Updated on 2025/09/27

写真a

 
OZAWA Shinichirou
 
Organization
Scheduled update Associate Professor
Position
Associate Professor
Contact information
メールアドレス
Homepage
http://www.rib.okayama-u.ac.jp/RECTOR/
External link

Degree

  • Biochemical characterization of Photosystem I complex assembly in the green alga Chlamydomonas reinhardtii ( Okayama University )

Research Interests

  • pigment

  • Arabidopsis

  • Chlamydomonas

  • Barley

  • Photosystem

  • Proteomics

  • Chloroplast ATP synthase

  • Biogenesis/Assembly of photosynthesis complexes

  • mass spectrometry

  • structural biology

  • protein purification

  • photosystemⅠ

  • photosynthesis

  • cytochrome b6f complex

Research Areas

  • Life Science / Biophysics

  • Life Science / Molecular biology

  • Life Science / Structural biochemistry

  • Life Science / Cell biology

  • Life Science / Plant molecular biology and physiology

Education

  • Okayama University   自然科学研究科博士後期課程   バイオサイエンス専攻

    2005.4 - 2009.9

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    Country： Japan

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  • Okayama University   自然科学研究科博士前期課程   分子・生物科学専攻

    2003.4 - 2005.3

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    Country： Japan

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  • Okayama University   理学部   生物学科

    1999.4 - 2003.3

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    Country： Japan

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Research History

  • Okayama University   Institute of Plant Science and Resources   Associate Professor

    2024.10

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    Country：Japan

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  • Institute of Plant Science and Resources, Okayama University   Assistant Professor (specially appointed)

    2019.10 - 2024.9

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  • Okayama University   Research Institute for Interdisciplinary Science   Research Associate

    2016.4 - 2019.9

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  • Okayama University Grad Sch Nat Sci Tech   Fac of Sci, Dept Biol, Yuichiro Takahashi lab   Research Assistant Professor

    2013.12 - 2016.3

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  • CNRS   UMR7141/UPMC IBPC   PostDoc

    2010.5 - 2013.11

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  • Okayama University Grad Sch Nat Sci Tech   Fac of Sci, Dept Biol, Yuichiro Takahashi lab   PostDoc

    2009.10 - 2010.4

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Professional Memberships

  • The American Society of Plant Biologists

    2022.12

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  • THE JAPANESE SOCIETY OF PLANT PHYSIOLOGISTS

    2003.1

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  • Genetic Society of America

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  • THE BOTANICAL SOCIETY OF JAPAN

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  • THE JAPANESE SOCIETY OF PHOTOSYNTHESIS RESEARCH

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Papers

  • Geranylgeranylated‐chlorophyll‐protein complexes in lhl3 mutant of the green alga Chlamydomonas reinhardtii Reviewed International coauthorship International journal

    Sireesha Kodru, Sreedhar Nellaepalli, Shin‐Ichiro Ozawa, Chihiro Satoh, Hiroshi Kuroda, Ryouichi Tanaka, Katharine Guan, Marilyn Kobayashi, Phoi Tran, Sarah McCarthy, Setsuko Wakao, Krishna K. Niyogi, Yuichiro Takahashi

    The Plant Journal   2024.10

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

    SUMMARY

    Chlorophylls a and b (Chl a and b) are involved in light harvesting, photochemical reactions, and electron transfer reactions in plants and green algae. The core complexes of the photosystems (PSI and PSII) associate with Chl a, while the peripheral antenna complexes (LHCI and LHCII) bind Chls a and b. One of the final steps of Chl biosynthesis is the conversion of geranylgeranylated Chls (ChlsGG) to phytylated Chls by geranylgeranyl reductase (GGR). Here, we isolated and characterized a pale green mutant of the green alga Chlamydomonas reinhardtii that was very photosensitive and was unable to grow photoautotrophically. This mutant has a 16‐bp deletion in the LHL3 gene, which resulted in the loss of LHL3 and GGR and accumulated only ChlsGG. The lhl3 mutant cells grown in the dark accumulated PSII and PSI proteins at 25–50% of WT levels, lacked PSII activity, and retained a decreased PSI activity. The PSII and PSI proteins were depleted to trace amounts in the mutant cells grown in light. In contrast, the accumulation of LHCI and LHCII was unaffected except for LHCA3. Our results suggest that the replacement of Chls with ChlsGG strongly affects the structural and functional integrity of PSII and PSI complexes but their associating LHC complexes to a lesser extent. Affinity purification of HA‐tagged LHL3 confirmed the formation of a stable LHL3‐GGR complex, which is vital for GGR stability. The LHL3‐GGR complex contained a small amount of PSI complex assembly factors, suggesting a putative coupling between Chl synthesis and PSI complex assembly.

    DOI： 10.1111/tpj.17071

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  • The plastidial protein acetyltransferase GNAT1 forms a complex with GNAT2, yet their interaction is dispensable for state transitions Reviewed International coauthorship International journal

    Annika Brünje, Magdalena Füßl, Jürgen Eirich, Jean-Baptiste Boyer, Paulina Heinkow, Ulla Neumann, Minna Konert, Aiste Ivanauskaite, Julian Seidel, Shin-Ichiro Ozawa, Wataru Sakamoto, Thierry Meinnel, Dirk Schwarzer, Paula Mulo, Carmela Giglione, Iris Finkemeier

    Molecular & Cellular Proteomics   100850 - 100850   2024.9

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    Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.mcpro.2024.100850

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  • Chemical Protein Crosslinking-Coupled Mass Spectrometry Reveals Interaction of LHCI with LHCII and LHCSR3 in Chlamydomonas reinhardtii Reviewed International coauthorship International journal

    Laura Mosebach, Shin-Ichiro Ozawa, Muhammad Younas, Huidan Xue, Martin Scholz, Yuichiro Takahashi, Michael Hippler

    Plants   13 ( 12 )   1632 - 1632   2024.6

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    Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

    The photosystem I (PSI) of the green alga Chlamydomonas reinhardtii associates with 10 light-harvesting proteins (LHCIs) to form the PSI-LHCI complex. In the context of state transitions, two LHCII trimers bind to the PSAL, PSAH and PSAO side of PSI to produce the PSI-LHCI-LHCII complex. In this work, we took advantage of chemical crosslinking of proteins in conjunction with mass spectrometry to identify protein–protein interactions between the light-harvesting proteins of PSI and PSII. We detected crosslinks suggesting the binding of LHCBM proteins to the LHCA1-PSAG side of PSI as well as protein–protein interactions of LHCSR3 with LHCA5 and LHCA3. Our data indicate that the binding of LHCII to PSI is more versatile than anticipated and imply that LHCSR3 might be involved in the regulation of excitation energy transfer to the PSI core via LHCA5/LHCA3.

    DOI： 10.3390/plants13121632

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  • Characterization of the far-red light absorbing light-harvesting chlorophyll a/b binding complex, a derivative of the distinctive Lhca gene family in green algae Reviewed

    Makiko Kosugi, Shuji Ohtani, Kojiro Hara, Atsushi Toyoda, Hiroyo Nishide, Shin-Ichiro Ozawa, Yuichiro Takahashi, Yasuhiro Kashino, Sakae Kudoh, Hiroyuki Koike, Jun Minagawa

    Frontiers in Plant Science   2024.6

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    Publishing type：Research paper (scientific journal)  

    <jats:p><jats:italic>Prasiola crispa</jats:italic>, an aerial green alga, exhibits remarkable adaptability to the extreme conditions of Antarctica by forming layered colonies capable of utilizing far-red light for photosynthesis. Despite a recent report on the structure of <jats:italic>P. crispa</jats:italic>’s unique light-harvesting chlorophyll (Chl)-binding protein complex (Pc-frLHC), which facilitates far-red light absorption and uphill excitation energy transfer to photosystem II, the specific genes encoding the subunits of Pc-frLHC have not yet been identified. Here, we report a draft genome sequence of <jats:italic>P. crispa</jats:italic> strain 4113, originally isolated from soil samples on Ongul Island, Antarctica. We obtained a 92 Mbp sequence distributed in 1,045 scaffolds comprising 10,244 genes, reflecting 87.1% of the core eukaryotic gene set. Notably, 26 genes associated with the light-harvesting Chl <jats:italic>a</jats:italic>/<jats:italic>b</jats:italic> binding complex (LHC) were identified, including four Pc-frLHC genes, with similarity to a noncanonical Lhca gene with four transmembrane helices, such as Ot_Lhca6 in <jats:italic>Ostreococcus tauri</jats:italic> and Cr_LHCA2 in <jats:italic>Chlamydomonas reinhardtii</jats:italic>. A comparative analysis revealed that Pc-frLHC shares homology with certain Lhca genes found in <jats:italic>Coccomyxa</jats:italic> and <jats:italic>Trebouxia</jats:italic> species. This similarity indicates that Pc-frLHC has evolved from an ancestral Lhca gene with four transmembrane helices and branched out within the Trebouxiaceae family. Furthermore, RNA-seq analysis conducted during the initiation of Pc-frLHC gene induction under red light illumination indicated that Pc-frLHC genes were induced independently from other genes associated with photosystems or LHCs. Instead, the genes of transcription factors, helicases, chaperones, heat shock proteins, and components of blue light receptors were identified to coexpress with Pc-frLHC. Those kinds of information could provide insights into the expression mechanisms of Pc-frLHC and its evolutional development.</jats:p>

    DOI： 10.3389/fpls.2024.1409116

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  • Dysfunction of Chloroplast Protease Activity Mitigates pgr5 Phenotype in the Green Algae Chlamydomonas reinhardtii Reviewed International coauthorship International journal

    Shin-Ichiro Ozawa, Guoxian Zhang, Wataru Sakamoto

    Plants   13 ( 5 )   606 - 606   2024.2

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    Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

    Researchers have described protection mechanisms against the photoinhibition of photosystems under strong-light stress. Cyclic Electron Flow (CEF) mitigates electron acceptor-side limitation, and thus contributes to Photosystem I (PSI) protection. Chloroplast protease removes damaged protein to assist with protein turn over, which contributes to the quality control of Photosystem II (PSII). The PGR5 protein is involved in PGR5-dependent CEF. The FTSH protein is a chloroplast protease which effectively degrades the damaged PSII reaction center subunit, D1 protein. To investigate how the PSI photoinhibition phenotype in pgr5 would be affected by adding the ftsh mutation, we generated double-mutant pgr5ftsh via crossing, and its phenotype was characterized in the green algae Chlamydomonas reinhardtii. The cells underwent high-light incubation as well as low-light incubation after high-light incubation. The time course of Fv/Fm values in pgr5ftsh showed the same phenotype with ftsh1-1. The amplitude of light-induced P700 photo-oxidation absorbance change was measured. The amplitude was maintained at a low value in the control and pgr5ftsh during high-light incubation, but was continuously decreased in pgr5. During the low-light incubation after high-light incubation, amplitude was more rapidly recovered in pgr5ftsh than pgr5. We concluded that the PSI photoinhibition by the pgr5 mutation is mitigated by an additional ftsh1-1 mutation, in which plastoquinone pool would be less reduced due to damaged PSII accumulation.

    DOI： 10.3390/plants13050606

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  • Characterization of tryptophan oxidation affecting D1 degradation by FtsH in the photosystem II quality control of chloroplasts Reviewed International coauthorship International journal

    Yusuke Kato, Hiroshi Kuroda, Shin-Ichiro Ozawa, Keisuke Saito, Vivek Dogra, Martin Scholz, Guoxian Zhang, Catherine de Vitry, Hiroshi Ishikita, Chanhong Kim, Michael Hippler, Yuichiro Takahashi, Wataru Sakamoto

    eLife   12   2023.11

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    Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：eLife Sciences Publications, Ltd  

    Photosynthesis is one of the most important reactions for sustaining our environment. Photosystem II (PSII) is the initial site of photosynthetic electron transfer by water oxidation. Light in excess, however, causes the simultaneous production of reactive oxygen species (ROS), leading to photo-oxidative damage in PSII. To maintain photosynthetic activity, the PSII reaction center protein D1, which is the primary target of unavoidable photo-oxidative damage, is efficiently degraded by FtsH protease. In PSII subunits, photo-oxidative modifications of several amino acids such as Trp have been indeed documented, whereas the linkage between such modifications and D1 degradation remains elusive. Here, we show that an oxidative post-translational modification of Trp residue at the N-terminal tail of D1 is correlated with D1 degradation by FtsH during high-light stress. We revealed that Arabidopsis mutant lacking FtsH2 had increased levels of oxidative Trp residues in D1, among which an N-terminal Trp-14 was distinctively localized in the stromal side. Further characterization of Trp-14 using chloroplast transformation in Chlamydomonas indicated that substitution of D1 Trp-14 to Phe, mimicking Trp oxidation enhanced FtsH-mediated D1 degradation under high light, although the substitution did not affect protein stability and PSII activity. Molecular dynamics simulation of PSII implies that both Trp-14 oxidation and Phe substitution cause fluctuation of D1 N-terminal tail. Furthermore, Trp-14 to Phe modification appeared to have an additive effect in the interaction between FtsH and PSII core in vivo. Together, our results suggest that the Trp oxidation at its N-terminus of D1 may be one of the key oxidations in the PSII repair, leading to processive degradation by FtsH.

    DOI： 10.7554/elife.88822

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    Other Link： https://cdn.elifesciences.org/articles/88822/elife-88822-v1.xml

  • Chloroplast ATP synthase biogenesis requires peripheral stalk subunits AtpF and ATPG and stabilization of atpE mRNA by OPR protein MDE1 Reviewed International coauthorship International journal

    Frédéric Chaux, Domitille Jarrige, Marcio Rodrigues‐Azevedo, Sandrine Bujaldon, Oliver D. Caspari, Shin‐Ichiro Ozawa, Dominique Drapier, Olivier Vallon, Yves Choquet, Catherine de Vitry

    The Plant Journal   116 ( 6 )   1582 - 1599   2023.10

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    Publishing type：Research paper (scientific journal)   Publisher：Wiley  

    SUMMARY

    Chloroplast ATP synthase contains subunits of plastid and nuclear genetic origin. To investigate the coordinated biogenesis of this complex, we isolated novel ATP synthase mutants in the green alga Chlamydomonas reinhardtii by screening for high light sensitivity. We report here the characterization of mutants affecting the two peripheral stalk subunits b and b′, encoded respectively by the atpF and ATPG genes, and of three independent mutants which identify the nuclear factor MDE1, required to stabilize the chloroplast‐encoded atpE mRNA. Whole‐genome sequencing revealed a transposon insertion in the 3′UTR of ATPG while mass spectrometry shows a small accumulation of functional ATP synthase in this knock‐down ATPG mutant. In contrast, knock‐out ATPG mutants, obtained by CRISPR‐Cas9 gene editing, fully prevent ATP synthase function and accumulation, as also observed in an atpF frame‐shift mutant. Crossing ATP synthase mutants with the ftsh1‐1 mutant of the major thylakoid protease identifies AtpH as an FTSH substrate, and shows that FTSH significantly contributes to the concerted accumulation of ATP synthase subunits. In mde1 mutants, the absence of atpE transcript fully prevents ATP synthase biogenesis and photosynthesis. Using chimeric atpE genes to rescue atpE transcript accumulation, we demonstrate that MDE1, a novel octotricopeptide repeat (OPR) protein, genetically targets the atpE 5′UTR. In the perspective of the primary endosymbiosis (~1.5 Gy), the recruitment of MDE1 to its atpE target exemplifies a nucleus/chloroplast interplay that evolved rather recently, in the ancestor of the CS clade of Chlorophyceae, ~300 My ago.

    DOI： 10.1111/tpj.16448

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  • Two specific domains of the γ subunit of chloroplast F o F 1 provide redox regulation of the ATP synthesis through conformational changes Reviewed International journal

    Kentaro Akiyama, Shin-Ichiro Ozawa, Yuichiro Takahashi, Keisuke Yoshida, Toshiharu Suzuki, Kumiko Kondo, Ken-ichi Wakabayashi, Toru Hisabori

    Proceedings of the National Academy of Sciences   120 ( 6 )   e2218187120   2023.2

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of the National Academy of Sciences  

    Chloroplast Fo F1 -ATP synthase (CFo CF1) converts proton motive force into chemical energy during photosynthesis. Although many studies have been done to elucidate the catalytic reaction and its regulatory mechanisms, biochemical analyses using the CFo CF1 complex have been limited because of various technical barriers, such as the difficulty in generating mutants and a low purification efficiency from spinach chloroplasts. By taking advantage of the powerful genetics available in the unicellular green alga Chlamydomonas reinhardtii, we analyzed the ATP synthesis reaction and its regulation in CFo CF1. The domains in the γ subunit involved in the redox regulation of CFo CF1 were mutated based on the reported structure. An in vivo analysis of strains harboring these mutations revealed the structural determinants of the redox response during the light/dark transitions. In addition, we established a half day purification method for the entire CFo CF1 complex from
    C. reinhardtii and subsequently examined ATP synthesis activity by the acid–base transition method. We found that truncation of the β-hairpin domain resulted in a loss of redox regulation of ATP synthesis (i.e., constitutively active state) despite retaining redox-sensitive Cys residues. In contrast, truncation of the redox loop domain containing the Cys residues resulted in a marked decrease in the activity. Based on this mutation analysis, we propose a model of redox regulation of the ATP synthesis reaction by the cooperative function of the β-hairpin and the redox loop domains specific to CFo CF1.

    DOI： 10.1073/pnas.2218187120

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  • Algal PETC-Pro171-Leu suppresses electron transfer in cytochrome b6f under acidic lumenal conditions Reviewed International coauthorship International journal

    Shin-Ichiro Ozawa, Felix Buchert, Ruby Reuys, Michael Hippler, Yuichiro Takahashi

    Plant Physiology   191 ( 3 )   1803 - 1817   2022.12

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    Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

    Abstract

    Linear photosynthetic electron flow (LEF) produces NADPH and generates a proton electrochemical potential gradient across the thylakoid membrane to synthesize ATP, both of which are required for CO2 fixation. As cellular demand for ATP and NADPH varies, cyclic electron flow (CEF) between Photosystem I and the cytochrome b6f complex (b6f) produces extra ATP. b6f regulates LEF and CEF via photosynthetic control, which is a pH-dependent b6f slowdown of plastoquinol oxidation at the lumenal site. This protection mechanism is triggered at more alkaline lumen pH in the pgr1 (proton gradient regulation 1) mutant of the vascular plant Arabidopsis (Arabidopsis thaliana), which contains a Pro194Leu substitution in the b6f Rieske Iron-sulfur protein Photosynthetic Electron Transfer C (PETC) subunit. In this work, we introduced the equivalent pgr1 mutation in the green alga Chlamydomonas reinhardtii to generate PETC-P171L. Consistent with the pgr1 phenotype, PETC-P171L displayed impaired NPQ induction along with slower photoautotrophic growth under high light conditions. Our data provide evidence that the ΔpH component in PETC-P171L depends on oxygen availability. Only under low oxygen conditions was the ΔpH component sufficient to trigger a phenotype in algal PETC-P171L where the mutant b6f was more restricted to oxidize the plastoquinol pool and showed diminished electron flow through the b6f complex. These results demonstrate that photosynthetic control of different stringency are established in C. reinhardtii depending on the cellular metabolism, and the lumen pH-sensitive PETC-P171L was generated to read out various associated effects.

    DOI： 10.1093/plphys/kiac575

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  • Characterization of photosystem II assembly complexes containing ONE-HELIX PROTEIN1 in Arabidopsis thaliana Reviewed

    Hanaki Maeda, Koharu Takahashi, Yoshifumi Ueno, Kei Sakata, Akari Yokoyama, Kozue Yarimizu, Fumiyoshi Myouga, Kazuo Shinozaki, Shin-Ichiro Ozawa, Yuichiro Takahashi, Ayumi Tanaka, Hisashi Ito, Seiji Akimoto, Atsushi Takabayashi, Ryouichi Tanaka

    Journal of Plant Research   135 ( 2 )   361 - 376   2022.2

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    The assembly process of photosystem II (PSII) requires several auxiliary proteins to form assembly intermediates. In plants, early assembly intermediates comprise D1 and D2 subunits of PSII together with a few auxiliary proteins including at least ONE-HELIX PROTEIN1 (OHP1), OHP2, and HIGH-CHLOROPHYLL FLUORESCENCE 244 (HCF244) proteins. Herein, we report the basic characterization of the assembling intermediates, which we purified from Arabidopsis transgenic plants overexpressing a tagged OHP1 protein and named the OHP1 complexes. We analyzed two major forms of OHP1 complexes by mass spectrometry, which revealed that the complexes consist of OHP1, OHP2, and HCF244 in addition to the PSII subunits D1, D2, and cytochrome b559. Analysis of chlorophyll fluorescence showed that a major form of the complex binds chlorophyll a and carotenoids and performs quenching with a time constant of 420 ps. To identify the localization of the auxiliary proteins, we solubilized thylakoid membranes using a digitonin derivative, glycodiosgenin, and separated them into three fractions by ultracentrifugation, and detected these proteins in the loose pellet containing the stroma lamellae and the grana margins together with two chlorophyll biosynthesis enzymes. The results indicated that chlorophyll biosynthesis and assembly may take place in the same compartments of thylakoid membranes. Inducible suppression of the OHP2 mRNA substantially decreased the OHP2 protein in mature Arabidopsis leaves without a significant reduction in the maximum quantum yield of PSII under low-light conditions, but it compromised the yields under high-light conditions. This implies that the auxiliary protein is required for acclimation to high-light conditions.

    DOI： 10.1007/s10265-022-01376-x

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    Other Link： https://link.springer.com/article/10.1007/s10265-022-01376-x/fulltext.html

  • Assembly Apparatus of Light-Harvesting Complexes: Identification of Alb3.1–cpSRP–LHCP Complexes in the Green Alga Chlamydomonas reinhardtii Reviewed International coauthorship International journal

    Mithun Kumar Rathod, Sreedhar Nellaepalli, Shin-Ichiro Ozawa, Hiroshi Kuroda, Natsumi Kodama, Sandrine Bujaldon, Francis-André Wollman, Yuichiro Takahashi

    Plant and Cell Physiology   63 ( 1 )   70 - 81   2021.10

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    Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

    Abstract

    The unicellular green alga, Chlamydomonas reinhardtii, contains many light-harvesting complexes (LHCs) associating chlorophylls a/b and carotenoids; the major LHCIIs (types I, II, III and IV) and minor light-harvesting complexes, CP26 and CP29, for photosystem II, as well as nine LHCIs (LHCA1–9), for photosystem I. A pale green mutant BF4 exhibited impaired accumulation of LHCs due to deficiency in the Alb3.1 gene, which encodes the insertase involved in insertion, folding and assembly of LHC proteins in the thylakoid membranes. To elucidate the molecular mechanism by which ALB3.1 assists LHC assembly, we complemented BF4 to express ALB3.1 fused with no, single or triple Human influenza hemagglutinin (HA) tag at its C-terminus (cAlb3.1, cAlb3.1-HA or cAlb3.1–3HA). The resulting complemented strains accumulated most LHC proteins comparable to wild-type (WT) levels. The affinity purification of Alb3.1-HA and Alb3.1–3HA preparations showed that ALB3.1 interacts with cpSRP43 and cpSRP54 proteins of the chloroplast signal recognition particle (cpSRP) and several LHC proteins; two major LHCII proteins (types I and III), two minor LHCII proteins (CP26 and CP29) and eight LHCI proteins (LHCA1, 2, 3, 4, 5, 6, 8 and 9). Pulse-chase labeling experiments revealed that the newly synthesized major LHCII proteins were transiently bound to the Alb3.1 complex. We propose that Alb3.1 interacts with cpSRP43 and cpSRP54 to form an assembly apparatus for most LHCs in the thylakoid membranes. Interestingly, photosystem I (PSI) proteins were also detected in the Alb3.1 preparations, suggesting that the integration of LHCIs to a PSI core complex to form a PSI–LHCI subcomplex occurs before assembled LHCIs dissociate from the Alb3.1–cpSRP complex.

    DOI： 10.1093/pcp/pcab146

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    Other Link： https://academic.oup.com/pcp/article-pdf/63/1/70/42960753/pcab146.pdf

  • Phos-tag-based approach to study protein phosphorylation in the thylakoid membrane. Reviewed International journal

    Keiji Nishioka, Yusuke Kato, Shin-Ichiro Ozawa, Yuichiro Takahashi, Wataru Sakamoto

    Photosynthesis research   147 ( 1 )   107 - 124   2021.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    Protein phosphorylation is a fundamental post-translational modification in all organisms. In photoautotrophic organisms, protein phosphorylation is essential for the fine-tuning of photosynthesis. The reversible phosphorylation of the photosystem II (PSII) core and the light-harvesting complex of PSII (LHCII) contribute to the regulation of photosynthetic activities. Besides the phosphorylation of these major proteins, recent phosphoproteomic analyses have revealed that several proteins are phosphorylated in the thylakoid membrane. In this study, we utilized the Phos-tag technology for a comprehensive assessment of protein phosphorylation in the thylakoid membrane of Arabidopsis. Phos-tag SDS-PAGE enables the mobility shift of phosphorylated proteins compared with their non-phosphorylated isoform, thus differentiating phosphorylated proteins from their non-phosphorylated isoforms. We extrapolated this technique to two-dimensional (2D) SDS-PAGE for detecting protein phosphorylation in the thylakoid membrane. Thylakoid proteins were separated in the first dimension by conventional SDS-PAGE and in the second dimension by Phos-tag SDS-PAGE. In addition to the isolation of major phosphorylated photosynthesis-related proteins, 2D Phos-tag SDS-PAGE enabled the detection of several minor phosphorylated proteins in the thylakoid membrane. The analysis of the thylakoid kinase mutants demonstrated that light-dependent protein phosphorylation was mainly restricted to the phosphorylation of the PSII core and LHCII proteins. Furthermore, we assessed the phosphorylation states of the structural domains of the thylakoid membrane, grana core, grana margin, and stroma lamella. Overall, these results demonstrated that Phos-tag SDS-PAGE is a useful biochemical tool for studying in vivo protein phosphorylation in the thylakoid membrane protein.

    DOI： 10.1007/s11120-020-00803-1

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  • Red-shifted chlorophyll a bands allow uphill energy transfer to photosystem II reaction centers in an aerial green alga, Prasiola crispa, harvested in Antarctica Reviewed

    Kosugi M, Ozawa SI, Takahashi Y, Kamei Y, Itoh S, Kudoh S, Kashino Y, Koike H

    Biochim Biophys Acta Bioenerg   1861 ( 2 )   148139 - 148147   2020.2

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/J.BBABIO.2019.148139

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    Other Link： http://orcid.org/0000-0001-7698-5350

  • The OPR Protein MTHI1 Controls the Expression of Two Different Subunits of ATP Synthase CFo in Chlamydomonas reinhardtii Reviewed International coauthorship International journal

    Shin-Ichiro Ozawa, Marina Cavaiuolo, Domitille Jarrige, Richard Kuras, Mark Rutgers, Stephan Eberhard, Dominique Drapier, Francis-André Wollman, Yves Choquet

    The Plant Cell   32 ( 4 )   1179 - 1203   2020.1

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    Authorship：Lead author   Publishing type：Research paper (scientific journal)  

    DOI： 10.1105/tpc.19.00770

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  • The BF4 and p71 antenna mutants from Chlamydomonas reinhardtii. Reviewed International coauthorship International journal

    Bujaldon S, Kodama N, Rathod MK, Tourasse N, Ozawa SI, Sellés J, Vallon O, Takahashi Y, Wollman FA

    Biochimica et biophysica acta. Bioenergetics   1861 ( 4 )   148085 - 148085   2019.10

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    Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.bbabio.2019.148085

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  • Structure of the green algal photosystem I supercomplex with a decameric light-harvesting complex I Reviewed

    Michihiro Suga, Shin-Ichiro Ozawa, Kaori Yoshida-Motomura, Fusamichi Akita, Naoyuki Miyazaki, Yuichiro Takahashi

    Nature Plants   5 ( 6 )   626 - 636   2019.6

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    Authorship：Lead author   Publishing type：Research paper (scientific journal)  

    DOI： 10.1038/s41477-019-0438-4

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    Other Link： https://www.nature.com/articles/s41477-019-0438-4

  • The photosystem i assembly apparatus consisting of Ycf3-Y3IP1 and Ycf4 modules Reviewed

    Sreedhar Nellaepalli, Shin-Ichiro Ozawa, Hiroshi Kuroda, Yuichiro Takahashi

    Nature Communications   9 ( 1 )   2439   2018.12

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nature Publishing Group  

    DOI： 10.1038/s41467-018-04823-3

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  • Configuration of Ten Light-Harvesting Chlorophyll a/b Complex I Subunits in Chlamydomonas reinhardtii Photosystem I Reviewed International coauthorship International journal

    Ozawa Shin-Ichiro, Bald Till, Onishi Takahito, Xue Huidan, Matsumura Takunori, Kubo Ryota, Takahashi Hiroko, Hippler Michael, Takahashi Yuichiro

    Plant Physiology   178 ( 2 )   583 - 595   2018

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    DOI： 10.1104/pp.18.00749

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  • Directional cell expansion requires NIMA-related kinase 6 (NEK6)-mediated cortical microtubule destabilization Reviewed

    Shogo Takatani, Shinichiro Ozawa, Noriyoshi Yagi, Takashi Hotta, Takashi Hashimoto, Yuichiro Takahashi, Taku Takahashi, Hiroyasu Motose

    SCIENTIFIC REPORTS   7   2017.8

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    DOI： 10.1038/s41598-017-08453-5

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  • Chloroplast-mediated regulation of CO2-concentrating mechanism by Ca2+-binding protein CAS in the green alga Chlamydomonas reinhardtii Reviewed

    Lianyong Wang, Takashi Yamano, Shunsuke Takane, Yuki Niikawa, Chihana Toyokawa, Shin-ichiro Ozawa, Ryutaro Tokutsu, Yuichiro Takahashi, Jun Minagawa, Yu Kanesaki, Hirofumi Yoshikawa, Hideya Fukuzawa

    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA   113 ( 44 )   12586 - 12591   2016.11

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    DOI： 10.1073/pnas.1606519113

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  • D1 fragmentation in photosystem II repair caused by photo-damage of a two-step model Reviewed

    Yusuke Kato, Shin-ichiro Ozawa, Yuichiro Takahashi, Wataru Sakamoto

    PHOTOSYNTHESIS RESEARCH   126 ( 2-3 )   409 - 416   2015.12

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    DOI： 10.1007/s11120-015-0144-7

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  • Requirement for Asn298 on D1 Protein for Oxygen Evolution: Analyses by Exhaustive Amino Acid Substitution in the Green Alga Chlamydomonas reinhardtii Reviewed

    Hiroshi Kuroda, Natsumi Kodama, Xiao-Yu Sun, Shin-ichiro Ozawa, Yuichiro Takahashi

    PLANT AND CELL PHYSIOLOGY   55 ( 7 )   1266 - 1275   2014.7

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    DOI： 10.1093/pcp/pcu073

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  • Proton Gradient Regulation 5-Mediated Cyclic Electron Flow under ATP- or Redox-Limited Conditions: A Study of Delta ATPase pgr5 and Delta rbcL pgr5 Mutants in the Green Alga Chlamydomonas reinhardtii Reviewed International coauthorship International journal

    Xenie Johnson, Janina Steinbeck, Rachel M. Dent, Hiroko Takahashi, Pierre Richaud, Shin-Ichiro Ozawa, Laura Houille-Vernes, Dimitris Petroutsos, Fabrice Rappaport, Arthur R. Grossman, Krishna K. Niyogi, Michael Hippler, Jean Alric

    PLANT PHYSIOLOGY   165 ( 1 )   438 - 452   2014.5

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    DOI： 10.1104/pp.113.233593

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  • 5'-Monohydroxyphylloquinone is the Dominant Naphthoquinone of PSI in the Green Alga Chlamydomonas reinhardtii Reviewed

    Shin-ichiro Ozawa, Makiko Kosugi, Yasuhiro Kashino, Takashi Sugimura, Yuichiro Takahashi

    PLANT AND CELL PHYSIOLOGY   53 ( 1 )   237 - 243   2012.1

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    DOI： 10.1093/pcp/pcr168

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  • Ribosome rescue by Escherichia coli ArfA (YhdL) in the absence of trans-translation system Reviewed

    Yuhei Chadani, Katsuhiko Ono, Shin-ichiro Ozawa, Yuichiro Takahashi, Kazuyuki Takai, Hideaki Nanamiya, Yuzuru Tozawa, Kazuhiro Kutsukake, Tatsuhiko Abo

    MOLECULAR MICROBIOLOGY   78 ( 4 )   796 - 808   2010.11

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    DOI： 10.1111/j.1365-2958.2010.07375.x

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  • Light and Low-CO2-Dependent LCIB-LCIC Complex Localization in the Chloroplast Supports the Carbon-Concentrating Mechanism in Chlamydomonas reinhardtii Reviewed

    Takashi Yamano, Tomoki Tsujikawa, Kyoko Hatano, Shin-ichiro Ozawa, Yuichiro Takahashi, Hideya Fukuzawa

    PLANT AND CELL PHYSIOLOGY   51 ( 9 )   1453 - 1468   2010.9

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    DOI： 10.1093/pcp/pcq105

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  • Characterization of photosystem I antenna proteins in the prasinophyte Ostreococcus tauri Reviewed

    Wesley D. Swingley, Masakazu Iwai, Yang Chen, Shin-ichiro Ozawa, Kenji Takizawa, Yuichiro Takahashi, Jun Minagawa

    BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS   1797 ( 8 )   1458 - 1464   2010.8

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    DOI： 10.1016/j.bbabio.2010.04.017

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  • Identification and Characterization of an Assembly Intermediate Subcomplex of Photosystem I in the Green Alga Chlamydomonas reinhardtii Reviewed

    Shin-ichiro Ozawa, Takahito Onishi, Yuichiro Takahashi

    JOURNAL OF BIOLOGICAL CHEMISTRY   285 ( 26 )   20072 - 20079   2010.6

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    DOI： 10.1074/jbc.M109.098954

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  • Biochemical and Structural Studies of the Large Ycf4-Photosystem I Assembly Complex of the Green Alga Chlamydomonas reinhardtii Reviewed International coauthorship International journal

    Shin-ichiro Ozawa, Jon Nield, Akihiro Terao, Einar J. Stauber, Michael Hippler, Hiroyuki Koike, Jean-David Rochaix, Yuichiro Takahashi

    PLANT CELL   21 ( 8 )   2424 - 2442   2009.8

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    DOI： 10.1105/tpc.108.063313

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  • Photosystem II Complex in Vivo Is a Monomer Reviewed

    Takeshi Takahashi, Natsuko Inoue-Kashino, Shin-ichiro Ozawa, Yuichiro Takahashi, Yasuhiro Kashino, Kazuhiko Satoh

    JOURNAL OF BIOLOGICAL CHEMISTRY   284 ( 23 )   15598 - 15606   2009.6

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    DOI： 10.1074/jbc.M109.000372

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  • Chloroplast-encoded polypeptide PsbT is involved in the repair of primary electron acceptor Q(A) of photosystem II during photoinhibition in Chlamydomonas reinhardtii Reviewed

    Norikazu Ohnishi, Yasuhiro Kashino, Kazuhiko Satoh, Shin-ichiro Ozawa, Yuichiro Takahashi

    JOURNAL OF BIOLOGICAL CHEMISTRY   282 ( 10 )   7107 - 7115   2007.3

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    DOI： 10.1074/jbc.M606763200

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MISC

  • Mutants of cytochrome b6f complex for photosynthesis research in model organisms.

    OZAWA, Shin-Ichiro

    Low Temperature Science   83 ( 143 )   143 - 155   2025.3

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  • Recent Progress in the understanding of the molecular mechanism for the photosystem I complex assembly Reviewed

    Sreedhar Nellaepalli, Shin'Ichiro Ozawa, Yuichiro Takahashi

    28 ( 3 )   148 - 156   2018.12

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  • Identification of β-Cryptoxanthin in Oxygen-Evolving Photosystem II from Thermosynechococcus vulcanus Reviewed

    Keisuke Kawakami, Ritsuko Fujii, Yasufumi Umena, Shin-ichiro Ozawa, Yuichiro Takahashi, Hideki Hashimoto, Jian-Ren Shen, Nobuo Kamiya

    CAROTENOID SCIENCE   19   48 - 51   2015

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  • 緑藻クラミドモナスの無機炭素濃縮機構を制御する因子CCM1の相互作用因子および翻訳後修飾基の同定

    佐々木優, 中野博文, 山原洋佑, 小澤真一郎, 高橋裕一郎, 福澤秀哉

    日本植物生理学会年会要旨集   51st   2010

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  • STRUCTURE AND FUNCTION OF CCM1 COMPLEX CONTROLLING CO2-CONCENTRATING MECHANISM IN A GREEN ALGA, CHLAMYDOMONAS REINHARTII Reviewed

    H. Fukuzawa, Y. Yamahara, H. Nakano, S. Ozawa, Y. Takahashi

    PHYCOLOGIA   48 ( 4 )   33 - 33   2009.7

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  • Detergents Invited Reviewed

    Shin-Ichiro Ozawa, Yuichiro Takahashi

    低温科学   67   409 - 413   2009.3

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  • Column Chromatography Invited Reviewed

    Shin-Ichiro Ozawa, Akira Okamuro, Yuichiro Takahashi

    Low Temperature Science   67   397 - 407   2009.3

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  • Characterization of photosynthetic proteins by mass spectrometry Invited Reviewed

    Shin-Ichiro Ozawa, Natsuko Inoue-Kashino, Yuichiro Takahashi

    Low Temperature Science   67   387 - 395   2009.3

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  • 無機炭素濃縮機構を制御する因子CCM1複合体の構成因子P80の解析

    中野博文, 山原洋佑, 小澤真一郎, 高橋裕一郎, 福澤秀哉

    日本植物生理学会年会要旨集   50th   2009

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  • CO2濃縮機構を制御するCCM1複合体の構成因子P80の解析

    中野博文, 山原洋佑, 小澤真一郎, 高橋裕一郎, 福澤秀哉

    生化学   2009

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  • 緑藻クラミドモナスにおける無機炭素濃縮機構を制御するCCM1複合体の質量分析法を用いた解析

    山原洋佑, 中野博文, 小澤真一郎, 高橋裕一郎, 福澤秀哉

    日本植物生理学会年会要旨集   49th   2008

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  • Molecular dynamics of photosynthetic reaction center complexes using chloroplast transformation in the green alga Chlamydomonas reinhardtii Reviewed

    Yuichiro Takahashi, Shin-ichiro Ozawa, Takahito Onishi, Mei Funakawa

    GENES & GENETIC SYSTEMS   82 ( 6 )   514 - 514   2007.12

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  • Probing the structure of a Ycf4-containing protein complex involved in green algal Photosystem I assembly Reviewed

    M. Cullen, S. Ozawa, Y. Takahashi, J. Nield

    PHOTOSYNTHESIS RESEARCH   91 ( 2-3 )   207 - 207   2007.2

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  • Identification and characterization of a semi-stable assembly intermediate of photosystem I complex Reviewed

    Y. Takahashi, S. Ozawa, T. Onishi

    PHOTOSYNTHESIS RESEARCH   91 ( 2-3 )   205 - 206   2007.2

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  • Identification and characterization of an assembly intermediate of photosystem I complex in Chlamlydomonas reinhardtii Reviewed

    Shin-ichiro Ozawa, Takahito Onishi, Yuichiro Takahashi

    PLANT AND CELL PHYSIOLOGY   48   S127 - S127   2007

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  • Structure and assembly of photosystem I complex

    Y Takahashi, S Ozawa, T Ohnishi

    PLANT AND CELL PHYSIOLOGY   47   S10 - S10   2006

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  • Purification and biochemical characterization of the assembly apparatus of photosystem I complex

    S Ozawa, Y Takahashi

    PLANT AND CELL PHYSIOLOGY   46   S178 - S178   2005

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  • Purification of assembly apparatus of photosystem I complex in the green alga Chlamydomonas reinhardtii

    S Ozawa, H Koike, Y Takahashi

    PLANT AND CELL PHYSIOLOGY   45   S42 - S42   2004

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  • Purification of assembly apparatus of photosystem I complex in the green alga Chlamydomonas reinhardtii

    S Ozawa, A Terao, Y Takahashi

    PLANT AND CELL PHYSIOLOGY   44   S155 - S155   2003

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Presentations

  • イネ LHCI 四重欠損変異体の分子遺伝学的解析

    山谷浩史, 小澤真一郎, 高見常明, 坂本亘, 草場信

    日本育種学会第148回講演会  2025.9.11 

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    Event date： 2025.9.10 - 2025.9.11

    Presentation type：Poster presentation  

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  • Exploring CO₂-Dependent Carboxylation in Photosynthetic Protein Complexes of Chlamydomonas reinhardtii International coauthorship International conference

    Ole Jünemann, Martin Scholz, Shin-Ichiro Ozawa, Arthur Grossman, Michael Hippler

    The 21st International Conference on the Cell and Molecular Biology of Chlamydomonas  2025.8.25  Gaia Pigino, Michael Schroda, Michael Hippler

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    Event date： 2025.8.24 - 2025.8.29

    Language：English   Presentation type：Poster presentation  

    Venue：Münster  

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  • Functional Characterization of PETC K111 Carboxylation in CO₂-Dependent Electron Transfer Modulation International coauthorship International conference

    Shin-Ichiro Ozawa, Ole Jüneman, Michael Hippler

    The 21st International Conference on the Cell and Molecular Biology of Chlamydomonas  2025.8.25  Gaia Pigino, Michael Schroda, Michael Hippler

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    Event date： 2025.8.24 - 2025.8.29

    Language：English   Presentation type：Poster presentation  

    Venue：Münster  

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  • Chloroplastic HSP 70 affects dynamic behavior of VIPP1 by interacting with VIPP1 C-terminal tail

    Di Li, Shin-Ichiro Ozawa, Michael Hippler, Wataru Sakamoto

    The 66th annual meeting of the Japanese society of plant physiologist  2025.3.15 

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    Event date： 2025.3.14 - 2025.3.16

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  • シトクロムb6fのクロロフィル結合タンパク質蓄積への影響

    小澤真一郎

    第18回クラミドモナス研究会  2025.3.7 

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    Event date： 2025.3.7 - 2025.3.8

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • The molecular machinery of photosynthesis – electron transfer regulation mechanics of the cytochrome b6f complex

    Shin-Ichiro Ozawa

    40th IPSR International Symposium and 16th Symposium on Plant Stress Sciences  2025.3.3 

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    Event date： 2025.3.3 - 2025.3.4

    Language：English   Presentation type：Symposium, workshop panel (nominated)  

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  • Chemical protein crosslinking-coupled mass spectrometry reveals interaction of LHCI with LHCII and LHCSR3 in Chlamydomonas reinhardtii

    Laura Mosebach, Shin-Ichiro Ozawa, Muhammad Younas, Huidan Xue, Martin Scholz, Yuichiro Takahashi, Michael Hippler

    2nd Asia-Oceania International Congress on Photosynthesis  2024.9.20 

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    Event date： 2024.9.18 - 2024.9.21

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  • Structural basis for the pH-dependent functional regulation of cytochrome b6f complex from Chlamydomonas reinhardtii

    Hatsuki Tanabe, Shin-Ichiro Ozawa, Akihiro Kawamoto, Hideaki Tanaka, Yuichiro Takahashi, Genji Kurisu

    International Union of Pure and Applied Biophysics 2024 

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    Event date： 2024.6.24 - 2024.6.28

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  • Light harvesting complexes of model organisms and other organisms

    Shin-Ichiro Ozawa

    The 65th annual meeting of the Japanese society of plant physiologist  2024.3.17 

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    Event date： 2024.3.17 - 2024.3.19

    Language：Japanese   Presentation type：Symposium, workshop panel (public)  

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  • 緑藻クラミドモナスにおける、光捕集タンパク質複合体構成サブユニット欠損株の解析

    小澤真一郎

    第17回クラミドモナス研究会  2023.9.27 

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    Event date： 2023.9.26 - 2023.9.27

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  • LIL3/GGRを欠損した変異株のクロロフィルタンパク質の機能解析

    Kodru Sireesha, Nellaepalli Sreedhar, 小澤真一郎, 佐藤千紘, 黒田洋詩, 田中亮一, Niyogi Krishuna, 高橋裕一郎

    第87回日本植物学会年会 

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    Event date： 2023.9.7 - 2023.9.9

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  • The mutant analysis of amino acid substitution at PETC subunit in the cytochrome b6f complex in the green alga Chlamydomonas reinhardtii

    Shin-Ichiro Ozawa, Felix Bucher, Ruby Reuys, Yuval Milrad, Frauke Bayman, Michael Hippler, Yuichiro Takahashi

    2023.6.3 

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    Event date： 2023.6.3 - 2023.6.4

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  • ゲラニルゲラニルクロロフィルをもつクロロフィルタンパク複合体の解析

    Sireesha Kodru, Sreedhar Nellaepalli, 小澤真一郎, 佐藤千紘, 黒田洋詩, 田中亮一, Krishna K Niyogi, 高橋裕一郎

    第13回日本光合成学会年会およびシンポジウム  2023.6.3 

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    Event date： 2023.6.3 - 2023.6.4

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  • Affinity purification of HA-tagged cpSRP involved in translocation of LHCP in Chlamydomonas reinhardtii

    Hiroshi Kuroda, Shin-ichiro Ozawa, Yuichiro Takahashi

    The 64th annual meeting of the Japanese society of plant physiologist  2023.3.16 

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    Event date： 2023.3.15 - 2023.3.17

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  • The amino acid substitution, PETC-Pro171Leu, slowdown electron transfer in the cytochrome b6f complex under anoxic conditions in the green alga Chlamydomonas reinhardtii

    Shin-Ichiro Ozawa, Felix Bucher, Ruby Reuys, Michael Hippler, Yuichiro Takahashi

    The 64th annual meeting of the Japanese society of plant physiologist 

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    Event date： 2023.3.15 - 2023.3.17

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  • 光捕集タンパク質複合体構成サブユニットの安定性

    小澤 真一郎

    第16回クラミドモナス研究会  2023.3.4 

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    Event date： 2023.3.3 - 2023.3.4

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  • The algal PETC-Pro171-Leu suppresses electron transfer in the cytochrome b6f complex under acidic lumenal condition

    Shin-Ichiro Ozawa, Felix Bucher, Ruby Reuys, Michael Hippler, Yuichiro Takahashi

    International Symposium on Photosynthesis and Chloroplast Regulation  2022.11.15 

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    Event date： 2022.11.15 - 2022.11.18

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  • 緑藻クラミドモナス由来シトクロムb6f複合体のクライオ電子顕微鏡構造が示すRieske鉄硫黄蛋白質の機能的構造変化

    田辺初希, 小澤真一郎, 川本晃大, 田中秀明, 高橋裕一郎, 栗栖源嗣

    第60回日本生物物理学会年会 

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    Event date： 2022.9.28 - 2022.9.30

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  • Effects of the LHCA3 or LHCA7 subunit deletion on the structure and function of the Photosystem I Light-Harvesting Complex I in the green alga Chlamydomonas reinhardtii

    Shin-Ichiro Ozawa, Michiyo Takagi, André Vidal-Meireles, Felix Bucher, Michael Hippler, Yuichiro Takahashi

    International Congress on Photosynthesis Research 2022 

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    Event date： 2022.7.31 - 2022.8.5

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  • 緑藻クラミドモナスのシトクロムb6f のPETC-Pro171-Leu変異株解析

    小澤真一郎, Felix Bucher, Ruby Reuys, Michael Hipple, 高橋裕一郎

    第12回日本光合成学会年会 

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    Event date： 2022.5.20 - 2022.5.21

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  • 緑藻クラミドモナスcpSRP はcpSRP43とcpSRP54 から構成され，ALB3.1を介してチラコイド膜に結合する

    黒田洋詩, 小澤真一郎, 濱尾志乃, 高橋裕一郎

    第63回日本植物生理学会年会 

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    Event date： 2022.3.22 - 2022.3.24

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  • 緑藻クラミドモナスのシトクロムb6f のPETC-171-Pro をLeu に置換した変異株はルーメン酸性下条件で電子伝達速度を強く抑制する

    小澤真一郎, ブッハート フェリックス, ルイス ルビー, ヒップラー ミヒャエル, 高橋裕一郎

    第63回日本植物生理学会年会 

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    Event date： 2022.3.22 - 2022.3.24

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  • LHCA3またはLHCA7欠損株におけるPSI-LHCIの生化学的解析

    小澤 真一郎, 髙木 理世, 高橋 裕一郎

    第15回クラミドモナス研究会  2022.3.5 

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    Event date： 2022.3.5

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Awards

  • Poster recognition

    2006.6   The 12th International Conference on the Cell and Molecular Biology of Chlamydomonas  

    Shin-Ichiro Ozawa

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  • 岡山大学自然科学研究科研究科長賞

    2005.3   岡山大学自然科学研究科  

    小澤 真一郎

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Research Projects

  • Elucidating photosynthetic adaptation through the structure of thylakoid membrane remodeling

    Grant number：23H04959  2023.04 - 2028.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Transformative Research Areas (A)

    坂本 亘, 小澤 真一郎

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    Grant amount：\111540000 （ Direct expense: \85800000 、 Indirect expense：\25740000 ）

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  • Verification of mutual regulation hypothesis for electron flow and light harvesting system in photosynthesis

    Grant number：21K06217  2021.04 - 2024.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    小澤 真一郎

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    Grant amount：\4160000 （ Direct expense: \3200000 、 Indirect expense：\960000 ）

    光合成明反応では電子伝達と集光性アンテナによる光エネルギー利用効率が適切に制御されることが重要となる。本研究では両者の相関を明らかにすることをめざす。広い範囲の光強度で適切に電子伝達を制御し光合成を行ない、遺伝子情報が整備され遺伝子改変も可能な緑藻クラミドモナスを材料とする。
    強光下でチラコイド膜ルーメンが過度に酸性化するとPhotosynthetic controlが誘導され電子伝達活性を抑制し光合成器官の損傷を防ぐと考えられている。シロイヌナズナの pgr1 変異株は、より弱いルーメン酸性化で電子伝達速度が抑制されるため、プロトン駆動力の形成が不十分となり、NPQの誘導が低下する。緑藻クラミドモナスにシロイヌナズナpgr1変異に相当する変異を導入したPETC-P171L株を作出し解析した。PETC-P171L株はシロイヌナズナよりも低い光強度下でPhotosynthetic controlが誘導された。またPETC-P171L株は強光下で光合成的生育速度が低下し、NPQ誘導が低下することを見いだした。
    緑藻クラミドモナスの光化学系Ｉ複合体（PSI）に結合するアンテナタンパク質複合体（LHCI）は高い光エネルギー利用調節機能をもつことが構造から示唆された。緑藻クラミドモナスのLHCIを構成するサブユニットをコードする９種類の遺伝子のうち７種類の遺伝子について、それぞれの単一遺伝子欠損株を解析した。細胞の蛍光発光スペクトルを液体窒素温度で測定すると、LHCA3またはLHCA7欠損株において700 nm近傍の成分が野生株と比較して短波長側へシフトしシグナル強度も大きかった。さらにこれらの欠損株からPSIを精製すると、LHCIの構造が不安定となっていた。よってLHCA3またはLHCA7欠損はLHCIの構造を不安定化しLHCIからPSIへのエネルギー移動効率が低下すると考えられる。

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  • Purification and Biochemical characterization of the Assembly apparatus of PhotosystemⅠ complex

    2005 - 2007

    Grant-in-Aid for Scientific Research 

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    Grant type：Competitive

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  • 光化学系Ⅰ複合体の分子集合装置の精製ならびにその機能と構造の解析

    2005 - 2007

    その他の研究制度 

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    Grant type：Competitive

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  • 光化学系I複合体の分子集合装置の精製ならびにその機能と構造の解析

    Grant number：05J03605  2005 - 2007

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    小澤 真一郎

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    Grant amount：\2700000 （ Direct expense: \2700000 ）

    系I複合体の分子集合メカニズムには未知の部分が多い。本研究では、緑藻クラミドモナスを材料として、系I複合体の分子集合に必須であるYcf4を含む大きな複合体(以下、分子集合装置と略記)の構造・機能解析を進める。アフィニティーカラムで精製した分子集合装置をショ糖密度勾配超遠心分離で精製後、ゲル濾過カラムクロマトグラフィーと電子顕微鏡を用いた単粒子解析を行い、1500kDa以上の大きな構造体であることを示した。
    系I複合体が分子集合する過程を明確に示した研究はこれまで殆どなされていない。本研究では、パルスラベル・チェイス実験と、カラムクロマトグラフィー、SDS-PAGEを駆使し、研究を進めた。その結果、系I複合体の周辺部に位置しているPsaG、Kサブユニットが結合することにより、LHCIとPSIコアとの結合が安定化し、系I複合体の分子集合が完結するという過程を示した。
    より詳細に系I複合体の分子集合過程を研究するためには、PSI-LHCIの構造を知る必要がある。そこで本研究では、PSI-LHCIのアンテナザイズ、LHCIタンパク質のコピー数を生化学的に求めた。
    クラミドモナスにおけるPSI-LHCIのアンテナザイズを、P700の光酸化とHPLCにより求めた。これらの結果により、アンテナサイズを270-300クロロフィル程度であると決定した。次に、PSI-LHCIにおける、PSIコアに対するLHCIタンパク質のコピー数を求めた。High-TrisとMES-Trisを組み合わせた二種類の電気泳動システムによって、各LHCIタンパク質をシングルスポットとして高度に分離したのち、蛍光色素によって染色し定量した。PSIコアに対して8-9のLHCIタンパク質が結合しており、これはアンテナサイズの結果とも良く一致している。

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