研究者詳細 - 沈　建仁

論文 - 沈　建仁

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Aggregation-Induced Excitation-Energy Quenching in Fucoxanthin Chlorophyll a/c-Binding Proteins from the Diatom Phaeodactylum tricornutum

Yoshifumi Ueno, Ou-Yang Li, Jian-Ren Shen, Tatsuya Tomo, Seiji Akimoto, Ryo Nagao

The Journal of Physical Chemistry B 2025年3月

Structural study of the chlorophyll between Lhca8 and PsaJ in an Antarctica green algal photosystem I-LHCI supercomplex revealed by its atomic structure

Pi-Cheng Tsai, Koji Kato, Jian-Ren Shen, Fusamichi Akita

Biochimica et Biophysica Acta (BBA) - Bioenergetics 149543 - 149543 2025年2月

Biochemical evidence for the diversity of LHCI proteins in PSI-LHCI from the red alga Galdieria sulphuraria NIES-3638. 国際誌

Ryo Nagao, Haruya Ogawa, Takehiro Suzuki, Naoshi Dohmae, Koji Kato, Yoshiki Nakajima, Jian-Ren Shen

Photosynthesis research 163 ( 1 ) 14 - 14 2025年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

Red algae are photosynthetic eukaryotes whose light-harvesting complexes (LHCs) associate with photosystem I (PSI). In this study, we examined characteristics of PSI-LHCI, PSI, and LHCI isolated from the red alga Galdieria sulphuraria NIES-3638. The PSI-LHCI supercomplexes were purified using anion-exchange chromatography followed by hydrophobic-interaction chromatography, and finally by trehalose density gradient centrifugation. PSI and LHCI were similarly prepared following the dissociation of PSI-LHCI with Anzergent 3-16. Polypeptide analysis of PSI-LHCI revealed the presence of PSI and LHC proteins, along with red-lineage chlorophyll a/b-binding-like protein (RedCAP), which is distinct from LHC proteins within the LHC protein superfamily. RedCAP, rather than LHC proteins, exhibited tight binding to PSI. Carotenoid analysis of LHCI identified zeaxanthin, β-cryptoxanthin, and β-carotene, with zeaxanthin particularly enriched, which is consistent with other red algal LHCIs. A Qy peak of chlorophyll a in the LHCI absorption spectrum was blue-shifted compared with those of PSI-LHCI and PSI, and a fluorescence emission peak was similarly shifted to shorter wavelengths. Based on these results, we discuss the diversity of LHC proteins and RedCAP in red algal PSI-LHCI supercomplexes.

DOI： 10.1007/s11120-024-01134-1

Conformational Flexibility of D1-Glu189: A Crucial Determinant in Substrate Water Selection, Positioning, and Stabilization within the Oxygen-Evolving Complex of Photosystem II

Hiroshi Isobe, Takayoshi Suzuki, Michihiro Suga, Jian-Ren Shen, Kizashi Yamaguchi

ACS OMEGA 9 ( 50 ) 50041 - 50048 2024年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Photosynthetic water oxidation is a vital process responsible for producing dioxygen and supplying the energy necessary to sustain life on Earth. This fundamental reaction is catalyzed by the oxygen-evolving complex (OEC) of photosystem II, which houses the Mn4CaO5 cluster as its catalytic core. In this study, we specifically focus on the D1-Glu189 amino acid residue, which serves as a direct ligand to the Mn4CaO5 cluster. Our primary goal is to explore, using density functional theory (DFT), how the conformational flexibility of the D1-Glu189 side chain influences crucial catalytic processes, particularly the selection, positioning, and stabilization of a substrate water molecule within the OEC. Our investigation is based on a hypothesis put forth by Li et al. (Nature, 2024, 626, 670), which suggests that during the transition from the S2 to S3 state, a specific water molecule temporarily coordinating with the Ca ion, referred to as O6*, may exist as a hydroxide ion (OH-). Our results demonstrate a key mechanism by which the detachment of the D1-Glu189 carboxylate group from its coordination with the Ca ion allows the creation of a specialized microenvironment within the OEC that enables the selective attraction of O6* in its deprotonated form (OH-) and stabilizes it at the catalytic metal (MnD) site. Our findings indicate that D1-Glu189 is not only a structural ligand for the Ca ion but may also play an active and dynamic role in the catalytic process, positioning O6* optimally for its subsequent participation in the oxidation sequence during the water-splitting cycle.

DOI： 10.1021/acsomega.4c09981

Structural basis for molecular assembly of fucoxanthin chlorophyll a/c-binding proteins in a diatom photosystem I supercomplex

Koji Kato, Yoshiki Nakajima, Jian Xing, Minoru Kumazawa, Haruya Ogawa, Jian-Ren Shen, Kentaro Ifuku, Ryo Nagao

eLife 13 2024年10月

掲載種別：研究論文（学術雑誌）出版者・発行元：eLife Sciences Publications, Ltd

Photosynthetic organisms exhibit remarkable diversity in their light-harvesting complexes (LHCs). LHCs are associated with photosystem I (PSI), forming a PSI-LHCI supercomplex. The number of LHCI subunits, along with their protein sequences and pigment compositions, has been found to differ greatly among the PSI-LHCI structures. However, the mechanisms by which LHCIs recognize their specific binding sites within the PSI core remain unclear. In this study, we determined the cryo-electron microscopy structure of a PSI supercomplex incorporating fucoxanthin chlorophyll a/c-binding proteins (FCPs), designated as PSI-FCPI, isolated from the diatom Thalassiosira pseudonana CCMP1335. Structural analysis of PSI-FCPI revealed five FCPI subunits associated with a PSI monomer; these subunits were identified as RedCAP, Lhcr3, Lhcq10, Lhcf10, and Lhcq8. Through structural and sequence analyses, we identified specific protein–protein interactions at the interfaces between FCPI and PSI subunits, as well as among FCPI subunits themselves. Comparative structural analyses of PSI-FCPI supercomplexes, combined with phylogenetic analysis of FCPs from T. pseudonana and the diatom Chaetoceros gracilis, underscore the evolutionary conservation of protein motifs crucial for the selective binding of individual FCPI subunits. These findings provide significant insights into the molecular mechanisms underlying the assembly and selective binding of FCPIs in diatoms.

DOI： 10.7554/elife.99858.3

その他リンク： https://cdn.elifesciences.org/articles/99858/elife-99858-v1.xml

Presence of low-energy chlorophylls d in photosystem I trimer and monomer cores isolated from Acaryochloris sp. NBRC 102871. 査読国際誌

Ryo Nagao, Haruki Yamamoto, Haruya Ogawa, Hibiki Ito, Yuma Yamamoto, Takehiro Suzuki, Koji Kato, Yoshiki Nakajima, Naoshi Dohmae, Jian-Ren Shen

Photosynthesis research 161 ( 3 ) 203 - 212 2024年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

Acaryochloris species belong to a special category of cyanobacteria possessing chlorophyll (Chl) d. One of the photosynthetic characteristics of Acaryochloris marina MBIC11017 is that the absorption spectra of photosystem I (PSI) showed almost no bands and shoulders of low-energy Chls d over 740 nm. In contrast, the absorption spectra of other Acaryochloris species showed a shoulder around 740 nm, suggesting that low-energy Chls d within PSI are diversified among Acaryochloris species. In this study, we purified PSI trimer and monomer cores from Acaryochloris sp. NBRC 102871 and examined their protein and pigment compositions and spectral properties. The protein bands and pigment compositions of the PSI trimer and monomer of NBRC102871 were virtually identical to those of MBIC11017. The absorption spectra of the NBRC102871 PSIs exhibited a shoulder around 740 nm, whereas the fluorescence spectra of PSI trimer and monomer displayed maximum peaks at 754 and 767 nm, respectively. These spectral properties were different from those of MBIC11017, indicating the presence of low-energy Chls d within the NBRC102871 PSIs. Moreover, we analyzed the NBRC102871 genome to identify amino acid sequences of PSI proteins and compared them with those of the A. marina MBIC11017 and MBIC10699 strains whose genomes are available. The results showed that some of the sequences in NBRC102871 were distinct from those in MBIC11017 and MBIC10699. These findings provide insights into the variety of low-energy Chls d with respect to the protein environments of PSI cores among the three Acaryochloris strains.

DOI： 10.1007/s11120-024-01108-3

Structural and spectroscopic insights into fucoxanthin chlorophyll a/c-binding proteins of diatoms in diverse oligomeric states. 査読国際誌

Cuicui Zhou, Yue Feng, Zhenhua Li, Lili Shen, Xiaoyi Li, Yumei Wang, Guangye Han, Tingyun Kuang, Cheng Liu, Jian-Ren Shen, Wenda Wang

Plant communications 101041 - 101041 2024年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

Diatoms, a group of prevalent marine algae, contribute significantly to global primary productivity. Their substantial biomass is linked to enhanced absorption of blue-green light underwater, facilitated by fucoxanthin chlorophyll (Chl) a/c-binding proteins (FCPs), which exhibit oligomeric diversity across diatom species. Using mild clear native PAGE analysis of solubilized thylakoid membranes, we displayed monomeric, dimeric, trimeric, tetrameric, and pentameric FCPs in diatoms. Mass spectrometry analysis revealed that each oligomeric FCP has a specific protein composition, and together they constitute a large Lhcf family of FCP antennas. In addition, we resolved the structures of the Thalassiosira pseudonana FCP (Tp-FCP) homotrimer and the Chaetoceros gracilis FCP (Cg-FCP) pentamer by cryoelectron microscopy at 2.73-Å and 2.65-Å resolution, respectively. The distinct pigment compositions and organizations of various oligomeric FCPs affect their blue-green light-harvesting, excitation energy transfer pathways. Compared with dimeric and trimeric FCPs, the Cg-FCP tetramer and Cg-FCP pentamer exhibit stronger absorption by Chl c, redshifted and broader Chl a fluorescence emission, and more robust circular dichroism signals originating from Chl a-carotenoid dimers. These spectroscopic characteristics indicate that Chl a molecules in the Cg-FCP tetramer and Cg-FCP pentamer are more heterogeneous than in both dimers and the Tp-FCP trimer. The structural and spectroscopic insights provided by this study contribute to a better understanding of the mechanisms that empower diatoms to adapt to fluctuating light environments.

DOI： 10.1016/j.xplc.2024.101041

Strong interaction of CpcL with photosystem I cores induced in heterocysts of Anabaena sp. PCC 7120 査読

Takehiro Suzuki, Haruya Ogawa, Naoshi Dohmae, Jian-Ren Shen, Shigeki Ehira, Ryo Nagao

microPublication Biology 2024年5月

Structure of a unique PSII-Pcb tetrameric megacomplex in a chlorophyll d-containing cyanobacterium. 査読国際誌

Liangliang Shen, Yuanzhu Gao, Kailu Tang, Ruxi Qi, Lutang Fu, Jing-Hua Chen, Wenda Wang, Xiaomin Ma, Peiyao Li, Min Chen, Tingyun Kuang, Xing Zhang, Jian-Ren Shen, Peiyi Wang, Guangye Han

Science advances 10 ( 8 ) eadk7140 2024年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

Acaryochloris marina is a unique cyanobacterium using chlorophyll d (Chl d) as its major pigment and thus can use far-red light for photosynthesis. Photosystem II (PSII) of A. marina associates with a number of prochlorophyte Chl-binding (Pcb) proteins to act as the light-harvesting system. We report here the cryo-electron microscopic structure of a PSII-Pcb megacomplex from A. marina at a 3.6-angstrom overall resolution and a 3.3-angstrom local resolution. The megacomplex is organized as a tetramer consisting of two PSII core dimers flanked by sixteen symmetrically related Pcb proteins, with a total molecular weight of 1.9 megadaltons. The structure reveals the detailed organization of PSII core consisting of 15 known protein subunits and an unknown subunit, the assembly of 4 Pcb antennas within each PSII monomer, and possible pathways of energy transfer within the megacomplex, providing deep insights into energy transfer and dissipation mechanisms within the PSII-Pcb megacomplex involved in far-red light utilization.

DOI： 10.1126/sciadv.adk7140

Structures and organizations of PSI-AcpPCI supercomplexes from red tidal and coral symbiotic photosynthetic dinoflagellates. 査読国際誌

Xiaoyi Li, Zhenhua Li, Fangfang Wang, Songhao Zhao, Caizhe Xu, Zhiyuan Mao, Jialin Duan, Yue Feng, Yang Yang, Lili Shen, Guanglei Wang, Yanyan Yang, Long-Jiang Yu, Min Sang, Guangye Han, Xuchu Wang, Tingyun Kuang, Jian-Ren Shen, Wenda Wang

Proceedings of the National Academy of Sciences of the United States of America 121 ( 7 ) e2315476121 2024年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

Marine photosynthetic dinoflagellates are a group of successful phytoplankton that can form red tides in the ocean and also symbiosis with corals. These features are closely related to the photosynthetic properties of dinoflagellates. We report here three structures of photosystem I (PSI)-chlorophylls (Chls) a/c-peridinin protein complex (PSI-AcpPCI) from two species of dinoflagellates by single-particle cryoelectron microscopy. The crucial PsaA/B subunits of a red tidal dinoflagellate Amphidinium carterae are remarkably smaller and hence losing over 20 pigment-binding sites, whereas its PsaD/F/I/J/L/M/R subunits are larger and coordinate some additional pigment sites compared to other eukaryotic photosynthetic organisms, which may compensate for the smaller PsaA/B subunits. Similar modifications are observed in a coral symbiotic dinoflagellate Symbiodinium species, where two additional core proteins and fewer AcpPCIs are identified in the PSI-AcpPCI supercomplex. The antenna proteins AcpPCIs in dinoflagellates developed some loops and pigment sites as a result to accommodate the changed PSI core, therefore the structures of PSI-AcpPCI supercomplex of dinoflagellates reveal an unusual protein assembly pattern. A huge pigment network comprising Chls a and c and various carotenoids is revealed from the structural analysis, which provides the basis for our deeper understanding of the energy transfer and dissipation within the PSI-AcpPCI supercomplex, as well as the evolution of photosynthetic organisms.

DOI： 10.1073/pnas.2315476121

Oxygen-evolving photosystem II structures during S1-S2-S3 transitions. 査読国際誌

Hongjie Li, Yoshiki Nakajima, Eriko Nango, Shigeki Owada, Daichi Yamada, Kana Hashimoto, Fangjia Luo, Rie Tanaka, Fusamichi Akita, Koji Kato, Jungmin Kang, Yasunori Saitoh, Shunpei Kishi, Huaxin Yu, Naoki Matsubara, Hajime Fujii, Michihiro Sugahara, Mamoru Suzuki, Tetsuya Masuda, Tetsunari Kimura, Tran Nguyen Thao, Shinichiro Yonekura, Long-Jiang Yu, Takehiko Tosha, Kensuke Tono, Yasumasa Joti, Takaki Hatsui, Makina Yabashi, Minoru Kubo, So Iwata, Hiroshi Isobe, Kizashi Yamaguchi, Michihiro Suga, Jian-Ren Shen

Nature 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

Photosystem II (PSII) catalyses the oxidation of water through a four-step cycle of Si states (i = 0-4) at the Mn4CaO5 cluster1-3, during which an extra oxygen (O6) is incorporated at the S3 state to form a possible dioxygen4-7. Structural changes of the metal cluster and its environment during the S-state transitions have been studied on the microsecond timescale. Here we use pump-probe serial femtosecond crystallography to reveal the structural dynamics of PSII from nanoseconds to milliseconds after illumination with one flash (1F) or two flashes (2F). YZ, a tyrosine residue that connects the reaction centre P680 and the Mn4CaO5 cluster, showed structural changes on a nanosecond timescale, as did its surrounding amino acid residues and water molecules, reflecting the fast transfer of electrons and protons after flash illumination. Notably, one water molecule emerged in the vicinity of Glu189 of the D1 subunit of PSII (D1-E189), and was bound to the Ca2+ ion on a sub-microsecond timescale after 2F illumination. This water molecule disappeared later with the concomitant increase of O6, suggesting that it is the origin of O6. We also observed concerted movements of water molecules in the O1, O4 and Cl-1 channels and their surrounding amino acid residues to complete the sequence of electron transfer, proton release and substrate water delivery. These results provide crucial insights into the structural dynamics of PSII during S-state transitions as well as O-O bond formation.

DOI： 10.1038/s41586-023-06987-5

Quantifying the Energy Spillover between Photosystems II and I in Cyanobacterial Thylakoid Membranes and Cells. 査読

Parveen Akhtar, Fanny Balog-Vig, Wenhui Han, Xingyue Li, Guangye Han, Jian-Ren Shen, Petar H Lambrev

Plant & cell physiology 65 ( 1 ) 95 - 106 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

The spatial separation of photosystems I and II (PSI and PSII) is thought to be essential for efficient photosynthesis by maintaining a balanced flow of excitation energy between them. Unlike the thylakoid membranes of plant chloroplasts, cyanobacterial thylakoids do not form tightly appressed grana stacks that enforce strict lateral separation. The coexistence of the two photosystems provides a ground for spillover-excitation energy transfer from PSII to PSI. Spillover has been considered as a pathway of energy transfer from the phycobilisomes to PSI and may also play a role in state transitions as means to avoid overexcitation of PSII. Here, we demonstrate a significant degree of energy spillover from PSII to PSI in reconstituted membranes and isolated thylakoid membranes of Thermosynechococcus (Thermostichus) vulcanus and Synechocystis sp. PCC 6803 by steady-state and time-resolved fluorescence spectroscopy. The quantum yield of spillover in these systems was determined to be up to 40%. Spillover was also found in intact cells but to a considerably lower degree (20%) than in isolated thylakoid membranes. The findings support a model of coexistence of laterally separated microdomains of PSI and PSII in the cyanobacterial cells as well as domains where the two photosystems are energetically connected. The methodology presented here can be applied to probe spillover in other photosynthetic organisms.

DOI： 10.1093/pcp/pcad127

Structural insights into photosystem II supercomplex and trimeric FCP antennae of a centric diatom Cyclotella meneghiniana. 査読国際誌

Songhao Zhao, Lili Shen, Xiaoyi Li, Qiushuang Tao, Zhenhua Li, Caizhe Xu, Cuicui Zhou, Yanyan Yang, Min Sang, Guangye Han, Long-Jiang Yu, Tingyun Kuang, Jian-Ren Shen, Wenda Wang

Nature communications 14 ( 1 ) 8164 - 8164 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Diatoms are dominant marine algae and contribute around a quarter of global primary productivity, the success of which is largely attributed to their photosynthetic capacity aided by specific fucoxanthin chlorophyll-binding proteins (FCPs) to enhance the blue-green light absorption under water. We purified a photosystem II (PSII)-FCPII supercomplex and a trimeric FCP from Cyclotella meneghiniana (Cm) and solved their structures by cryo-electron microscopy (cryo-EM). The structures reveal detailed organizations of monomeric, dimeric and trimeric FCP antennae, as well as distinct assemblies of Lhcx6_1 and dimeric FCPII-H in PSII core. Each Cm-PSII-FCPII monomer contains an Lhcx6_1, an FCP heterodimer and other three FCP monomers, which form an efficient pigment network for harvesting energy. More diadinoxanthins and diatoxanthins are found in FCPs, which may function to quench excess energy. The trimeric FCP contains more chlorophylls c and fucoxanthins. These diversified FCPs and PSII-FCPII provide a structural basis for efficient light energy harvesting, transfer, and dissipation in C. meneghiniana.

DOI： 10.1038/s41467-023-44055-8

Structure of PSI-LHCI fromCyanidium caldariumprovides evolutionary insights into conservation and diversity of red-lineage LHCs

Koji Kato, Tasuku Hamaguchi, Minoru Kumazawa, Yoshiki Nakajima, Kentaro Ifuku, Shunsuke Hirooka, Yuu Hirose, Shin-ya Miyagishima, Takehiro Suzuki, Keisuke Kawakami, Naoshi Dohmae, Koji Yonekura, Jian-Ren Shen, Ryo Nagao

2023年10月

出版者・発行元：Cold Spring Harbor Laboratory

Abstract

Light-harvesting complexes (LHCs) are diversified among photosynthetic organisms, and their structural variety in photosystem I-LHC (PSI-LHCI) supercomplexes has been shown. However, structural and evolutionary correlations of red-lineage LHCs are unknown. Here we determined a 1.92-Å resolution cryo-electron microscopic structure of a PSI-LHCI supercomplex isolated from the red algaCyanidium caldariumRK-1 (NIES-2137) which is an important taxon in the Cyanidiophyceae, and subsequently investigated these correlations through structural comparisons and phylogenetic analysis. The PSI-LHCI structure shows five LHCI subunits together with a PSI-monomer core. The five LHCIs are composed of two Lhcr1s, two Lhcr2s, and one Lhcr3. Phylogenetic analysis of LHCs bound to PSI in red-lineage algae showed clear orthology of LHCs betweenC. caldariumandCyanidioschyzon merolae, whereas no orthologous relationships were found betweenC. caldariumLhcr1–3 and LHCs in other red-lineage PSI-LHCI structures. These findings provide evolutionary insights into conservation and diversity of red-lineage LHCs associated with PSI.

DOI： 10.1101/2023.10.25.563911

Structure of a diatom photosystem II supercomplex containing a member of Lhcx family and dimeric FCPII. 査読国際誌

Yue Feng, Zhenhua Li, Xiaoyi Li, Lili Shen, Xueyang Liu, Cuicui Zhou, Jinyang Zhang, Min Sang, Guangye Han, Wenqiang Yang, Tingyun Kuang, Wenda Wang, Jian-Ren Shen

Science advances 9 ( 43 ) eadi8446 2023年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Diatoms rely on fucoxanthin chlorophyll a/c-binding proteins (FCPs) for their great success in oceans, which have a great diversity in their pigment, protein compositions, and subunit organizations. We report a unique structure of photosystem II (PSII)-FCPII supercomplex from Thalassiosira pseudonana at 2.68-Å resolution by cryo-electron microscopy. FCPIIs within this PSII-FCPII supercomplex exist in dimers and monomers, and a homodimer and a heterodimer were found to bind to a PSII core. The FCPII homodimer is formed by Lhcf7 and associates with PSII through an Lhcx family antenna Lhcx6_1, whereas the heterodimer is formed by Lhcf6 and Lhcf11 and connects to the core together with an Lhcf5 monomer through Lhca2 monomer. An extended pigment network consisting of diatoxanthins, diadinoxanthins, fucoxanthins, and chlorophylls a/c is revealed, which functions in efficient light harvesting, energy transfer, and dissipation. These results provide a structural basis for revealing the energy transfer and dissipation mechanisms and also for the structural diversity of FCP antennas in diatoms.

DOI： 10.1126/sciadv.adi8446

Structural and functional properties of different types of siphonous LHCII trimers from an intertidal green alga Bryopsis corticulans. 査読国際誌

Zhenhua Li, Cuicui Zhou, Songhao Zhao, Jinyang Zhang, Xueyang Liu, Min Sang, Xiaochun Qin, Yanyan Yang, Guangye Han, Tingyun Kuang, Jian-Ren Shen, Wenda Wang

Structure (London, England : 1993) 31 ( 10 ) 1247 - 1258 2023年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Light-harvesting complexes of photosystem II (LHCIIs) in green algae and plants are vital antenna apparatus for light harvesting, energy transfer, and photoprotection. Here we determined the structure of a siphonous-type LHCII trimer from the intertidal green alga Bryopsis corticulans by X-ray crystallography and cryo-electron microscopy (cryo-EM), and analyzed its functional properties by spectral analysis. The Bryopsis LHCII (Bry-LHCII) structures in both homotrimeric and heterotrimeric form show that green light-absorbing siphonaxanthin and siphonein occupied the sites of lutein and violaxanthin in plant LHCII, and two extra chlorophylls (Chls) b replaced Chls a. Binding of these pigments expands the blue-green light absorption of B. corticulans in the tidal zone. We observed differences between the Bry-LHCII homotrimer crystal and cryo-EM structures, and also between Bry-LHCII homotrimer and heterotrimer cryo-EM structures. These conformational changes may reflect the flexibility of Bry-LHCII, which may be required to adapt to light fluctuations from tidal rhythms.

DOI： 10.1016/j.str.2023.08.001

Tight association of CpcL with photosystem I in Anabaena sp. PCC 7120 grown under iron-deficient conditions. 査読国際誌

Shota Shimizu, Haruya Ogawa, Naoki Tsuboshita, Takehiro Suzuki, Koji Kato, Yoshiki Nakajima, Naoshi Dohmae, Jian-Ren Shen, Ryo Nagao

Biochimica et biophysica acta. Bioenergetics 148993 - 148993 2023年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

Phycobilisomes (PBSs), which are huge pigment-protein complexes displaying distinctive color variations, bind to photosystem cores for excitation-energy transfer. It is known that the isolation of supercomplexes consisting of PBSs and photosystem I (PSI) or PBSs and photosystem II (PSII) is challenging due to weak interactions between PBSs and the photosystem cores. In this study, we succeeded in purifying PSI-monomer-PBS and PSI-dimer-PBS supercomplexes from the cyanobacterium Anabaena sp. PCC 7120 grown under iron-deficient conditions by anion-exchange chromatography, followed by trehalose density gradient centrifugation. The absorption spectra of the two types of supercomplexes showed apparent bands originating from PBSs, and their fluorescence-emission spectra exhibited characteristic peaks of PBSs. Two-dimensional blue-native (BN)/SDS-PAGE of the two samples showed a band of CpcL, which is a linker protein of PBS, in addition to PsaA/B subunits. Since interactions of PBSs with PSI are easily dissociated during BN-PAGE using thylakoids from this cyanobacterium grown under iron-replete conditions, it is suggested that iron deficiency for Anabaena induces tight associations of CpcL with PSI, resulting in the formation of PSI-monomer-PBS and PSI-dimer-PBS supercomplexes. Based on these findings, we discuss interactions of PBSs with PSI in Anabaena in response to growth conditions.

DOI： 10.1016/j.bbabio.2023.148993

Structural insights into the action mechanisms of artificial electron acceptors in photosystem II. 査読国際誌

Shinji Kamada, Yoshiki Nakajima, Jian-Ren Shen

The Journal of biological chemistry 299 ( 7 ) 104839 - 104839 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

Photosystem II (PSII) utilizes light energy to split water, and the electrons extracted from water are transferred to QB, a plastoquinone molecule bound to the D1 subunit of PSII. Many artificial electron acceptors (AEAs) with molecular structures similar to that of plastoquinone can accept electrons from PSII. However, the molecular mechanism by which AEAs act on PSII is unclear. Here, we solved the crystal structure of PSII treated with three different AEAs, 2,5-dibromo-1,4-benzoquinone, 2,6-dichloro-1,4-benzoquinone, and 2-phenyl-1,4-benzoquinone, at 1.95 to 2.10 Å resolution. Our results show that all AEAs substitute for QB and are bound to the QB-binding site (QB site) to receive electrons, but their binding strengths are different, resulting in differences in their efficiencies to accept electrons. The acceptor 2-phenyl-1,4-benzoquinone binds most weakly to the QB site and showed the highest oxygen-evolving activity, implying a reverse relationship between the binding strength and oxygen-evolving activity. In addition, a novel quinone-binding site, designated the QD site, was discovered, which is located in the vicinity of QB site and close to QC site, a binding site reported previously. This QD site is expected to play a role as a channel or a storage site for quinones to be transported to the QB site. These results provide the structural basis for elucidating the actions of AEAs and exchange mechanism of QB in PSII and also provide information for the design of more efficient electron acceptors.

DOI： 10.1016/j.jbc.2023.104839

Isolation and characterization of trimeric and monomeric PSI cores from Acaryochloris marina MBIC11017 査読

Ryo Nagao, Haruya Ogawa, Naoki Tsuboshita, Koji Kato, Reona Toyofuku, Tatsuya Tomo, Jian-Ren Shen

Photosynthesis Research 2023年5月

Structural insights into a unique PSI-LHCI-LHCII-Lhcb9 supercomplex from moss Physcomitrium patens. 査読国際誌

Song Zhang, Kailu Tang, Qiujing Yan, Xingyue Li, Liangliang Shen, Wenda Wang, Yi-Kun He, Tingyun Kuang, Guangye Han, Jian-Ren Shen, Xing Zhang

Nature plants 9 ( 5 ) 832 - 846 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

Photosystem I (PSI) possesses a variable supramolecular organization among different photosynthetic organisms to adapt to different light environments. Mosses are evolutionary intermediates that diverged from aquatic green algae and evolved into land plants. The moss Physcomitrium patens (P. patens) has a light-harvesting complex (LHC) superfamily more diverse than those of green algae and higher plants. Here, we solved the structure of a PSI-LHCI-LHCII-Lhcb9 supercomplex from P. patens at 2.68 Å resolution using cryo-electron microscopy. This supercomplex contains one PSI-LHCI, one phosphorylated LHCII trimer, one moss-specific LHC protein, Lhcb9, and one additional LHCI belt with four Lhca subunits. The complete structure of PsaO was observed in the PSI core. One Lhcbm2 in the LHCII trimer interacts with PSI core through its phosphorylated N terminus, and Lhcb9 mediates assembly of the whole supercomplex. The complicated pigment arrangement provided important information for possible energy-transfer pathways from the peripheral antennae to the PSI core.

DOI： 10.1038/s41477-023-01401-4

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