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Bertil Andersson - One of the best experts on this subject based on the ideXlab platform.
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Photodamage and D1 Protein Turnover in Photosystem II
Regulation of Photosynthesis, 2020Co-Authors: Bertil AnderssonAbstract:Photosystem II is frequently undergoing photoinduced damages targeted to its reaction center in a process normally referred to as photoinhibition. Photosynthesis is maintained through an intricate repair mechanism involving degradation of the damaged D1 reaction center Protein and insertion of a new Protein copy into the photosystem. The photoinhibition process is induced by inoptimal electron transfer at the acceptor or donor side of Photosystem II. Photoinhibition induced from the acceptor side is caused by a stepwise accumulation of stably reduced abnormal QA species that lead to formation of chlorophyll triplets and production of singlet oxygen, resulting in oxidative damage to the D1 Protein. Photoinhibition induced from the donor side involves formation of long-lived highly oxidizing P680+ and finally D1 Protein damage. A damaged D1 Protein is triggered to be degraded via a multistep proteolytic reaction requiring GTP and ATP and catalyzed by chloroplast Deg P2 and FtsH, homologues to known bacterial proteases. Synthesis and assembly of the new D1 copy into PS II is also a multistep process. After targeting of the psbA mRNA ribosome complex to the thylakoid membrane, the elongating D1 Protein is cotranslationally inserted into the thylakoid membrane and concomitantly assembled with the D2 Protein. Both the cotranslational and post-translational assembly steps of the D1 Protein into PS II are under strict redox control.
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Dissecting a cyanobacterial proteolytic system: efficiency in inducing degradation of the D1 Protein of photosystem II in cyanobacteria and plants.
Biochimica et biophysica acta, 2003Co-Authors: Eira Kanervo, Norio Murata, Cornelia Spetea, Yoshitaka Nishiyama, Bertil AnderssonAbstract:A chromatography fraction, prepared from isolated thylakoids of a fatty acid desaturation mutant (Fad6/desA Colon, two colons Km(r)) of the cyanobacterium Synechocystis 6803, could induce an initial cleavage of the D1 Protein in Photosystem II (PSII) particles of Synechocystis 6803 mutant and Synechococcus 7002 wild type as well as in supercomplexes of PSII-light harvesting complex II of spinach. Proteolysis was demonstrated both in darkness and in light as a reduction in the amount of full-length D1 Protein or as a production of C-terminal initial degradation fragments. In the Synechocystis mutant, the main degradation fragment was a 10-kDa C-terminal one, indicating an initial cleavage occurring in the cytoplasmic DE-loop of the D1 Protein. A Protein component of 70-90 kDa isolated from the chromatographic fraction was found to be involved in the production of this 10-kDa fragment. In spinach, only traces of the corresponding fragment were detected, whereas a 24-kDa C-terminal fragment accumulated, indicating an initial cleavage in the lumenal AB-loop of the D1 Protein. Also in Synechocystis the 24-kDa fragment was detected as a faint band. An antibody raised against the Arabidopsis DegP2 protease recognized a 35-kDa band in the proteolytically active chromatographic fraction, suggesting the existence of a lumenal protease that may be the homologue DegP of Synechocystis. The identity of the other protease cleaving the D1 Protein in the DE-loop exposed on the stromal (cytoplasmic) side of the membrane is discussed.
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Dissecting a cyanobacterial proteolytic system: efficiency in inducing degradation of the D1 Protein of photosystem II in cyanobacteria and plants
Biochimica et Biophysica Acta, 2003Co-Authors: Eira Kanervo, Norio Murata, Cornelia Spetea, Yoshitaka Nishiyama, Bertil AnderssonAbstract:A chromatography fraction, prepared from isolated thylakoids of a fatty acid desaturation mutant (Fad6/desAKmr) of the cyanobacterium Synechocystis 6803, could induce an initial cleavage of the D1 Protein in Photosystem II (PSII) particles of Synechocystis 6803 mutant and Synechococcus 7002 wild type as well as in supercomplexes of PSII-light harvesting complex II of spinach. Proteolysis was demonstrated both in darkness and in light as a reduction in the amount of full-length D1 Protein or as a production of C-terminal initial degradation fragments. In the Synechocystis mutant, the main degradation fragment was a 10-kDa C-terminal one, indicating an initial cleavage occurring in the cytoplasmic DE-loop of the D1 Protein. A Protein component of 70-90 kDa isolated from the chromatographic fraction was found to be involved in the production of this 10-kDa fragment. In spinach, only traces of the corresponding fragment were detected, whereas a 24-kDa C-terminal fragment accumulated, indicating an initial cleavage in the lumenal AB-loop of the D1 Protein. Also in Synechocystis the 24-kDa fragment was detected as a faint band. An antibody raised against the Arabidopsis DegP2 protease recognized a 35-kDa band in the proteolytically active chromatographic fraction, suggesting the existence of a lumenal protease that may be the homologue DegP of Synechocystis. The identity of the other protease cleaving the D1 Protein in the DE-loop exposed on the stromal (cytoplasmic) side of the membrane is discussed. ⌐ 2003 Elsevier B.V. All rights reserved.
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a chloroplast degp2 protease performs the primary cleavage of the photodamaged D1 Protein in plant photosystem ii
The EMBO Journal, 2001Co-Authors: Kirsten Hausuhl, Bertil Andersson, Iwona AdamskaAbstract:Although light is the ultimate substrate in photosynthesis, it can also be harmful and lead to oxidative damage of the photosynthetic apparatus. The main target for light stress is the central oxygen-evolving photosystem II (PSII) and its D1 reaction centre Protein. Degradation of the damaged D1 Protein and its rapid replacement by a de novo synthesized copy represent the important repair mechanism of PSII crucial for plant survival under light stress conditions. Here we report the isolation of a single-copy nuclear gene from Arabidopsis thaliana, encoding a protease that performs GTP-dependent primary cleavage of the photodamaged D1 Protein and hence catalysing the key step in the repair cycle in plants. This protease, designated DegP2, is a homologue of the prokaryotic Deg/Htr family of serine endopeptidases and is associated with the stromal side of the non-appressed region of the thylakoid membranes. Increased expression of DegP2 under high salt, desiccation and light stress conditions was measured at the Protein level.
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GTP enhances the degradation of the photosystem II D1 Protein irrespective of its conformational heterogeneity at the Q(B) site
Journal of Biological Chemistry, 2000Co-Authors: Cornelia Spetea, Torill Hundal, Itzhak Ohad, Nir Keren, Jean-michel Doan, Bertil AnderssonAbstract:The light exposure history and/or binding of different herbicides at the Q(B) site may induce heterogeneity of photosystem II acceptor side conformation that affects D1 Protein degradation under photoinhibitory conditions. GTP was recently found to stimulate the D1 Protein degradation of photoinactivated photosystem II (Spetea C., Hundal, T., Lohmann, F., and Andersson, B. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 6547-6552). Here we report that GTP enhances the cleavage of the D1 Protein D-E loop following exposure of thylakoid membranes to either high light, low light, or repetitive single turnover flashes but not to trypsin. GTP does not stimulate D1 Protein degradation in the presence of herbicides known to affect the accessibility of the cleavage site to proteolysis. However, GTP stimulates degradation that can be induced even in darkness in some photosystem II conformers following binding of the PNO8 herbicide (Nakajima, Y., Yoshida, S., Inoue, Y., Yoneyama, K., and Ono, T. (1995) Biochim. Biophys. Acta 1230, 38-44). Both the PNO8- and the light-induced primary cleavage of the D1 Protein occur in the grana membrane domains. The subsequent migration of photo-system II containing the D1 Protein fragments to the stroma domains for secondary proteolysis is light-activated. We conclude that the GTP effect is not confined to a specific photoinactivation pathway nor to the conformational state of the photosystem II acceptor side. Consequently, GTP does not interact with the site of D1 Protein cleavage but rather enhances the activity of the endogenous proteolytic system.
Lixin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Maintenance of functional photosystem II by D1 Protein turnover
Science Access, 2020Co-Authors: Lixin Zhang, Virpi Paakkarinen, Marjaana Suorsa, Natalia BattchikovaAbstract:Water splitting of oxygenic photosynthesis produces various radicals and active oxygen species with harmful effects on PSII. Such photodamage to PSII occurs at all light intensities. Damaged PSII centers, however, do not usually accumulate in the thylakoid membrane due to a rapid and efficient repair mechanism. A grant design of PSII protects most of the Protein components with the damage targeted to only one Protein, the reaction center D1 Protein. Repair of PSII via turnover of the D1 Protein is a complex process. Central for such turnover and repair is a regulated reversible phosphorylation of PSII Proteins, changes between dimer/monomer organization of PSII, migration of PS II between grana and stroma-exposed thylakoid domains, partial PSII disassembly and a multistep highly specific proteolysis of the D1 Protein. Replacement of the damaged D1 with a new copy requires targeting of ribosome psbA mRNA complexes to the thylakoid membrane and subsequent light-regulated translation elongation. Concomitantly with D1 elongation, the Protein is inserted into the thylakoid membrane, probably via a cpSecY-related translocation channel. Before termination of translation the nascent D1 chain starts interacting with other PSII Proteins, particularly with the D2 Protein, the presence of which seems to be a prerequisite for D1 elongation to be completed. CP47 is next integrated into the complex and finally, after termination of translation and maturation of the D1 Protein, the CP43 Protein is associated. Various assembly steps of PSII are highly regulated and require proper redox conditions and maintenance of the trans-thylakoid proton gradient.
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formation of deg5 and deg8 complexes and their involvement in the degradation of photodamaged photosystem ii reaction center D1 Protein in arabidopsis
The Plant Cell, 2007Co-Authors: Lianwei Peng, Congming Lu, Lixin ZhangAbstract:The widely distributed DEGP proteases play important roles in the degradation of damaged and misfolded Proteins. Arabidopsis thaliana contains 16 DEGP-like proteases, four of which are located in the chloroplast. Here, we show that DEG5 and DEG8 form a hexamer in the thylakoid lumen and that recombinant DEG8 is proteolytically active toward both a model substrate (β-casein) and photodamaged D1 Protein of photosystem II (PSII), producing 16-kD N-terminal and 18-kD C-terminal fragments. Inactivation of DEG5 and DEG8 resulted in increased sensitivity to photoinhibition. Turnover of newly synthesized D1 Protein in the deg5 deg8 double mutant was impaired, and the degradation of D1 in the presence of the chloroplast Protein synthesis inhibitor lincomycin under high-light treatment was slowed in the mutants. Thus, DEG5 and DEG8 are important for efficient turnover of the D1 Protein and for protection against photoinhibition in vivo. The deg5 deg8 double mutant showed increased photosensitivity and reduced rates of D1 degradation compared with single mutants of deg5 and deg8. A 16-kD N-terminal degradation fragment of the D1 Protein was detected in wild-type plants but not in the deg5 deg8 mutant following in vivo photoinhibition. Therefore, our results suggest that DEG5 and DEG8 have a synergistic function in the primary cleavage of the CD loop of the PSII reaction center Protein D1.
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Synthesis, membrane insertion and assembly of the chloroplast-encoded D1 Protein into photosystem II
FEBS Letters, 2002Co-Authors: Lixin ZhangAbstract:Rapid light-dependent turnover of the chloroplast-encoded D1 Protein maintains photosystem II (PS II) functional over a wide range of light intensities. Following initiation of psbA mRNA translation, the elongating D1 is targeted, possibly by chloroplast signal recognition particle 54 (cpSRP54), to the thylakoid cpSecY translocation channel. Transmembrane domains of nascent D1 start interacting with other PS II core Proteins already during the translocation process to ensure an efficient assembly of the multiProtein membrane complex. Here we review the progress recently made concerning the synthesis, targeting, membrane insertion and assembly to PS II of the chloroplast-encoded D1 Protein and discuss the possible convergence of targeting and translocation of chloroplast- and nuclear-encoded thylakoid Proteins.
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A SecY Homologue Is Involved in Chloroplast-encoded D1 Protein Biogenesis
Journal of Biological Chemistry, 2001Co-Authors: Lixin Zhang, Virpi Paakkarinen, Marjaana SuorsaAbstract:Abstract We have used the photosystem II reaction center D1 Protein as a model to study the mechanisms of targeting and insertion of chloroplast-encoded thylakoid membrane Proteins. The unusually high turnover rate and distinct pausing intermediates during translation make the D1 Protein biogenesis particularly suitable for these purposes. Here we show that cpSecY, a chloroplast homologue of bacterial essential translocon component SecY, interacts tightly with thylakoid membrane-bound ribosomes, suggesting its involvement in Protein translocation and insertion. Co-immunoprecipitation and cross-linking experiments indicated that cpSecY resides in the vicinity of D1 elongation intermediates and provided evidence for a transient interaction of cpSecY with D1 elongation intermediates during the biogenesis of D1. After termination of translation, such interactions no longer existed. Our results indicate that, in addition to a well characterized role of cpSecY in posttranslational translocation of nuclear-encoded Proteins, it seems to be also involved in cotranslational membrane Protein translocation and insertion in chloroplasts.
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co translational assembly of the D1 Protein into photosystem ii
Journal of Biological Chemistry, 1999Co-Authors: Lixin Zhang, Virpi Paakkarinen, Klaas J. Van WijkAbstract:Abstract Assembly of multi-subunit membrane Protein complexes is poorly understood. In this study, we present direct evidence that the D1 Protein, a multiple membrane spanning Protein, assembles co-translationally into the large membrane-bound complex, photosystem II. During pulse-chase studies in intact chloroplasts, incorporation of the D1 Protein occurred without transient accumulation of free labeled Protein in the thylakoid membrane, and photosystem II subcomplexes contained nascent D1 intermediates of 17, 22, and 25 kDa. These N-terminal D1 intermediates could be co-immunoprecipitated with antiserum directed against the D2 Protein, suggesting co-translational assembly of the D1 Protein into PS II complexes. Further evidence for a co-translational assembly of the D1 Protein into photosystem II was obtained by analyzing ribosome nascent chain complexes liberated from the thylakoid membrane after a short pulse labeling. Radiolabeled D1 intermediates could be immunoprecipitated under nondenaturing conditions with antisera raised against the D1 and D2 Protein as well as CP47. However, when the ribosome pellets were solubilized with SDS, the interaction of these intermediates with CP47 was completely lost, but strong interaction of a 25-kDa D1 intermediate with the D2 Protein still remained. Taken together, our results indicate that during the repair of photosystem II, the assembly of the newly synthesized D1 Protein into photosystem II occurs co-translationally involving direct interaction of the nascent D1 chains with the D2 Protein.
Akiyoshi Nishikawa - One of the best experts on this subject based on the ideXlab platform.
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sesamin a lignan of sesame down regulates cyclin D1 Protein expression in human tumor cells
Cancer Science, 2007Co-Authors: Tomoya Yokota, Youichirou Matsuzaki, Makoto Koyama, Toshiaki Hitomi, Mayumi Kawanaka, Masako Enokikonishi, Yusuke Okuyama, Junko Takayasu, Hoyoku Nishino, Akiyoshi NishikawaAbstract:Sesamin is a major lignan constituent of sesame and possesses multiple functions such as antihypertensive, cholesterol-lowering, lipid-lowering and anticancer activities. Several groups have previously reported that sesamin induces growth inhibition in human cancer cells. However, the nature of this growth inhibitory mechanism remains unknown. The authors here report that sesamin induces growth arrest at the G1 phase in cell cycle progression in the human breast cancer cell line MCF-7. Furthermore, sesamin dephosphorylates tumor-suppressor retinoblastoma Protein (RB). It is also shown that inhibition of MCF-7 cell proliferation by sesamin is correlated with down-regulated cyclin D1 Protein expression, a proto-oncogene that is overexpressed in many human cancer cells. It was found that sesamin-induced down-regulation of cyclin D1 was inhibited by proteasome inhibitors, suggesting that sesamin suppresses cyclin D1 Protein expression by promoting proteasome degradation of cyclin D1 Protein. Sesamin down-regulates cyclin D1 Protein expression in various kinds of human tumor cells, including lung cancer, transformed renal cells, immortalized keratinocyte, melanoma and osteosarcoma. Furthermore, depletion of cyclin D1 Protein using small interfering RNA rendered MCF-7 cells insensitive to the growth inhibitory effects of sesamin, implicating that cyclin D1 is at least partially related to the antiproliferative effects of sesamin. Taken together, these results suggest that the ability of sesamin to down-regulate cyclin D1 Protein expression through the activation of proteasome degradation could be one of the mechanisms of the antiproliferative activity of this agent. (Cancer Sci 2007; 98: 1447–1453)
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Sesamin, a lignan of sesame, down‐regulates cyclin D1 Protein expression in human tumor cells
Cancer Science, 2007Co-Authors: Tomoya Yokota, Youichirou Matsuzaki, Makoto Koyama, Toshiaki Hitomi, Mayumi Kawanaka, Yusuke Okuyama, Junko Takayasu, Hoyoku Nishino, Masako Enoki-konishi, Akiyoshi NishikawaAbstract:Sesamin is a major lignan constituent of sesame and possesses multiple functions such as antihypertensive, cholesterol-lowering, lipid-lowering and anticancer activities. Several groups have previously reported that sesamin induces growth inhibition in human cancer cells. However, the nature of this growth inhibitory mechanism remains unknown. The authors here report that sesamin induces growth arrest at the G1 phase in cell cycle progression in the human breast cancer cell line MCF-7. Furthermore, sesamin dephosphorylates tumor-suppressor retinoblastoma Protein (RB). It is also shown that inhibition of MCF-7 cell proliferation by sesamin is correlated with down-regulated cyclin D1 Protein expression, a proto-oncogene that is overexpressed in many human cancer cells. It was found that sesamin-induced down-regulation of cyclin D1 was inhibited by proteasome inhibitors, suggesting that sesamin suppresses cyclin D1 Protein expression by promoting proteasome degradation of cyclin D1 Protein. Sesamin down-regulates cyclin D1 Protein expression in various kinds of human tumor cells, including lung cancer, transformed renal cells, immortalized keratinocyte, melanoma and osteosarcoma. Furthermore, depletion of cyclin D1 Protein using small interfering RNA rendered MCF-7 cells insensitive to the growth inhibitory effects of sesamin, implicating that cyclin D1 is at least partially related to the antiproliferative effects of sesamin. Taken together, these results suggest that the ability of sesamin to down-regulate cyclin D1 Protein expression through the activation of proteasome degradation could be one of the mechanisms of the antiproliferative activity of this agent. (Cancer Sci 2007; 98: 1447–1453)
Torill Hundal - One of the best experts on this subject based on the ideXlab platform.
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GTP enhances the degradation of the photosystem II D1 Protein irrespective of its conformational heterogeneity at the Q(B) site
Journal of Biological Chemistry, 2000Co-Authors: Cornelia Spetea, Torill Hundal, Itzhak Ohad, Nir Keren, Jean-michel Doan, Bertil AnderssonAbstract:The light exposure history and/or binding of different herbicides at the Q(B) site may induce heterogeneity of photosystem II acceptor side conformation that affects D1 Protein degradation under photoinhibitory conditions. GTP was recently found to stimulate the D1 Protein degradation of photoinactivated photosystem II (Spetea C., Hundal, T., Lohmann, F., and Andersson, B. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 6547-6552). Here we report that GTP enhances the cleavage of the D1 Protein D-E loop following exposure of thylakoid membranes to either high light, low light, or repetitive single turnover flashes but not to trypsin. GTP does not stimulate D1 Protein degradation in the presence of herbicides known to affect the accessibility of the cleavage site to proteolysis. However, GTP stimulates degradation that can be induced even in darkness in some photosystem II conformers following binding of the PNO8 herbicide (Nakajima, Y., Yoshida, S., Inoue, Y., Yoneyama, K., and Ono, T. (1995) Biochim. Biophys. Acta 1230, 38-44). Both the PNO8- and the light-induced primary cleavage of the D1 Protein occur in the grana membrane domains. The subsequent migration of photo-system II containing the D1 Protein fragments to the stroma domains for secondary proteolysis is light-activated. We conclude that the GTP effect is not confined to a specific photoinactivation pathway nor to the conformational state of the photosystem II acceptor side. Consequently, GTP does not interact with the site of D1 Protein cleavage but rather enhances the activity of the endogenous proteolytic system.
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the thylakoid ftsh protease plays a role in the light induced turnover of the photosystem ii D1 Protein
The Plant Cell, 2000Co-Authors: Marika Lindahl, Bertil Andersson, Torill Hundal, Cornelia Spetea, Amos B Oppenheim, Zach AdamAbstract:The photosystem II reaction center D1 Protein is known to turn over frequently. This Protein is prone to irreversible damage caused by reactive oxygen species that are formed in the light; the damaged, nonfunctional D1 Protein is degraded and replaced by a new copy. However, the proteases responsible for D1 Protein degradation remain unknown. In this study, we investigate the possible role of the FtsH protease, an ATP-dependent zinc metalloprotease, during this process. The primary light-induced cleavage product of the D1 Protein, a 23-kD fragment, was found to be degraded in isolated thylakoids in the dark during a process dependent on ATP hydrolysis and divalent metal ions, suggesting the involvement of FtsH. Purified FtsH degraded the 23-kD D1 fragment present in isolated photosystem II core complexes, as well as that in thylakoid membranes depleted of endogenous FtsH. In this study, we definitively identify the chloroplast protease acting on the D1 Protein during its light-induced turnover. Unlike previously identified membrane-bound substrates for FtsH in bacteria and mitochondria, the 23-kD D1 fragment represents a novel class of FtsH substrate— functionally assembled Proteins that have undergone irreversible photooxidative damage and cleavage.
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GTP bound to chloroplast thylakoid membranes is required for light-induced, multienzyme degradation of the photosystem II D1 Protein
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Cornelia Spetea, Torill Hundal, Felix Lohmann, Bertil AnderssonAbstract:Even though light is the driving force in photosynthesis, it also can be harmful to plants. The water-splitting photosystem II is the main target for this light stress, leading to inactivation of photosynthetic electron transport and photooxidative damage to its reaction center. The plant survives through an intricate repair mechanism involving proteolytic degradation and replacement of the photodamaged reaction center D1 Protein. Based on experiments with isolated chloroplast thylakoid membranes and photosystem II core complexes, we report several aspects concerning the rapid turnover of the D1 Protein. (i) The primary cleavage step is a GTP-dependent process, leading to accumulation of a 23-kDa N-terminal fragment. (ii) Proteolysis of the D1 Protein is inhibited below basal levels by nonhydrolyzable GTP analogues and apyrase treatment, indicating the existence of endogenous GTP tightly bound to the thylakoid membrane. This possibility was corroborated by binding studies. (iii) The proteolysis of the 23-kDa primary degradation fragment (but not of the D1 Protein) is an ATP- and zinc-dependent process. (iv) D1 Protein degradation is a multienzyme event involving a strategic (primary) protease and a cleaning-up (secondary) protease. (v) The chloroplast FtsH protease is likely to be involved in the secondary degradation steps. Apart from its significance for understanding the repair of photoinhibition, the discovery of tightly bound GTP should have general implications for other regulatory reactions and signal transduction pathways associated with the photosynthetic membrane.
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Involvement of GTP in the Primary Proteolysis of the D1 Protein During Photoinhibition of Photosystem II
Photosynthesis: Mechanisms and Effects, 1998Co-Authors: Cornelia Spetea, Torill Hundal, Felix Lohmann, Bertil AnderssonAbstract:The photosystem II (PSII) complex is the main target for light-induced inactivation of photosynthetic electron transport [1,2], leading to proteolytic degradation and replacement (turn-over) of the reaction centre II D1 Protein [1,3]. A 23 lcDa N-terminal and the corresponding 10 kDa C-terminal degradation fragments have been detected in vivo as well as during photoinhibition of isolated systems like thylakoid membranes and oxygen-evolving PSII core complexes [3]. There are sufficient experimental data to support the concept of a light-induced structural modification of the D1 Protein initiating the proteolytic process [1,3,4]. The degradation of the damaged Protein is thought to involve at least two proteolytic activities, although the proteases have not yet been identified [3]. The D1 Protein proteolysis was demonstrated to be of serine-type, with a pH optimum of 7.5, stimulated by Mg2+, ATP-independent, and catalyzed by a membrane bound enzyme most likely associated with the PSII complex [3].
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In vitro studies on light-induced inhibition of Photosystem II and D1-Protein degradation at low temperatures
Biochimica et Biophysica Acta, 1990Co-Authors: Torill Hundal, Inger Carlberg, Bertil AnderssonAbstract:Abstract In order to get information on the molecular background behind the aggrevated photodamage to photosynthesis at low temperatures and to investigate the general mechanism of D1-Protein degradation, isolated spinach thylakoids were subjected to photoinhibitory treatment at various temperatures. The results reveal that: (i) the Photosystem II electron transport per se is less sensitive to high light at low temperatures in contrast to the overall photosynthetic process; (ii) the degradation of D1-Protein is severely retarded below 7°C; (iii) inhibition of Photosystem II electron transport and D1-Protein degradation are separate events the two reactions could be completely separated in time; (iv) D1-Protein is degraded by enzymatic proteolysis and not by a direct photocleavage reaction; (v) degradation of the D1-Protein readily proceeds in the dark but its triggering for the proteolytic attack requires light; (vi) strong illumination at low temperature does not induce any lateral rearrangement in the location of Photosystem II; and (vii) D1-Protein fragments can be identified in vitro and be used to verify the specificity of D1-Protein degradation under various experimental conditions.
Yasusi Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Heat stress and light stress cooperatively damage the D1 Protein in PS II
Science Access, 2020Co-Authors: Satoshi Ohira, Yasusi YamamotoAbstract:Heat stress, as well as light stress, damages the D1 Protein. When spinach thylakoids were incubated at 40oC for 10 min in the dark, D1 cross-linked with D2 and a 23kDa D1N fragment was detected. In spinach leaf-discs, PS II activity monitored by Fv/Fm was dramatically decreased under illumination (600 µE m-2 s-1) at 40oC, compared with 25oC. The amount of the D1/D2 cross-linked products illuminated at 40oC was 2-4 times larger than that at 25oC. Obviously, the damage of the D1 Protein by light stress was amplified by heat stress. Scavengers for reactive oxygen species suppressed the heat-induced cross-linking. However, these scavengers had no significant effect on the digestion of the D1 Protein to the 23kDa D1N fragment. It was shown recently that phosphorylated Proteins in PS II are dephosphorylated by heat (Rintamaki et al., 1996). We studied the relationship between dephosphorylation and degradation of the D1 Protein under heat stress in vitro. It was observed that the D1 dephosphorylation does not affect the D1 degradation. Both the D1/D2 cross-linked products and the 23kDa D1N fragments generated by the heat stress were degraded by a stromal protease(s) at the non-appressed region of thylakoids.
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Regulation of photo-induced cross-linking of the D1 Protein and CP43 in PSII by ATP
Science Access, 2020Co-Authors: Hitomi Baba, Syoko Miyake, Miwa Ohtake, Yasusi YamamotoAbstract:One of the remarkable phenomena in photoinhibition of PS II is generation of cross-linked products between the D1 Protein and the nearby polypeptides in PS II and the following digestion of these products by a stromal protease(s). When spinach PS II membranes that had been treated with 0.8 M Tris (pH 9.0) were illuminated with strong light, more than 30% of the total D1 Protein appeared as cross-linked products. By studying the details of the related processes, we concluded that the D1 cross-linking and degradation of the cross-linked products comprise a novel pathway of the D1 turnover. In the present study, we found that the light-induced D1 cross-linking is suppressed completely by the addition of ATP to the PSII membranes. The cross-linking was stimulated when ATP was omitted and the endogenous ATP was hydrolyzed by the addition of apyrase in the reaction mixture before the illumination. These results suggest that the cross-linking of the D1 Protein and CP43 is dependent not only on the photooxidation of amino acids in the both Proteins, but also on the conformation of the Proteins probably determined by the phosphorylation/dephosphorylation conditions.
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quality control of photosystem ii cleavage of reaction center D1 Protein in spinach thylakoids by ftsh protease under moderate heat stress
Journal of Biological Chemistry, 2006Co-Authors: Miho Yoshioka, Keisuke Komayama, Satoshi Ohira, Noriko Morita, Suguru Uchida, Hiroki Mori, Tohru Nakanishi, Yasusi YamamotoAbstract:Next Section Abstract When spinach thylakoids were subjected to moderate heat stress (40 °C for 30 min), oxygen evolution was inhibited, and cleavage of the reaction center-binding Protein D1 of photosystem II took place, producing 23-kDa N-terminal fragments. The D1 cleavage was greatly facilitated by the addition of 0.15 mm ZnCl2 and 1 mm ATP and was completely inhibited by 1 mm EDTA, indicating the participation of an ATP-dependent metalloprotease(s) in the D1 cleavage. Herbicides 3-(3,4-dichlorophenyl)-1,1-dimethyl urea, bromoxynil, and ioxynil, all of which bind to the QB site, inhibited the D1 cleavage, suggesting that the DE-loop of the D1 Protein is the heat-sensitive cleavage site. We solubilized the protease by treating the thylakoids with 2 m KSCN and detected a protease activity in the supernatant by gelatin activity gel electrophoresis in the 70–80-kDa region. The antibodies against tobacco FtsH and Arabidopsis FtsH2 reacted with a 70–80-kDa band of the KSCN-solubilized fraction, which suggests the presence of FtsH in the fraction. In accordance with this finding, we identified the homolog to Arabidopsis FtsH8 in the 70–80-kDa region by matrix-assisted laser desorption ionization time-of-flight mass analysis of the thylakoids. The KSCN-solubilized fraction was successively reconstituted with thylakoids to show heat-induced cleavage of the D1 Protein and production of the D1 fragment. These results strongly suggest that an FtsH protease(s) is involved in the primary cleavage of the D1 Protein under moderate heat stress.
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Post-illumination-related loss of photochemical efficiency of Photosystem II and degradation of the D1 Protein are temperature-dependent.
Journal of Plant Physiology, 2005Co-Authors: Munna Singh, Kimiyuki Satoh, Yasusi Yamamoto, Eira KanervoAbstract:Photosystem II (PSII) photochemical efficiency (chlorophyll fluorescence ratio Fv/Fm) was recorded in vivo in Synechocystis 6803 during high light illumination and during a subsequent shift of the cells to darkness. A continuing decrease in the Fv/Fm ratio was observed even after the cells were transferred to darkness, provided the temperature was high enough. The decrease in the PSII efficiency after the shifting of the cells to darkness correlated directly with the loss of the D1 Protein under different temperatures, suggesting that temperature-dependent proteolysis of the D1 Protein in darkness induces the loss of PSII photochemical efficiency under these conditions. Furthermore, the amount of FtsH protease was found to increase during the high light treatment. This observation suggests that the synthesis of the FtsH Protein is a light-regulated process and that this protease most probably has a key role in an efficient degradation of the D1 Protein even under post-illuminative conditions, provided the temperature is high enough to prevent the initial reversible steps of photoinhibition.
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Quality control of photosystem II under light stress - turnover of aggregates of the D1 Protein in vivo.
Photosynthesis Research, 2005Co-Authors: Satoshi Ohira, Noriko Morita, Jin Jung, Yasusi YamamotoAbstract:When photodamaged under excessive light, the D1 Protein is digested and removed from Photosystem (PS) II to facilitate turnover of the Protein. In vitro studies have shown that part of the photodamaged D1 Protein forms aggregates with surrounding polypeptides before being digested by a protease(s) in the stroma [Yamamoto Y (2001) Plant Cell Physiol 42: 121–128]. The aim of this study was to examine whether light-induced aggregation of the D1 Protein also occurs in vivo. The following results were obtained: (1) PS II activity in spinach leaves was significantly inhibited by weak illumination (light intensity, 20–100 μE m−2 s−1), as monitored by chlorophyll fluorescence Fv/Fm, when the leaves were kept at higher temperatures (35–40 °C); (2) aggregation of the D1 Protein, as well as cleavage of the Protein, was detected in thylakoids isolated from spinach leaves that had been subjected to heat/light stress; (3) aggregates of the D1 Protein disappeared after incubation of the leaves at 25 °C in the dark or under illumination with weak light. Since it is dependent on the presence of oxygen, aggregation of the D1 Protein is probably induced by reactive oxygen species produced in thylakoids upon illumination at elevated temperatures. Consistent with this notion, singlet oxygen production in thylakoid samples under illumination was shown to be stimulated significantly at higher temperatures.
