are encoded by the mitochondrial genome, (ii) its mitochondrial transcripts undergo extensive maturation processes (e.g. RNA editing, trans-splicing), (iii) its assembly follows unique routes, (iv) it includes an additional functional domain which contains carbonic anhydrases and (v) it is, indirectly, involved in photosynthesis. Comprising about 50 distinct protein subunits, complex I of plants is very large. However, an even larger number of proteins are required to synthesize these subunits and assemble the enzyme complex. This review aims to follow the complete "life cycle" of plant complex I from various molecular perspectives. We provide arguments that complex I represents an ideal model system for studying the interplay of respiration and photosynthesis, the cooperation of mitochondria and the nucleus during organelle biogenesis and the evolution of the mitochondrial oxidative phosphorylation system.
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Affiliation(s)
- Hans-Peter Braun
- Institut für Pflanzengenetik, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
| | - Stefan Binder
- Molekulare Botanik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany
| | - Axel Brennicke
- Molekulare Botanik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany
| | - Holger Eubel
- Institut für Pflanzengenetik, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Alisdair R Fernie
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Iris Finkemeier
- Plant Sciences, Ludwig Maximilians Universität München, Grosshadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
| | - Jennifer Klodmann
- Institut für Pflanzengenetik, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Ann-Christine König
- Plant Sciences, Ludwig Maximilians Universität München, Grosshadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
| | - Kristina Kühn
- Institut für Biologie/Molekulare Zellbiologie der Pflanzen, Humboldt Universität zu Berlin, Philippstraße 13, 10115 Berlin, Germany
| | - Etienne Meyer
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Toshihiro Obata
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Markus Schwarzländer
- INRES - Chemical Signalling, Rheinische Friedrich-Wilhelms-Universität Bonn, Friedrich-Ebert-Allee 144, D-53113 Bonn, Germany
| | - Mizuki Takenaka
- Molekulare Botanik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany
| | - Anja Zehrmann
- Molekulare Botanik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany
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Murcha MW, Wang Y, Narsai R, Whelan J. The plant mitochondrial protein import apparatus - the differences make it interesting. Biochim Biophys Acta Gen Subj 2013; 1840:1233-45. [PMID: 24080405 DOI: 10.1016/j.bbagen.2013.09.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 09/17/2013] [Accepted: 09/18/2013] [Indexed: 12/25/2022]
Abstract
BACKGROUND Mitochondria play essential roles in the life and death of almost all eukaryotic cells, ranging from single-celled to multi-cellular organisms that display tissue and developmental differentiation. As mitochondria only arose once in evolution, much can be learned from studying single celled model systems such as yeast and applying this knowledge to other organisms. However, two billion years of evolution have also resulted in substantial divergence in mitochondrial function between eukaryotic organisms. SCOPE OF REVIEW Here we review our current understanding of the mechanisms of mitochondrial protein import between plants and yeast (Saccharomyces cerevisiae) and identify a high level of conservation for the essential subunits of plant mitochondrial import apparatus. Furthermore, we investigate examples whereby divergence and acquisition of functions have arisen and highlight the emerging examples of interactions between the import apparatus and components of the respiratory chain. MAJOR CONCLUSIONS After more than three decades of research into the components and mechanisms of mitochondrial protein import of plants and yeast, the differences between these systems are examined. Specifically, expansions of the small gene families that encode the mitochondrial protein import apparatus in plants are detailed, and their essential role in seed viability is revealed. GENERAL SIGNIFICANCE These findings point to the essential role of the inner mitochondrial protein translocases in Arabidopsis, establishing their necessity for seed viability and the crucial role of mitochondrial biogenesis during germination. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.
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Affiliation(s)
- Monika W Murcha
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia.
| | - Yan Wang
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
| | - Reena Narsai
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia; Computational Systems Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia
| | - James Whelan
- ARC Centre of Excellence in Plant Energy Biology, Bayliss Building M316, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia; Department of Botany, School of Life Science, La Trobe University, Bundoora 3086, Victoria, Australia
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Organellar oligopeptidase (OOP) provides a complementary pathway for targeting peptide degradation in mitochondria and chloroplasts. Proc Natl Acad Sci U S A 2013; 110:E3761-9. [PMID: 24043784 DOI: 10.1073/pnas.1307637110] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Both mitochondria and chloroplasts contain distinct proteolytic systems for precursor protein processing catalyzed by the mitochondrial and stromal processing peptidases and for the degradation of targeting peptides catalyzed by presequence protease. Here, we have identified and characterized a component of the organellar proteolytic systems in Arabidopsis thaliana, the organellar oligopeptidase, OOP (At5g65620). OOP belongs to the M3A family of peptide-degrading metalloproteases. Using two independent in vivo methods, we show that the protease is dually localized to mitochondria and chloroplasts. Furthermore, we localized the OPP homolog At5g10540 to the cytosol. Analysis of peptide degradation by OOP revealed substrate size restriction from 8 to 23 aa residues. Short mitochondrial targeting peptides (presequence of the ribosomal protein L29 and presequence of 1-aminocyclopropane-1-carboxylic acid deaminase 1) and N- and C-terminal fragments derived from the presequence of the ATPase beta subunit ranging in size from 11 to 20 aa could be degraded. MS analysis showed that OOP does not exhibit a strict cleavage pattern but shows a weak preference for hydrophobic residues (F/L) at the P1 position. The crystal structures of OOP, at 1.8-1.9 Å, exhibit an ellipsoidal shape consisting of two major domains enclosing the catalytic cavity of 3,000 Å(3). The structural and biochemical data suggest that the protein undergoes conformational changes to allow peptide binding and proteolysis. Our results demonstrate the complementary role of OOP in targeting-peptide degradation in mitochondria and chloroplasts.
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Nagpal J, Tan JL, Truscott KN, Heras B, Dougan DA. Control of protein function through regulated protein degradation: biotechnological and biomedical applications. J Mol Microbiol Biotechnol 2013; 23:335-44. [PMID: 23920496 DOI: 10.1159/000352043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Targeted protein degradation is crucial for the correct function and maintenance of a cell. In bacteria, this process is largely performed by a handful of ATP-dependent machines, which generally consist of two components - an unfoldase and a peptidase. In some cases, however, substrate recognition by the protease may be regulated by specialized delivery factors (known as adaptor proteins). Our detailed understanding of how these machines are regulated to prevent uncontrolled degradation within a cell has permitted the identification of novel antimicrobials that dysregulate these machines, as well as the development of tunable degradation systems that have applications in biotechnology. Here, we focus on the physiological role of the ClpP peptidase in bacteria, its role as a novel antibiotic target and the use of protein degradation as a biotechnological approach to artificially control the expression levels of a protein of interest.
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Affiliation(s)
- Jyotsna Nagpal
- Department of Biochemistry, La Trobe Institute for Molecular Science LIMS, La Trobe University, Melbourne, Vic., Australia
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Abstract
SIGNIFICANCE For a plant to grow and develop, energy and appropriate building blocks are a fundamental requirement. Mitochondrial respiration is a vital source for both. The delicate redox processes that make up respiration are affected by the plant's changing environment. Therefore, mitochondrial regulation is critically important to maintain cellular homeostasis. This involves sensing signals from changes in mitochondrial physiology, transducing this information, and mounting tailored responses, by either adjusting mitochondrial and cellular functions directly or reprogramming gene expression. RECENT ADVANCES Retrograde (RTG) signaling, by which mitochondrial signals control nuclear gene expression, has been a field of very active research in recent years. Nevertheless, no mitochondrial RTG-signaling pathway is yet understood in plants. This review summarizes recent advances toward elucidating redox processes and other bioenergetic factors as a part of RTG signaling of plant mitochondria. CRITICAL ISSUES Novel insights into mitochondrial physiology and redox-regulation provide a framework of upstream signaling. On the other end, downstream responses to modified mitochondrial function have become available, including transcriptomic data and mitochondrial phenotypes, revealing processes in the plant that are under mitochondrial control. FUTURE DIRECTIONS Drawing parallels to chloroplast signaling and mitochondrial signaling in animal systems allows to bridge gaps in the current understanding and to deduce promising directions for future research. It is proposed that targeted usage of new technical approaches, such as quantitative in vivo imaging, will provide novel leverage to the dissection of plant mitochondrial signaling.
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Abstract
Bacteria are frequently exposed to changes in environmental conditions, such as fluctuations in temperature, pH or the availability of nutrients. These assaults can be detrimental to cell as they often result in a proteotoxic stress, which can cause the accumulation of unfolded proteins. In order to restore a productive folding environment in the cell, bacteria have evolved a network of proteins, known as the protein quality control (PQC) network, which is composed of both chaperones and AAA+ proteases. These AAA+ proteases form a major part of this PQC network, as they are responsible for the removal of unwanted and damaged proteins. They also play an important role in the turnover of specific regulatory or tagged proteins. In this review, we describe the general features of an AAA+ protease, and using two of the best-characterised AAA+ proteases in Escherichia coli (ClpAP and ClpXP) as a model for all AAA+ proteases, we provide a detailed mechanistic description of how these machines work. Specifically, the review examines the physiological role of these machines, as well as the substrates and the adaptor proteins that modulate their substrate specificity.
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Voos W, Ward LA, Truscott KN. The role of AAA+ proteases in mitochondrial protein biogenesis, homeostasis and activity control. Subcell Biochem 2013; 66:223-263. [PMID: 23479443 DOI: 10.1007/978-94-007-5940-4_9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Mitochondria are specialised organelles that are structurally and functionally integrated into cells in the vast majority of eukaryotes. They are the site of numerous enzymatic reactions, some of which are essential for life. The double lipid membrane of the mitochondrion, that spatially defines the organelle and is necessary for some functions, also creates a physical but semi-permeable barrier to the rest of the cell. Thus to ensure the biogenesis, regulation and maintenance of a functional population of proteins, an autonomous protein handling network within mitochondria is required. This includes resident mitochondrial protein translocation machinery, processing peptidases, molecular chaperones and proteases. This review highlights the contribution of proteases of the AAA+ superfamily to protein quality and activity control within the mitochondrion. Here they are responsible for the degradation of unfolded, unassembled and oxidatively damaged proteins as well as the activity control of some enzymes. Since most knowledge about these proteases has been gained from studies in the eukaryotic microorganism Saccharomyces cerevisiae, much of the discussion here centres on their role in this organism. However, reference is made to mitochondrial AAA+ proteases in other organisms, particularly in cases where they play a unique role such as the mitochondrial unfolded protein response. As these proteases influence mitochondrial function in both health and disease in humans, an understanding of their regulation and diverse activities is necessary.
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Affiliation(s)
- Wolfgang Voos
- Institut für Biochemie und Molekularbiologie (IBMB), Universität Bonn, Nussallee 11, 53115, Bonn, Germany,
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Kmiec B, Urantowka A, Lech M, Janska H. Two-step processing of AtFtsH4 precursor by mitochondrial processing peptidase in Arabidopsis thaliana. MOLECULAR PLANT 2012; 5:1417-9. [PMID: 22986791 DOI: 10.1093/mp/sss099] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
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Teixeira PF, Glaser E. Processing peptidases in mitochondria and chloroplasts. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:360-70. [PMID: 22495024 DOI: 10.1016/j.bbamcr.2012.03.012] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 03/21/2012] [Accepted: 03/22/2012] [Indexed: 12/12/2022]
Abstract
Most of the mitochondrial and chloroplastic proteins are nuclear encoded and synthesized in the cytosol as precursor proteins with N-terminal extensions called targeting peptides. Targeting peptides function as organellar import signals, they are recognized by the import receptors and route precursors through the protein translocons across the organellar membranes. After the fulfilled function, targeting peptides are proteolytically cleaved off inside the organelles by different processing peptidases. The processing of mitochondrial precursors is catalyzed in the matrix by the Mitochondrial Processing Peptidase, MPP, the Mitochondrial Intermediate Peptidase, MIP (recently called Octapeptidyl aminopeptidase 1, Oct1) and the Intermediate cleaving peptidase of 55kDa, Icp55. Furthermore, different inner membrane peptidases (Inner Membrane Proteases, IMPs, Atp23, rhomboids and AAA proteases) catalyze additional processing functions, resulting in intra-mitochondrial sorting of proteins, the targeting to the intermembrane space or in the assembly of proteins into inner membrane complexes. Chloroplast targeting peptides are cleaved off in the stroma by the Stromal Processing Peptidase, SPP. If the protein is further translocated to the thylakoid lumen, an additional thylakoid-transfer sequence is removed by the Thylakoidal Processing Peptidase, TPP. Proper function of the D1 protein of Photosystem II reaction center requires its C-terminal processing by Carboxy-terminal processing protease, CtpA. Both in mitochondria and in chloroplasts, the cleaved targeting peptides are finally degraded by the Presequence Protease, PreP. The organellar proteases involved in precursor processing and targeting peptide degradation constitute themselves a quality control system ensuring the correct maturation and localization of proteins as well as assembly of protein complexes, contributing to sustenance of organelle functions. Dysfunctions of several mitochondrial processing proteases have been shown to be associated with human diseases. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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Affiliation(s)
- Pedro Filipe Teixeira
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-106 91 Stockholm, Sweden
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