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Ozawa SI, Zhang G, Sakamoto W. Dysfunction of Chloroplast Protease Activity Mitigates pgr5 Phenotype in the Green Algae Chlamydomonas reinhardtii. Plants (Basel) 2024; 13:606. [PMID: 38475453 DOI: 10.3390/plants13050606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 02/16/2024] [Accepted: 02/18/2024] [Indexed: 03/14/2024]
Abstract
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.
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Affiliation(s)
- Shin-Ichiro Ozawa
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
| | - Guoxian Zhang
- College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China
| | - Wataru Sakamoto
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
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Chaux F, Jarrige D, Rodrigues-Azevedo M, Bujaldon S, Caspari OD, Ozawa SI, Drapier D, Vallon O, Choquet Y, de Vitry C. Chloroplast ATP synthase biogenesis requires peripheral stalk subunits AtpF and ATPG and stabilization of atpE mRNA by OPR protein MDE1. Plant J 2023; 116:1582-1599. [PMID: 37824282 DOI: 10.1111/tpj.16448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 08/15/2023] [Accepted: 08/21/2023] [Indexed: 10/14/2023]
Abstract
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.
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Affiliation(s)
- Frédéric Chaux
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Domitille Jarrige
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Marcio Rodrigues-Azevedo
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Sandrine Bujaldon
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Oliver D Caspari
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Shin-Ichiro Ozawa
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Dominique Drapier
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Olivier Vallon
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Yves Choquet
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
| | - Catherine de Vitry
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Sorbonne Université, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
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Kato Y, Kuroda H, Ozawa SI, Saito K, Dogra V, Scholz M, Zhang G, de Vitry C, Ishikita H, Kim C, Hippler M, Takahashi Y, Sakamoto W. Characterization of tryptophan oxidation affecting D1 degradation by FtsH in the photosystem II quality control of chloroplasts. eLife 2023; 12:RP88822. [PMID: 37986577 PMCID: PMC10665015 DOI: 10.7554/elife.88822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023] Open
Abstract
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.
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Affiliation(s)
- Yusuke Kato
- Institute of Plant Science and Resources (IPSR), Okayama UniversityOkayamaJapan
- Faculty of Agriculture, Setsunan UniversityOsakaJapan
| | - Hiroshi Kuroda
- Research Institute for Interdisciplinary Science, Okayama UniversityOkayamaJapan
| | - Shin-Ichiro Ozawa
- Institute of Plant Science and Resources (IPSR), Okayama UniversityOkayamaJapan
- Research Institute for Interdisciplinary Science, Okayama UniversityOkayamaJapan
| | - Keisuke Saito
- Research Center for Advanced Science and Technology, The University of TokyoTokyoJapan
| | - Vivek Dogra
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of SciencesShanghaiChina
- Biotechnology Division, CSIR-Institute of Himalayan Bioresource TechnologyPalampurIndia
| | - Martin Scholz
- Institute of Plant Biology and Biotechnology, University of MünsterMünsterGermany
| | - Guoxian Zhang
- Institute of Plant Science and Resources (IPSR), Okayama UniversityOkayamaJapan
| | - Catherine de Vitry
- Institut de Biologie Physico-Chimique, Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université Pierre et Marie CurieParisFrance
| | - Hiroshi Ishikita
- Research Center for Advanced Science and Technology, The University of TokyoTokyoJapan
| | - Chanhong Kim
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of SciencesShanghaiChina
| | - Michael Hippler
- Institute of Plant Science and Resources (IPSR), Okayama UniversityOkayamaJapan
- Institute of Plant Biology and Biotechnology, University of MünsterMünsterGermany
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama UniversityOkayamaJapan
| | - Wataru Sakamoto
- Institute of Plant Science and Resources (IPSR), Okayama UniversityOkayamaJapan
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Okuwaki M, Ozawa SI, Ebine S, Juichi M, Umeki T, Niioka K, Kikuchi T, Tanaka N. The stability of NPM1 oligomers regulated by acidic disordered regions controls the quality of liquid droplets. J Biochem 2023; 174:461-476. [PMID: 37540843 DOI: 10.1093/jb/mvad061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/24/2023] [Accepted: 08/01/2023] [Indexed: 08/06/2023] Open
Abstract
The nucleolus is a membrane-less nuclear body that typically forms through the process of liquid-liquid phase separation (LLPS) involving its components. NPM1 drives LLPS within the nucleolus and its oligomer formation and inter-oligomer interactions play a cooperative role in inducing LLPS. However, the molecular mechanism underlaying the regulation of liquid droplet quality formed by NPM1 remains poorly understood. In this study, we demonstrate that the N-terminal and central acidic residues within the intrinsically disordered regions (IDR) of NPM1 contribute to attenuating oligomer stability, although differences in the oligomer stability were observed only under stringent conditions. Furthermore, the impact of the IDRs is augmented by an increase in net negative charges resulting from phosphorylation within the IDRs. Significantly, we observed an increase in fluidity of liquid droplets formed by NPM1 with decreased oligomer stability. These results indicate that the difference in oligomer stability only observed biochemically under stringent conditions has a significant impact on liquid droplet quality formed by NPM1. Our findings provide new mechanistic insights into the regulation of nucleolar dynamics during the cell cycle.
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Affiliation(s)
- Mitsuru Okuwaki
- Laboratory of Biochemistry, School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-Ku, 108-8641 Tokyo, Japan
| | - Shin-Ichiro Ozawa
- Laboratory of Physical Chemistry for Drug Design, School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-Ku, 108-8641 Tokyo, Japan
| | - Shuhei Ebine
- Laboratory of Biochemistry, School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-Ku, 108-8641 Tokyo, Japan
| | - Motoki Juichi
- Laboratory of Biochemistry, School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-Ku, 108-8641 Tokyo, Japan
| | - Tadanobu Umeki
- Laboratory of Biochemistry, School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-Ku, 108-8641 Tokyo, Japan
| | - Kazuki Niioka
- Laboratory of Biochemistry, School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-Ku, 108-8641 Tokyo, Japan
| | - Taiyo Kikuchi
- Laboratory of Biochemistry, School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-Ku, 108-8641 Tokyo, Japan
| | - Nobutada Tanaka
- Laboratory of Physical Chemistry for Drug Design, School of Pharmacy, Kitasato University, 5-9-1, Shirokane, Minato-Ku, 108-8641 Tokyo, Japan
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Ozawa SI, Buchert F, Reuys R, Hippler M, Takahashi Y. Algal PETC-Pro171-Leu suppresses electron transfer in cytochrome b6f under acidic lumenal conditions. Plant Physiol 2023; 191:1803-1817. [PMID: 36516417 PMCID: PMC10022631 DOI: 10.1093/plphys/kiac575] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
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.
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Affiliation(s)
| | - Felix Buchert
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Ruby Reuys
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Michael Hippler
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
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Maeda H, Takahashi K, Ueno Y, Sakata K, Yokoyama A, Yarimizu K, Myouga F, Shinozaki K, Ozawa SI, Takahashi Y, Tanaka A, Ito H, Akimoto S, Takabayashi A, Tanaka R. Characterization of photosystem II assembly complexes containing ONE-HELIX PROTEIN1 in Arabidopsis thaliana. J Plant Res 2022; 135:361-376. [PMID: 35146632 DOI: 10.1007/s10265-022-01376-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 01/20/2022] [Indexed: 06/14/2023]
Abstract
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.
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Affiliation(s)
- Hanaki Maeda
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan
| | - Koharu Takahashi
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan
| | - Yoshifumi Ueno
- Graduate School of Science, Kobe University, Kobe, 657‑8501, Japan
| | - Kei Sakata
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan
| | - Akari Yokoyama
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan
| | - Kozue Yarimizu
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan
| | - Fumiyoshi Myouga
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japan
| | - Kazuo Shinozaki
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japan
| | - Shin-Ichiro Ozawa
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan
- Institute of Plant Science and Resources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, 710-0046, Japan
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan
| | - Ayumi Tanaka
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan
| | - Hisashi Ito
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan
| | - Seiji Akimoto
- Graduate School of Science, Kobe University, Kobe, 657‑8501, Japan
| | - Atsushi Takabayashi
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan
| | - Ryouichi Tanaka
- Institute of Low Temperature Science, N19W8 Kita-ku, Sapporo, 060-0819, Japan.
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Rathod MK, Nellaepalli S, Ozawa SI, Kuroda H, Kodama N, Bujaldon S, Wollman FA, Takahashi Y. Assembly Apparatus of Light-Harvesting Complexes: Identification of Alb3.1-cpSRP-LHCP Complexes in the Green Alga Chlamydomonas reinhardtii. Plant Cell Physiol 2022; 63:70-81. [PMID: 34592750 DOI: 10.1093/pcp/pcab146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 09/24/2021] [Accepted: 09/30/2021] [Indexed: 06/13/2023]
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.
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Affiliation(s)
- Mithun Kumar Rathod
- Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530 Japan
| | - Sreedhar Nellaepalli
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530 Japan
| | - Shin-Ichiro Ozawa
- Institute of Plant Science and Resources, Okayama University, Kurashiki, 710-0046 Japan
| | - Hiroshi Kuroda
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530 Japan
| | - Natsumi Kodama
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530 Japan
| | - Sandrine Bujaldon
- Institut de Biologie Physico-Chimique, UMR7141 CNRS-Sorbonne Université, Paris 75005, France
| | - Francis-André Wollman
- Institut de Biologie Physico-Chimique, UMR7141 CNRS-Sorbonne Université, Paris 75005, France
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530 Japan
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Morishita K, Ito Y, Otake K, Takahashi K, Yamamoto M, Kitao T, Ozawa SI, Hirono S, Shirahase H. Synthesis and Evaluation of a Novel Series of 2,7-Substituted-6-tetrazolyl-1,2,3,4-tetrahydroisoquinoline Derivatives as Selective Peroxisome Proliferator-Activated Receptor γ Partial Agonists. Chem Pharm Bull (Tokyo) 2021; 69:333-351. [PMID: 33790079 DOI: 10.1248/cpb.c20-00841] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A novel series of 7-substituted-2-[3-(2-furyl)acryloyl]-6-tetrazolyl-1,2,3,4-tetrahydroisoquinoline derivatives were synthesized to clarify structure-activity relationships for peroxisome proliferator-activated receptor γ (PPARγ) partial agonist activity and identify more efficacious PPARγ partial agonists with minor adverse effects. Among the derivatives synthesized, compound 26v with a 2-(2,5-dihydropyrrol-1-yl)-5-methyloxazol-4-ylmethoxy group at the 7-position of the tetrahydroisoquinoline structure exhibited stronger PPARγ agonist and antagonist activities (EC50 = 6 nM and IC50 = 101 nM) than previously reported values for compound 1 (EC50 = 13 nM and IC50 = 512 nM). Compound 26v had very weak protein tyrosine phosphatase 1B (PTP1B) inhibitory activity and showed higher oral absorption (Cmax = 11.4 µg/mL and area under the curve (AUC) = 134.7 µg·h/mL) than compound 1 (Cmax = 7.0 µg/mL and AUC = 63.9 µg·h/mL) in male Sprague-Dawley (SD) rats. A computational docking calculation revealed that 26v bound to PPARγ in a similar manner to that of compound 1. In male Zucker fatty rats, 26v and pioglitazone at 10 and 30 mg/kg for 4 weeks similarly reduced plasma triglyceride levels, increased plasma adiponectin levels, and attenuated increases in plasma glucose levels in the oral glucose tolerance test, while only pioglitazone decreased hematocrit values. In conclusion, 6-tetrazolyl-1,2,3,4-tetrahydroisoquinoline derivatives provide a novel scaffold for selective PPARγ partial agonists and 26v attenuates insulin resistance possibly by adiponectin enhancements with minor adverse effects.
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Affiliation(s)
- Ko Morishita
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Yuma Ito
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Kazuya Otake
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Kenji Takahashi
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Megumi Yamamoto
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Tatsuya Kitao
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | | | | | - Hiroaki Shirahase
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
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9
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Nishioka K, Kato Y, Ozawa SI, Takahashi Y, Sakamoto W. Phos-tag-based approach to study protein phosphorylation in the thylakoid membrane. Photosynth Res 2021; 147:107-124. [PMID: 33269435 PMCID: PMC7728655 DOI: 10.1007/s11120-020-00803-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 11/19/2020] [Indexed: 06/12/2023]
Abstract
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.
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Affiliation(s)
- Keiji Nishioka
- Institute of Plant Science and Resources (IPSR), Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, 710-0046, Japan
| | - Yusuke Kato
- Institute of Plant Science and Resources (IPSR), Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, 710-0046, Japan.
- Faculty of Agriculture, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan.
| | - Shin-Ichiro Ozawa
- Institute of Plant Science and Resources (IPSR), Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, 710-0046, Japan
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama City, Okayama, 700-8530, Japan
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama City, Okayama, 700-8530, Japan
| | - Wataru Sakamoto
- Institute of Plant Science and Resources (IPSR), Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, 710-0046, Japan.
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10
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Ozawa SI, Cavaiuolo M, Jarrige D, Kuras R, Rutgers M, Eberhard S, Drapier D, Wollman FA, Choquet Y. The OPR Protein MTHI1 Controls the Expression of Two Different Subunits of ATP Synthase CFo in Chlamydomonas reinhardtii. Plant Cell 2020; 32:1179-1203. [PMID: 31988263 PMCID: PMC7145495 DOI: 10.1105/tpc.19.00770] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 01/02/2020] [Accepted: 01/27/2020] [Indexed: 05/19/2023]
Abstract
In the green alga Chlamydomonas (Chlamydomonas r einhardtii), chloroplast gene expression is tightly regulated posttranscriptionally by gene-specific trans-acting protein factors. Here, we report the identification of the octotricopeptide repeat protein MTHI1, which is critical for the biogenesis of chloroplast ATP synthase oligomycin-sensitive chloroplast coupling factor. Unlike most trans-acting factors characterized so far in Chlamydomonas, which control the expression of a single gene, MTHI1 targets two distinct transcripts: it is required for the accumulation and translation of atpH mRNA, encoding a subunit of the selective proton channel, but it also enhances the translation of atpI mRNA, which encodes the other subunit of the channel. MTHI1 targets the 5' untranslated regions of both the atpH and atpI genes. Coimmunoprecipitation and small RNA sequencing revealed that MTHI1 binds specifically a sequence highly conserved among Chlorophyceae and the Ulvale clade of Ulvophyceae at the 5' end of triphosphorylated atpH mRNA. A very similar sequence, located ∼60 nucleotides upstream of the atpI initiation codon, was also found in some Chlorophyceae and Ulvale algae species and is essential for atpI mRNA translation in Chlamydomonas. Such a dual-targeted trans-acting factor provides a means to coregulate the expression of the two proton hemi-channels.
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Affiliation(s)
- Shin-Ichiro Ozawa
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
| | - Marina Cavaiuolo
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
| | - Domitille Jarrige
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
| | - Richard Kuras
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
| | - Mark Rutgers
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
| | - Stephan Eberhard
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
| | - Dominique Drapier
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
| | - Francis-André Wollman
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
| | - Yves Choquet
- Unité Mixte de Recherche 7141, Centre National de la Recherche Scientifique and Sorbonne Université, Institut de Biologie Physico-Chimique, F-75005 Paris, France
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11
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Kosugi M, Ozawa SI, Takahashi Y, Kamei Y, Itoh S, Kudoh S, Kashino Y, Koike H. Red-shifted chlorophyll a bands allow uphill energy transfer to photosystem II reaction centers in an aerial green alga, Prasiola crispa, harvested in Antarctica. Biochimica et Biophysica Acta (BBA) - Bioenergetics 2020; 1861:148139. [DOI: 10.1016/j.bbabio.2019.148139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 11/14/2019] [Accepted: 12/04/2019] [Indexed: 12/22/2022]
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12
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Morishita K, Miike T, Takeda S, Fukui M, Ito Y, Kitao T, Ozawa SI, Hirono S, Shirahase H. (S)-1,2,3,4-Tetrahydroisoquinoline Derivatives Substituted with an Acidic Group at the 6-Position as a Selective Peroxisome Proliferator-Activated Receptor γ Partial Agonist. Chem Pharm Bull (Tokyo) 2019; 67:1211-1224. [PMID: 31685749 DOI: 10.1248/cpb.c19-00541] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A novel series of 2,6,7-substituted 3-unsubstituted 1,2,3,4-tetrahydroisoquinoline derivatives were synthesized to find a peroxisome proliferator-activated receptor γ (PPARγ) partial agonist. Among the derivatives, (E)-7-[2-(cyclopent-3-eny)-5-methyloxazol-4-ylmethoxy]-2-[3-(2-furyl)acryloyl]-6-(1H-tetrazol-5-yl)-1,2,3,4-tetrahydroisoquinoline (20g) exhibited potent partial agonist activity (EC50 = 13 nM, maximal response 30%) and very weak protein tyrosine phosphatase 1B (PTP1B) inhibition (IC50 = 1100 nM), indicating a selective PPARγ partial agonist. A computational docking calculation revealed that 20g bound to PPARγ in a similar manner to that of known partial agonists. In male and female KK-Ay mice with insulin resistance and hyperglycemia, 20g at 30 mg/kg for 7 d significantly reduced plasma glucose levels, but not triglyceride levels. The effects of 20g were similar to those of pioglitazone at 10 mg/kg. In conclusion, the 2,6,7-substituted 1,2,3,4-tetrahydroisoquinoline with an acidic group at the 6-position provides a novel scaffold for selective PPARγ partial agonists and 20g exerted anti-diabetic effects via the partial activation of PPARγ.
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Affiliation(s)
- Ko Morishita
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Tomohiro Miike
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Shigemitsu Takeda
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Masaki Fukui
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Yuma Ito
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | - Tatsuya Kitao
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
| | | | | | - Hiroaki Shirahase
- Drug Discovery Research Department, Kyoto Pharmaceutical Industries, Ltd
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13
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Suga M, Ozawa SI, Yoshida-Motomura K, Akita F, Miyazaki N, Takahashi Y. Structure of the green algal photosystem I supercomplex with a decameric light-harvesting complex I. Nat Plants 2019; 5:626-636. [PMID: 31182847 DOI: 10.1038/s41477-019-0438-4] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 05/02/2019] [Indexed: 05/05/2023]
Abstract
In plants and green algae, the core of photosystem I (PSI) is surrounded by a peripheral antenna system consisting of light-harvesting complex I (LHCI). Here we report the cryo-electron microscopic structure of the PSI-LHCI supercomplex from the green alga Chlamydomonas reinhardtii. The structure reveals that eight Lhca proteins form two tetrameric LHCI belts attached to the PsaF side while the other two Lhca proteins form an additional Lhca2/Lhca9 heterodimer attached to the opposite side. The spatial arrangement of light-harvesting pigments reveals that Chlorophylls b are more abundant in the outer LHCI belt than in the inner LHCI belt and are absent from the core, thereby providing the downhill energy transfer pathways to the PSI core. PSI-LHCI is complexed with a plastocyanin on the patch of lysine residues of PsaF at the luminal side. The assembly provides a structural basis for understanding the mechanism of light-harvesting, excitation energy transfer of the PSI-LHCI supercomplex and electron transfer with plastocyanin.
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Affiliation(s)
- Michihiro Suga
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, Japan
- JST, PRESTO, Kawaguchi, Japan
| | - Shin-Ichiro Ozawa
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, Japan
| | | | - Fusamichi Akita
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, Japan
- JST, PRESTO, Kawaguchi, Japan
| | - Naoyuki Miyazaki
- Institute for Protein Research, Osaka University, Osaka, Japan.
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Japan.
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, Japan.
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14
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Ozawa SI, Takahashi M, Yamaotsu N, Hirono S. Structure-based virtual screening for novel chymase inhibitors by in silico fragment mapping. J Mol Graph Model 2019; 89:102-108. [PMID: 30884446 DOI: 10.1016/j.jmgm.2019.03.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 03/06/2019] [Accepted: 03/07/2019] [Indexed: 01/22/2023]
Abstract
The term chymase refers to a family of chymotrypsin-like serine proteases stored within the secretory granules of mast cells. Recently, a variety of small molecule inhibitors for chymase have been developed with a primary focus on the treatment of cardiovascular diseases. Despite the expected therapeutic benefit of these chymase inhibitors, they have not been used clinically. Here, we attempted to identify new chymase inhibitors using a multistep structure-based virtual screening protocol combined with our knowledge-based in silico fragment mapping technique. The mapping procedure identified fragments with novel modes of interaction at the oxyanion hole of chymase. Next, we constructed a three-dimensional (3D) pharmacophore model and retrieved eight candidate chymase inhibitors from a commercial database that included approximately five million compounds. This selection was achieved using a multistep virtual screening protocol, which combined a 3D pharmacophore-based search, docking calculations, and analyses of binding free energy. One of the eight compounds exhibited concentration-dependent chymase inhibitory activity, which could be further optimized to develop more potent chymase inhibitors.
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Affiliation(s)
- Shin-Ichiro Ozawa
- Department of Pharmaceutical Sciences, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan.
| | - Miki Takahashi
- Department of Pharmaceutical Sciences, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Noriyuki Yamaotsu
- Department of Pharmaceutical Sciences, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Shuichi Hirono
- Department of Pharmaceutical Sciences, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
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15
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Ozawa SI, Bald T, Onishi T, Xue H, Matsumura T, Kubo R, Takahashi H, Hippler M, Takahashi Y. Configuration of Ten Light-Harvesting Chlorophyll a/ b Complex I Subunits in Chlamydomonas reinhardtii Photosystem I. Plant Physiol 2018; 178:583-595. [PMID: 30126869 PMCID: PMC6181050 DOI: 10.1104/pp.18.00749] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 08/07/2018] [Indexed: 05/03/2023]
Abstract
In plants, the photosystem I (PSI) core complex stably associates with its light-harvesting chlorophyll a/b complex I (LHCI) to form the PSI-LHCI supercomplex. The vascular plant PSI core complex associates with four distinct LHCI subunits, whereas that of the green alga Chlamydomonas reinhardtii binds nine distinct LHCI subunits (LHCA1-LHCA9). The stoichiometry and configuration of these LHCI subunits in the PSI-LHCI supercomplex of C. reinhardtii remain controversial. Here, we determined the stoichiometry of the nine distinct LHCI subunits relative to PSI subunits through uniform labeling of total proteins using 14C. We separated the nine LHCI polypeptides by three different sodium dodecyl sulfate-polyacrylamide gel electrophoresis systems. Our data revealed that the PSI-LHCI supercomplex contains two LHCA1 proteins and one of each of the other eight LHCI subunits. Subsequently, we identified their cross-linked products by immunodetection and mass spectrometry to determine the configuration of the 10 LHCI subunits within the PSI-LHCI supercomplex. Furthermore, analyses of PSI-LHCI complexes isolated from ΔLHCA2 and ΔLHCA5 mutants and oligomeric LHCI from a PSI-deficient (ΔpsaA/B) mutant provided supporting evidence for the LHCI subunit configuration. In conclusion, eight LHCI subunits bind to the PSI core at the site of PSAF subunit in two layers: LHCA1-LHCA8-LHCA7-LHCA3 from PSAG to PSAK, in the inner layer, and LHCA1-LHCA4-LHCA6-LHCA5 in the outer layer. The other two LHCI subunits, LHCA2 and LHCA9, bind PSAB between PSAG and PSAH, PSAG-LHCA9-LHCA2-PSAH. Our study provides new insights into the LHCI configuration linked to the PSI core.
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Affiliation(s)
- Shin-Ichiro Ozawa
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
- Japan Science and Technology Agency-CREST, 4-1-8 Kawaguchi, Saitama 332-0012, Japan
| | - Till Bald
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Takahito Onishi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Huidan Xue
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Takunori Matsumura
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Ryota Kubo
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Hiroko Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Michael Hippler
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
- Japan Science and Technology Agency-CREST, 4-1-8 Kawaguchi, Saitama 332-0012, Japan
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16
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Nellaepalli S, Ozawa SI, Kuroda H, Takahashi Y. The photosystem I assembly apparatus consisting of Ycf3-Y3IP1 and Ycf4 modules. Nat Commun 2018; 9:2439. [PMID: 29934511 PMCID: PMC6015050 DOI: 10.1038/s41467-018-04823-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 05/24/2018] [Indexed: 12/22/2022] Open
Abstract
In oxygenic photosynthesis, light energy is converted into redox energy by two photosystems (PSI and PSII). PSI forms one of the largest multiprotein complexes in thylakoid membranes consisting of a core complex, peripheral light-harvesting complexes (LHCIs) and cofactors. Although the high-resolution structure of the PSI–LHCI complex has been determined, the assembly process remains unclear due to the rapid nature of the assembly process. Here we show that two conserved chloroplast-encoded auxiliary factors, Ycf3 and Ycf4, form modules that mediate PSI assembly. The first module consists of the tetratricopeptide repeat protein Ycf3 and its interacting partner, Y3IP1, and mainly facilitates the assembly of reaction center subunits. The second module consists of oligomeric Ycf4 and facilitates the integration of peripheral PSI subunits and LHCIs into the PSI reaction center subcomplex. We reveal that these two modules are major mediators of the PSI–LHCI assembly process. Photosystem I is a large multiprotein complex embedded in the chloroplast thylakoid membrane. Here the authors provide evidence for a modular assembly process, whereby Ycf3 facilitates assembly of the reaction center, while Ycf4 incorporates peripheral core and light harvesting complex subunits to the reaction center.
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Affiliation(s)
- Sreedhar Nellaepalli
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan.,JST-CREST, Tokyo, Japan
| | - Shin-Ichiro Ozawa
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan.,JST-CREST, Tokyo, Japan
| | - Hiroshi Kuroda
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan.,JST-CREST, Tokyo, Japan
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan. .,JST-CREST, Tokyo, Japan.
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17
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Koyama T, Yamaotsu N, Nakagome I, Ozawa SI, Yoshida T, Hayakawa D, Hirono S. Multi-step virtual screening to develop selective DYRK1A inhibitors. J Mol Graph Model 2017; 72:229-239. [PMID: 28129593 DOI: 10.1016/j.jmgm.2017.01.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 01/12/2017] [Accepted: 01/12/2017] [Indexed: 11/29/2022]
Abstract
Developing selective inhibitors for a particular kinase remains a major challenge in kinase-targeted drug discovery. Here we performed a multi-step virtual screening for dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) inhibitors by focusing on the selectivity for DYRK1A over cyclin-dependent kinase 5 (CDK5). To examine the key factors contributing to the selectivity, we constructed logistic regression models to discriminate between actives and inactives for DYRK1A and CDK5, respectively, using residue-based binding free energies. The residue-based parameters were calculated by molecular mechanics-generalized Born surface area (MM-GBSA) decomposition methods for kinase-ligand complexes modeled by computer ligand docking. Based on the findings from the logistic regression models, we built a three-dimensional (3D) pharmacophore model and chose filter criteria for the multi-step virtual screening. The virtual hit compounds obtained from the screening were assessed for their inhibitory activities against DYRK1A and CDK5 by in vitro assay. Our screening identified two novel selective DYRK1A inhibitors with IC50 values of several μM for DYRK1A and >100μM for CDK5, which can be further optimized to develop more potent selective DYRK1A inhibitors.
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Affiliation(s)
- Tomoko Koyama
- School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
| | - Noriyuki Yamaotsu
- School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Izumi Nakagome
- School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Shin-Ichiro Ozawa
- School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Tomoki Yoshida
- School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Daichi Hayakawa
- School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Shuichi Hirono
- School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
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18
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Wang L, Yamano T, Takane S, Niikawa Y, Toyokawa C, Ozawa SI, Tokutsu R, Takahashi Y, Minagawa J, Kanesaki Y, Yoshikawa H, Fukuzawa H. Chloroplast-mediated regulation of CO2-concentrating mechanism by Ca2+-binding protein CAS in the green alga Chlamydomonas reinhardtii. Proc Natl Acad Sci U S A 2016; 113:12586-12591. [PMID: 27791081 PMCID: PMC5098658 DOI: 10.1073/pnas.1606519113] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Aquatic photosynthetic organisms, including the green alga Chlamydomonas reinhardtii, induce a CO2-concentrating mechanism (CCM) to maintain photosynthetic activity in CO2-limiting conditions by sensing environmental CO2 and light availability. Previously, a novel high-CO2-requiring mutant, H82, defective in the induction of the CCM, was isolated. A homolog of calcium (Ca2+)-binding protein CAS, originally found in Arabidopsis thaliana, was disrupted in H82 cells. Although Arabidopsis CAS is reported to be associated with stomatal closure or immune responses via a chloroplast-mediated retrograde signal, the relationship between a Ca2+ signal and the CCM associated with the function of CAS in an aquatic environment is still unclear. In this study, the introduction of an intact CAS gene into H82 cells restored photosynthetic affinity for inorganic carbon, and RNA-seq analyses revealed that CAS could function in maintaining the expression levels of nuclear-encoded CO2-limiting-inducible genes, including the HCO3- transporters high-light activated 3 (HLA3) and low-CO2-inducible gene A (LCIA). CAS changed its localization from dispersed across the thylakoid membrane in high-CO2 conditions or in the dark to being associated with tubule-like structures in the pyrenoid in CO2-limiting conditions, along with a significant increase of the fluorescent signals of the Ca2+ indicator in the pyrenoid. Chlamydomonas CAS had Ca2+-binding activity, and the perturbation of intracellular Ca2+ homeostasis by a Ca2+-chelator or calmodulin antagonist impaired the accumulation of HLA3 and LCIA. These results suggest that Chlamydomonas CAS is a Ca2+-mediated regulator of CCM-related genes via a retrograde signal from the pyrenoid in the chloroplast to the nucleus.
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Affiliation(s)
- Lianyong Wang
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Takashi Yamano
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Shunsuke Takane
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Yuki Niikawa
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Chihana Toyokawa
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Shin-Ichiro Ozawa
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Ryutaro Tokutsu
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Jun Minagawa
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan
| | - Yu Kanesaki
- NODAI Genome Research Center, Tokyo University of Agriculture, Tokyo 156-8502, Japan
| | - Hirofumi Yoshikawa
- Department of Bioscience, Tokyo University of Agriculture, Tokyo 156-8502, Japan
| | - Hideya Fukuzawa
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan;
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19
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Kato Y, Ozawa SI, Takahashi Y, Sakamoto W. D1 fragmentation in photosystem II repair caused by photo-damage of a two-step model. Photosynth Res 2015; 126:409-16. [PMID: 25893898 DOI: 10.1007/s11120-015-0144-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 04/09/2015] [Indexed: 05/26/2023]
Abstract
Light energy drives photosynthesis, but it simultaneously inactivates photosynthetic mechanisms. A major target site of photo-damage is photosystem II (PSII). It further targets one reaction center protein, D1, which is maintained efficiently by the PSII repair cycle. Two proteases, FtsH and Deg, are known to contribute to this process, respectively, by efficient degradation of photo-damaged D1 protein processively and endoproteolytically. This study tested whether the D1 cleavage accomplished by these proteases is affected by different monochromic lights such as blue and red light-emitting-diode light sources, remaining mindful that the use of these lights distinguishes the current models for photoinhibition: the excess-energy model and the two-step model. It is noteworthy that in the two-step model, primary damage results from the absorption of light energy in the Mn-cluster, which can be enhanced by a blue rather than a red light source. Results showed that blue and red lights affect D1 degradation differently. One prominent finding was that D1 fragmentation that is specifically generated by luminal Deg proteases was enhanced by blue light but not by red light in the mutant lacking FtsH2. Although circumstantial, this evidence supports a two-step model of PSII photo-damage. We infer that enhanced D1 fragmentation by luminal Deg proteases is a response to primary damage at the Mn-cluster.
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Affiliation(s)
- Yusuke Kato
- Institute of Plant Science and Resources (IPSR), Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, 710-0046, Japan
| | - Shin-Ichiro Ozawa
- Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama City, Okayama, 700-8530, Japan
| | - Yuichiro Takahashi
- Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama City, Okayama, 700-8530, Japan
| | - Wataru Sakamoto
- Institute of Plant Science and Resources (IPSR), Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, 710-0046, Japan.
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Johnson X, Steinbeck J, Dent RM, Takahashi H, Richaud P, Ozawa SI, Houille-Vernes L, Petroutsos D, Rappaport F, Grossman AR, Niyogi KK, Hippler M, Alric J. Proton gradient regulation 5-mediated cyclic electron flow under ATP- or redox-limited conditions: a study of ΔATpase pgr5 and ΔrbcL pgr5 mutants in the green alga Chlamydomonas reinhardtii. Plant Physiol 2014; 165:438-52. [PMID: 24623849 PMCID: PMC4012601 DOI: 10.1104/pp.113.233593] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 03/07/2014] [Indexed: 05/18/2023]
Abstract
The Chlamydomonas reinhardtii proton gradient regulation5 (Crpgr5) mutant shows phenotypic and functional traits similar to mutants in the Arabidopsis (Arabidopsis thaliana) ortholog, Atpgr5, providing strong evidence for conservation of PGR5-mediated cyclic electron flow (CEF). Comparing the Crpgr5 mutant with the wild type, we discriminate two pathways for CEF and determine their maximum electron flow rates. The PGR5/proton gradient regulation-like1 (PGRL1) ferredoxin (Fd) pathway, involved in recycling excess reductant to increase ATP synthesis, may be controlled by extreme photosystem I acceptor side limitation or ATP depletion. Here, we show that PGR5/PGRL1-Fd CEF functions in accordance with an ATP/redox control model. In the absence of Rubisco and PGR5, a sustained electron flow is maintained with molecular oxygen instead of carbon dioxide serving as the terminal electron acceptor. When photosynthetic control is decreased, compensatory alternative pathways can take the full load of linear electron flow. In the case of the ATP synthase pgr5 double mutant, a decrease in photosensitivity is observed compared with the single ATPase-less mutant that we assign to a decreased proton motive force. Altogether, our results suggest that PGR5/PGRL1-Fd CEF is most required under conditions when Fd becomes overreduced and photosystem I is subjected to photoinhibition. CEF is not a valve; it only recycles electrons, but in doing so, it generates a proton motive force that controls the rate of photosynthesis. The conditions where the PGR5 pathway is most required may vary in photosynthetic organisms like C. reinhardtii from anoxia to high light to limitations imposed at the level of carbon dioxide fixation.
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Chadani Y, Ono K, Ozawa SI, Takahashi Y, Takai K, Nanamiya H, Tozawa Y, Kutsukake K, Abo T. Ribosome rescue by Escherichia coli ArfA (YhdL) in the absence of trans-translation system. Mol Microbiol 2010; 78:796-808. [PMID: 21062370 DOI: 10.1111/j.1365-2958.2010.07375.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Although SsrA(tmRNA)-mediated trans-translation is thought to maintain the translation capacity of bacterial cells by rescuing ribosomes stalled on messenger RNA lacking an in-frame stop codon, single disruption of ssrA does not crucially hamper growth of Escherichia coli. Here, we identified YhdL (renamed ArfA for alternative ribosome-rescue factor) as a factor essential for the viability of E. coli in the absence of SsrA. The ssrA-arfA synthetic lethality was alleviated by SsrA(DD) , an SsrA variant that adds a proteolysis-refractory tag through trans-translation, indicating that ArfA-deficient cells require continued translation, rather than subsequent proteolysis of the truncated polypeptide. In accordance with this notion, depletion of SsrA in the ΔarfA background led to reduced translation of a model protein without affecting transcription, and puromycin, a codon-independent mimic of aminoacyl-tRNA, rescued the bacterial growth under such conditions. That ArfA takes over the role of SsrA was suggested by the observation that its overexpression enabled detection of the polypeptide encoded by a model non-stop mRNA, which was otherwise SsrA-tagged and degraded. In vitro, purified ArfA acted on a ribosome-nascent chain complex to resolve the peptidyl-tRNA. These results indicate that ArfA rescues the ribosome stalled at the 3' end of a non-stop mRNA without involving trans-translation.
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Affiliation(s)
- Yuhei Chadani
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
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Ozawa SI, Onishi T, Takahashi Y. Identification and characterization of an assembly intermediate subcomplex of photosystem I in the green alga Chlamydomonas reinhardtii. J Biol Chem 2010; 285:20072-9. [PMID: 20413595 DOI: 10.1074/jbc.m109.098954] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Photosystem I (PSI) is a multiprotein complex consisting of the PSI core and peripheral light-harvesting complex I (LHCI) that together form the PSI-LHCI supercomplex in algae and higher plants. The supercomplex is synthesized in steps during which 12-15 core and 4-9 LHCI subunits are assembled. Here we report the isolation of a PSI subcomplex that separated on a sucrose density gradient from the thylakoid membranes isolated from logarithmic growth phase cells of the green alga Chlamydomonas reinhardtii. Pulse-chase labeling of total cellular proteins revealed that the subcomplex was synthesized de novo within 1 min and was converted to the mature PSI-LHCI during the 2-h chase period, indicating that the subcomplex was an assembly intermediate. The subcomplex was functional; it photo-oxidized P700 and demonstrated electron transfer activity. The subcomplex lacked PsaK and PsaG, however, and it bound PsaF and PsaJ weakly and was not associated with LHCI. It seemed likely that LHCI had been integrated into the subcomplex unstably and was dissociated during solubilization and/or fractionation. We, thus, infer that PsaK and PsaG stabilize the association between PSI core and LHCI complexes and that PsaK and PsaG bind to the PSI core complex after the integration of LHCI in one of the last steps of PSI complex assembly.
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Affiliation(s)
- Shin-Ichiro Ozawa
- Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Kita-ku, Tsushima-naka, Okayama 700-8530, Japan
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Igarashi S, Osawa M, Ozawa SI, Shimada I. Backbone resonance assignments for the ligand binding subunit of the histidine permease complex (HisJ) from Escherichia coli, under histidine-bound and unbound states. Biomol NMR Assign 2010; 4:17-20. [PMID: 19921465 DOI: 10.1007/s12104-009-9200-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2009] [Accepted: 11/05/2009] [Indexed: 05/28/2023]
Abstract
HisJ is a histidine binding subunit of the histidine permease, which exists in the outer membrane of Gram-negative bacteria. In order to incorporate the periplasmic histidine into the cell, HisJ captures histidine in the periplasm, and transfers the histidine to the transmembrane complex of histidine permease that is an ABC transporter. We established the backbone resonance assignments of (1)H/(13)C/(15)N-labeled HisJ from Escherichia coli, in the histidine-bound and unbound states.
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Affiliation(s)
- Shunsuke Igarashi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Ozawa SI, Nield J, Terao A, Stauber EJ, Hippler M, Koike H, Rochaix JD, Takahashi Y. Biochemical and structural studies of the large Ycf4-photosystem I assembly complex of the green alga Chlamydomonas reinhardtii. Plant Cell 2009; 21:2424-42. [PMID: 19700633 PMCID: PMC2751955 DOI: 10.1105/tpc.108.063313] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Revised: 07/20/2009] [Accepted: 08/07/2009] [Indexed: 05/19/2023]
Abstract
Ycf4 is a thylakoid protein essential for the accumulation of photosystem I (PSI) in Chlamydomonas reinhardtii. Here, a tandem affinity purification tagged Ycf4 was used to purify a stable Ycf4-containing complex of >1500 kD. This complex also contained the opsin-related COP2 and the PSI subunits PsaA, PsaB, PsaC, PsaD, PsaE, and PsaF, as identified by mass spectrometry (liquid chromatography-tandem mass spectrometry) and immunoblotting. Almost all Ycf4 and COP2 in wild-type cells copurified by sucrose gradient ultracentrifugation and subsequent ion exchange column chromatography, indicating the intimate and exclusive association of Ycf4 and COP2. Electron microscopy revealed that the largest structures in the purified preparation measure 285 x 185 A; these particles may represent several large oligomeric states. Pulse-chase protein labeling revealed that the PSI polypeptides associated with the Ycf4-containing complex are newly synthesized and partially assembled as a pigment-containing subcomplex. These results indicate that the Ycf4 complex may act as a scaffold for PSI assembly. A decrease in COP2 to 10% of wild-type levels by RNA interference increased the salt sensitivity of the Ycf4 complex stability but did not affect the accumulation of PSI, suggesting that COP2 is not essential for PSI assembly.
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Affiliation(s)
- Shin-Ichiro Ozawa
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
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Ohnishi N, Kashino Y, Satoh K, Ozawa SI, Takahashi Y. Chloroplast-encoded Polypeptide PsbT Is Involved in the Repair of Primary Electron Acceptor QA of Photosystem II during Photoinhibition in Chlamydomonas reinhardtii. J Biol Chem 2007; 282:7107-15. [PMID: 17215255 DOI: 10.1074/jbc.m606763200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PsbT is a small chloroplast-encoded hydrophobic polypeptide associated with the D1/D2 heterodimer of the photosystem II (PSII) reaction center and is required for the efficient post-translational repair of photodamaged PSII. Here we addressed that role in detail in Chlamydomonas reinhardtii wild type and DeltapsbT cells by analyzing the activities of PSII, the assembly of PSII proteins, and the redox components of PSII during photoinhibition and repair. Strong illumination of cells for 15 min decreased the activities of electron transfer through PSII and Q(A) photoreduction by 50%, and it reduced the amount of atomic manganese by 20%, but it did not affect the steady-state level of PSII proteins, photoreduction of pheophytin (pheo(D1)), and the amount of bound plastoquinone (Q(A)), indicating that the decrease in PSII activity resulted mainly from inhibition of the electron transfer from pheo(D1) to Q(A). In wild type cells, we observed parallel recovery of electron transfer activity through PSII and Q(A) photoreduction, suggesting that the recovery of Q(A) activity is one of the rate-limiting steps of PSII repair. In DeltapsbT cells, the repairs of electron transfer activity through PSII and of Q(A) photoreduction activity were both impaired, but PSII protein turnover was unaffected. Moreover, about half the Q(A) was lost from the PSII core complex during purification. Since PsbT is intimately associated with the Q(A)-binding region on D2, we propose that this polypeptide enhances the efficient recovery of Q(A) photoreduction by stabilizing the structure of the Q(A)-binding region.
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Affiliation(s)
- Norikazu Ohnishi
- The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
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