1
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Yoshimura R, Minamikawa S, Suzuki T, Goto K, Latrasse D, Sicar S, Raynaud C, Benhamed M, Yoshioka Y. CRUMPLED LEAF supports plastid OUTER ENVELOPE PROTEIN OF 80 KDA complex formation in Arabidopsis. PLANT PHYSIOLOGY 2024; 194:2422-2433. [PMID: 38235762 DOI: 10.1093/plphys/kiae005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 11/17/2023] [Accepted: 11/22/2023] [Indexed: 01/19/2024]
Abstract
Embedded β-barrel proteins in the outer envelope membrane mediate most cellular trafficking between the cytoplasm and plastids. Although the TRANSLOCON AT THE OUTER ENVELOPE MEMBRANE OF CHLOROPLASTS 75-V (TOC75-V)/OUTER ENVELOPE PROTEIN OF 80 KDA (OEP80) complex has been implicated in the insertion and assembly of β-barrel proteins in the outer envelope membrane of Arabidopsis (Arabidopsis thaliana) chloroplasts, relatively little is known about this process. CRUMPLED LEAF (CRL) encodes a chloroplast outer envelope membrane-localized protein, and its loss-of-function mutation results in pleiotropic defects, including altered plant morphogenesis, growth retardation, suppression of plastid division, and spontaneous light intensity-dependent localized cell death. A suppressor screen conducted on mutagenized crl mutants revealed that a missense mutation in OEP80 suppresses the pleiotropic defects of crl. Furthermore, we found that OEP80 complex formation is compromised in crl. Additionally, we demonstrated that CRL interacts with OEP80 in vivo and that a portion of CRL is present at the same molecular weight as the OEP80 complex. Our results suggest that CRL interacts with OEP80 to facilitate its complex formation. CRL is involved in plastid protein import; therefore, the pleiotropic defects in crl are likely due to the combined effects of decreased plastid protein import and altered membrane integration of β-barrel proteins in the outer envelope membrane. This study sheds light on the mechanisms that allow β-barrel protein integration into the plastid outer envelope membrane and the importance of this finding for plant cellular processes.
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Affiliation(s)
- Ryo Yoshimura
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Syun Minamikawa
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takamasa Suzuki
- Department of Biological Chemistry, College of Bioscience and Biotechnology, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501, Japan
| | - Kotaro Goto
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - David Latrasse
- CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, 91405 Orsay, France
- CNRS, INRAE, Institute of Plant Sciences Paris-Saclay (IPS2), Université de Paris, 91405 Orsay, France
| | - Sanchari Sicar
- CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, 91405 Orsay, France
- CNRS, INRAE, Institute of Plant Sciences Paris-Saclay (IPS2), Université de Paris, 91405 Orsay, France
| | - Cécile Raynaud
- CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, 91405 Orsay, France
- CNRS, INRAE, Institute of Plant Sciences Paris-Saclay (IPS2), Université de Paris, 91405 Orsay, France
| | - Moussa Benhamed
- CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, 91405 Orsay, France
- CNRS, INRAE, Institute of Plant Sciences Paris-Saclay (IPS2), Université de Paris, 91405 Orsay, France
- Institut Universitaire de France (IUF)
| | - Yasushi Yoshioka
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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2
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Schwenkert S, Lo WT, Szulc B, Yip CK, Pratt AI, Cusack SA, Brandt B, Leister D, Kunz HH. Probing the physiological role of the plastid outer-envelope membrane using the oemiR plasmid collection. G3 (BETHESDA, MD.) 2023; 13:jkad187. [PMID: 37572358 PMCID: PMC10542568 DOI: 10.1093/g3journal/jkad187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 07/20/2023] [Accepted: 08/04/2023] [Indexed: 08/14/2023]
Abstract
Plastids are the site of complex biochemical pathways, most prominently photosynthesis. The organelle evolved through endosymbiosis with a cyanobacterium, which is exemplified by the outer envelope membrane that harbors more than 40 proteins in Arabidopsis. Their evolutionary conservation indicates high significance for plant cell function. While a few proteins are well-studied as part of the protein translocon complex the majority of outer envelope protein functions is unclear. Gaining a deeper functional understanding has been complicated by the lack of observable loss-of-function mutant phenotypes, which is often rooted in functional genetic redundancy. Therefore, we designed outer envelope-specific artificial micro RNAs (oemiRs) capable of downregulating transcripts from several loci simultaneously. We successfully tested oemiR function by performing a proof-of-concept screen for pale and cold-sensitive mutants. An in-depth analysis of pale mutant alleles deficient in the translocon component TOC75 using proteomics provided new insights into putative compensatory import pathways. The cold stress screen not only recapitulated 3 previously known phenotypes of cold-sensitive mutants but also identified 4 mutants of additional oemiR outer envelope loci. Altogether our study revealed a role of the outer envelope to tolerate cold conditions and showcasts the power of the oemiR collection to research the significance of outer envelope proteins.
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Affiliation(s)
- Serena Schwenkert
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Wing Tung Lo
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Beata Szulc
- Plant Biochemistry, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Chun Kwan Yip
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Anna I Pratt
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164-4236, USA
| | | | - Benjamin Brandt
- Plant Biochemistry, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Dario Leister
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
| | - Hans-Henning Kunz
- Plant Biochemistry, Faculty of Biology, Ludwig-Maximilians-Universität Munich, 82152 Planegg-Martinsried, Germany
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164-4236, USA
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3
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Günsel U, Klöpfer K, Häusler E, Hitzenberger M, Bölter B, Sperl LE, Zacharias M, Soll J, Hagn F. Structural basis of metabolite transport by the chloroplast outer envelope channel OEP21. Nat Struct Mol Biol 2023:10.1038/s41594-023-00984-y. [PMID: 37156968 DOI: 10.1038/s41594-023-00984-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 03/31/2023] [Indexed: 05/10/2023]
Abstract
Triose phosphates (TPs) are the primary products of photosynthetic CO2 fixation in chloroplasts, which need to be exported into the cytosol across the chloroplast inner envelope (IE) and outer envelope (OE) membranes to sustain plant growth. While transport across the IE is well understood, the mode of action of the transporters in the OE remains unclear. Here we present the high-resolution nuclear magnetic resonance (NMR) structure of the outer envelope protein 21 (OEP21) from garden pea, the main exit pore for TPs in C3 plants. OEP21 is a cone-shaped β-barrel pore with a highly positively charged interior that enables binding and translocation of negatively charged metabolites in a competitive manner, up to a size of ~1 kDa. ATP stabilizes the channel and keeps it in an open state. Despite the broad substrate selectivity of OEP21, these results suggest that control of metabolite transport across the OE might be possible.
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Affiliation(s)
- Umut Günsel
- Bavarian NMR Center (BNMRZ), Department of Bioscience, School of Natural Sciences, Technical University of Munich, Garching, Germany
- Institute of Structural Biology, Helmholtz Munich, Neuherberg, Germany
| | - Kai Klöpfer
- Bavarian NMR Center (BNMRZ), Department of Bioscience, School of Natural Sciences, Technical University of Munich, Garching, Germany
| | - Elisabeth Häusler
- Institute of Structural Biology, Helmholtz Munich, Neuherberg, Germany
| | - Manuel Hitzenberger
- Lehrstuhl für Theoretische Biophysik (T38), Department of Bioscience, School of Natural Sciences, Technical University of Munich, Garching, Germany
| | - Bettina Bölter
- Biozentrum, LMU München, Department of Biology, Planegg-Martinsried, Germany
| | - Laura E Sperl
- Bavarian NMR Center (BNMRZ), Department of Bioscience, School of Natural Sciences, Technical University of Munich, Garching, Germany
| | - Martin Zacharias
- Lehrstuhl für Theoretische Biophysik (T38), Department of Bioscience, School of Natural Sciences, Technical University of Munich, Garching, Germany
| | - Jürgen Soll
- Biozentrum, LMU München, Department of Biology, Planegg-Martinsried, Germany
| | - Franz Hagn
- Bavarian NMR Center (BNMRZ), Department of Bioscience, School of Natural Sciences, Technical University of Munich, Garching, Germany.
- Institute of Structural Biology, Helmholtz Munich, Neuherberg, Germany.
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4
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Barth MA, Soll J, Akbaş Ş. Prokaryotic and eukaryotic traits support the biological role of the chloroplast outer envelope. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119224. [PMID: 35120999 DOI: 10.1016/j.bbamcr.2022.119224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 01/22/2022] [Accepted: 01/26/2022] [Indexed: 06/14/2023]
Abstract
The plastid outer envelope (OE) is a mixture of components inherited from their prokaryotic ancestor like galactolipids, carotenoids and porin type ion channels supplemented with eukaryotic inventions to make the endosymbiotic process successful as well as to control plastid biogenesis and differentiation. In this review we wanted to highlight the importance of the OE proteins and its evolutionary origin. For a long time, the OE was thought to be a diffusion barrier only, but with the recent discoveries of all kinds of different proteins in the OE it has been shown that the OE can modulate various functions within the cell. The phenotypic changes show that channels like the outer envelope proteins OEP40, OEP16 or JASSY have a pronounced ion selectivity that cannot be replaced by other ion channels present in the OE. Eukaryotic additions, like the GTPase receptors Toc33 and Toc159 or the ubiquitin proteasome system for chloroplast protein quality control, round up the profile of the OE.
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Affiliation(s)
- Melanie Anette Barth
- Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany
| | - Jürgen Soll
- Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany.
| | - Şebnem Akbaş
- Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany
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5
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Rottet S, Förster B, Hee WY, Rourke LM, Price GD, Long BM. Engineered Accumulation of Bicarbonate in Plant Chloroplasts: Known Knowns and Known Unknowns. FRONTIERS IN PLANT SCIENCE 2021; 12:727118. [PMID: 34531888 PMCID: PMC8438413 DOI: 10.3389/fpls.2021.727118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 08/06/2021] [Indexed: 05/10/2023]
Abstract
Heterologous synthesis of a biophysical CO2-concentrating mechanism (CCM) in plant chloroplasts offers significant potential to improve the photosynthetic efficiency of C3 plants and could translate into substantial increases in crop yield. In organisms utilizing a biophysical CCM, this mechanism efficiently surrounds a high turnover rate Rubisco with elevated CO2 concentrations to maximize carboxylation rates. A critical feature of both native biophysical CCMs and one engineered into a C3 plant chloroplast is functional bicarbonate (HCO3 -) transporters and vectorial CO2-to-HCO3 - converters. Engineering strategies aim to locate these transporters and conversion systems to the C3 chloroplast, enabling elevation of HCO3 - concentrations within the chloroplast stroma. Several CCM components have been identified in proteobacteria, cyanobacteria, and microalgae as likely candidates for this approach, yet their successful functional expression in C3 plant chloroplasts remains elusive. Here, we discuss the challenges in expressing and regulating functional HCO3 - transporter, and CO2-to-HCO3 - converter candidates in chloroplast membranes as an essential step in engineering a biophysical CCM within plant chloroplasts. We highlight the broad technical and physiological concerns which must be considered in proposed engineering strategies, and present our current status of both knowledge and knowledge-gaps which will affect successful engineering outcomes.
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Affiliation(s)
- Sarah Rottet
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
| | - Britta Förster
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Wei Yih Hee
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
| | - Loraine M. Rourke
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
| | - G. Dean Price
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Benedict M. Long
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, Australia
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6
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Gross LE, Klinger A, Spies N, Ernst T, Flinner N, Simm S, Ladig R, Bodensohn U, Schleiff E. Insertion of plastidic β-barrel proteins into the outer envelopes of plastids involves an intermembrane space intermediate formed with Toc75-V/OEP80. THE PLANT CELL 2021; 33:1657-1681. [PMID: 33624803 PMCID: PMC8254496 DOI: 10.1093/plcell/koab052] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/03/2021] [Indexed: 06/12/2023]
Abstract
The insertion of organellar membrane proteins with the correct topology requires the following: First, the proteins must contain topogenic signals for translocation across and insertion into the membrane. Second, proteinaceous complexes in the cytoplasm, membrane, and lumen of organelles are required to drive this process. Many complexes required for the intracellular distribution of membrane proteins have been described, but the signals and components required for the insertion of plastidic β-barrel-type proteins into the outer membrane are largely unknown. The discovery of common principles is difficult, as only a few plastidic β-barrel proteins exist. Here, we provide evidence that the plastidic outer envelope β-barrel proteins OEP21, OEP24, and OEP37 from pea (Pisum sativum) and Arabidopsis thaliana contain information defining the topology of the protein. The information required for the translocation of pea proteins across the outer envelope membrane is present within the six N-terminal β-strands. This process requires the action of translocon of the outer chloroplast (TOC) membrane. After translocation into the intermembrane space, β-barrel proteins interact with TOC75-V, as exemplified by OEP37 and P39, and are integrated into the membrane. The membrane insertion of plastidic β-barrel proteins is affected by mutation of the last β-strand, suggesting that this strand contributes to the insertion signal. These findings shed light on the elements and complexes involved in plastidic β-barrel protein import.
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Affiliation(s)
- Lucia E Gross
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Anna Klinger
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Nicole Spies
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Theresa Ernst
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Nadine Flinner
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Stefan Simm
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
- Frankfurt Institute for Advanced Studies, D-60438 Frankfurt, Germany
| | - Roman Ladig
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Uwe Bodensohn
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
| | - Enrico Schleiff
- Department of Molecular Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9; D-60438 Frankfurt, Germany
- Frankfurt Institute for Advanced Studies, D-60438 Frankfurt, Germany
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7
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Zhang Y, Wang C, Jia H. Biogenesis and maintenance of the apicoplast in model apicomplexan parasites. Parasitol Int 2020; 81:102270. [PMID: 33321224 DOI: 10.1016/j.parint.2020.102270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 12/08/2020] [Accepted: 12/09/2020] [Indexed: 11/27/2022]
Abstract
The apicoplast is a non-photosynthetic relict plastid of Apicomplexa that evolved from a secondary symbiotic system. During its evolution, most of the genes derived from its alga ancestor were lost. Only genes involved in several valuable metabolic pathways, such as the synthesis of isoprenoid precursors, heme, and fatty acids, have been transferred to the host genome and retained to help these parasites adapt to a complex life cycle and various living environments. The biological function of an apicoplast is essential for most apicomplexan parasites. Considering their potential as drug targets, the metabolic functions of this symbiotic organelle have been intensively investigated through computational and biological means. Moreover, we know that not only organellar metabolic functions are linked with other organelles, but also their biogenesis processes have developed and evolved to tailor their biological functions and proper inheritance. Several distinct features have been found in the biogenesis process of apicoplasts. For example, the apicoplast borrows a dynamin-related protein (DrpA) from its host to implement organelle division. The autophagy system has also been repurposed for linking the apicoplast and centrosome during replication and the division process. However, many vital questions remain to be answered about how these parasites maintain and properly inherit this symbiotic organelle. Here we review our current knowledge about its biogenesis process and discuss several critical questions remaining to be answered in this field.
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Affiliation(s)
- Ying Zhang
- Heilongjiang Provincial Key Laboratory of Prevention and Control of Bovine Diseases, College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province 163319, PR China; State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Haping Street 678, Nangang District, Harbin 150069, PR China
| | - Chunren Wang
- Heilongjiang Provincial Key Laboratory of Prevention and Control of Bovine Diseases, College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province 163319, PR China
| | - Honglin Jia
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Haping Street 678, Nangang District, Harbin 150069, PR China.
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8
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Roumia AF, Theodoropoulou MC, Tsirigos KD, Nielsen H, Bagos PG. Landscape of Eukaryotic Transmembrane Beta Barrel Proteins. J Proteome Res 2020; 19:1209-1221. [PMID: 32008325 DOI: 10.1021/acs.jproteome.9b00740] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Even though in the last few years several families of eukaryotic β-barrel outer membrane proteins have been discovered, their computational characterization and their annotation in public databases are far from complete. The PFAM database includes only very few characteristic profiles for these families, and in most cases, the profile hidden Markov models (pHMMs) have been trained using prokaryotic and eukaryotic proteins together. Here, we present for the first time a comprehensive computational analysis of eukaryotic transmembrane β-barrels. Twelve characteristic pHMMs were built, based on an extensive literature search, which can discriminate eukaryotic β-barrels from other classes of proteins (globular and bacterial β-barrel ones), as well as between mitochondrial and chloroplastic ones. We built eight novel profiles for the chloroplastic β-barrel families that are not present in the PFAM database and also updated the profile for the MDM10 family (PF12519) in the PFAM database and divide the porin family (PF01459) into two separate families, namely, VDAC and TOM40.
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Affiliation(s)
- Ahmed F Roumia
- Department of Computer Science and Biomedical Informatics, University of Thessaly, 35100 Lamia, Greece
| | | | - Konstantinos D Tsirigos
- Disease Systems Biology Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark.,Department of Health Technology, Section for Bioinformatics, Technical University of Denmark, DK-2800 Kgs Lyngby, Denmark
| | - Henrik Nielsen
- Department of Health Technology, Section for Bioinformatics, Technical University of Denmark, DK-2800 Kgs Lyngby, Denmark
| | - Pantelis G Bagos
- Department of Computer Science and Biomedical Informatics, University of Thessaly, 35100 Lamia, Greece
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9
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Day PM, Inoue K, Theg SM. Chloroplast Outer Membrane β-Barrel Proteins Use Components of the General Import Apparatus. THE PLANT CELL 2019; 31:1845-1855. [PMID: 31217220 PMCID: PMC6713306 DOI: 10.1105/tpc.19.00001] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 05/20/2019] [Accepted: 06/15/2019] [Indexed: 05/12/2023]
Abstract
Chloroplasts evolved from a cyanobacterial endosymbiont that resided within a eukaryotic cell. Due to their prokaryotic heritage, chloroplast outer membranes contain transmembrane β-barrel proteins. While most chloroplast proteins use N-terminal transit peptides to enter the chloroplasts through the translocons at the outer and inner chloroplast envelope membranes (TOC/TIC), only one β-barrel protein, Toc75, has been shown to use this pathway. The route other β-barrel proteins use has remained unresolved. Here we use in vitro pea (Pisum sativum) chloroplast import assays and transient expression in Nicotiana benthamiana to address this. We show that a paralog of Toc75, outer envelope protein 80 kD (OEP80), also uses a transit peptide but has a distinct envelope sorting signal. Our results additionally indicate that β-barrels that do not use transit peptides also enter the chloroplast using components of the general import pathway.
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Affiliation(s)
- Philip M Day
- Department of Plant Biology, University of California-Davis, Davis, California 95616
| | - Kentaro Inoue
- Department of Plant Sciences, University of California-Davis, Davis, California 95616
| | - Steven M Theg
- Department of Plant Biology, University of California-Davis, Davis, California 95616
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10
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Vigani G, Solti ÏDM, Thomine SB, Philippar K. Essential and Detrimental - an Update on Intracellular Iron Trafficking and Homeostasis. PLANT & CELL PHYSIOLOGY 2019; 60:1420-1439. [PMID: 31093670 DOI: 10.1093/pcp/pcz091] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 05/06/2019] [Indexed: 05/22/2023]
Abstract
Chloroplasts, mitochondria and vacuoles represent characteristic organelles of the plant cell, with a predominant function in cellular metabolism. Chloroplasts are the site of photosynthesis and therefore basic and essential for photoautotrophic growth of plants. Mitochondria produce energy during respiration and vacuoles act as internal waste and storage compartments. Moreover, chloroplasts and mitochondria are sites for the biosynthesis of various compounds of primary and secondary metabolism. For photosynthesis and energy generation, the internal membranes of chloroplasts and mitochondria are equipped with electron transport chains. To perform proper electron transfer and several biosynthetic functions, both organelles contain transition metals and here iron is by far the most abundant. Although iron is thus essential for plant growth and development, it becomes toxic when present in excess and/or in its free, ionic form. The harmful effect of the latter is caused by the generation of oxidative stress. As a consequence, iron transport and homeostasis have to be tightly controlled during plant growth and development. In addition to the corresponding transport and homeostasis proteins, the vacuole plays an important role as an intracellular iron storage and release compartment at certain developmental stages. In this review, we will summarize current knowledge on iron transport and homeostasis in chloroplasts, mitochondria and vacuoles. In addition, we aim to integrate the physiological impact of intracellular iron homeostasis on cellular and developmental processes.
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Affiliation(s)
- Gianpiero Vigani
- Plant Physiology Unit, Department of Life Sciences and Systems Biology, University of Turin, via Quarello 15/A, Turin I, Italy
| | - Ï Dï M Solti
- Department of Plant Physiology and Molecular Plant Biology, E�tv�s Lor�nd University, Budapest H, Hungary
| | - Sï Bastien Thomine
- Institut de Biologie Int�grative de la Cellule, CNRS, Avenue de la Terrasse, Gif-sur-Yvette, France
| | - Katrin Philippar
- Plant Biology, Center for Human- and Molecular Biology (ZHMB), Saarland University, Campus A2.4, Saarbr�cken D, Germany
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11
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Voith von Voithenberg L, Park J, Stübe R, Lux C, Lee Y, Philippar K. A Novel Prokaryote-Type ECF/ABC Transporter Module in Chloroplast Metal Homeostasis. FRONTIERS IN PLANT SCIENCE 2019; 10:1264. [PMID: 31736987 PMCID: PMC6828968 DOI: 10.3389/fpls.2019.01264] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 09/11/2019] [Indexed: 05/18/2023]
Abstract
During evolution, chloroplasts, which originated by endosymbiosis of a prokaryotic ancestor of today's cyanobacteria with a eukaryotic host cell, were established as the site for photosynthesis. Therefore, chloroplast organelles are loaded with transition metals including iron, copper, and manganese, which are essential for photosynthetic electron transport due to their redox capacity. Although transport, storage, and cofactor-assembly of metal ions in chloroplasts are tightly controlled and crucial throughout plant growth and development, knowledge on the molecular nature of chloroplast metal-transport proteins is still fragmentary. Here, we characterized the soluble, ATP-binding ABC-transporter subunits ABCI10 and ABCI11 in Arabidopsis thaliana, which show similarities to components of prokaryotic, multisubunit ABC transporters. Both ABCI10 and ABCI11 proteins appear to be strongly attached to chloroplast-intrinsic membranes, most likely inner envelopes for ABCI10 and possibly plastoglobuli for ABCI11. Loss of ABCI10 and ABCI11 gene products in Arabidopsis leads to extremely dwarfed, albino plants showing impaired chloroplast biogenesis and deregulated metal homeostasis. Further, we identified the membrane-intrinsic protein ABCI12 as potential interaction partner for ABCI10 in the inner envelope. Our results suggest that ABCI12 inserts into the chloroplast inner envelope membrane most likely with five predicted α-helical transmembrane domains and represents the membrane-intrinsic subunit of a prokaryotic-type, energy-coupling factor (ECF) ABC-transporter complex. In bacteria, these multisubunit ECF importers are widely distributed for the uptake of nickel and cobalt metal ions as well as for import of vitamins and several other metabolites. Therefore, we propose that ABCI10 (as the ATPase A-subunit) and ABCI12 (as the membrane-intrinsic, energy-coupling T-subunit) are part of a novel, chloroplast envelope-localized, AAT energy-coupling module of a prokaryotic-type ECF transporter, most likely involved in metal ion uptake.
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Affiliation(s)
| | - Jiyoung Park
- Department of Life Science, Pohang University of Science and Technology, Pohang, South Korea
| | - Roland Stübe
- Plant Biochemistry and Physiology, Department of Biology I, LMU München, Planegg-Martinsried, Germany
| | - Christopher Lux
- Plant Biology, Center for Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
| | - Youngsook Lee
- Department of Life Science, Pohang University of Science and Technology, Pohang, South Korea
| | - Katrin Philippar
- Plant Biology, Center for Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
- *Correspondence: Katrin Philippar,
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12
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Voith von Voithenberg L, Park J, Stübe R, Lux C, Lee Y, Philippar K. A Novel Prokaryote-Type ECF/ABC Transporter Module in Chloroplast Metal Homeostasis. FRONTIERS IN PLANT SCIENCE 2019; 10:1264. [PMID: 31736987 DOI: 10.3389/fpls201901264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 09/11/2019] [Indexed: 05/22/2023]
Abstract
During evolution, chloroplasts, which originated by endosymbiosis of a prokaryotic ancestor of today's cyanobacteria with a eukaryotic host cell, were established as the site for photosynthesis. Therefore, chloroplast organelles are loaded with transition metals including iron, copper, and manganese, which are essential for photosynthetic electron transport due to their redox capacity. Although transport, storage, and cofactor-assembly of metal ions in chloroplasts are tightly controlled and crucial throughout plant growth and development, knowledge on the molecular nature of chloroplast metal-transport proteins is still fragmentary. Here, we characterized the soluble, ATP-binding ABC-transporter subunits ABCI10 and ABCI11 in Arabidopsis thaliana, which show similarities to components of prokaryotic, multisubunit ABC transporters. Both ABCI10 and ABCI11 proteins appear to be strongly attached to chloroplast-intrinsic membranes, most likely inner envelopes for ABCI10 and possibly plastoglobuli for ABCI11. Loss of ABCI10 and ABCI11 gene products in Arabidopsis leads to extremely dwarfed, albino plants showing impaired chloroplast biogenesis and deregulated metal homeostasis. Further, we identified the membrane-intrinsic protein ABCI12 as potential interaction partner for ABCI10 in the inner envelope. Our results suggest that ABCI12 inserts into the chloroplast inner envelope membrane most likely with five predicted α-helical transmembrane domains and represents the membrane-intrinsic subunit of a prokaryotic-type, energy-coupling factor (ECF) ABC-transporter complex. In bacteria, these multisubunit ECF importers are widely distributed for the uptake of nickel and cobalt metal ions as well as for import of vitamins and several other metabolites. Therefore, we propose that ABCI10 (as the ATPase A-subunit) and ABCI12 (as the membrane-intrinsic, energy-coupling T-subunit) are part of a novel, chloroplast envelope-localized, AAT energy-coupling module of a prokaryotic-type ECF transporter, most likely involved in metal ion uptake.
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Affiliation(s)
| | - Jiyoung Park
- Department of Life Science, Pohang University of Science and Technology, Pohang, South Korea
| | - Roland Stübe
- Plant Biochemistry and Physiology, Department of Biology I, LMU München, Planegg-Martinsried, Germany
| | - Christopher Lux
- Plant Biology, Center for Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
| | - Youngsook Lee
- Department of Life Science, Pohang University of Science and Technology, Pohang, South Korea
| | - Katrin Philippar
- Plant Biology, Center for Human and Molecular Biology (ZHMB), Saarland University, Saarbrücken, Germany
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13
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Day PM, Theg SM. Evolution of protein transport to the chloroplast envelope membranes. PHOTOSYNTHESIS RESEARCH 2018; 138:315-326. [PMID: 30291507 DOI: 10.1007/s11120-018-0540-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 06/20/2018] [Indexed: 05/11/2023]
Abstract
Chloroplasts are descendants of an ancient endosymbiotic cyanobacterium that lived inside a eukaryotic cell. They inherited the prokaryotic double membrane envelope from cyanobacteria. This envelope contains prokaryotic protein sorting machineries including a Sec translocase and relatives of the central component of the bacterial outer membrane β-barrel assembly module. As the endosymbiont was integrated with the rest of the cell, the synthesis of most of its proteins shifted from the stroma to the host cytosol. This included nearly all the envelope proteins identified so far. Consequently, the overall biogenesis of the chloroplast envelope must be distinct from cyanobacteria. Envelope proteins initially approach their functional locations from the exterior rather than the interior. In many cases, they have been shown to use components of the general import pathway that also serves the stroma and thylakoids. If the ancient prokaryotic protein sorting machineries are still used for chloroplast envelope proteins, their activities must have been modified or combined with the general import pathway. In this review, we analyze the current knowledge pertaining to chloroplast envelope biogenesis and compare this to bacteria.
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Affiliation(s)
- Philip M Day
- Department of Plant Biology, University of California at Davis, 1 Shields Avenue, Davis, CA, USA
| | - Steven M Theg
- Department of Plant Biology, University of California at Davis, 1 Shields Avenue, Davis, CA, USA.
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Könnel A, Bugaeva W, Gügel IL, Philippar K. BANFF: bending of bilayer membranes by amphiphilic α-helices is necessary for form and function of organelles 1. Biochem Cell Biol 2018; 97:243-256. [PMID: 30208283 DOI: 10.1139/bcb-2018-0150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
By binding to and inserting into the lipid bilayer, amphiphilic α-helices of proteins are involved in the curvature of biological membranes in all organisms. In particular, they are involved in establishing the complex membrane architecture of intracellular organelles like the endoplasmatic reticulum, Golgi apparatus, mitochondria, and chloroplasts. Thus, amphiphilic α-helices are essential for maintenance of cellular metabolism and fitness of organisms. Here we focus on the structure and function of membrane-intrinsic proteins, which are involved in membrane curvature by amphiphilic α-helices, in mitochondria and chloroplasts of the eukaryotic model organisms yeast and Arabidopsis thaliana. Further, we propose a model for transport of fatty acids and lipid compounds across the envelope of chloroplasts in which amphiphilic α-helices might play a role.
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Affiliation(s)
- Anne Könnel
- a Center for Human- and Molecular Biology (ZHMB) - Plant Biology, Saarland University, Campus A 2.4, 66123 Saarbrücken, Germany
| | - Wassilina Bugaeva
- a Center for Human- and Molecular Biology (ZHMB) - Plant Biology, Saarland University, Campus A 2.4, 66123 Saarbrücken, Germany
| | - Irene L Gügel
- b Department of Biology I - Botany, Ludwig-Maximilians University München, Großhaderner-Str. 2, 82152 Planegg-Martinsried, Germany
| | - Katrin Philippar
- a Center for Human- and Molecular Biology (ZHMB) - Plant Biology, Saarland University, Campus A 2.4, 66123 Saarbrücken, Germany
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Affiliation(s)
- Tobias Jores
- Interfaculty Institute of Biochemistry; University of Tuebingen; Germany
| | - Doron Rapaport
- Interfaculty Institute of Biochemistry; University of Tuebingen; Germany
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16
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Harsman A, Schock A, Hemmis B, Wahl V, Jeshen I, Bartsch P, Schlereth A, Pertl-Obermeyer H, Goetze TA, Soll J, Philippar K, Wagner R. OEP40, a Regulated Glucose-permeable β-Barrel Solute Channel in the Chloroplast Outer Envelope Membrane. J Biol Chem 2016; 291:17848-60. [PMID: 27339897 DOI: 10.1074/jbc.m115.712398] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Indexed: 12/20/2022] Open
Abstract
Chloroplasts and mitochondria are unique endosymbiotic cellular organelles surrounded by two membranes. Essential metabolic networking between these compartments and their hosting cells requires the exchange of a large number of biochemical pathway intermediates in a directed and coordinated fashion across their inner and outer envelope membranes. Here, we describe the identification and functional characterization of a highly specific, regulated solute channel in the outer envelope of chloroplasts, named OEP40. Loss of OEP40 function in Arabidopsis thaliana results in early flowering under cold temperature. The reconstituted recombinant OEP40 protein forms a high conductance β-barrel ion channel with subconductant states in planar lipid bilayers. The OEP40 channel is slightly cation-selective PK+/PCl- ≈ 4:1 and rectifying (i⃗/i⃖ ≅ 2) with a slope conductance of Ḡmax ≅ 690 picosiemens. The OEP40 channel has a restriction zone diameter of ≅1.4 nm and is permeable for glucose, glucose 1-phosphate and glucose 6-phosphate, but not for maltose. Moreover, channel properties are regulated by trehalose 6-phosphate, which cannot permeate. Altogether, our results indicate that OEP40 is a "glucose-gate" in the outer envelope membrane of chloroplasts, facilitating selective metabolite exchange between chloroplasts and the surrounding cell.
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Affiliation(s)
- Anke Harsman
- From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück
| | - Annette Schock
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Birgit Hemmis
- From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück
| | - Vanessa Wahl
- the Department of Metabolic Networks, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Ingrid Jeshen
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Philipp Bartsch
- From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück
| | - Armin Schlereth
- the Department of Metabolic Networks, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Heidi Pertl-Obermeyer
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Tom Alexander Goetze
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Jürgen Soll
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Katrin Philippar
- the Chair of Plant Biochemistry and Physiology, Department Biology I-Botany, Ludwig-Maximilians-University München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, the Munich Centre for Integrated Protein Science, Ludwig-Maximilians-University München, D-81377 München, and
| | - Richard Wagner
- From the Institute of Biophysics, Department of Biology, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück,
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17
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Pottosin I, Shabala S. Transport Across Chloroplast Membranes: Optimizing Photosynthesis for Adverse Environmental Conditions. MOLECULAR PLANT 2016; 9:356-370. [PMID: 26597501 DOI: 10.1016/j.molp.2015.10.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 10/17/2015] [Accepted: 10/19/2015] [Indexed: 05/18/2023]
Abstract
Chloroplasts are central to solar light harvesting and photosynthesis. Optimal chloroplast functioning is vitally dependent on a very intensive traffic of metabolites and ions between the cytosol and stroma, and should be attuned for adverse environmental conditions. This is achieved by an orchestrated regulation of a variety of transport systems located at chloroplast membranes such as porines, solute channels, ion-specific cation and anion channels, and various primary and secondary active transport systems. In this review we describe the molecular nature and functional properties of the inner and outer envelope and thylakoid membrane channels and transporters. We then discuss how their orchestrated regulation affects thylakoid structure, electron transport and excitation energy transfer, proton-motive force partition, ion homeostasis, stromal pH regulation, and volume regulation. We link the activity of key cation and anion transport systems with stress-specific signaling processes in chloroplasts, and discuss how these signals interact with the signals generated in other organelles to optimize the cell performance, with a special emphasis on Ca(2+) and reactive oxygen species signaling.
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Affiliation(s)
- Igor Pottosin
- Biomedical Centre, University of Colima, Colima, Colima 28045, Mexico; School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia
| | - Sergey Shabala
- School of Land and Food, University of Tasmania, Hobart, TAS 7001, Australia.
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18
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Pottosin I, Dobrovinskaya O. Ion Channels in Native Chloroplast Membranes: Challenges and Potential for Direct Patch-Clamp Studies. Front Physiol 2015; 6:396. [PMID: 26733887 PMCID: PMC4686732 DOI: 10.3389/fphys.2015.00396] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 12/04/2015] [Indexed: 11/29/2022] Open
Abstract
Photosynthesis without any doubt depends on the activity of the chloroplast ion channels. The thylakoid ion channels participate in the fine partitioning of the light-generated proton-motive force (p.m.f.). By regulating, therefore, luminal pH, they affect the linear electron flow and non-photochemical quenching. Stromal ion homeostasis and signaling, on the other hand, depend on the activity of both thylakoid and envelope ion channels. Experimentally, intact chloroplasts and swollen thylakoids were proven to be suitable for direct measurements of the ion channels activity via conventional patch-clamp technique; yet, such studies became infrequent, although their potential is far from being exhausted. In this paper we wish to summarize existing challenges for direct patch-clamping of native chloroplast membranes as well as present available results on the activity of thylakoid Cl− (ClC?) and divalent cation-permeable channels, along with their tentative roles in the p.m.f. partitioning, volume regulation, and stromal Ca2+ and Mg2+ dynamics. Patch-clamping of the intact envelope revealed both large-conductance porin-like channels, likely located in the outer envelope membrane and smaller conductance channels, more compatible with the inner envelope location. Possible equivalent model for the sandwich-like arrangement of the two envelope membranes within the patch electrode will be discussed, along with peculiar properties of the fast-activated cation channel in the context of the stromal pH control.
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Affiliation(s)
- Igor Pottosin
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima Colima, Mexico
| | - Oxana Dobrovinskaya
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima Colima, Mexico
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19
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Mindthoff S, Grunau S, Steinfort LL, Girzalsky W, Hiltunen JK, Erdmann R, Antonenkov VD. Peroxisomal Pex11 is a pore-forming protein homologous to TRPM channels. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:271-83. [PMID: 26597702 DOI: 10.1016/j.bbamcr.2015.11.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 10/16/2015] [Accepted: 11/16/2015] [Indexed: 01/16/2023]
Abstract
More than 30 proteins (Pex proteins) are known to participate in the biogenesis of peroxisomes-ubiquitous oxidative organelles involved in lipid and ROS metabolism. The Pex11 family of homologous proteins is responsible for division and proliferation of peroxisomes. We show that yeast Pex11 is a pore-forming protein sharing sequence similarity with TRPM cation-selective channels. The Pex11 channel with a conductance of Λ=4.1 nS in 1.0M KCl is moderately cation-selective (PK(+)/PCl(-)=1.85) and resistant to voltage-dependent closing. The estimated size of the channel's pore (r~0.6 nm) supports the notion that Pex11 conducts solutes with molecular mass below 300-400 Da. We localized the channel's selectivity determining sequence. Overexpression of Pex11 resulted in acceleration of fatty acids β-oxidation in intact cells but not in the corresponding lysates. The β-oxidation was affected in cells by expression of the Pex11 protein carrying point mutations in the selectivity determining sequence. These data suggest that the Pex11-dependent transmembrane traffic of metabolites may be a rate-limiting step in the β-oxidation of fatty acids. This conclusion was corroborated by analysis of the rate of β-oxidation in yeast strains expressing Pex11 with mutations mimicking constitutively phosphorylated (S165D, S167D) or unphosphorylated (S165A, S167A) protein. The results suggest that phosphorylation of Pex11 is a mechanism that can control the peroxisomal β-oxidation rate. Our results disclose an unexpected function of Pex11 as a non-selective channel responsible for transfer of metabolites across peroxisomal membrane. The data indicate that peroxins may be involved in peroxisomal metabolic processes in addition to their role in peroxisome biogenesis.
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Affiliation(s)
- Sabrina Mindthoff
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Ruhr-Universität, Bochum, Germany
| | - Silke Grunau
- Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Laura L Steinfort
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Ruhr-Universität, Bochum, Germany
| | - Wolfgang Girzalsky
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Ruhr-Universität, Bochum, Germany
| | - J Kalervo Hiltunen
- Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Ralf Erdmann
- Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Ruhr-Universität, Bochum, Germany.
| | - Vasily D Antonenkov
- Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, Oulu, Finland.
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20
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Antonenkov VD, Isomursu A, Mennerich D, Vapola MH, Weiher H, Kietzmann T, Hiltunen JK. The Human Mitochondrial DNA Depletion Syndrome Gene MPV17 Encodes a Non-selective Channel That Modulates Membrane Potential. J Biol Chem 2015; 290:13840-61. [PMID: 25861990 DOI: 10.1074/jbc.m114.608083] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Indexed: 12/17/2022] Open
Abstract
The human MPV17-related mitochondrial DNA depletion syndrome is an inherited autosomal recessive disease caused by mutations in the inner mitochondrial membrane protein MPV17. Although more than 30 MPV17 gene mutations were shown to be associated with mitochondrial DNA depletion syndrome, the function of MPV17 is still unknown. Mice deficient in Mpv17 show signs of premature aging. In the present study, we used electrophysiological measurements with recombinant MPV17 to reveal that this protein forms a non-selective channel with a pore diameter of 1.8 nm and located the channel's selectivity filter. The channel was weakly cation-selective and showed several subconductance states. Voltage-dependent gating of the channel was regulated by redox conditions and pH and was affected also in mutants mimicking a phosphorylated state. Likewise, the mitochondrial membrane potential (Δψm) and the cellular production of reactive oxygen species were higher in embryonic fibroblasts from Mpv17(-/-) mice. However, despite the elevated Δψm, the Mpv17-deficient mitochondria showed signs of accelerated fission. Together, these observations uncover the role of MPV17 as a Δψm-modulating channel that apparently contributes to mitochondrial homeostasis under different conditions.
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Affiliation(s)
- Vasily D Antonenkov
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - Antti Isomursu
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - Daniela Mennerich
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - Miia H Vapola
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - Hans Weiher
- the Heinrich Pette Institute, Leibniz Institute for Experimental Virology, 20251 Hamburg, Germany
| | - Thomas Kietzmann
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - J Kalervo Hiltunen
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
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21
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Goetze TA, Patil M, Jeshen I, Bölter B, Grahl S, Soll J. Oep23 forms an ion channel in the chloroplast outer envelope. BMC PLANT BIOLOGY 2015; 15:47. [PMID: 25849634 PMCID: PMC4331141 DOI: 10.1186/s12870-015-0445-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 01/30/2015] [Indexed: 05/20/2023]
Abstract
BACKGROUND Metabolite, ion and protein translocation into chloroplasts occurs across two membranes, the inner and the outer envelope. Solute and metabolite channels fulfill very important functions in integrating the organelles into the metabolic network of the cell. However so far only a few have been identified. Here we describe the identification and the characterization of the outer envelope protein of 23 kDa, Oep23 from garden pea. RESULTS Oep23 is found in the entire plant lineage from green algae to flowering plants. It is expressed in all organs and developmental states tested so far. The reconstituted recombinant protein Oep23 from pea forms a high conductance ion channel with a maximal conductance in the fully open state of 466 ± 14pS at a holding potential of +100 mV (in 250 mM KCl). The Oep23 channel is cation selective (PK+ : PCl- = 15 : 1) with a voltage dependent open probability of maximal Vmem = 0 mV. CONCLUSION The data indicate that the Oep23 activity represents a single channel unit and does not assemble into a multiple pore complex like bacterial type porins or mitochondrial voltage dependent anion channel. Thus, Oep23 represents a new member of ion channels in the outer envelope of chloroplasts involved in solute exchange.
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Affiliation(s)
- Tom Alexander Goetze
- />Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany
- />Nanion Technologies GmbH, Gabrielenstr. 9, 80636 München, Germany
| | - Manali Patil
- />Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany
- />The Munich Center of Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 München, Germany
| | - Ingrid Jeshen
- />Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany
- />The Munich Center of Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 München, Germany
| | - Bettina Bölter
- />Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany
- />The Munich Center of Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 München, Germany
| | - Sabine Grahl
- />Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany
- />The Munich Center of Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 München, Germany
| | - Jürgen Soll
- />Department Biologie 1, Botanik, Ludwig-Maximilians-Universität München, Großhaderner Str. 2-4, 82152 Planegg-Martinsried, Germany
- />The Munich Center of Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 München, Germany
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22
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Lung SC, Smith MD, Weston JK, Gwynne W, Secord N, Chuong SDX. The C-terminus of Bienertia sinuspersici Toc159 contains essential elements for its targeting and anchorage to the chloroplast outer membrane. FRONTIERS IN PLANT SCIENCE 2014; 5:722. [PMID: 25566294 PMCID: PMC4274882 DOI: 10.3389/fpls.2014.00722] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Accepted: 11/30/2014] [Indexed: 05/11/2023]
Abstract
Most nucleus-encoded chloroplast proteins rely on an N-terminal transit peptide (TP) as a post-translational sorting signal for directing them to the organelle. Although Toc159 is known to be a receptor for specific preprotein TPs at the chloroplast surface, the mechanism for its own targeting and integration into the chloroplast outer membrane is not completely understood. In a previous study, we identified a novel TP-like sorting signal at the C-terminus (CT) of a Toc159 homolog from the single-cell C4 species, Bienertia sinuspersici. In the current study, we have extended our understanding of the sorting signal using transient expression of fluorescently-tagged fusion proteins of variable-length, and with truncated and swapped versions of the CT. As was shown in the earlier study, the 56 residues of the CT contain crucial sorting information for reversible interaction of the receptor with the chloroplast envelope. Extension of this region to 100 residues in the current study stabilized the interaction via membrane integration, as demonstrated by more prominent plastid-associated signals and resistance of the fusion protein to alkaline extraction. Despite a high degree of sequence similarity, the plastid localization signals of the equivalent CT regions of Arabidopsis thaliana Toc159 homologs were not as strong as that of the B. sinuspersici counterparts. Together with computational and circular dichroism analyses of the CT domain structures, our data provide insights into the critical elements of the CT for the efficient targeting and anchorage of Toc159 receptors to the dimorphic chloroplasts in the single-cell C4 species.
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Affiliation(s)
- Shiu-Cheung Lung
- School of Biological Sciences, The University of Hong KongHong Kong SAR, China
| | - Matthew D. Smith
- Department of Biology, Wilfrid Laurier UniversityWaterloo, ON, Canada
| | - J. Kyle Weston
- Department of Biology, Wilfrid Laurier UniversityWaterloo, ON, Canada
| | - William Gwynne
- Department of Biology, University of WaterlooWaterloo, ON, Canada
| | - Nathan Secord
- Department of Biology, University of WaterlooWaterloo, ON, Canada
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Oh YJ, Hwang I. Targeting and biogenesis of transporters and channels in chloroplast envelope membranes: Unsolved questions. Cell Calcium 2014; 58:122-30. [PMID: 25465895 DOI: 10.1016/j.ceca.2014.10.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 10/23/2014] [Accepted: 10/24/2014] [Indexed: 01/10/2023]
Abstract
Chloroplasts produce carbohydrates, hormones, vitamins, amino acids, pigments, nucleotides, ATP, and secondary metabolites. Channels and transporters are required for the movement of molecules across the two chloroplast envelope membranes. These transporters and channel proteins are grouped into two different types, including β-barrel proteins and transmembrane-domain (TMD) containing proteins. Most β-barrel proteins are localized at the outer chloroplast membrane, and TMD-containing proteins are localized at the inner chloroplast membrane. Many of these transporters and channels are encoded by nuclear genes; therefore, they have to be imported into chloroplasts after translation on cytosolic ribosomes. These proteins should have specific targeting signals for their final destination in the chloroplast membrane and for assembly into specific complexes. In this review, we summarize recent progress in the identification, functional characterization, and biogenesis of transporters and channels at the chloroplast envelope membranes, and discuss outstanding questions regarding transporter and channel protein biogenesis.
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Affiliation(s)
- Young Jun Oh
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
| | - Inhwan Hwang
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea; Department Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
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Pick TR, Weber APM. Unknown components of the plastidial permeome. FRONTIERS IN PLANT SCIENCE 2014; 5:410. [PMID: 25191333 PMCID: PMC4137279 DOI: 10.3389/fpls.2014.00410] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 08/01/2014] [Indexed: 05/29/2023]
Abstract
Beyond their role in photosynthesis plastids provide a plethora of additional metabolic functions to plant cells. For example, they harbor complete biosynthetic pathways for the de novo synthesis of carotenoids, fatty acids, and amino acids. Furthermore plastids contribute important reactions to multi-compartmentalized pathways, such as photorespiration or plant hormone syntheses, and they depend on the import of essential molecules that they cannot synthesize themselves, such as ascorbic acid. This causes a high traffic of metabolites across the plastid envelope. Although it was recently shown that non-polar substrates could be exchanged between the plastid and the ER without involving transporters, various essential transport processes are mediated by highly selective but still unknown metabolite transporters. This review focuses on selected components of the plastidial permeome that are predicted to exist but that have not yet been identified as molecular entities, such as the transporters for isopentenyl diphosphate (IPP) or ascorbic acid.
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Affiliation(s)
| | - Andreas P. M. Weber
- *Correspondence: Andreas P. M. Weber, Institut für Biochemie der Pflanzen, Cluster of Excellence on Plant Sciences, Heinrich-Heine Universität Düsseldorf, Universitätstrasse 1, D-40225 Düsseldorf, Germany e-mail:
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Gutierrez-Carbonell E, Takahashi D, Lattanzio G, Rodríguez-Celma J, Kehr J, Soll J, Philippar K, Uemura M, Abadía J, López-Millán AF. The distinct functional roles of the inner and outer chloroplast envelope of Pea (Pisum sativum) as revealed by proteomic approaches. J Proteome Res 2014; 13:2941-53. [PMID: 24792535 DOI: 10.1021/pr500106s] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Protein profiles of inner (IE) and outer (OE) chloroplast envelope membrane preparations from pea were studied using shotgun nLC-MS/MS and two-dimensional electrophoresis, and 589 protein species (NCBI entries) were identified. The relative enrichment of each protein in the IE/OE pair of membranes was used to provide an integrated picture of the chloroplast envelope. From the 546 proteins identified with shotgun, 321 showed a significant differential distribution, with 180 being enriched in IE and 141 in OE. To avoid redundancy and facilitate in silico localization, Arabidopsis homologues were used to obtain a nonredundant list of 409 envelope proteins, with many showing significant OE or IE enrichment. Functional classification reveals that IE is a selective barrier for transport of many metabolites and plays a major role in controlling protein homeostasis, whereas proteins in OE are more heterogeneous and participate in a wide range of processes. Data support that metabolic processes previously described to occur in the envelope such as chlorophyll and tocopherol biosynthesis can be ascribed to the IE, whereas others such as carotenoid or lipid biosynthesis occur in both membranes. Furthermore, results allow empirical assignation to the IE and/or OE of many proteins previously assigned to the bulk chloroplast envelope proteome.
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Affiliation(s)
- Elain Gutierrez-Carbonell
- Plant Nutrition Department, Aula Dei Experimental Station, CSIC , P.O. Box 13034, 50080 Zaragoza, Spain
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26
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Manandhar-Shrestha K, Tamot B, Pratt EPS, Saitie S, Bräutigam A, Weber APM, Hoffmann-Benning S. Comparative proteomics of chloroplasts envelopes from bundle sheath and mesophyll chloroplasts reveals novel membrane proteins with a possible role in c4-related metabolite fluxes and development. FRONTIERS IN PLANT SCIENCE 2013; 4:65. [PMID: 23543921 PMCID: PMC3610082 DOI: 10.3389/fpls.2013.00065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 03/08/2013] [Indexed: 05/08/2023]
Abstract
As the world population grows, our need for food increases drastically. Limited amounts of arable land lead to a competition between food and fuel crops, while changes in the global climate may impact future crop yields. Thus, a second "green revolution" will need a better understanding of the processes essential for plant growth and development. One approach toward the solution of this problem is to better understand regulatory and transport processes in C4 plants. C4 plants display an up to 10-fold higher apparent CO2 assimilation and higher yields while maintaining high water use efficiency. This requires differential regulation of mesophyll (M) and bundle sheath (BS) chloroplast development as well as higher metabolic fluxes of photosynthetic intermediates between cells and particularly across chloroplast envelopes. While previous analyses of overall chloroplast membranes have yielded significant insight, our comparative proteomics approach using enriched BS and M chloroplast envelopes of Zea mays allowed us to identify 37 proteins of unknown function that have not been seen in these earlier studies. We identified 280 proteins, 84% of which are known/predicted to be present in chloroplasts. Seventy-four percent have a known or predicted membrane association. Twenty-one membrane proteins were 2-15 times more abundant in BS cells, while 36 of the proteins were more abundant in M chloroplast envelopes. These proteins could represent additional candidates of proteins essential for development or metabolite transport processes in C4 plants. RT-PCR confirmed differential expression of 13 candidate genes. Chloroplast association for seven proteins was confirmed using YFP/GFP labeling. Gene expression of four putative transporters was examined throughout the leaf and during the greening of leaves. Genes for a PIC-like protein and an ER-AP-like protein show an early transient increase in gene expression during the transition to light. In addition, PIC gene expression is increased in the immature part of the leaf and was lower in the fully developed parts of the leaf, suggesting a need for/incorporation of the protein during chloroplast development.
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Affiliation(s)
- K. Manandhar-Shrestha
- Department of Biochemistry and Molecular Biology, Michigan State UniversityEast Lansing, MI, USA
| | - B. Tamot
- Department of Biochemistry and Molecular Biology, Michigan State UniversityEast Lansing, MI, USA
| | - E. P. S. Pratt
- Department of Biochemistry and Molecular Biology, Michigan State UniversityEast Lansing, MI, USA
| | - S. Saitie
- Department of Biochemistry and Molecular Biology, Michigan State UniversityEast Lansing, MI, USA
| | - A. Bräutigam
- Plant Biochemistry, Heinrich-Heine University DüsseldorfDüsseldorf, Germany
| | - A. P. M. Weber
- Plant Biochemistry, Heinrich-Heine University DüsseldorfDüsseldorf, Germany
| | - Susanne Hoffmann-Benning
- Department of Biochemistry and Molecular Biology, Michigan State UniversityEast Lansing, MI, USA
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Haferkamp I, Linka N. Functional expression and characterisation of membrane transport proteins. PLANT BIOLOGY (STUTTGART, GERMANY) 2012; 14:675-90. [PMID: 22639981 DOI: 10.1111/j.1438-8677.2012.00591.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Membrane transporters set the framework organising the complexity of plant metabolism in cells, tissues and organisms. Their substrate specificity and controlled activity in different cells is a crucial part for plant metabolism to run pathways in concert. Transport proteins catalyse the uptake and exchange of ions, substrates, intermediates, products and cofactors across membranes. Given the large number of metabolites, a wide spectrum of transporters is required. The vast majority of in silico annotated membrane transporters in plant genomes, however, has not yet been functionally characterised. Hence, to understand the metabolic network as a whole, it is important to understand how transporters connect and control the metabolic pathways of plant cells. Heterologous expression and in vitro activity studies of recombinant transport proteins have highly improved their functional analysis in the last two decades. This review provides a comprehensive overview of the recent advances in membrane protein expression and functional characterisation using various host systems and transport assays.
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Affiliation(s)
- I Haferkamp
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - N Linka
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
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28
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Lung SC, Chuong SD. A transit peptide-like sorting signal at the C terminus directs the Bienertia sinuspersici preprotein receptor Toc159 to the chloroplast outer membrane. THE PLANT CELL 2012; 24:1560-78. [PMID: 22517318 PMCID: PMC3398564 DOI: 10.1105/tpc.112.096248] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Revised: 03/07/2012] [Accepted: 04/02/2012] [Indexed: 05/21/2023]
Abstract
Although Toc159 is known to be one of the key GTPase receptors for selective recognition of chloroplast preproteins, the mechanism for its targeting to the chloroplast surface remains unclear. To compare the targeting of these GTPase receptors, we identified two Toc159 isoforms and a Toc34 from Bienertia sinuspersici, a single-cell C₄ species with dimorphic chloroplasts in individual chlorenchyma cells. Fluorescent protein tagging and immunogold studies revealed that the localization patterns of Toc159 were distinctive from those of Toc34, suggesting different targeting pathways. Bioinformatics analyses indicated that the C-terminal tails (CTs) of Toc159 possess physicochemical and structural properties of chloroplast transit peptides (cTPs). These results were further confirmed by fluorescent protein tagging, which showed the targeting of CT fusion proteins to the chloroplast surface. The CT of Bs Toc159 in reverse orientation functioned as a cleavable cTP that guided the fluorescent protein to the stroma. Moreover, a Bs Toc34 mutant protein was retargeted to the chloroplast envelope using the CTs of Toc159 or reverse sequences of other cTPs, suggesting their conserved functions. Together, our data show that the C terminus and the central GTPase domain represent a novel dual domain-mediated sorting mechanism that might account for the partitioning of Toc159 between the cytosol and the chloroplast envelope for preprotein recognition.
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Affiliation(s)
| | - Simon D.X. Chuong
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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29
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Homblé F, Krammer EM, Prévost M. Plant VDAC: facts and speculations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1486-501. [PMID: 22155681 DOI: 10.1016/j.bbamem.2011.11.028] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 11/12/2011] [Accepted: 11/22/2011] [Indexed: 01/01/2023]
Abstract
The voltage-dependent anion-selective channel (VDAC) is the most abundant protein in the mitochondrial outer membrane and the major transport pathway for a large variety of compounds ranging from ions to large polymeric molecules such as DNA and tRNA. Plant VDACs feature a secondary structure content and electrophysiological properties akin to those of VDACs from other organisms. They however undergo a specific regulation. The general importance of VDAC in plant physiology has only recently emerged. Besides their role in metabolite transport, plant VDACs are also involved in the programmed cell death triggered in response to biotic and abiotic stresses. Moreover, their colocalization in non-mitochondrial membranes suggests a diversity of function. This review summarizes our current understanding of the structure and function of plant VDACs. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.
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Affiliation(s)
- Fabrice Homblé
- Structure et Fontion des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles, Boulevard du Triomphe CP, Brussels, Belgium.
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30
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Ni DQ, Zook J, Klewer DA, Nieman RA, Soll J, Fromme P. Isolation, folding and structural investigations of the amino acid transporter OEP16. Protein Expr Purif 2011; 80:157-68. [PMID: 21878393 DOI: 10.1016/j.pep.2011.08.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2011] [Revised: 08/03/2011] [Accepted: 08/04/2011] [Indexed: 11/18/2022]
Abstract
Membrane proteins compose more than 30% of all proteins in the living cell. However, many membrane proteins have low abundance in the cell and cannot be isolated from natural sources in concentrations suitable for structure analysis. The overexpression, reconstitution, and stabilization of membrane proteins are complex and remain a formidable challenge in membrane protein characterization. Here we describe a novel, in vitro folding procedure for a cation-selective channel protein, the outer envelope membrane protein 16 (OEP16) of pea chloroplast, overexpressed in Escherichia coli in the form of inclusion bodies. The protein is purified and then folded with detergent on a Ni-NTA affinity column. Final concentrations of reconstituted OEP16 of up to 24 mg/ml have been achieved, which provides samples that are sufficient for structural studies by NMR and crystallography. Reconstitution of OEP16 in detergent micelles was monitored by circular dichroism, fluorescence, and NMR spectroscopy. Tryptophan fluorescence spectra of heterologous expressed OEP16 in micelles are similar to spectra of functionally active OEP16 in liposomes, which indicates folding of the membrane protein in detergent micelles. CD spectroscopy studies demonstrate a folded protein consisting primarily of α-helices. ¹⁵N-HSQC NMR spectra also provide evidence for a folded protein. We present here a convenient, effective and quantitative method to screen large numbers of conditions for optimal protein stability by using microdialysis chambers in combination with fluorescence spectroscopy. Recent collection of multidimensional NMR data at 500, 600 and 800 MHz demonstrated that the protein is suitable for structure determination by NMR and stable for weeks during data collection.
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Affiliation(s)
- Da Qun Ni
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA
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31
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Ladig R, Sommer MS, Hahn A, Leisegang MS, Papasotiriou DG, Ibrahim M, Elkehal R, Karas M, Zickermann V, Gutensohn M, Brandt U, Klösgen RB, Schleiff E. A high-definition native polyacrylamide gel electrophoresis system for the analysis of membrane complexes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 67:181-94. [PMID: 21418111 DOI: 10.1111/j.1365-313x.2011.04577.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Native polyacrylamide gel electrophoresis (PAGE) is an important technique for the analysis of membrane protein complexes. A major breakthrough was the development of blue native (BN-) and high resolution clear native (hrCN-) PAGE techniques. Although these techniques are very powerful, they could not be applied to all systems with the same resolution. We have developed an alternative protocol for the analysis of membrane protein complexes of plant chloroplasts and cyanobacteria, which we termed histidine- and deoxycholate-based native (HDN-) PAGE. We compared the capacity of HDN-, BN- and hrCN-PAGE to resolve the well-studied respiratory chain complexes in mitochondria of bovine heart muscle and Yarrowia lipolytica, as well as thylakoid localized complexes of Medicago sativa, Pisum sativum and Anabaena sp. PCC7120. Moreover, we determined the assembly/composition of the Anabaena sp. PCC7120 thylakoids and envelope membranes by HDN-PAGE. The analysis of isolated chloroplast envelope complexes by HDN-PAGE permitted us to resolve complexes such as the translocon of the outer envelope migrating at approximately 700 kDa or of the inner envelope of about 230 and 400 kDa with high resolution. By immunodecoration and mass spectrometry of these complexes we present new insights into the assembly/composition of these translocation machineries. The HDN-PAGE technique thus provides an important tool for future analyses of membrane complexes such as protein translocons.
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Affiliation(s)
- Roman Ladig
- Institute of Biology - Plant Physiology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, D-06120 Halle/Saale, Germany
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Bölter B, Soll J. Protein Import into Chloroplasts: Dealing with the (Membrane) Integration Problem. Chembiochem 2011; 12:1655-61. [DOI: 10.1002/cbic.201100118] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Indexed: 11/10/2022]
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Breuers FKH, Bräutigam A, Weber APM. The Plastid Outer Envelope - A Highly Dynamic Interface between Plastid and Cytoplasm. FRONTIERS IN PLANT SCIENCE 2011; 2:97. [PMID: 22629266 PMCID: PMC3355566 DOI: 10.3389/fpls.2011.00097] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 11/29/2011] [Indexed: 05/09/2023]
Abstract
Plastids are the defining organelles of all photosynthetic eukaryotes. They are the site of photosynthesis and of a large number of other essential metabolic pathways, such as fatty acid and amino acid biosyntheses, sulfur and nitrogen assimilation, and aromatic and terpenoid compound production, to mention only a few examples. The metabolism of plastids is heavily intertwined and connected with that of the surrounding cytosol, thus causing massive traffic of metabolic precursors, intermediates, and products. Two layers of biological membranes that are called the inner (IE) and the outer (OE) plastid envelope membranes bound the plastids of Archaeplastida. While the IE is generally accepted as the osmo-regulatory barrier between cytosol and stroma, the OE was considered to represent an unspecific molecular sieve, permeable for molecules of up to 10 kDa. However, after the discovery of small substrate specific pores in the OE, this view has come under scrutiny. In addition to controlling metabolic fluxes between plastid and cytosol, the OE is also crucial for protein import into the chloroplast. It contains the receptors and translocation channel of the TOC complex that is required for the canonical post-translational import of nuclear-encoded, plastid-targeted proteins. Further, the OE is a metabolically active compartment of the chloroplast, being involved in, e.g., fatty acid metabolism and membrane lipid production. Also, recent findings hint on the OE as a defense platform against several biotic and abiotic stress conditions, such as cold acclimation, freezing tolerance, and phosphate deprivation. Moreover, dynamic non-covalent interactions between the OE and the endomembrane system are thought to play important roles in lipid and non-canonical protein trafficking between plastid and endoplasmic reticulum. While proteomics and bioinformatics has provided us with comprehensive but still incomplete information on proteins localized in the plastid IE, the stroma, and the thylakoids, our knowledge of the protein composition of the plastid OE is far from complete. In this article, we report on the recent progress in discovering novel OE proteins to draw a conclusive picture of the OE. A "parts list" of the plastid OE will be presented, using data generated by proteomics of plastids isolated from various plant sources.
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Affiliation(s)
| | - Andrea Bräutigam
- Institut für Biochemie der Pflanzen, Heinrich-Heine Universität DüsseldorfDüsseldorf, Germany
| | - Andreas P. M. Weber
- Institut für Biochemie der Pflanzen, Heinrich-Heine Universität DüsseldorfDüsseldorf, Germany
- *Correspondence: Andreas P. M. Weber, Institut für Biochemie der Pflanzen, Heinrich-Heine Universität Düsseldorf, Universitätstrasse 1, D-40225 Düsseldorf, Germany. e-mail:
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35
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Lim L, McFadden GI. The evolution, metabolism and functions of the apicoplast. Philos Trans R Soc Lond B Biol Sci 2010; 365:749-63. [PMID: 20124342 PMCID: PMC2817234 DOI: 10.1098/rstb.2009.0273] [Citation(s) in RCA: 197] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The malaria parasite, Plasmodium falciparum, harbours a relict plastid known as the ‘apicoplast’. The discovery of the apicoplast ushered in an exciting new prospect for drug development against the parasite. The eubacterial ancestry of the organelle offers a wealth of opportunities for the development of therapeutic interventions. Morphological, biochemical and bioinformatic studies of the apicoplast have further reinforced its ‘plant-like’ characteristics and potential as a drug target. However, we are still not sure why the apicoplast is essential for the parasite's survival. This review explores the origins and metabolic functions of the apicoplast. In an attempt to decipher the role of the organelle within the parasite we also take a closer look at the transporters decorating the plastid to better understand the metabolic exchanges between the apicoplast and the rest of the parasite cell.
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Affiliation(s)
- Liting Lim
- School of Botany, University of Melbourne, Parkville, Victoria 3010, Australia
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36
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Abstract
Plastids are a heterogeneous family of organelles found ubiquitously in plants and algal cells. Most prominent are the chloroplasts, which carry out such essential processes as photosynthesis and the biosynthesis of fatty acids as well as of amino acids. As mitochondria, chloroplasts are derived from a single endosymbiotic event. They are believed to have evolved from an ancient cyanobacterium, which was engulfed by an early eukaryotic ancestor. During evolution the plastid genome has been greatly reduced and most of the genes have been transferred to the host nucleus. Consequently, more than 98% of all plastid proteins are translated on cytosolic ribosomes. They have to be posttranslationally targeted to and imported into the organelle. Targeting is assisted by cytosolic proteins which interact with proteins destined for plastids and thereby keep them in an import competent state. After reaching the target organelle, many proteins have to conquer the barrier of the chloroplast outer and inner envelope. This process is mediated by complex molecular machines in the outer (Toc complex) and inner (Tic complex) envelope of chloroplasts, respectively. Most proteins destined for the compartments inside the chloroplast contain a cleavable N-terminal transit peptide, whereas most of the outer envelope components insert into the membrane without such a targeting peptide.
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Affiliation(s)
- Penelope Strittmatter
- Department Biologie I-Botanik, Ludwig-Maximilians-Universität, Planegg-Martinsried and Munich Center for Integrated Protein Science, CiPSM, Ludwig-Maximilians- Universität, Munich, Germany
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Liguori L, Blesneac I, Madern D, Vivaudou M, Lenormand JL. Single-step production of functional OEP24 proteoliposomes. Protein Expr Purif 2010; 69:106-11. [DOI: 10.1016/j.pep.2009.07.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Revised: 07/07/2009] [Accepted: 07/07/2009] [Indexed: 10/20/2022]
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Jouhet J, Gray JC. Interaction of actin and the chloroplast protein import apparatus. J Biol Chem 2009; 284:19132-41. [PMID: 19435889 PMCID: PMC2707226 DOI: 10.1074/jbc.m109.012831] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 05/08/2009] [Indexed: 11/06/2022] Open
Abstract
Actin filaments are major components of the cytoskeleton and play numerous essential roles, including chloroplast positioning and plastid stromule movement, in plant cells. Actin is present in pea chloroplast envelope membrane preparations and is localized at the surface of the chloroplasts, as shown by agglutination of intact isolated chloroplasts by antibodies to actin. To identify chloroplast envelope proteins involved in actin binding, we have carried out actin co-immunoprecipitation and co-sedimentation experiments on detergent-solubilized pea chloroplast envelope membranes. Proteins co-immunoprecipitated with actin were identified by mass spectrometry and by Western blotting and included the Toc159, Toc75, Toc34, and Tic110 components of the TOC-TIC protein import apparatus. A direct interaction of actin with Escherichia coli-expressed Toc159, but not Toc33, was shown by co-sedimentation experiments, suggesting that Toc159 is the component of the TOC complex that interacts with actin on the cytosolic side of the outer envelope membrane. The physiological significance of this interaction is unknown, but it may play a role in the import of nuclear-encoded photosynthesis proteins.
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Affiliation(s)
- Juliette Jouhet
- From the Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, United Kingdom
| | - John C. Gray
- From the Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, United Kingdom
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Bräutigam A, Hoffmann-Benning S, Hofmann-Benning S, Weber APM. Comparative proteomics of chloroplast envelopes from C3 and C4 plants reveals specific adaptations of the plastid envelope to C4 photosynthesis and candidate proteins required for maintaining C4 metabolite fluxes. PLANT PHYSIOLOGY 2008; 148:568-79. [PMID: 18599648 PMCID: PMC2528119 DOI: 10.1104/pp.108.121012] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 06/23/2008] [Indexed: 05/19/2023]
Abstract
C(4) plants have up to 10-fold higher apparent CO(2) assimilation rates than the most productive C(3) plants. This requires higher fluxes of metabolic intermediates across the chloroplast envelope membranes of C(4) plants in comparison with those of C(3) plants. In particular, the fluxes of metabolites involved in the biochemical inorganic carbon pump of C(4) plants, such as malate, pyruvate, oxaloacetate, and phosphoenolpyruvate, must be considerably higher in C(4) plants because they exceed the apparent rate of photosynthetic CO(2) assimilation, whereas they represent relatively minor fluxes in C(3) plants. While the enzymatic steps involved in the C(4) biochemical inorganic carbon pump have been studied in much detail, little is known about the metabolite transporters in the envelope membranes of C(4) chloroplasts. In this study, we used comparative proteomics of chloroplast envelope membranes from the C(3) plant pea (Pisum sativum) and mesophyll cell chloroplast envelopes from the C(4) plant maize (Zea mays) to analyze the adaptation of the mesophyll cell chloroplast envelope proteome to the requirements of C(4) photosynthesis. We show that C(3)- and C(4)-type chloroplasts have qualitatively similar but quantitatively very different chloroplast envelope membrane proteomes. In particular, translocators involved in the transport of triosephosphate and phosphoenolpyruvate as well as two outer envelope porins are much more abundant in C(4) plants. Several putative transport proteins have been identified that are highly abundant in C(4) plants but relatively minor in C(3) envelopes. These represent prime candidates for the transport of C(4) photosynthetic intermediates, such as pyruvate, oxaloacetate, and malate.
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Affiliation(s)
- Andrea Bräutigam
- Institute for Plant Biochemistry, Heinrich-Heine-University, D-40225 Duesseldorf, Germany
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Karnataki A, Derocher A, Coppens I, Nash C, Feagin JE, Parsons M. Cell cycle-regulated vesicular trafficking of Toxoplasma APT1, a protein localized to multiple apicoplast membranes. Mol Microbiol 2007; 63:1653-68. [PMID: 17367386 DOI: 10.1111/j.1365-2958.2007.05619.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The apicoplast is a relict plastid essential for viability of the apicomplexan parasites Toxoplasma and Plasmodium. It is surrounded by multiple membranes that proteins, substrates and metabolites must traverse. Little is known about apicoplast membrane proteins, much less their sorting mechanisms. We have identified two sets of apicomplexan proteins that are homologous to plastid membrane proteins that transport phosphosugars or their derivatives. Members of the first set bear N-terminal extensions similar to those that target proteins to the apicoplast lumen. While Toxoplasma gondii lacks this type of translocator, the N-terminal extension from the Plasmodium falciparum sequence was shown to be functional in T. gondii. The second set of translocators lacks an N-terminal targeting sequence. This translocator, TgAPT1, when tagged with HA, localized to multiple apicoplast membranes in T. gondii. Contrasting with the constitutive targeting of luminal proteins, the localization of the translocator varied during the cell cycle. Early-stage parasites showed circumplastid distribution, but as the plastid elongated in preparation for division, vesicles bearing TgAPT1 appeared adjacent to the plastid. After plastid division, the protein resumes a circumplastid colocalization. These studies demonstrate for the first time that vesicular trafficking likely plays a role in the apicoplast biogenesis.
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Affiliation(s)
- Anuradha Karnataki
- Seattle Biomedical Research Institute, 307 Westlake Ave. N., Seattle, WA 98109, USA
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41
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Block MA, Douce R, Joyard J, Rolland N. Chloroplast envelope membranes: a dynamic interface between plastids and the cytosol. PHOTOSYNTHESIS RESEARCH 2007; 92:225-44. [PMID: 17558548 PMCID: PMC2394710 DOI: 10.1007/s11120-007-9195-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Accepted: 05/03/2007] [Indexed: 05/15/2023]
Abstract
Chloroplasts are bounded by a pair of outer membranes, the envelope, that is the only permanent membrane structure of the different types of plastids. Chloroplasts have had a long and complex evolutionary past and integration of the envelope membranes in cellular functions is the result of this evolution. Plastid envelope membranes contain a wide diversity of lipids and terpenoid compounds serving numerous biochemical functions and the flexibility of their biosynthetic pathways allow plants to adapt to fluctuating environmental conditions (for instance phosphate deprivation). A large body of knowledge has been generated by proteomic studies targeted to envelope membranes, thus revealing an unexpected complexity of this membrane system. For instance, new transport systems for metabolites and ions have been identified in envelope membranes and new routes for the import of chloroplast-specific proteins have been identified. The picture emerging from our present understanding of plastid envelope membranes is that of a key player in plastid biogenesis and the co-ordinated gene expression of plastid-specific protein (owing to chlorophyll precursors), of a major hub for integration of metabolic and ionic networks in cell metabolism, of a flexible system that can divide, produce dynamic extensions and interact with other cell constituents. Envelope membranes are indeed one of the most complex and dynamic system within a plant cell. In this review, we present an overview of envelope constituents together with recent insights into the major functions fulfilled by envelope membranes and their dynamics within plant cells.
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Duy D, Soll J, Philippar K. Solute channels of the outer membrane: from bacteria to chloroplasts. Biol Chem 2007; 388:879-89. [PMID: 17696771 DOI: 10.1515/bc.2007.120] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Chloroplasts, unique organelles of plants, originated from endosymbiosis of an ancestor of today's cyanobacteria with a mitochondria-containing host cell. It is assumed that the outer envelope membrane, which delimits the chloroplast from the surrounding cytosol, was thus inherited from its Gram-negative bacterial ancestor. This plastid-specific membrane is thus equipped with elements of prokaryotic and eukaryotic origin. In particular, the membrane-intrinsic outer envelope proteins (OEPs) form solute channels with properties reminiscent of porins and channels in the bacterial outer membrane. OEP channels are characterised by distinct specificities for metabolites and a quite peculiar expression pattern in specialised plant organs and plastids, thus disproving the assumption that the outer envelope is a non-specific molecular sieve. The same is true for the outer membrane of Gram-negative bacteria, which functions as a permeability barrier in addition to the cytoplasmic membrane, and embeds different classes of channel pores. The channels of these prokaryotic prototype proteins, ranging from unspecific porins to specific channels to ligand-gated receptors, are exclusively built of beta-barrels. Although most of the OEP channels are formed by beta-strands as well, phylogeny based on sequence homology alone is not feasible. Thus, the comparison of structural and functional properties of chloroplast outer envelope and bacterial outer membrane channels is required to pinpoint the ancestral OEP 'portrait gallery'.
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Affiliation(s)
- Daniela Duy
- Department Biologie 1, Botanik, Biochemie und Physiologie der Pflanzen, Ludwig-Maximilians-Universität München, Menzingerstrasse 67, D-80638 Munich, Germany
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43
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Abstract
Plastids are a heterogeneous family of organelles found ubiquitously in plant and algal cells. Most prominent are the chloroplasts, which carry out such essential processes as photosynthesis and the biosynthesis of fatty acids as well as of amino acids. As mitochondria, chloroplasts derived from a single endosymbiotic event. They are believed to have evolved from an ancient cyanobacterium, which was engulfed by an early eukaryotic ancestor. During evolution the plastid genome has been greatly reduced and most of the genes have been transferred to the host nucleus. Consequently, more than 98% of all plastid proteins are translated on cytosolic ribosomes. They have to be posttranslationally targeted to and imported into the organelle. Targeting is assisted by cytosolic proteins, which interact with proteins destined for plastids and thereby keep them in an import-competent state. After reaching the target organelle, many proteins have to conquer the barrier of the chloroplast outer and inner envelopes. This process is mediated by complex molecular machines in the outer (Toc complex) and inner (Tic complex) envelope of chloroplasts, respectively. Most proteins destined for compartments inside the chloroplast contain a cleavable N-terminal transit peptide, whereas most of the outer envelope components insert into the membrane without such a targeting peptide.
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Affiliation(s)
- Friederike Hörmann
- Department Biologie I, Ludwig-Maximilians-Universität, Menzingerst, Germany
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Jaquinod M, Villiers F, Kieffer-Jaquinod S, Hugouvieux V, Bruley C, Garin J, Bourguignon J. A proteomics dissection of Arabidopsis thaliana vacuoles isolated from cell culture. Mol Cell Proteomics 2006; 6:394-412. [PMID: 17151019 PMCID: PMC2391258 DOI: 10.1074/mcp.m600250-mcp200] [Citation(s) in RCA: 248] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
To better understand the mechanisms governing cellular traffic, storage of various metabolites, and their ultimate degradation, Arabidopsis thaliana vacuole proteomes were established. To this aim, a procedure was developed to prepare highly purified vacuoles from protoplasts isolated from Arabidopsis cell cultures using Ficoll density gradients. Based on the specific activity of the vacuolar marker alpha-mannosidase, the enrichment factor of the vacuoles was estimated at approximately 42-fold with an average yield of 2.1%. Absence of significant contamination by other cellular compartments was validated by Western blot using antibodies raised against specific markers of chloroplasts, mitochondria, plasma membrane, and endoplasmic reticulum. Based on these results, vacuole preparations showed the necessary degree of purity for proteomics study. Therefore, a proteomics approach was developed to identify the protein components present in both the membrane and soluble fractions of the Arabidopsis cell vacuoles. This approach includes the following: (i) a mild oxidation step leading to the transformation of cysteine residues into cysteic acid and methionine to methionine sulfoxide, (ii) an in-solution proteolytic digestion of very hydrophobic proteins, and (iii) a prefractionation of proteins by short migration by SDS-PAGE followed by analysis by liquid chromatography coupled to tandem mass spectrometry. This procedure allowed the identification of more than 650 proteins, two-thirds of which copurify with the membrane hydrophobic fraction and one-third of which copurifies with the soluble fraction. Among the 416 proteins identified from the membrane fraction, 195 were considered integral membrane proteins based on the presence of one or more predicted transmembrane domains, and 110 transporters and related proteins were identified (91 putative transporters and 19 proteins related to the V-ATPase pump). With regard to function, about 20% of the proteins identified were known previously to be associated with vacuolar activities. The proteins identified are involved in ion and metabolite transport (26%), stress response (9%), signal transduction (7%), and metabolism (6%) or have been described to be involved in typical vacuolar activities, such as protein and sugar hydrolysis. The subcellular localization of several putative vacuolar proteins was confirmed by transient expression of green fluorescent protein fusion constructs.
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Affiliation(s)
- Michel Jaquinod
- Développement de la protéomique comme outil d'investigation fonctionelle et d'annotation des génomes
INSERM : ERM0201CEA17, rue des Martyrs 38054 Grenoble Cedex,FR
- * Correspondence should be adressed to: Michel Jaquinod
| | - Florent Villiers
- LPCV, Laboratoire de physiologie cellulaire végétale
CNRS : UMR5168INRA : UR1200CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble Ibat. C2
17 Rue des martyrs
38054 GRENOBLE CEDEX 9,FR
| | - Sylvie Kieffer-Jaquinod
- Développement de la protéomique comme outil d'investigation fonctionelle et d'annotation des génomes
INSERM : ERM0201CEA17, rue des Martyrs 38054 Grenoble Cedex,FR
| | - Véronique Hugouvieux
- LPCV, Laboratoire de physiologie cellulaire végétale
CNRS : UMR5168INRA : UR1200CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble Ibat. C2
17 Rue des martyrs
38054 GRENOBLE CEDEX 9,FR
| | - Christophe Bruley
- Développement de la protéomique comme outil d'investigation fonctionelle et d'annotation des génomes
INSERM : ERM0201CEA17, rue des Martyrs 38054 Grenoble Cedex,FR
| | - Jérôme Garin
- Développement de la protéomique comme outil d'investigation fonctionelle et d'annotation des génomes
INSERM : ERM0201CEA17, rue des Martyrs 38054 Grenoble Cedex,FR
| | - Jacques Bourguignon
- LPCV, Laboratoire de physiologie cellulaire végétale
CNRS : UMR5168INRA : UR1200CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble Ibat. C2
17 Rue des martyrs
38054 GRENOBLE CEDEX 9,FR
- * Correspondence should be adressed to: Jacques Bourguignon
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Syam Prakash SR, Jayabaskaran C. Expression and localization of calcium-dependent protein kinase isoforms in chickpea. JOURNAL OF PLANT PHYSIOLOGY 2006; 163:1135-49. [PMID: 16716453 DOI: 10.1016/j.jplph.2006.04.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Accepted: 04/05/2006] [Indexed: 05/09/2023]
Abstract
Calcium-dependent protein kinases (CPKs) play important roles in multiple signal transduction pathways but the precise role of individual CPK is largely unknown. We isolated two cDNAs encoding two CPK isoforms (Cicer arietinum CPKs-CaCPK1 and CaCPK2) of chickpea. Their expression in various organs and in response to various phytohormones, and dehydration, high salt stress and fungal spore in excised leaves as well as localization in leaf and stem tissues were analyzed in this study. CaCPK1 protein and its activity were ubiquitous in all tissues examined. In contrast, CaCPK2 transcript, CaCPK2 protein and its activity were almost undetectable in flowers and fruits. Both CaCPK1 and CaCPK2 transcripts and proteins were abundant in roots but in minor quantities in leaves and stems. Of the three phytohormones tested, viz. indole-3-acetic acid (IAA), gibberellin (GA(3)) and benzyladenine (BA), only BA increased both CaCPK1 and CaCPK2 transcripts, proteins and their activities. GA(3) induced accumulation of CaCPK2 transcript and protein but CaCPK1 remained unaffected. The expression of CaCPK1 and CaCPK2 in leaves was enhanced in response to high salt stress. Treatments with Aspergillus sp. spores increased expression of CaCPK1 in chickpea leaf tissue but had no effect on CaCPK2. Excised leaves subjected to dehydration showed increase in CaCPK2 expression but not in CaCPK1. Both isoforms were located in the plasma membrane (PM) and chloroplast membrane of leaf mesophyll cells as well as in the PM of stem xylem parenchyma cells. These results suggest specific roles for CaCPK isoforms in phytohormone/defense/stress signaling pathways.
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Affiliation(s)
- S R Syam Prakash
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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46
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Goetze TA, Philippar K, Ilkavets I, Soll J, Wagner R. OEP37 Is a New Member of the Chloroplast Outer Membrane Ion Channels. J Biol Chem 2006; 281:17989-98. [PMID: 16624824 DOI: 10.1074/jbc.m600700200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The chloroplast outer envelope protein OEP37 is a member of the growing beta-barrel protein family of the outer chloroplast membrane. The reconstituted recombinant protein OEP37 from pea forms a rectifying high conductance channel with a main conductance (lambda) of Lambda= 500 picosiemens (symmetrical 250 mm KCl). The OEP37 channel is cation-selective (P(K+)/P(K-) = 14:1) with a voltage-dependent open probability maximal at V(mem) = 0 mV. The channel pore reveals an hourglass-shaped form with different diameters for the vestibule and restriction zone. The diameters of the vestibule at the high conductance side were estimated by d = 3.0 nm and the restriction zone by d = 1.5 nm. The OEP37 channel displayed a nanomolar affinity for the precursor of the chloroplast inner membrane protein Tic32, which is imported into the chloroplast through a yet unknown pathway. Pre-proteins imported through the usual Toc pathway and synthetic control peptides, however, did not show a comparable block of the OEP37 channel. In addition to the electrophysiological characterization, we studied the gene expression of OEP37 in the model plant Arabidopsis thaliana. Here, transcripts of AtOEP37 are ubiquitously expressed throughout plant development and accumulate in early germinating seedlings as well as in late embryogenesis. The plastid intrinsic protein could be detected in isolated chloroplasts of cotyledons and rosette leaves. However, the knock-out mutant oep37-1 shows that the proper function of this single copy gene is not essential for development of the mature plant. Moreover, import of Tic32 into chloroplasts of oep37-1 was not impaired when compared with wild type. Thus, OEP37 may constitute a novel peptide-sensitive ion channel in the outer envelope of plastids with function during embryogenesis and germination.
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Affiliation(s)
- Tom Alexander Goetze
- Biophysik, Universität Osnabrück, FB Biologie/Chemie, Barbarastrasse 13, D-49076 Osnabrück, Germany
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47
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Hemmler R, Becker T, Schleiff E, Bölter B, Stahl T, Soll J, Götze TA, Braams S, Wagner R. Molecular properties of Oep21, an ATP-regulated anion-selective solute channel from the outer chloroplast membrane. J Biol Chem 2006; 281:12020-9. [PMID: 16473880 DOI: 10.1074/jbc.m513586200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The flux of phosphorylated carbohydrates, the major export products of chloroplasts, is regulated at the level of the inner and presumably also at the level of the outer membrane. This is achieved through modulation of the outer membrane Oep21 channel currents and tuning of its ion selectivity. Refined analysis of the Oep21 channel properties by biochemical and electrophysiological methods revealed a channel formed by eight beta-strands with a wider pore vestibule of dvest approximately 2.4 nm at the intermembrane site and a narrower filter pore of drestr approximately 1 nm. The Oep21 pore contains two high affinity sites for ATP, one located at a relative transmembrane electrical distance delta = 0.56 and the second close to the vestibule at the intermembrane site. The ATP-dependent current block and reduction in anion selectivity of the Oep21 channel is relieved by the competitive binding of phosphorylated metabolic intermediates like 3-phosphoglycerate and glycerinaldehyde 3-phosphate. Deletion of a C-terminal putative FX4K binding motif in Oep21 decreased the capability of the channel to tune its ion selectivity by about 50%, whereas current block remained unchanged.
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Affiliation(s)
- Roland Hemmler
- Biophysik, Universität Osnabrück, FB Biologie/Chemie, Barbarastrasse 11, D-49034 Osnabrück, Germany
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Vothknecht UC, Soll J. Chloroplast membrane transport: interplay of prokaryotic and eukaryotic traits. Gene 2005; 354:99-109. [PMID: 15979252 DOI: 10.1016/j.gene.2005.04.021] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2005] [Revised: 02/15/2005] [Accepted: 04/15/2005] [Indexed: 11/25/2022]
Abstract
Chloroplasts are specific plant organelles of prokaryotic origin. They are separated from the surrounding cell by a double membrane, which represents an effective barrier for the transport of metabolites and proteins. Specific transporters in the inner envelope membrane have been described, which facilitate the exchange of metabolites. In contrast, the outer envelope has been viewed for a long time as a molecular sieve that offers a mere size constriction to the passage of molecules. This view has been challenged lately, and a number of specific and regulated pore proteins of the outer envelope (OEPs) have been identified. These pores seem to have originated by adaptation of outer membrane proteins of the cyanobacterial ancestor of the chloroplast. In a similar fashion, the transport of proteins across the two envelope membranes is achieved by two hetero-oligomeric protein complexes called Toc (translocon in the outer envelope of chloroplasts) and Tic (translocon in the inner envelope of chloroplasts). The phylogenetic provenance of the translocon components is less clear, but at least the channel protein of the Toc translocon is of cyanobacterial origin. Characteristic of cyanobacteria and chloroplasts is furthermore a specialized internal membrane system, the thylakoids, on which the components of the photosynthetic machinery are located. Despite the importance of this membrane, very little is known about its phylogenetic origin or the manner of its synthesis. Vipp1 appears to be a ubiquitous component of thylakoid formation, while in chloroplasts of land plants, additionally a vesicle transport system of eukaryotic origin might be involved in this process.
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Affiliation(s)
- Ute C Vothknecht
- Department of Biology I, Botanisches Institut der LMU München, Menzinger Street 67, München D-80638, Germany.
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49
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Hofmann NR, Theg SM. Chloroplast outer membrane protein targeting and insertion. TRENDS IN PLANT SCIENCE 2005; 10:450-7. [PMID: 16085449 DOI: 10.1016/j.tplants.2005.07.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Revised: 06/29/2005] [Accepted: 07/26/2005] [Indexed: 05/03/2023]
Abstract
Proteins in the chloroplast outer envelope membrane are nuclear encoded and post-translationally targeted to the chloroplast. The targeting and membrane insertion of these proteins is not well understood. Although early work suggested otherwise, the best-studied outer membrane proteins (OMPs) use both proteins within the chloroplast and NTPs for insertion. There have been conflicting reports in the field regarding protein targeting and insertion, which have probably arisen because of differences in experimental methodology and different interpretations of reduction (versus abolition) of integration. This review summarizes what is known to date about the mechanism of chloroplast OMP targeting.
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Affiliation(s)
- Nancy R Hofmann
- Section of Plant Biology, University of California - Davis, Davis, CA 95616, USA
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50
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Teardo E, Frare E, Segalla A, De Marco V, Giacometti GM, Szabò I. Localization of a putative ClC chloride channel in spinach chloroplasts. FEBS Lett 2005; 579:4991-6. [PMID: 16115625 DOI: 10.1016/j.febslet.2005.08.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Accepted: 08/02/2005] [Indexed: 11/29/2022]
Abstract
Seven genes seem to encode for putative ClC chloride channels (AtClC-a to AtClC-g) in Arabidopsis thaliana. Their function and localization is still largely unknown. AtClC-f shares considerable sequence similarity with putative ClC channel proteins from Synechocystis, considered to represent the precursor of chloroplasts. We show by biochemical and mass spectrometry analysis that ClC-f is located in the outer envelope membrane of spinach chloroplasts. Consistent with the plastidial localization of ClC-f, p-chlorophenoxy-acetic acid (CPA) reduces photosynthetic activity and the protein is expressed in etioplasts and chloroplasts but not in root tissue. These findings may represent a step toward the molecular identification of ion channel activities in chloroplast membranes.
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Affiliation(s)
- Enrico Teardo
- Department of Biology, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
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