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  • 1.
    Carlberg, Inger
    et al.
    Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University.
    Hansson, Maria
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Kieselbach, Thomas
    Department of Medical Nutrition and Biosciences, Karolinska Institute, Huddinge, Sweden.
    Schröder, Wolfgang P.
    Department of Biochemistry, Umeå University, Umeå, Sweden .
    Andersson, Bertil
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Vener, Alexander V.
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    A novel plant protein undergoing light-induced phosphorylation and release from the photosynthetic thylakoid membranes2003In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 100, no 2, p. 757-762Article in journal (Refereed)
    Abstract [en]

    The characteristics of a phosphoprotein with a relative electrophoretic mobility of 12 kDa have been unknown during two decades of studies on redox-dependent protein phosphorylation in plant photosynthetic membranes. Digestion of this protein from spinach thylakoid membranes with trypsin and subsequent tandem nanospray-quadrupole-time-of-flight mass spectrometry of the peptides revealed a protein sequence that did not correspond to any previously known protein. Sequencing of the corresponding cDNA uncovered a gene for a precursor protein with a transit peptide followed by a strongly basic mature protein with a molecular mass of 8,640 Da. Genes encoding homologous proteins were found on chromosome 3 of Arabidopsis and rice as well as in ESTs from 20 different plant species, but not from any other organisms. The protein can be released from the membrane with high salt and is also partially released in response to light-induced phosphorylation of thylakoids, in contrast to all other known thylakoid phosphoproteins, which are integral to the membrane. On the basis of its properties, this plant-specific protein is named thylakoid soluble phosphoprotein of 9 kDa (TSP9). Mass spectrometric analyses revealed the existence of non-, mono-, di-, and triphosphorylated forms of TSP9 and phosphorylation of three distinct threonine residues in the central part of the protein. The phosphorylation and release of TSP9 from the photosynthetic membrane on illumination favor participation of this basic protein in cell signaling and regulation of plant gene expression in response to changing light conditions.

  • 2.
    Hansson, Maria
    Linköping University, Department of Clinical and Experimental Medicine, Cellbiology. Linköping University, Faculty of Health Sciences.
    Molecular characterization of protein phosphorylation in plant photosynthetic membranes2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Higher plants cannot move to a more favorable place when the environmental conditions are changing. To adapt to changes in light, temperature and access to water the plants had to evolve special mechanisms at the molecular level. Post-translational modifications of proteins, like phosphorylation, often serve as “on-and-off” switches in regulation of cellular activity and may affect protein-protein interactions. Photosynthesis in higher plants is regulated by reversible protein phosphorylation events, in a unique light- and redox-controlled system. Several biochemical methods are effectively used for characterization of phosphorylated proteins in photosynthetic membranes. Nevertheless, mass spectrometry is the most effective technique when it comes to identification of exact phosphorylation site(s) in the protein sequence, which is the ultimate evidence of protein phosphorylation. The same tandem mass spectrometry analysis identifies other in vivo post-translational modifications as well, such as acetylation of the N-terminus of mature protein. To study membrane proteins is a challenging project. In the present work the “shaving” of surface-exposed part of the membrane proteins, where phosphorylation occur, is used. In combination with mass spectrometry, this technique does not require the use of radioactive labeling or antibodies. The present work in spinach and Arabidopsis thaliana has identified and characterized several known phosphoproteins, new phosphorylation sites in well-known photosynthetic proteins, as well as two phosphoproteins previously unknown to be present in the photosynthetic membrane. Several photosystem II (PSII) core proteins become phosphorylated in their N-termini (D1, D2, CP43, PsbH), process involved in the regulation of the repair cycle of photo-damaged PSII complexes. The protein-protein interactions between PSII and its light harvesting complex (LHCII) seem to be affected by phosphorylation events in the interface area. In higher plants, phosphorylation sites have been identified in LHCII polypeptides, in one of the proteins (CP29) present in the interface area, as well as in the peripheral TSP9 protein. The TSP9 protein is unique among photosynthetic phosphoproteins, since it is a plant-specific soluble protein that becomes triple-phosphorylated in the middle part of the protein. It is also shown that photosystem I (PSI) is subjected to protein phosphorylation. The extrinsic PSI subunit PsaD becomes phosphorylated in its N-terminus. In addition, the latest characterized subunit of PSI, PsaP, is identified as a phosphoprotein. PsaP is an intrinsic protein assembled on the same side of the PSI complex as LHCII attaches. Several kinases are involved in phosphorylation of photosynthetic proteins, some more specific to PSII core proteins whereas others recognize LHCII proteins better. The STN8 kinase does not phosphorylate LHCII proteins, but is involved in the phosphorylation of the PSII core proteins D1, D2, CP43 and PsbH. STN8 is light-activated and is also specific in phosphorylation of threonine-4 (Thr-4) in the PsbH protein, but only after another kinase has phosphorylated Thr-2 first. A common feature of all kinases in plant photosynthetic membranes is the specificity for Thr residues and that the phosphorylation reactions occur in the N-terminal sequence of the proteins, except for the TSP9 protein. Nowadays, research is on the way to solve the complex network of regulation of photosynthetic activity via protein phosphorylation, but far more efforts are needed to get a complete view of the importance of all phosphorylation events and enzymatic specificity.

    List of papers
    1. Identification of three previosly unknown in vivo phosphorylation sites in thylakoid membranes of Arabidopsis thaliana
    Open this publication in new window or tab >>Identification of three previosly unknown in vivo phosphorylation sites in thylakoid membranes of Arabidopsis thaliana
    2003 (English)In: Molecular and Cellular Proteomics, ISSN 1535-9476, Vol. 2, no 8, p. 550-559Article in journal (Refereed) Published
    Abstract [en]

    The proteins in plant photosynthetic thylakoid membranes undergo light-induced phosphorylation, but only a few phosphoproteins have been characterized. To access the unknown sites of in vivo protein phosphorylation the thylakoid membranes were isolated from Arabidopsis thaliana grown in normal light, and the surface-exposed peptides were cleaved from the membranes by trypsin. The peptides were methylated and subjected to immobilized metal affinity chromatography, and the enriched phosphopeptides were sequenced using tandem nanospray quadrupole time-of-flight mass spectrometry. Three new phosphopeptides were revealed in addition to the five known phosphorylation sites in photosystem II proteins. All phosphopeptides are found phosphorylated at threonine residues implementing a strict threonine specificity of the thylakoid kinases. For the first time protein phosphorylation is found in photosystem I. The phosphorylation site is localized to the first threonine in the N terminus of PsaD protein that assists in the electron transfer from photosystem I to ferredoxin. A new phosphorylation site is also revealed in the acetylated N terminus of the minor chlorophyll a-binding protein CP29. The third novel phosphopeptide, composed of 25 amino acids, belongs to a nuclear encoded protein annotated as "expressed protein" in the Arabidopsis database. The protein precursor has a chloroplast-targeting peptide followed by the mature protein with two transmembrane helices and a molecular mass of 14 kDa. This previously uncharacterized protein is named thylakoid membrane phosphoprotein of 14 kDa (TMP14). The finding of the novel phosphoproteins extends involvement of the redox-regulated protein phosphorylation in photosynthetic membranes beyond the photosystem II and its light-harvesting antennae.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13859 (URN)10.1074/mcp.M300050-MCP200 (DOI)
    Available from: 2006-09-07 Created: 2006-09-07
    2. A previosly found thylakoid membrane protein of 14 kDa (TMP14) is a novel subunit of photosystem I and is designated PSI-P
    Open this publication in new window or tab >>A previosly found thylakoid membrane protein of 14 kDa (TMP14) is a novel subunit of photosystem I and is designated PSI-P
    Show others...
    2005 (English)In: FEBS Letters, ISSN 0014-5793, Vol. 579, no 21, p. 4808-4812Article in journal (Refereed) Published
    Abstract [en]

    We show that the thylakoid membrane phosphoprotein TMP14 is a novel subunit of plant photosystem I (PSI). Blue native/SDS–PAGE and sucrose gradient fractionation demonstrated the association of the protein exclusively with PSI. We designate the protein PSI-P. The presence of PSI-P subunit in Arabidopsis mutants lacking other PSI subunits was analyzed and suggested a location in the proximity of PSI-L, -H and -O subunits. The PSI-P protein was not differentially phosphorylated in state 1 and state 2.

    Keywords
    Photosystem I; Protein phosphorylation; State transitions; Thylakoids; Arabidopsis
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13860 (URN)10.1016/j.febslet.2005.07.061 (DOI)
    Available from: 2006-09-07 Created: 2006-09-07
    3. A novel plant protein undergoing light-induced phosphorylation and release from the photosynthetic thylakoid membranes
    Open this publication in new window or tab >>A novel plant protein undergoing light-induced phosphorylation and release from the photosynthetic thylakoid membranes
    Show others...
    2003 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 100, no 2, p. 757-762Article in journal (Refereed) Published
    Abstract [en]

    The characteristics of a phosphoprotein with a relative electrophoretic mobility of 12 kDa have been unknown during two decades of studies on redox-dependent protein phosphorylation in plant photosynthetic membranes. Digestion of this protein from spinach thylakoid membranes with trypsin and subsequent tandem nanospray-quadrupole-time-of-flight mass spectrometry of the peptides revealed a protein sequence that did not correspond to any previously known protein. Sequencing of the corresponding cDNA uncovered a gene for a precursor protein with a transit peptide followed by a strongly basic mature protein with a molecular mass of 8,640 Da. Genes encoding homologous proteins were found on chromosome 3 of Arabidopsis and rice as well as in ESTs from 20 different plant species, but not from any other organisms. The protein can be released from the membrane with high salt and is also partially released in response to light-induced phosphorylation of thylakoids, in contrast to all other known thylakoid phosphoproteins, which are integral to the membrane. On the basis of its properties, this plant-specific protein is named thylakoid soluble phosphoprotein of 9 kDa (TSP9). Mass spectrometric analyses revealed the existence of non-, mono-, di-, and triphosphorylated forms of TSP9 and phosphorylation of three distinct threonine residues in the central part of the protein. The phosphorylation and release of TSP9 from the photosynthetic membrane on illumination favor participation of this basic protein in cell signaling and regulation of plant gene expression in response to changing light conditions.

    Place, publisher, year, edition, pages
    National Academy of Sciences, 2003
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13861 (URN)10.1073/pnas.0235452100 (DOI)
    Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2017-12-13Bibliographically approved
    4. The mobile thylakoid phosphoprotein TSP9 interacts with the light harvesting complex II and the peripheries of both photosystems
    Open this publication in new window or tab >>The mobile thylakoid phosphoprotein TSP9 interacts with the light harvesting complex II and the peripheries of both photosystems
    Show others...
    2006 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 282, no 22, p. 16214-16222Article in journal (Refereed) Published
    Abstract [en]

    The localization of the plant-specific thylakoid-soluble phosphoprotein of 9 kDa, TSP9, within the chloroplast thylakoid membrane of spinach has been established by the combined use of fractionation, immunoblotting, cross-linking, and mass spectrometry. TSP9 was found to be exclusively confined to the thylakoid membranes, where it is enriched in the stacked grana membrane domains. After mild solubilization of the membranes, TSP9 migrated together with the major light-harvesting antenna (LHCII) of photosystem II (PSII) and with PSII-LHCII supercomplexes upon separation of the protein complexes by either native gel electrophoresis or sucrose gradient centrifugation. Studies with a cleavable cross-linking agent revealed the interaction of TSP9 with both major and minor LHCII proteins as identified by mass spectrometric sequencing. Cross-linked complexes that in addition to TSP9 contain the peripheral PSII subunits CP29, CP26, and PsbS, which form the interface between LHCII and the PSII core, were found. Our observations also clearly suggest an interaction of TSP9 with photosystem I (PSI) as shown by both immunodetection and mass spectrometry. Sequencing identified the peripheral PSI subunits PsaL, PsaF, and PsaE, originating from cross-linked protein complexes of around 30 kDa that also contained TSP9. The distribution of TSP9 among the cross-linked forms was found to be sensitive to conditions such as light exposure. An association of TSP9 with LHCII as well as the peripheries of the photosystems suggests its involvement in regulation of photosynthetic light harvesting.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13862 (URN)10.1074/jbc.M605833200 (DOI)
    Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2010-05-24
    5. STN8 protein kinase in Arabidopsis thaliana is specific in phosphorylation of photosystem II core proteins
    Open this publication in new window or tab >>STN8 protein kinase in Arabidopsis thaliana is specific in phosphorylation of photosystem II core proteins
    2005 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 280, no 39, p. 33679-33686Article in journal (Refereed) Published
    Abstract [en]

    Combination of reversed genetics with analyses of in vivo protein phosphorylation in Arabidopsis thaliana revealed that STN8 protein kinase is specific in phosphorylation of N-terminal threonine residues in D1, D2, and CP43 proteins, and Thr-4 in the PsbH protein of photosystem II. Phosphorylation of D1, D2, and CP43 in the light-exposed leaves of two Arabidopsis lines with T-DNA insertions in the stn8 gene was found significantly reduced in the assays with anti-phosphothreonine antibodies. Protein phosphorylation in each of the mutants was quantified comparatively to the wild type by mass spectrometric analyses of phosphopeptides released from the photosynthetic membranes and differentially labeled with stable isotopes. The lack of STN8 caused 50-60% reduction in D1 and D2 phosphorylation, but did not change the phosphorylation level of two peptides that could correspond to light-harvesting proteins encoded by seven different genes in Arabidopsis. Phosphorylation of the PsbH protein at Thr-4 was completely abolished in the plants lacking STN8. Phosphorylation of Thr-4 in the wild type required both light and prior phosphorylation at Thr-2, indicating that STN8 is a light-activated kinase that phosphorylates Thr-4 only after another kinase phosphorylates Thr-2. Analysis of the STN8 catalytic domain suggests that selectivity of STN8 in phosphorylation of the very N-terminal residues in D1, D2, and CP43, and Thr-4 in PsbH pre-phosphorylated at Thr-2 may be explained by the long loops obstructing entrance into the kinase active site and seven additional basic residues in the vicinity of the catalytic site, as compared with the homologous STN7 kinase responsible for phosphorylation of light-harvesting proteins.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-13863 (URN)10.1074/jbc.M505729200 (DOI)
    Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2009-06-08
  • 3.
    Hansson, Maria
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Dupuis, Tiphaine
    Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden .
    Strömquist, Ragna
    Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden .
    Andersson, Bertil
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Vener, Alexander V.
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Carlberg, Inger
    Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden .
    The mobile thylakoid phosphoprotein TSP9 interacts with the light harvesting complex II and the peripheries of both photosystems2006In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 282, no 22, p. 16214-16222Article in journal (Refereed)
    Abstract [en]

    The localization of the plant-specific thylakoid-soluble phosphoprotein of 9 kDa, TSP9, within the chloroplast thylakoid membrane of spinach has been established by the combined use of fractionation, immunoblotting, cross-linking, and mass spectrometry. TSP9 was found to be exclusively confined to the thylakoid membranes, where it is enriched in the stacked grana membrane domains. After mild solubilization of the membranes, TSP9 migrated together with the major light-harvesting antenna (LHCII) of photosystem II (PSII) and with PSII-LHCII supercomplexes upon separation of the protein complexes by either native gel electrophoresis or sucrose gradient centrifugation. Studies with a cleavable cross-linking agent revealed the interaction of TSP9 with both major and minor LHCII proteins as identified by mass spectrometric sequencing. Cross-linked complexes that in addition to TSP9 contain the peripheral PSII subunits CP29, CP26, and PsbS, which form the interface between LHCII and the PSII core, were found. Our observations also clearly suggest an interaction of TSP9 with photosystem I (PSI) as shown by both immunodetection and mass spectrometry. Sequencing identified the peripheral PSI subunits PsaL, PsaF, and PsaE, originating from cross-linked protein complexes of around 30 kDa that also contained TSP9. The distribution of TSP9 among the cross-linked forms was found to be sensitive to conditions such as light exposure. An association of TSP9 with LHCII as well as the peripheries of the photosystems suggests its involvement in regulation of photosynthetic light harvesting.

  • 4.
    Hansson, Maria
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Cellbiology. Linköping University, Faculty of Health Sciences.
    Vener, Alexander V.
    Linköping University, Department of Clinical and Experimental Medicine, Cellbiology. Linköping University, Faculty of Health Sciences.
    Identification of three previosly unknown in vivo phosphorylation sites in thylakoid membranes of Arabidopsis thaliana2003In: Molecular and Cellular Proteomics, ISSN 1535-9476, Vol. 2, no 8, p. 550-559Article in journal (Refereed)
    Abstract [en]

    The proteins in plant photosynthetic thylakoid membranes undergo light-induced phosphorylation, but only a few phosphoproteins have been characterized. To access the unknown sites of in vivo protein phosphorylation the thylakoid membranes were isolated from Arabidopsis thaliana grown in normal light, and the surface-exposed peptides were cleaved from the membranes by trypsin. The peptides were methylated and subjected to immobilized metal affinity chromatography, and the enriched phosphopeptides were sequenced using tandem nanospray quadrupole time-of-flight mass spectrometry. Three new phosphopeptides were revealed in addition to the five known phosphorylation sites in photosystem II proteins. All phosphopeptides are found phosphorylated at threonine residues implementing a strict threonine specificity of the thylakoid kinases. For the first time protein phosphorylation is found in photosystem I. The phosphorylation site is localized to the first threonine in the N terminus of PsaD protein that assists in the electron transfer from photosystem I to ferredoxin. A new phosphorylation site is also revealed in the acetylated N terminus of the minor chlorophyll a-binding protein CP29. The third novel phosphopeptide, composed of 25 amino acids, belongs to a nuclear encoded protein annotated as "expressed protein" in the Arabidopsis database. The protein precursor has a chloroplast-targeting peptide followed by the mature protein with two transmembrane helices and a molecular mass of 14 kDa. This previously uncharacterized protein is named thylakoid membrane phosphoprotein of 14 kDa (TMP14). The finding of the novel phosphoproteins extends involvement of the redox-regulated protein phosphorylation in photosynthetic membranes beyond the photosystem II and its light-harvesting antennae.

  • 5.
    Khrouchtchova, Anastassia
    et al.
    Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural University, Copenhagen, Denmark.
    Hansson, Maria
    Linköping University, Department of Clinical and Experimental Medicine, Cellbiology. Linköping University, Faculty of Health Sciences.
    Paakkarinen, Virpi
    Department of Biology, Plant Physiology and Molecular Biology, University of Turku, Turku, Finland.
    Vainonen, Julia P.
    Linköping University, Department of Clinical and Experimental Medicine, Cellbiology. Linköping University, Faculty of Health Sciences.
    Zhang, Suping
    Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural University, Copenhagen, Denmark.
    Jensen, Poul Erik
    Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural University, Copenhagen, Denmark.
    Vibe Scheller, Henrik
    Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural University, Copenhagen, Denmark.
    Vener, Alexander V.
    Linköping University, Department of Clinical and Experimental Medicine, Cellbiology. Linköping University, Faculty of Health Sciences.
    Aro, Eva-Mari
    Department of Biology, Plant Physiology and Molecular Biology, University of Turku, Turku, Finland.
    Haldrup, Anna
    Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural University, Copenhagen, Denmark.
    A previosly found thylakoid membrane protein of 14 kDa (TMP14) is a novel subunit of photosystem I and is designated PSI-P2005In: FEBS Letters, ISSN 0014-5793, Vol. 579, no 21, p. 4808-4812Article in journal (Refereed)
    Abstract [en]

    We show that the thylakoid membrane phosphoprotein TMP14 is a novel subunit of plant photosystem I (PSI). Blue native/SDS–PAGE and sucrose gradient fractionation demonstrated the association of the protein exclusively with PSI. We designate the protein PSI-P. The presence of PSI-P subunit in Arabidopsis mutants lacking other PSI subunits was analyzed and suggested a location in the proximity of PSI-L, -H and -O subunits. The PSI-P protein was not differentially phosphorylated in state 1 and state 2.

  • 6.
    Lundin, Björn
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Hansson, Maria
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Schoefs, Benoít
    Dynamique Vacuolaire et Réponses aux Stress de l'Environnement, Université de Bourgogne, Dijon cedex, France.
    Vener, Alexander V
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Spetea (Wiklund), Cornelia
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Arabidopsis PsbO2 protein regulates dephosphorylation and turnover of the photosystem II reaction centre D1 protein2007In: The Plant Journal, ISSN 0960-7412, Vol. 49, no 3, p. 528-539Article in journal (Refereed)
    Abstract [en]

    The extrinsic photosystem II (PSII) protein of 33 kDa (PsbO), which stabilizes the water-oxidizing complex, is represented in Arabidopsis thaliana (Arabidopsis) by two isoforms. Two T-DNA insertion mutant lines deficient in either the PsbO1 or the PsbO2 protein were retarded in growth in comparison with the wild type, while differing from each other phenotypically. Both PsbO proteins were able to support the oxygen evolution activity of PSII, although PsbO2 was less efficient than PsbO1 under photoinhibitory conditions. Prolonged high light stress led to reduced growth and fitness of the mutant lacking PsbO2 as compared with the wild type and the mutant lacking PsbO1. During a short period of treatment of detached leaves or isolated thylakoids at high light levels, inactivation of PSII electron transport in the PsbO2-deficient mutant was slowed down, and the subsequent degradation of the D1 protein was totally inhibited. The steady-state levels of in vivo phosphorylation of the PSII reaction centre proteins D1 and D2 were specifically reduced in the mutant containing only PsbO2, in comparison with the mutant containing only PsbO1 or with wild-type plants. Phosphorylation of PSII proteins in vitro proceeded similarly in thylakoid membranes from both mutants and wild-type plants. However, dephosphorylation of the D1 protein occurred much faster in the thylakoids containing only PsbO2. We conclude that the function of PsbO1 in Arabidopsis is mostly in support of PSII activity, whereas the interaction of PsbO2 with PSII regulates the turnover of the D1 protein, increasing its accessibility to the phosphatases and proteases involved in its degradation.

  • 7.
    Sirpio, Sari
    et al.
    Department of Biology, Plant Physiology and Molecular Biology University of Turku, Turku, Finland.
    Khrouchtchova, Anastassia
    Department of Plant Biology University of Copenhagen, Frederiksberg, Denmark.
    Allahverdiyeva, Yagut
    Department of Biology, Plant Physiology and Molecular Biology University of Turku, Turku, Finland.
    Hansson, Maria
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Cell Biology.
    Fristedt, Rikard
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Cell Biology.
    Vener, Alexander
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Cell Biology.
    Scheller, Henrik Vibe
    Department of Plant Biology University of Copenhagen, Frederiksberg, Denmark.
    Jensen, Poul Erik
    Department of Plant Biology University of Copenhagen, Frederiksberg, Denmark.
    Haldrup, Anna
    Department of Plant Biology University of Copenhagen, Frederiksberg, Denmark.
    Aro, Eva-Mari
    Department of Biology, Plant Physiology and Molecular Biology University of Turku, Turku, Finland.
    AtCYP38 ensures early biogenesis, correct assembly and sustenance of photosystem II2008In: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 55, no 4, p. 639-651Article in journal (Refereed)
    Abstract [en]

    AtCYP38 is a thylakoid lumen protein comprising the immunophilin domain and the phosphatase inhibitor module. Here we show the association of AtCYP38 with the photosystem II (PSII) monomer complex and address its functional role using AtCYP38-deficient mutants. The dynamic greening process of etiolated leaves failed in the absence of AtCYP38, due to specific problems in the biogenesis of PSII complexes. Also the development of leaves under short-day conditions was severely disturbed. Detailed biophysical and biochemical analysis of mature AtCYP38-deficient plants from favorable growth conditions (long photoperiod) revealed: (i) intrinsic malfunction of PSII, which (ii) occurred on the donor side of PSII and (iii) was dependent on growing light intensity. AtCYP38 mutant plants also showed decreased accumulation of PSII, which was shown not to originate from impaired D1 synthesis or assembly of PSII monomers, dimers and supercomplexes as such but rather from the incorrect fine-tuning of the oxygen-evolving side of PSII. This, in turn, rendered PSII centers extremely susceptible to photoinhibition. AtCYP38 deficiency also drastically decreased the in vivo phosphorylation of PSII core proteins, probably related to the absence of the AtCYP38 phosphatase inhibitor domain. It is proposed that during PSII assembly AtCYP38 protein guides the proper folding of D1 (and CP43) into PSII, thereby enabling the correct assembly of the water-splitting Mn 4-Ca cluster even with high turnover of PSII. © 2008 The Authors.

  • 8.
    Vainonen, Julia P.
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Hansson, Maria
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Vener, Alexander V.
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    STN8 protein kinase in Arabidopsis thaliana is specific in phosphorylation of photosystem II core proteins2005In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 280, no 39, p. 33679-33686Article in journal (Refereed)
    Abstract [en]

    Combination of reversed genetics with analyses of in vivo protein phosphorylation in Arabidopsis thaliana revealed that STN8 protein kinase is specific in phosphorylation of N-terminal threonine residues in D1, D2, and CP43 proteins, and Thr-4 in the PsbH protein of photosystem II. Phosphorylation of D1, D2, and CP43 in the light-exposed leaves of two Arabidopsis lines with T-DNA insertions in the stn8 gene was found significantly reduced in the assays with anti-phosphothreonine antibodies. Protein phosphorylation in each of the mutants was quantified comparatively to the wild type by mass spectrometric analyses of phosphopeptides released from the photosynthetic membranes and differentially labeled with stable isotopes. The lack of STN8 caused 50-60% reduction in D1 and D2 phosphorylation, but did not change the phosphorylation level of two peptides that could correspond to light-harvesting proteins encoded by seven different genes in Arabidopsis. Phosphorylation of the PsbH protein at Thr-4 was completely abolished in the plants lacking STN8. Phosphorylation of Thr-4 in the wild type required both light and prior phosphorylation at Thr-2, indicating that STN8 is a light-activated kinase that phosphorylates Thr-4 only after another kinase phosphorylates Thr-2. Analysis of the STN8 catalytic domain suggests that selectivity of STN8 in phosphorylation of the very N-terminal residues in D1, D2, and CP43, and Thr-4 in PsbH pre-phosphorylated at Thr-2 may be explained by the long loops obstructing entrance into the kinase active site and seven additional basic residues in the vicinity of the catalytic site, as compared with the homologous STN7 kinase responsible for phosphorylation of light-harvesting proteins.

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