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Vedalankar P, Tripathy BC. Light dependent protochlorophyllide oxidoreductase: a succinct look. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2024; 30:719-731. [PMID: 38846463 PMCID: PMC11150229 DOI: 10.1007/s12298-024-01454-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 03/01/2024] [Accepted: 04/29/2024] [Indexed: 06/09/2024]
Abstract
Reducing protochlorophyllide (Pchlide) to chlorophyllide (Chlide) is a major regulatory step in the chlorophyll biosynthesis pathway. This reaction is catalyzed by light-dependent protochlorophyllide oxidoreductase (LPOR) in oxygenic phototrophs, particularly angiosperms. LPOR-NADPH and Pchlide form a ternary complex to be efficiently photo-transformed to synthesize Chlide and, subsequently, chlorophyll during the transition from skotomorphogenesis to photomorphogenesis. Besides lipids, carotenoids and poly-cis xanthophylls influence the formation of the photoactive LPOR complexes and the PLBs. The crystal structure of LPOR reveals evolutionarily conserved cysteine residues implicated in the Pchlide binding and catalysis around the active site. Different isoforms of LPOR viz PORA, PORB, and PORC expressed at different stages of chloroplast development play a photoprotective role by quickly transforming the photosensitive Pchlide to Chlide. Non-photo-transformed Pchlide acts as a photosensitizer to generate singlet oxygen that causes oxidative stress and cell death. Therefore, different isoforms of LPOR have evolved and differentially expressed during plant development to protect plants from photodamage and thus play a pivotal role during photomorphogenesis. This review brings out the salient features of LPOR structure, structure-function relationships, and ultra-fast photo transformation of Pchlide to Chlide by oligomeric and polymeric forms of LPOR.
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Affiliation(s)
| | - Baishnab C. Tripathy
- Department of Biotechnology, Sharda University, Greater Noida, Uttar Pradesh 201310 India
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Klasek L, Inoue K. Dual Protein Localization to the Envelope and Thylakoid Membranes Within the Chloroplast. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 323:231-63. [PMID: 26944623 DOI: 10.1016/bs.ircmb.2015.12.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The chloroplast houses various metabolic processes essential for plant viability. This organelle originated from an ancestral cyanobacterium via endosymbiosis and maintains the three membranes of its progenitor. Among them, the outer envelope membrane functions mainly in communication with cytoplasmic components while the inner envelope membrane houses selective transport of various metabolites and the biosynthesis of several compounds, including membrane lipids. These two envelope membranes also play essential roles in import of nuclear-encoded proteins and in organelle division. The third membrane, the internal membrane system known as the thylakoid, houses photosynthetic electron transport and chemiosmotic phosphorylation. The inner envelope and thylakoid membranes share similar lipid composition. Specific targeting pathways determine their defined proteomes and, thus, their distinct functions. Nonetheless, several proteins have been shown to exist in both the envelope and thylakoid membranes. These proteins include those that play roles in protein transport, tetrapyrrole biosynthesis, membrane dynamics, or transport of nucleotides or inorganic phosphate. In this review, we summarize the current knowledge about proteins localized to both the envelope and thylakoid membranes in the chloroplast, discussing their roles in each membrane and potential mechanisms of their dual localization. Addressing the unanswered questions about these dual-localized proteins should help advance our understanding of chloroplast development, protein transport, and metabolic regulation.
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Affiliation(s)
- Laura Klasek
- Department of Plant Sciences, University of California at Davis, Davis, CA, United States of America
| | - Kentaro Inoue
- Department of Plant Sciences, University of California at Davis, Davis, CA, United States of America.
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Cell growth defect factor 1 is crucial for the plastid import of NADPH:protochlorophyllide oxidoreductase A in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2015; 112:5838-43. [PMID: 25901327 DOI: 10.1073/pnas.1506339112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Tetrapyrroles such as chlorophyll, heme, and bacteriochlorophyll play fundamental roles in the energy absorption and transduction of all photosynthetic organisms. They are synthesized via a complex pathway taking place in chloroplasts. Chlorophyll biosynthesis in angiosperms involves 16 steps of which only one is light-requiring and driven by the NADPH:protochlorophyllide oxidoreductase (POR). Three POR isoforms have been identified in Arabidopsis thaliana--designated PORA, PORB, and PORC--that are differentially expressed in etiolated, light-exposed, and light-adapted plants. All three isoforms are encoded by nuclear genes, are synthesized as larger precursors in the cytosol (pPORs), and are imported posttranslationally into the plastid compartment. Import of the precursor to the dark-specific isoform PORA (pPORA) is protochlorophyllide (Pchlide)-dependent and due to the operation of a unique translocon complex dubbed PTC (Pchlide-dependent translocon complex) in the plastid envelope. Here, we identified a ∼30-kDa protein that participates in pPORA import. The ∼30-kDa protein is identical to the previously identified CELL GROWTH DEFECT FACTOR 1 (CDF1) in Arabidopsis that is conserved in higher plants and Synechocystis. CDF1 operates in pPORA import and stabilization and hereby acts as a chaperone for PORA protein translocation. CDF1 permits tight interactions between Pchlide synthesized in the plastid envelope and the importing PORA polypeptide chain such that no photoexcitative damage occurs through the generation of singlet oxygen operating as a cell death inducer. Together, our results identify an ancient mechanism dating back to the endosymbiotic origin of chloroplasts as a key element of Pchlide-dependent pPORA import.
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Solymosi K, Aronsson H. Etioplasts and Their Significance in Chloroplast Biogenesis. PLASTID DEVELOPMENT IN LEAVES DURING GROWTH AND SENESCENCE 2013. [DOI: 10.1007/978-94-007-5724-0_3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Tanaka R, Kobayashi K, Masuda T. Tetrapyrrole Metabolism in Arabidopsis thaliana. THE ARABIDOPSIS BOOK 2011; 9:e0145. [PMID: 22303270 PMCID: PMC3268503 DOI: 10.1199/tab.0145] [Citation(s) in RCA: 152] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Higher plants produce four classes of tetrapyrroles, namely, chlorophyll (Chl), heme, siroheme, and phytochromobilin. In plants, tetrapyrroles play essential roles in a wide range of biological activities including photosynthesis, respiration and the assimilation of nitrogen/sulfur. All four classes of tetrapyrroles are derived from a common biosynthetic pathway that resides in the plastid. In this article, we present an overview of tetrapyrrole metabolism in Arabidopsis and other higher plants, and we describe all identified enzymatic steps involved in this metabolism. We also summarize recent findings on Chl biosynthesis and Chl breakdown. Recent advances in this field, in particular those on the genetic and biochemical analyses of novel enzymes, prompted us to redraw the tetrapyrrole metabolic pathways. In addition, we also summarize our current understanding on the regulatory mechanisms governing tetrapyrrole metabolism. The interactions of tetrapyrrole biosynthesis and other cellular processes including the plastid-to-nucleus signal transduction are discussed.
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Affiliation(s)
- Ryouichi Tanaka
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | | | - Tatsuru Masuda
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
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Solymosi K, Schoefs B. Etioplast and etio-chloroplast formation under natural conditions: the dark side of chlorophyll biosynthesis in angiosperms. PHOTOSYNTHESIS RESEARCH 2010; 105:143-66. [PMID: 20582474 DOI: 10.1007/s11120-010-9568-2] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2009] [Accepted: 05/30/2010] [Indexed: 05/03/2023]
Abstract
Chloroplast development is usually regarded as proceeding from proplastids. However, direct or indirect conversion pathways have been described in the literature, the latter involving the etioplast or the etio-chloroplast stages. Etioplasts are characterized by the absence of chlorophylls (Chl-s) and the presence of a unique inner membrane network, the prolamellar body (PLB), whereas etio-chloroplasts contain Chl-s and small PLBs interconnected with chloroplast thylakoids. As etioplast development requires growth in darkness for several days, this stage is generally regarded as a nonnatural pathway of chloroplast development occurring only under laboratory conditions. In this article, we have reviewed the data in favor of the involvement of etioplasts and etio-chloroplasts as intermediary stage(s) in chloroplast formation under natural conditions, the molecular aspects of PLB formation and we propose a dynamic model for its regulation.
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Affiliation(s)
- Katalin Solymosi
- Department of Plant Anatomy, Institute of Biology, Eötvös University, Pázmány P. s. 1/C, 1117 Budapest, Hungary.
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Yuan M, Yuan S, Zhang ZW, Xu F, Chen YE, Du JB, Lin HH. Putative Mutation Mechanism and Light Responses of a Protochlorophyllide Oxidoreductase-Less Barley Mutant NYB. ACTA ACUST UNITED AC 2010; 51:1361-71. [DOI: 10.1093/pcp/pcq097] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Amirjani MR. Protochlorophyllide spectral forms. Pak J Biol Sci 2010; 13:563-576. [PMID: 21061907 DOI: 10.3923/pjbs.2010.563.576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Abstract: This study summarized recent results on POR and plastid development in order to find an explanation for the existence of Pchlide spectral forms. This review has summarized many researches about the Pchlide spectral forms and their phototransformability in different higher plants which have been published. Chlorophyll (Chl) is the most important pigment on the Earth. Each spring millions of tons Chl are formed during bud break and leaf development. The sun light needed for photosynthesis is captured by Chl and transformed to chemical energy. In the Biosynthesis of chlorophyll (Chl) begins with the synthesis of delta-aminolevulinic acid (ALA) from glutamic acid. Chl biosynthetic pathway, a light dependent enzyme protochlorophyllide oxidoreductase (POR) catalyses a key light-driven reaction, trans addition of hydrogen across the C-17-C-18 double bond of the Chl precursor, protochlorophyllide (Pchlide), that triggers a profound transformation in plant development. Pchlide is spectrally heterogeneous and exist in different spectral forms having slightly different absorption and fluorescence peaks. The identified Pchlide spectral forms can be sorted into three groups. The first group is designated as short-wavelength forms. This group with fluorescence in the 625-646 nm spectral region has a heterogeneous nature and is made by four components. The second group includes the long-wavelength Pchlide forms with emission maxima between 652 and 657 nm. The third group is found in the extreme red region (670-730 nm) of the fluorescence emission spectra and includes a number of pigment forms with spectral bands of low intensity. This region is also influenced by vibrational bands of the short-and long-wavelength Pchlide forms.
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Boij P, Patel R, Garcia C, Jarvis P, Aronsson H. In vivo studies on the roles of Tic55-related proteins in chloroplast protein import in Arabidopsis thaliana. MOLECULAR PLANT 2009; 2:1397-1409. [PMID: 19995737 DOI: 10.1093/mp/ssp079] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The Tic55 (Translocon at the inner envelope membrane of chloroplasts, 55 kDa) protein was identified in pea as a putative regulator, possibly linking chloroplast protein import to the redox state of the photosynthetic machinery. Two Tic55 homologs have been proposed to exist in Arabidopsis: atTic55-II and AtPTC52 (Protochlorophyllide-dependent Translocon Component, 52 kDa; has also been called atTic55-IV). Our phylogenetic analysis shows that atTic55-II is an ortholog of psTic55 from pea (Pisum sativum), and that AtPTC52 is a more distant homolog of the two. AtPTC52 was included in this study to rule out possible functional links between the proteins in Arabidopsis. No detectable mutant phenotypes were found in two independent T-DNA knockout mutant plant lines for each Arabidopsis protein, when compared with wild-type: visible appearance, chlorophyll content, photosynthetic performance, and chloroplast protein import, for example, were all normal. Both wild-type and tic55-II mutant chloroplasts exhibited deficient protein import when treated with diethylpyrocarbonate, indicating that Tic55 is not the sole target of this reagent in relation to protein import. Furthermore, ptc52 mutant chloroplasts were not defective with respect to pPORA import, which was previously reported to involve PTC52 in barley. Thus, we conclude that atTic55-II and AtPTC52 are not strictly required for functional protein import in Arabidopsis.
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Affiliation(s)
- Patrik Boij
- Department of Plant and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Gothenburg, Sweden
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Joyard J, Ferro M, Masselon C, Seigneurin-Berny D, Salvi D, Garin J, Rolland N. Chloroplast proteomics and the compartmentation of plastidial isoprenoid biosynthetic pathways. MOLECULAR PLANT 2009; 2:1154-80. [PMID: 19969518 DOI: 10.1093/mp/ssp088] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Recent advances in the proteomic field have allowed high-throughput experiments to be conducted on chloroplast samples. Many proteomic investigations have focused on either whole chloroplast or sub-plastidial fractions. To date, the Plant Protein Database (PPDB, Sun et al., 2009) presents the most exhaustive chloroplast proteome available online. However, the accurate localization of many proteins that were identified in different sub-plastidial compartments remains hypothetical. Ferro et al. (2009) went a step further into the knowledge of Arabidopsis thaliana chloroplast proteins with regards to their accurate localization within the chloroplast by using a semi-quantitative proteomic approach known as spectral counting. Their proteomic strategy was based on the accurate mass and time tags (AMT) database approach and they built up AT_CHLORO, a comprehensive chloroplast proteome database with sub-plastidial localization and curated information on envelope proteins. Comparing these two extensive databases, we focus here on about 100 enzymes involved in the synthesis of chloroplast-specific isoprenoids. Well known pathways (i.e. compartmentation of the methyl erythritol phosphate biosynthetic pathway, of tetrapyrroles and chlorophyll biosynthesis and breakdown within chloroplasts) validate the spectral counting-based strategy. The same strategy was then used to identify the precise localization of the biosynthesis of carotenoids and prenylquinones within chloroplasts (i.e. in envelope membranes, stroma, and/or thylakoids) that remains unclear until now.
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Affiliation(s)
- Jacques Joyard
- Laboratoire de Physiologie Cellulaire Végétale, UMR 5168, CEA, CNRS, INRA, Université Joseph Fourier, iRTSV, CEA-Grenoble, 38054 Grenoble-cedex 9, France
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Plöscher M, Granvogl B, Reisinger V, Eichacker LA. Identification of the N-termini of NADPH : protochlorophyllide oxidoreductase A and B from barley etioplasts (Hordeum vulgare L.). FEBS J 2009; 276:1074-81. [DOI: 10.1111/j.1742-4658.2008.06850.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Aronsson H, Jarvis P. The Chloroplast Protein Import Apparatus, Its Components, and Their Roles. PLANT CELL MONOGRAPHS 2008. [DOI: 10.1007/978-3-540-68696-5_3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Abstract
Most chloroplast proteins are encoded in the nucleus and synthesized on free, cytosolic ribosomes in precursor form. Each precursor has an amino-terminal extension called a transit peptide, which directs the protein through a post-translational targeting pathway and is removed upon arrival inside the organelle. This 'protein import' process is mediated by the coordinate action of two multiprotein complexes, one in each of the envelope membranes: the TOC and TIC (Translocon at the Outer/ Inner envelope membrane of Chloroplasts) machines. Many components of these complexes have been identified biochemically in pea; these include transit peptide receptors, channel proteins, and molecular chaperones. Intriguingly, the Arabidopsis genome encodes multiple, homologous genes for receptor components of the TOC complex. Careful analysis indicated that the different receptor isoforms operate in different import pathways with distinct precursor recognition specificities. These 'substrate-specific' import pathways might play a role in the differentiation of different plastid types, and/or act to prevent deleterious competition effects between abundant and nonabundant precursors. Until recently, all proteins destined for internal chloroplast compartments were thought to possess a cleavable transit peptide, and to engage the TOC/TIC machinery. New studies using proteomics and other approaches have revealed that this is far from true. Remarkably, a significant number of chloroplast proteins are transported via a pathway that involves the endoplasmic reticulum and Golgi apparatus. Other recent reports have elucidated an intriguing array of protein targeting routes leading to the envelope membranes themselves.
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Affiliation(s)
- Paul Jarvis
- Department of Biology, University of Leicester, Leicester LE1 7RH, UK
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Masuda T. Recent overview of the Mg branch of the tetrapyrrole biosynthesis leading to chlorophylls. PHOTOSYNTHESIS RESEARCH 2008; 96:121-43. [PMID: 18273690 DOI: 10.1007/s11120-008-9291-4] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Accepted: 01/29/2008] [Indexed: 05/20/2023]
Abstract
In plants, chlorophylls (chlorophyll a and chlorophyll b) are the most abundant tetrapyrrole molecules and are essential for photosynthesis. The first committed step of chlorophyll biosynthesis is the insertion of Mg(2+) into protoporphyrin IX, and thus subsequent steps of the biosynthesis are called the Mg branch. As the Mg branch in higher plants is complex, it was not until the last decade--after many years of intensive research--that most of the genes encoding the enzymes for the pathway were identified. Biochemical and molecular genetic analyses have certainly modified the classic metabolic map of tetrapyrrole biosynthesis, and only recently have the molecular mechanisms of regulatory pathways governing chlorophyll metabolism been elucidated. As a result, novel functions of tetrapyrroles and biosynthetic enzymes have been proposed. In this review, I summarize the recent findings on enzymes involved in the Mg branch, mainly in higher plants.
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Affiliation(s)
- Tatsuru Masuda
- Graduate School of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan.
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The Chloroplast Protein Import Apparatus, Its Components, and Their Roles. PLANT CELL MONOGRAPHS 2008. [DOI: 10.1007/7089_2008_40] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Schemenewitz A, Pollmann S, Reinbothe C, Reinbothe S. A substrate-independent, 14:3:3 protein-mediated plastid import pathway of NADPH:protochlorophyllide oxidoreductase A. Proc Natl Acad Sci U S A 2007; 104:8538-43. [PMID: 17483469 PMCID: PMC1895985 DOI: 10.1073/pnas.0702058104] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2007] [Indexed: 11/18/2022] Open
Abstract
Plastids are semiautonomous organelles that contain only limited coding information in their own DNA. Because most of their genome was transferred to the nucleus after their endosymbiotic origin, plastids must import the major part of their protein constituents from the cytosol. The exact role of cytosolic targeting factors in the regulation of plastid protein import has not been determined. Here, we report that the nucleus-encoded NADPH:protochlorophyllide (Pchlide) oxidoreductase A plastid precursor (pPORA) can use two different plastid import pathways that differ by the requirements for cytosolic 14:3:3 proteins and Hsp70. pPORA synthesized in a wheat germ lysate segregated into different precursor fractions. While import of free pPORA and only Hsp70-complexed pPORA was Pchlide-dependent and involved the previously identified Pchlide-dependent translocon, 14:3:3 protein- and Hsp70-complexed pPORA was transported into Pchlide-free chloroplasts through the Toc75-containing standard translocon at the outer chloroplast membrane/translocon at the inner chloroplast membrane machinery. A 14:3:3 protein binding site was identified in the mature region of the (35)S-pPORA, which governed 14:3:3 protein- and Hsp70-mediated, Pchlide-independent plastid import. Collectively, our results reveal that the import of pPORA into the plastids is tightly regulated and involves different cytosolic targeting factors and plastid envelope translocon complexes.
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Affiliation(s)
- Andreas Schemenewitz
- Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität Bochum, Universitätsstrasse 150, Gebäude ND, D-44801 Bochum, Germany
| | - Stephan Pollmann
- Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität Bochum, Universitätsstrasse 150, Gebäude ND, D-44801 Bochum, Germany
| | - Christiane Reinbothe
- Lehrstuhl für Pflanzenphysiologie, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany; and
- Unité Mixte de Recherche 5575, Université Joseph Fourier et Centre National de la Recherche Scientifique, BP53, F-38041 Grenoble Cedex 9, France
| | - Steffen Reinbothe
- Unité Mixte de Recherche 5575, Université Joseph Fourier et Centre National de la Recherche Scientifique, BP53, F-38041 Grenoble Cedex 9, France
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Pollmann S, Springer A, Buhr F, Lahroussi A, Samol I, Bonneville JM, Tichtinsky G, von Wettstein D, Reinbothe C, Reinbothe S. A plant porphyria related to defects in plastid import of protochlorophyllide oxidoreductase A. Proc Natl Acad Sci U S A 2007; 104:2019-23. [PMID: 17261815 PMCID: PMC1794315 DOI: 10.1073/pnas.0610934104] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2006] [Indexed: 11/18/2022] Open
Abstract
The plastid envelope of higher plant chloroplasts is a focal point of plant metabolism. It is involved in numerous pathways, including tetrapyrrole biosynthesis and protein translocation. Chloroplasts need to import a large number of proteins from the cytosol because most are encoded in the nucleus. Here we report that a loss-of-function mutation in the outer plastid envelope 16-kDa protein (oep16) gene causes a conditional seedling lethal phenotype related to defects in import and assembly of NADPH:protochlorophyllide (Pchlide) oxidoreductase A. In the isolated knockout mutant of Arabidopsis thaliana, excess Pchlide accumulated in the dark operated as photosensitizer and provoked cell death during greening. Our results highlight the essential role of the substrate-dependent plastid import pathway of precursor Pchlide oxidoreductase A for seedling survival and the avoidance of developmentally programmed porphyria in higher plants.
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Affiliation(s)
- Stephan Pollmann
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
| | - Armin Springer
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
- Lehrstuhl für Pflanzenphysiologie, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany; and
| | - Frank Buhr
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
- Lehrstuhl für Pflanzenphysiologie, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany; and
| | - Abder Lahroussi
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
| | - Iga Samol
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
| | - Jean-Marc Bonneville
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
| | - Gabrielle Tichtinsky
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
| | - Diter von Wettstein
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
- Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164-6420
| | - Christiane Reinbothe
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
| | - Steffen Reinbothe
- *Université Joseph Fourier et Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, CERMO, BP53, F-38041 Grenoble Cedex 9, France
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Philippar K, Geis T, Ilkavets I, Oster U, Schwenkert S, Meurer J, Soll J. Chloroplast biogenesis: the use of mutants to study the etioplast-chloroplast transition. Proc Natl Acad Sci U S A 2007; 104:678-83. [PMID: 17202255 PMCID: PMC1766443 DOI: 10.1073/pnas.0610062104] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In angiosperm plants, the etioplast-chloroplast transition is light-dependent. A key factor in this process is the protochlorophyllide oxidoreductase A (PORA), which catalyzes the light-induced reduction of protochlorophyllide to chlorophyllide. The import pathway of the precursor protein prePORA into chloroplasts was analyzed in vivo and in vitro by using homozygous loss-of-function mutants in genes coding for chlorophyllide a oxygenase (CAO) or for members of the outer-envelope solute-channel protein family of 16 kDa (OEP16), both of which have been implied to be key factors for the import of prePORA. Our in vivo analyses show that cao or oep16 mutants contain a normally structured prolamellar body that contains the protochlorophyllide holochrome. Furthermore, etioplasts from cao and oep16 mutants contain PORA protein as found by mass spectrometry. Our data demonstrate that both CAO and OEP16 are dispensable for chloroplast biogenesis and play no central role in the import of prePORA in vivo and in vitro as further indicated by protein import studies.
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Affiliation(s)
- Katrin Philippar
- Department Biology I, Botany, Ludwig-Maximilians-University of Munich, Menzingerstrasse 67, D-80638 Munich, Germany
| | - Tina Geis
- Department Biology I, Botany, Ludwig-Maximilians-University of Munich, Menzingerstrasse 67, D-80638 Munich, Germany
| | - Iryna Ilkavets
- Department Biology I, Botany, Ludwig-Maximilians-University of Munich, Menzingerstrasse 67, D-80638 Munich, Germany
| | - Ulrike Oster
- Department Biology I, Botany, Ludwig-Maximilians-University of Munich, Menzingerstrasse 67, D-80638 Munich, Germany
| | - Serena Schwenkert
- Department Biology I, Botany, Ludwig-Maximilians-University of Munich, Menzingerstrasse 67, D-80638 Munich, Germany
| | - Jörg Meurer
- Department Biology I, Botany, Ludwig-Maximilians-University of Munich, Menzingerstrasse 67, D-80638 Munich, Germany
| | - Jürgen Soll
- Department Biology I, Botany, Ludwig-Maximilians-University of Munich, Menzingerstrasse 67, D-80638 Munich, Germany
- *To whom correspondence should be addressed. E-mail:
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Reumann S, Inoue K, Keegstra K. Evolution of the general protein import pathway of plastids (review). Mol Membr Biol 2005; 22:73-86. [PMID: 16092526 DOI: 10.1080/09687860500041916] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The evolutionary process that transformed a cyanobacterial endosymbiont into contemporary plastids involved not only inheritance but also invention. Because gram-negative bacteria lack a system for polypeptide import, the envelope translocon complex of the general protein import pathway was the most important invention of organelle evolution resulting in a pathway to import back into plastids those nuclear-encoded proteins supplemented with a transit peptide. Genome information of cyanobacteria, phylogenetically diverse plastids, and the nuclei of the first red alga, a diatom, and Arabidopsis thaliana allows us to trace back the evolutionary origin of the twelve currently known translocon components and to partly deduce their assembly sequence. Development of the envelope translocon was initiated by recruitment of a cyanobacterial homolog of the protein-import channel Toc75, which belongs to a ubiquitous and essential family of Omp85/D15 outer membrane proteins of gram-negative bacteria that mediate biogenesis of beta-barrel proteins. Likewise, three other translocon subunits (Tic20, Tic22, and Tic55) and several stromal chaperones have been inherited from the ancestral cyanobacterium and modified to take over the novel function of precursor import. Most of the remaining subunits seem to be of eukaryotic origin, recruited from pre-existing nuclear genes. The next subunits that joined the evolving protein import complex likely were Toc34 and Tic110, as indicated by the presence of homologous genes in the red alga Cyanidioschyzon merolae, followed by the stromal processing peptidase, members of the Toc159 receptor family, Toc64, Tic40, and finally some regulatory redox components (Tic62, Tic32), all of which were probably required to increase specificity and efficiency of precursor import.
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Affiliation(s)
- Sigrun Reumann
- Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Göttingen, Germany.
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Bédard J, Jarvis P. Recognition and envelope translocation of chloroplast preproteins. JOURNAL OF EXPERIMENTAL BOTANY 2005; 56:2287-320. [PMID: 16087701 DOI: 10.1093/jxb/eri243] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Plastids are a diverse group of plant organelles that perform essential functions including important steps in many biosynthetic pathways. Chloroplasts are the best characterized type of plastid, and constitute the site of oxygenic photosynthesis in plants, a process essential to all higher life forms. It is well established that the majority (>90%) of chloroplast proteins are nucleus-encoded and must be post-translationally imported into these envelope-bound compartments. Most nucleus-encoded chloroplast proteins are translated in precursor form on cytosolic ribosomes, targeted to the chloroplast surface, and then imported across the double-membrane envelope by translocons in the outer and inner envelope membranes of the chloroplast, termed TOC and TIC, respectively. Recently, significant progress has been made in our understanding of how proteins are targeted to the chloroplast surface and translocated across the chloroplast envelope into the stroma. Evidence suggesting the existence of multiple import pathways at the outer envelope membrane for different classes of precursor proteins has been presented. These pathways appear to utilize similar TOC complexes equipped with different combinations of homologous GTPase receptors, providing preprotein recognition specificity.
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Affiliation(s)
- Jocelyn Bédard
- Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, UK
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Kim C, Ham H, Apel K. Multiplicity of different cell- and organ-specific import routes for the NADPH-protochlorophyllide oxidoreductases A and B in plastids of Arabidopsis seedlings. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 42:329-40. [PMID: 15842619 DOI: 10.1111/j.1365-313x.2005.02374.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The NADPH-dependent protochlorophyllide (Pchlide) oxidoreductase (POR) is a photoenzyme that requires light for its catalytic activity and uses Pchlide itself as a photoreceptor. In Arabidopsis there are three PORs denoted PORA, PORB and PORC. The PORA and PORB genes are strongly expressed early in seedling development. In contrast to PORB the import of PORA into plastids of cotyledons is substrate-dependent and organ-specific. These differences in the import reactions between PORA and PORB most likely are due to different import mechanisms that are responsible for the uptake of these proteins. The two major core constituents of the translocon of the outer plastid envelope, Toc159 and Toc34, have been implicated in the binding and recognition of precursors of nuclear-encoded plastid proteins. Their involvement in conferring substrate dependency and organ specificity of PORA import was analyzed in intact Arabidopsis seedlings of wild type and the three mutants ppi3, ppi1 and ppi2 that are deficient in atToc34, atToc33, a closely related isoform of atToc34, and atToc159. Whereas none of these three Toc constituents is required for maintaining the organ specificity and substrate dependency of PORA import, atToc33 is indispensable for the import of PORB in cotyledons and true leaves suggesting that in these parts of the plant translocation of PORA and PORB occurs via two distinct import pathways. The analysis of PORA and PORB import into plastids of intact seedlings revealed an unexpected multiplicity of import routes that differed by their substrate, cell, tissue and organ specificities. This versatility of pathways for protein targeting to plastids suggests that in intact seedlings not only the constituents of the core complex of import channels but also other factors are involved in mediating the import of nuclear-encoded plastid proteins.
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Affiliation(s)
- Chanhong Kim
- Institute of Plant Sciences, Plant Genetics, Swiss Federal Institute of Technology (ETH), CH-8092, Zurich, Switzerland
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Becker T, Qbadou S, Jelic M, Schleiff E. Let's talk about...chloroplast import. PLANT BIOLOGY (STUTTGART, GERMANY) 2005; 7:1-14. [PMID: 15666210 DOI: 10.1055/s-2004-830447] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Affiliation(s)
- T Becker
- Botanisches Institut, Ludwig-Maximilian-Universität München, Menzinger Strasse 67, 80368 München, Germany
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Reinbothe S, Quigley F, Springer A, Schemenewitz A, Reinbothe C. The outer plastid envelope protein Oep16: role as precursor translocase in import of protochlorophyllide oxidoreductase A. Proc Natl Acad Sci U S A 2004; 101:2203-8. [PMID: 14769929 PMCID: PMC357075 DOI: 10.1073/pnas.0301962101] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A 16-kDa plastid envelope protein was identified by chemical crosslinking that interacts with the precursor of NADPH:protochlorophyllide oxdidoreductase A (pPORA) during its posttranslational import into isolated barley chloroplasts. Protein purification and subsequent protein sequencing showed that the 16-kDa protein is an ortholog of a previously identified outer plastid envelope protein, Oep16. A protein of identical size was present in barley etioplasts and interacted with pPORA. Similar 16-kDa protein-dependent crosslink products of pPORA were detected in wheat, pea, and Arabidopsis chloroplasts. Database analyses revealed that the 16-kDa protein belongs to a family of preprotein and amino acid transporters found in free-living bacteria and endosymbiotic mitochondria and chloroplasts. Antibodies raised against the 16-kDa protein inhibited import of pPORA, highlighting its role in protein import.
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Affiliation(s)
- Steffen Reinbothe
- Université Joseph Fourier et Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5575, BP53, F-38041 Grenoble Cedex 9, France.
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Kroth PG. Protein transport into secondary plastids and the evolution of primary and secondary plastids. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 221:191-255. [PMID: 12455749 DOI: 10.1016/s0074-7696(02)21013-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Chloroplasts are key organelles in algae and plants due to their photosynthetic abilities. They are thought to have evolved from prokaryotic cyanobacteria taken up by a eukaryotic host cell in a process termed primary endocytobiosis. In addition, a variety of organisms have evolved by subsequent secondary endocytobioses, in which a heterotrophic host cell engulfed a eukaryotic alga. Both processes dramatically enhanced the complexity of the resulting cells. Since the first version of the endosymbiotic theory was proposed more than 100 years ago, morphological, physiological, biochemical, and molecular data have been collected substantiating the emerging picture about the origin and the relationship of individual organisms with different primary or secondary chloroplast types. Depending on their origin, plastids in different lineages may have two, three, or four envelope membranes. The evolutionary success of endocytobioses depends, among other factors, on the specific exchange of molecules between the host and endosymbiont. This raises questions concerning how targeting of nucleus-encoded proteins into the different plastid types occurs and how these processes may have developed. Most studies of protein translocation into plastids have been performed on primary plastids, but in recent years more complex protein-translocation systems of secondary plastids have been investigated. Analyses of transport systems in different algal lineages with secondary plastids reveal that during evolution existing translocation machineries were recycled or recombined rather than being developed de novo. This review deals with current knowledge about the evolution and function of primary and secondary plastids and the respective protein-targeting systems.
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Affiliation(s)
- Peter G Kroth
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
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Aronsson H, Sundqvist C, Dahlin C. POR - import and membrane association of a key element in chloroplast development. PHYSIOLOGIA PLANTARUM 2003; 118:1-9. [PMID: 12702007 DOI: 10.1034/j.1399-3054.2003.00088.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The development of proplastids or etioplasts to chloroplast is visualized by the accumulation of chlorophyll in leaves of higher plants. The biosynthesis of chlorophyll includes a light-dependent reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide). This light-dependent step is catalysed by the nucleus-encoded NADPH:Pchlide oxidoreductase (POR, EC 1.6.99.1). POR is active within plastids and therefore has to be translocated over the plastid envelope membranes. The import of chloroplast proteins seems to follow a general import pathway using translocons at the outer and inner envelope membrane. POR cross-linking to Toc75, one of the major translocon components at the outer envelope membrane, indicates its use of the general import pathway. However, since variations exist within the so-called general import pathway one has to consider previous data suggesting a novel totally Pchlide-dependent import pathway of one POR isoform, PORA. The suggested Pchlide dependency of POR import is discussed since recent observations contradict this idea. In the stroma the POR transit peptide is cleaved off and the mature POR protein is targeted to the plastid inner membranes. The correct and stable association of POR to the membrane requires the cofactor NADPH. Functional activity of POR calls for formation of an NADPH-Pchlide-POR complex, a formation that probably takes place after the membrane association and is dependent on a phosphorylation reaction.
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Affiliation(s)
- Henrik Aronsson
- Department of Biology, Leicester University, University Road, Leicester, LE1 7RH, United Kingdom Department of Plant Physiology, Göteborg University, Box 461, SE-405 30 Göteborg, Sweden School of Business and Engineering, Halmstad University, Box 823, SE-301 18 Halmstad, Sweden
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Abstract
We present a simple, rapid and low-cost method for isolating a high yield of Arabidopsis chloroplasts that can be used to study chloroplast protein import. Efficiency of chloroplast isolation was dependent upon the ratio between amount of plant tissue and the buffer volume, the size and speed of the homogenisation equipment, and the size of the homogenisation beaker. The import method proved useful when characterising different precursor proteins, developmental stages and import-defective mutants. Time-course experiments enabled the measurement of import rates in the linear range. Compared to protoplastation, this isolation method has significant time and cost savings (approximately 80% and approximately 95%, respectively), and yields chloroplasts with a higher capacity to import proteins.
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Affiliation(s)
- Henrik Aronsson
- Department of Biology, University of Leicester, University Road, LE1 7RH, Leicester, UK
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Abstract
The vast majority of chloroplast proteins are synthesized in precursor form on cytosolic ribosomes. Chloroplast precursor proteins have cleavable, N-terminal targeting signals called transit peptides. Transit peptides direct precursor proteins to the chloroplast in an organelle-specific way. They can be phosphorylated by a cytosolic protein kinase, and this leads to the formation of a cytosolic guidance complex. The guidance complex--comprising precursor, hsp70 and 14-3-3 proteins, as well as several unidentified components--docks at the outer envelope membrane. Translocation of precursor proteins across the envelope is achieved by the joint action of molecular machines called Toc (translocon at the outer envelope membrane of chloroplasts) and Tic (translocon at the inner envelope membrane of chloroplasts), respectively. The action of the Toc/Tic apparatus requires the hydrolysis of ATP and GTP at different levels, indicating energetic requirements and regulatory properties of the import process. The main subunits of the Toc and Tic complexes have been identified and characterized in vivo, in organello and in vitro. Phylogenetic evidence suggests that several translocon subunits are of cyanobacterial origin, indicating that today's import machinery was built around a prokaryotic core.
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Affiliation(s)
- Paul Jarvis
- Department of Biology, University of Leicester, UK.
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Abstract
The vast majority of chloroplast proteins are synthesized in precursor form on cytosolic ribosomes. Chloroplast precursor proteins have cleavable, N-terminal targeting signals called transit peptides. Transit peptides direct precursor proteins to the chloroplast in an organelle-specific way. They can be phosphorylated by a cytosolic protein kinase, and this leads to the formation of a cytosolic guidance complex. The guidance complex--comprising precursor, hsp70 and 14-3-3 proteins, as well as several unidentified components--docks at the outer envelope membrane. Translocation of precursor proteins across the envelope is achieved by the joint action of molecular machines called Toc (translocon at the outer envelope membrane of chloroplasts) and Tic (translocon at the inner envelope membrane of chloroplasts), respectively. The action of the Toc/Tic apparatus requires the hydrolysis of ATP and GTP at different levels, indicating energetic requirements and regulatory properties of the import process. The main subunits of the Toc and Tic complexes have been identified and characterized in vivo, in organello and in vitro. Phylogenetic evidence suggests that several translocon subunits are of cyanobacterial origin, indicating that today's import machinery was built around a prokaryotic core.
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Affiliation(s)
- P Jarvis
- Department of Biology, University of Leicester, UK.
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Engdahl S, Aronsson H, Sundqvist C, Timko MP, Dahlin C. Association of the NADPH:protochlorophyllide oxidoreductase (POR) with isolated etioplast inner membranes from wheat. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 27:297-304. [PMID: 11532175 DOI: 10.1046/j.1365-313x.2001.01094.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Membrane association of NADPH:protochlorophyllide oxidoreductase (POR, EC: 1.6.99.1) with isolated prolamellar bodies (PLBs) and prothylakoids (PTs) from wheat etioplasts was investigated. In vitro-expressed radiolabelled POR, with or without transit peptide, was used to characterize membrane association conditions. Proper association of POR with PLBs and PTs did not require the presequence, whereas NADPH and hydrolysable ATP were vital for the process. After treating the membranes with thermolysin, sodium hydroxide or carbonate, a firm attachment of the POR protein to the membrane was found. Although the PLBs and PTs differ significantly in their relative amount of POR in vivo, no major differences in POR association capacity could be observed between the two membrane systems when exogenous NADPH was added. Experiments run with only an endogenous NADPH source almost abolished association of POR with both PLBs and PTs. In addition, POR protein carrying a mutation in the putative nucleotide-binding site (ALA06) was unable to bind to the inner membranes in the presence of NADPH, which further demonstrates that the co-factor is essential for proper membrane association. POR protein carrying a mutation in the substrate-binding site (ALA24) showed less binding to the membranes as compared to the wild type. The results presented here introduce studies of a novel area of protein-membrane interaction, namely the association of proteins with a paracrystalline membrane structure, the PLB.
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Affiliation(s)
- S Engdahl
- Department of Plant Physiology, Göteborg University, Box 461, SE-405 30 Göteborg, Sweden
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Aronsson H, Sundqvist C, Timko MP, Dahlin C. The importance of the C-terminal region and Cys residues for the membrane association of the NADPH:protochlorophyllide oxidoreductase in pea. FEBS Lett 2001; 502:11-5. [PMID: 11478939 DOI: 10.1016/s0014-5793(01)02595-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In vitro chloroplast import reactions and thylakoid association reactions have been performed with a series of C-terminal deletions and Cys-to-Ser substitution mutants of the pea NADPH:protochlorophyllide oxidoreductase (POR; EC 1.6.99). C-terminal deletions of the precursor POR (Delta362-400, Delta338-400, Delta315-400 and Delta300-400) were efficiently translocated across the chloroplast envelope. However, except the Delta396-400 mutant, no C-terminal deletion mutants or Cys-to-Ser substitution (Cys119, Cys281 and Cys309) mutants resisted post-treatment with thermolysin after the thylakoid association reactions. This suggests that these mutants were unable to properly associate to the thylakoids due to changes of the protein conformation of POR.
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Affiliation(s)
- H Aronsson
- Department of Plant Physiology, Göteborg University, P.O. Box 461, SE-405 30 Göteborg, Sweden.
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