研究者詳細 - 沈　建仁

論文 - 沈　建仁

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Development of serial X-ray fluorescence holography for radiation-sensitive protein crystals. 査読国際誌

Artoni Kevin R Ang, Yasufumi Umena, Ayana Sato-Tomita, Naoya Shibayama, Naohisa Happo, Riho Marumi, Yuta Yamamoto, Koji Kimura, Naomi Kawamura, Yu Takano, Tomohiro Matsushita, Yuji C Sasaki, Jian Ren Shen, Kouichi Hayashi

Journal of synchrotron radiation 30 ( Pt 2 ) 368 - 378 2023年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

X-ray fluorescence holography (XFH) is a powerful atomic resolution technique capable of directly imaging the local atomic structure around atoms of a target element within a material. Although it is theoretically possible to use XFH to study the local structures of metal clusters in large protein crystals, the experiment has proven difficult to perform, especially on radiation-sensitive proteins. Here, the development of serial X-ray fluorescence holography to allow the direct recording of hologram patterns before the onset of radiation damage is reported. By combining a 2D hybrid detector and the serial data collection used in serial protein crystallography, the X-ray fluorescence hologram can be directly recorded in a fraction of the measurement time needed for conventional XFH measurements. This approach was demonstrated by obtaining the Mn Kα hologram pattern from the protein crystal Photosystem II without any X-ray-induced reduction of the Mn clusters. Furthermore, a method to interpret the fluorescence patterns as real-space projections of the atoms surrounding the Mn emitters has been developed, where the surrounding atoms produce large dark dips along the emitter-scatterer bond directions. This new technique paves the way for future experiments on protein crystals that aim to clarify the local atomic structures of their functional metal clusters, and for other related XFH experiments such as valence-selective XFH or time-resolved XFH.

DOI： 10.1107/S1600577522011833

Structure of a monomeric photosystem I core associated with iron-stress-induced-A proteins from Anabaena sp. PCC 7120. 査読国際誌

Ryo Nagao, Koji Kato, Tasuku Hamaguchi, Yoshifumi Ueno, Naoki Tsuboshita, Shota Shimizu, Miyu Furutani, Shigeki Ehira, Yoshiki Nakajima, Keisuke Kawakami, Takehiro Suzuki, Naoshi Dohmae, Seiji Akimoto, Koji Yonekura, Jian-Ren Shen

Nature communications 14 ( 1 ) 920 - 920 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

Iron-stress-induced-A proteins (IsiAs) are expressed in cyanobacteria under iron-deficient conditions. The cyanobacterium Anabaena sp. PCC 7120 has four isiA genes; however, their binding property and functional roles in PSI are still missing. We analyzed a cryo-electron microscopy structure of a PSI-IsiA supercomplex isolated from Anabaena grown under an iron-deficient condition. The PSI-IsiA structure contains six IsiA subunits associated with the PsaA side of a PSI core monomer. Three of the six IsiA subunits were identified as IsiA1 and IsiA2. The PSI-IsiA structure lacks a PsaL subunit; instead, a C-terminal domain of IsiA2 occupies the position of PsaL, which inhibits the oligomerization of PSI, leading to the formation of a PSI monomer. Furthermore, excitation-energy transfer from IsiAs to PSI appeared with a time constant of 55 ps. These findings provide insights into both the molecular assembly of the Anabaena IsiA family and the functional roles of IsiAs.

DOI： 10.1038/s41467-023-36504-1

Biochemical and spectroscopic characterization of PSI-LHCI from the red alga Cyanidium caldarium. 査読国際誌

Ryo Nagao, Yoshifumi Ueno, Miyu Furutani, Koji Kato, Jian-Ren Shen, Seiji Akimoto

Photosynthesis research 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

Light-harvesting complexes (LHCs) have been diversified in oxygenic photosynthetic organisms, and play an essential role in capturing light energy which is transferred to two types of photosystem cores to promote charge-separation reactions. Red algae are one of the groups of photosynthetic eukaryotes, and their chlorophyll (Chl) a-binding LHCs are specifically associated with photosystem I (PSI). In this study, we purified three types of preparations, PSI-LHCI supercomplexes, PSI cores, and isolated LHCIs, from the red alga Cyanidium caldarium, and examined their properties. The polypeptide bands of PSI-LHCI showed characteristic PSI and LHCI components without contamination by other proteins. The carotenoid composition of LHCI displayed zeaxanthins, β-cryptoxanthins, and β-carotenes. Among the carotenoids, zeaxanthins were enriched in LHCI. On the contrary, both zeaxanthins and β-cryptoxanthins could not be detected from PSI, suggesting that zeaxanthins and β-cryptoxanthins are bound to LHCI but not PSI. A Qy peak of Chl a in the absorption spectrum of LHCI was shifted to a shorter wavelength than those in PSI and PSI-LHCI. This tendency is in line with the result of fluorescence-emission spectra, in which the emission maxima of PSI-LHCI, PSI, and LHCI appeared at 727, 719, and 677 nm, respectively. Time-resolved fluorescence spectra of LHCI represented no 719 and 727-nm fluorescence bands from picoseconds to nanoseconds. These results indicate that energy levels of Chls around/within LHCIs and within PSI are changed by binding LHCIs to PSI. Based on these findings, we discuss the expression, function, and structure of red algal PSI-LHCI supercomplexes.

DOI： 10.1007/s11120-023-00999-y

Photoinduced chlorophyll charge transfer state identified in the light-harvesting complex II from a marine green alga Bryopsis corticulans. 査読国際誌

Dan-Hong Li, Wenda Wang, Cuicui Zhou, Yan Zhang, Songhao Zhao, Yi-Ming Zhou, Rong-Yao Gao, Hai-Dan Yao, Li-Min Fu, Peng Wang, Jian-Ren Shen, Tingyun Kuang, Jian-Ping Zhang

iScience 26 ( 1 ) 105761 - 105761 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

The light-harvesting complex II of Bryopsis corticulans (B-LHCII), a green alga, differs from that of spinach (S-LHCII) in chlorophyll (Chl) and carotenoid (Car) compositions. We investigated ultrafast excitation dynamics of B-LHCII with visible-to-near infrared time-resolved absorption spectroscopy. Absolute fluorescence quantum yield (Φ FL) of LHCII and spectroelectrochemical (SEC) spectra of Chl a and b were measured to assist the spectral analysis. Red-light excitation at Chl Qy-band, but not Car-band, induced transient features resembling the characteristic SEC spectra of Chl a ⋅+ and Chl b ⋅-, indicating ultrafast photogeneration of Chl-Chl charge transfer (CT) species; Φ FL and 3Car∗ declined whereas CT species increased upon prolonging excitation wavelength, showing positive correlation of 1Chl∗ deactivation with Chl-Chl CT formation. Moreover, ultrafast Chl b-to-Chl a and Car-to-Chl singlet excitation transfer were illustrated. The red-light induction of Chl-Chl CT species, as also observed for S-LHCII, is considered a general occurrence for LHCIIs in light-harvesting form.

DOI： 10.1016/j.isci.2022.105761

Cryo-electron microscopy structure of the intact photosynthetic light-harvesting antenna-reaction center complex from a green sulfur bacterium. 査読国際誌

Jing-Hua Chen, Weiwei Wang, Chen Wang, Tingyun Kuang, Jian-Ren Shen, Xing Zhang

Journal of integrative plant biology 65 ( 1 ) 223 - 234 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

The photosynthetic reaction center complex (RCC) of green sulfur bacteria (GSB) consists of the membrane-imbedded RC core and the peripheric energy transmitting proteins called Fenna-Matthews-Olson (FMO). Functionally, FMO transfers the absorbed energy from a huge peripheral light-harvesting antenna named chlorosome to the RC core where charge separation occurs. In vivo, one RC was found to bind two FMOs, however, the intact structure of RCC as well as the energy transfer mechanism within RCC remain to be clarified. Here we report a structure of intact RCC which contains a RC core and two FMO trimers from a thermophilic green sulfur bacterium Chlorobaculum tepidum at 2.9 Å resolution by cryo-electron microscopy. The second FMO trimer is attached at the cytoplasmic side asymmetrically relative to the first FMO trimer reported previously. We also observed two new subunits (PscE and PscF) and the N-terminal transmembrane domain of a cytochrome-containing subunit (PscC) in the structure. These two novel subunits possibly function to facilitate the binding of FMOs to RC core and to stabilize the whole complex. A new bacteriochlorophyll (numbered as 816) was identified at the interspace between PscF and PscA-1, causing an asymmetrical energy transfer from the two FMO trimers to RC core. Based on the structure, we propose an energy transfer network within this photosynthetic apparatus.

DOI： 10.1111/jipb.13367

Characterization of the Rate-Limiting Steps in the Dark-To-Light Transitions of Closed Photosystem II: Temperature Dependence and Invariance of Waiting Times during Multiple Light Reactions. 査読国際誌

Melinda Magyar, Gábor Sipka, Wenhui Han, Xingyue Li, Guangye Han, Jian-Ren Shen, Petar H Lambrev, Győző Garab

International journal of molecular sciences 24 ( 1 ) 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Rate-limiting steps in the dark-to-light transition of Photosystem II (PSII) were discovered by measuring the variable chlorophyll-a fluorescence transients elicited by single-turnover saturating flashes (STSFs). It was shown that in diuron-treated samples: (i) the first STSF, despite fully reducing the QA quinone acceptor molecule, generated only an F1(<Fm) fluorescence level; (ii) to produce the maximum (Fm) level, additional excitations were required, which, however, (iii) were effective only with sufficiently long Δτ waiting times between consecutive STSFs. Detailed studies revealed the gradual formation of the light-adapted charge-separated state, PSIIL. The data presented here substantiate this assignment: (i) the Δτ1/2 half-increment rise (or half-waiting) times of the diuron-treated isolated PSII core complexes (CCs) of Thermostichus vulcanus and spinach thylakoid membranes displayed similar temperature dependences between 5 and −80 °C, with substantially increased values at low temperatures; (ii) the Δτ1/2 values in PSII CC were essentially invariant on the Fk−to-Fk+1 (k = 1−4) increments both at 5 and at −80 °C, indicating the involvement of the same physical mechanism during the light-adaptation process of PSIIL. These data are in harmony with the earlier proposed role of dielectric relaxation processes in the formation of the light-adapted charge-separated state and in the variable chlorophyll-a fluorescence of PSII.

DOI： 10.3390/ijms24010094

Structure of a tetrameric photosystem I from a glaucophyte alga Cyanophora paradoxa 査読

Koji Kato, Ryo Nagao, Yoshifumi Ueno, Makio Yokono, Takehiro Suzuki, Tian-Yi Jiang, Naoshi Dohmae, Fusamichi Akita, Seiji Akimoto, Naoyuki Miyazaki, Jian-Ren Shen

Nature Communications 13 ( 1 ) 2022年12月

掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Science and Business Media LLC

Abstract

Photosystem I (PSI) is one of the two photosystems functioning in light-energy harvesting, transfer, and electron transfer in photosynthesis. However, the oligomerization state of PSI is variable among photosynthetic organisms. We present a 3.8-Å resolution cryo-electron microscopic structure of tetrameric PSI isolated from the glaucophyte alga Cyanophora paradoxa, which reveals differences with PSI from other organisms in subunit composition and organization. The PSI tetramer is organized in a dimer of dimers with a C2 symmetry. Unlike cyanobacterial PSI tetramers, two of the four monomers are rotated around 90°, resulting in a completely different pattern of monomer-monomer interactions. Excitation-energy transfer among chlorophylls differs significantly between Cyanophora and cyanobacterial PSI tetramers. These structural and spectroscopic features reveal characteristic interactions and excitation-energy transfer in the Cyanophora PSI tetramer, suggesting that the Cyanophora PSI could represent a turning point in the evolution of PSI from prokaryotes to eukaryotes.

DOI： 10.1038/s41467-022-29303-7

その他リンク： https://www.nature.com/articles/s41467-022-29303-7

Structural basis for different types of hetero-tetrameric light-harvesting complexes in a diatom PSII-FCPII supercomplex 査読

Ryo Nagao, Koji Kato, Minoru Kumazawa, Kentaro Ifuku, Makio Yokono, Takehiro Suzuki, Naoshi Dohmae, Fusamichi Akita, Seiji Akimoto, Naoyuki Miyazaki, Jian-Ren Shen

Nature Communications 13 ( 1 ) 2022年12月

掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Science and Business Media LLC

Abstract

Fucoxanthin chlorophyll (Chl) a/c-binding proteins (FCPs) function as light harvesters in diatoms. The structure of a diatom photosystem II-FCPII (PSII-FCPII) supercomplex have been solved by cryo-electron microscopy (cryo-EM) previously; however, the FCPII subunits that constitute the FCPII tetramers and monomers are not identified individually due to their low resolutions. Here, we report a 2.5 Å resolution structure of the PSII-FCPII supercomplex using cryo-EM. Two types of tetrameric FCPs, S-tetramer, and M-tetramer, are identified as different types of hetero-tetrameric complexes. In addition, three FCP monomers, m1, m2, and m3, are assigned to different gene products of FCP. The present structure also identifies the positions of most Chls c and diadinoxanthins, which form a complicated pigment network. Excitation-energy transfer from FCPII to PSII is revealed by time-resolved fluorescence spectroscopy. These structural and spectroscopic findings provide insights into an assembly model of FCPII and its excitation-energy transfer and quenching processes.

DOI： 10.1038/s41467-022-29294-5

その他リンク： https://www.nature.com/articles/s41467-022-29294-5

Natural and artificial photosynthesis: fundamentals, progress, and challenges. 査読国際誌

Mohammad Mahdi Najafpour, Jian-Ren Shen, Suleyman I Allakhverdiev

Photosynthesis research 154 ( 3 ) 229 - 231 2022年12月

A Possible Mechanism for Aggregation-Induced Chlorophyll Fluorescence Quenching in Light-Harvesting Complex II from the Marine Green Alga Bryopsis corticulans. 査読国際誌

Hai-Dan Yao, Dan-Hong Li, Rong-Yao Gao, Cuicui Zhou, Wenda Wang, Peng Wang, Jian-Ren Shen, Tingyun Kuang, Jian-Ping Zhang

The journal of physical chemistry. B 126 ( 46 ) 9580 - 9590 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

The light-harvesting complex II of a green alga Bryopsis corticulans (B-LHCII) is peculiar in that it contains siphonein and siphonaxathin as carotenoid (Car). Since the S1 state of siphonein and siphonaxathin lies substantially higher than the Qy state of chlorophyll a (Chl a), the Chl a(Qy)-to-Car(S1) excitation energy transfer is unfeasible. To understand the photoprotective mechanism of algal photosynthesis, we investigated the influence of temperature on the excitation dynamics of B-LHCII in trimeric and aggregated forms. At room temperature, the aggregated form showed a 10-fold decrease in fluorescence intensity and lifetime than the trimeric form. Upon lowering the temperature, the characteristic 680 nm fluorescence (F-680) of B-LHCII in both forms exhibited systematic intensity enhancement and spectral narrowing; however, only the aggregated form showed a red emission extending over 690-780 nm (F-RE) with pronounced blueshift, lifetime prolongation, and intensity boost. The remarkable T-dependence of F-RE is ascribed to the Chl-Chl charge transfer (CT) species involved directly in the aggregation-induced Chl deactivation. The CT-quenching mechanism, which is considered to be crucial for B. corticulans photoprotection, draws strong support from the positive correlation of the Chl deactivation rate with the CT state population, as revealed by comparing the fluorescence dynamics of B-LHCII with that of the plant LHCII.

DOI： 10.1021/acs.jpcb.2c05823

Crystal structures of photosystem II from a cyanobacterium expressing psbA2 in comparison to psbA3 reveal differences in the D1 subunit. 査読国際誌

Yoshiki Nakajima, Natsumi Ugai-Amo, Naoki Tone, Akiko Nakagawa, Masako Iwai, Masahiko Ikeuchi, Miwa Sugiura, Michihiro Suga, Jian-Ren Shen

The Journal of biological chemistry 298 ( 12 ) 102668 - 102668 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

Three psbA genes (psbA1, psbA2, and psbA3) encoding the D1 subunit of photosystem II (PSII) are present in the thermophilic cyanobacterium Thermosynechococcus elongatus and are expressed differently in response to changes in the growth environment. To clarify the functional differences of the D1 protein expressed from these psbA genes, PSII dimers from two strains, each expressing only one psbA gene (psbA2 or psbA3), were crystallized, and we analyzed their structures at resolutions comparable to previously studied PsbA1-PSII. Our results showed that the hydrogen bond between pheophytin/D1 (PheoD1) and D1-130 became stronger in PsbA2- and PsbA3-PSII due to change of Gln to Glu, which partially explains the increase in the redox potential of PheoD1 observed in PsbA3. In PsbA2, one hydrogen bond was lost in PheoD1 due to the change of D1-Y147F, which may explain the decrease in stability of PheoD1 in PsbA2. Two water molecules in the Cl-1 channel were lost in PsbA2 due to the change of D1-P173M, leading to the narrowing of the channel, which may explain the lower efficiency of the S-state transition beyond S2 in PsbA2-PSII. In PsbA3-PSII, a hydrogen bond between D1-Ser270 and a sulfoquinovosyl-diacylglycerol molecule near QB disappeared due to the change of D1-Ser270 in PsbA1 and PsbA2 to D1-Ala270. This may result in an easier exchange of bound QB with free plastoquinone, hence an enhancement of oxygen evolution in PsbA3-PSII due to its high QB exchange efficiency. These results provide a structural basis for further functional examination of the three PsbA variants.

DOI： 10.1016/j.jbc.2022.102668

Roles of the Flexible Primary Coordination Sphere of the Mn4CaOx Cluster: What Are the Immediate Decay Products of the S3 State? 査読国際誌

Hiroshi Isobe, Mitsuo Shoji, Takayoshi Suzuki, Jian-Ren Shen, Kizashi Yamaguchi

The journal of physical chemistry. B 126 ( 38 ) 7212 - 7228 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

The primary coordination sphere of the multinuclear cofactor (Mn4CaOx) in the oxygen-evolving complex (OEC) of photosystem II is absolutely conserved to maintain its structure and function. Recent time-resolved serial femtosecond crystallography identified large reorganization of the primary coordination sphere in the S2 to S3 transition, which elicits a cascade of events involving Mn oxidation and water molecule binding to a putative catalytic Mn site. We examined how the crystallographic fields, created by transient conformational states of the OEC at various time points, affect the thermodynamics of various isomers of the Mn cluster using DFT calculations, with an aim of comprehending the functional roles of the flexible primary coordination sphere in the S2 to S3 transition and in the recovery of the S2 state. The results show that the relative movements of surrounding residues change the size and shape of the cavity of the cluster and thereby affect the thermodynamics of various catalytic intermediates as well as the ability to capture a new water molecule at a coordinatively unsaturated site. The implication of these findings is that the protein dynamics may serve to gate the catalytic reaction efficiently by controlling the sequence of Mn oxidation/reduction and water binding/release. This interpretation is consistent with EPR experiments; g ∼ 5 and g ∼ 3 signals obtained after near-infrared (NIR) excitation of the S3 state at 4 K and a g ∼ 5 only signal produced after prolonged incubation of the S3 state at 77 K can be best explained as originating from water-bound S2 clusters (Stotal = 7/2) under a S3 ligand field, i.e., the immediate one-electron reduction products of the oxyl-oxo (Stotal = 6) and hydroxo-oxo (Stotal = 3) species in the S3 state.

DOI： 10.1021/acs.jpcb.2c02596

Simulating the low-temperature, metastable electrochromism of Photosystem I: Applications to Thermosynechococcus vulcanus and Chroococcidiopsis thermalis. 査読国際誌

J Langley, R Purchase, S Viola, A Fantuzzi, G A Davis, Jian-Ren Shen, A W Rutherford, E Krausz, N Cox

The Journal of chemical physics 157 ( 12 ) 125103 - 125103 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

Low-temperature, metastable electrochromism has been used as a tool to assign pigments in Photosystem I (PS I) from Thermosynechococcus vulcanus and both the white light and far-red light (FRL) forms of Chroococcidiopsis thermalis. We find that a minimum of seven pigments is required to satisfactorily model the electrochromism of PS I. Using our model, we provide a short list of candidates for the chlorophyll f pigment in FRL C. thermalis that absorbs at 756 nm, whose identity, to date, has proven to be controversial. Specifically, we propose the linker pigments A40 and B39 and two antenna pigments A26 and B24 as defined by crystal structure 1JB0. The pros and cons of these assignments are discussed, and we propose further experiments to better understand the functioning of FRL C. thermalis.

DOI： 10.1063/5.0100431

Excited-state intermediates in a designer protein encoding a phototrigger caught by an X-ray free-electron laser. 査読国際誌

Xiaohong Liu, Pengcheng Liu, Hongjie Li, Zhen Xu, Lu Jia, Yan Xia, Minling Yu, Wenqin Tang, Xiaolei Zhu, Chao Chen, Yuanlin Zhang, Eriko Nango, Rie Tanaka, Fangjia Luo, Koji Kato, Yoshiki Nakajima, Shunpei Kishi, Huaxin Yu, Naoki Matsubara, Shigeki Owada, Kensuke Tono, So Iwata, Long-Jiang Yu, Jian-Ren Shen, Jiangyun Wang

Nature chemistry 14 ( 9 ) 1054 - 1060 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

One of the primary objectives in chemistry research is to observe atomic motions during reactions in real time. Although X-ray free-electron lasers (XFELs) have facilitated the capture of reaction intermediates using time-resolved serial femtosecond crystallography (TR-SFX), only a few natural photoactive proteins have been investigated using this method, mostly due to the lack of suitable phototriggers. Here we report the genetic encoding of a xanthone amino acid (FXO), as an efficient phototrigger, into a rationally designed human liver fatty-acid binding protein mutant (termed XOM), which undergoes photo-induced C-H bond transformation with high selectivity and quantum efficiency. We solved the structures of XOM before and 10-300 ns after flash illumination, at 1.55-1.70 Å resolutions, and captured the elusive excited-state intermediates responsible for precise C-H bond activation. We expect that most redox enzymes can now be investigated by TR-SFX, using our method, to reveal reaction intermediates key for their efficiency and selectivity.

DOI： 10.1038/s41557-022-00992-3

Exciton quenching by oxidized chlorophyll Z across the two adjacent monomers in a photosystem II core dimer 査読

Ahmed Mohamed, Shunsuke Nishi, Keisuke Kawakami, Jian-Ren Shen, Shigeru Itoh, Hiroshi Fukumura, Yutaka Shibata

Photosynthesis Research 2022年8月

Excitation relaxation dynamics of carotenoids constituting the diadinoxanthin cycle 査読

Kohei Kagatani, Ryo Nagao, Jian-Ren Shen, Yumiko Yamano, Shinichi Takaichi, Seiji Akimoto

Photosynthesis Research 2022年8月

Effects of mutations of D1-R323, D1-N322, D1-D319, D1-H304 on the functioning of photosystem II in Thermosynechococcus vulcanus. 査読国際誌

Qingjun Zhu, Yanyan Yang, Yanan Xiao, Wenhui Han, Xingyue Li, Wenda Wang, Tingyun Kuang, Jian-Ren Shen, Guangye Han

Photosynthesis research 152 ( 2 ) 193 - 206 2022年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

Photosystem II (PSII) has a number of hydrogen-bonding networks connecting the manganese cluster with the lumenal bulk solution. The structure of PSII from Thermosynechococcus vulcanus (T. vulcanus) showed that D1-R323, D1-N322, D1-D319 and D1-H304 are involved in one of these hydrogen-bonding networks located in the interfaces between the D1, CP43 and PsbV subunits. In order to investigate the functions of these residues in PSII, we generated seven site-directed mutants D1-R323A, D1-R323E, D1-N322R, D1-D319L, D1-D319R, D1-D319Y and D1-H304D of T. vulcanus and examined the effects of these mutations on the growth and functions of the oxygen-evolving complex. The photoautotrophic growth rates of these mutants were similar to that of the wild type, whereas the oxygen-evolving activities of the mutant cells were decreased differently to 63-91% of that of the wild type at pH 6.5. The mutant cells showed a higher relative activity at higher pH region than the wild type cells, suggesting that higher pH facilitated proton egress in the mutants. In addition, oxygen evolution of thylakoid membranes isolated from these mutants showed an apparent decrease compared to that of the cells. This is due to the loss of PsbU during purification of the thylakoid membranes. Moreover, PsbV was also lost in the PSII core complexes purified from the mutants. Taken together, D1-R323, D1-N322, D1-D319 and D1-H304 are vital for the optimal function of oxygen evolution and functional binding of extrinsic proteins to PSII core, and may be involved in the proton egress pathway mediated by YZ.

DOI： 10.1007/s11120-022-00920-z

Ultrafast excitation quenching by the oxidized photosystem II reaction center. 査読国際誌

Parveen Akhtar, Gábor Sipka, Wenhui Han, Xingyue Li, Guangye Han, Jian-Ren Shen, Győző Garab, Howe-Siang Tan, Petar H Lambrev

The Journal of chemical physics 156 ( 14 ) 145101 - 145101 2022年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

Photosystem II (PSII) is the pigment-protein complex driving the photoinduced oxidation of water and reduction of plastoquinone in all oxygenic photosynthetic organisms. Excitations in the antenna chlorophylls are photochemically trapped in the reaction center (RC) producing the chlorophyll-pheophytin radical ion pair P+ Pheo-. When electron donation from water is inhibited, the oxidized RC chlorophyll P+ acts as an excitation quencher, but knowledge on the kinetics of quenching is limited. Here, we used femtosecond transient absorption spectroscopy to compare the excitation dynamics of PSII with neutral and oxidized RC (P+). We find that equilibration in the core antenna has a major lifetime of about 300 fs, irrespective of the RC redox state. Two-dimensional electronic spectroscopy revealed additional slower energy equilibration occurring on timescales of 3-5 ps, concurrent with excitation trapping. The kinetics of PSII with open RC can be described well with previously proposed models according to which the radical pair P+ Pheo- is populated with a main lifetime of about 40 ps, which is primarily determined by energy transfer between the core antenna and the RC chlorophylls. Yet, in PSII with oxidized RC (P+), fast excitation quenching was observed with decay lifetimes as short as 3 ps and an average decay lifetime of about 90 ps, which is shorter than the excited-state lifetime of PSII with open RC. The underlying mechanism of this extremely fast quenching prompts further investigation.

DOI： 10.1063/5.0086046

Structural basis for the absence of low-energy chlorophylls in a photosystem I trimer from Gloeobacter violaceus 査読

Koji Kato, Tasuku Hamaguchi, Ryo Nagao, Keisuke Kawakami, Yoshifumi Ueno, Takehiro Suzuki, Hiroko Uchida, Akio Murakami, Yoshiki Nakajima, Makio Yokono, Seiji Akimoto, Naoshi Dohmae, Koji Yonekura, Jian-Ren Shen

eLife 11 2022年4月

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

Photosystem I (PSI) is a multi-subunit pigment-protein complex that functions in light-harvesting and photochemical charge-separation reactions, followed by reduction of NADP to NADPH required for CO₂ fixation in photosynthetic organisms. PSI from different photosynthetic organisms has a variety of chlorophylls (Chls), some of which are at lower-energy levels than its reaction center P700, a special pair of Chls, and are called low-energy Chls. However, the sites of low-energy Chls are still under debate. Here, we solved a 2.04-Å resolution structure of a PSI trimer by cryo-electron microscopy from a primordial cyanobacterium Gloeobacter violaceus PCC 7421, which has no low-energy Chls. The structure shows the absence of some subunits commonly found in other cyanobacteria, confirming the primordial nature of this cyanobacterium. Comparison with the known structures of PSI from other cyanobacteria and eukaryotic organisms reveals that one dimeric and one trimeric Chls are lacking in the Gloeobacter PSI. The dimeric and trimeric Chls are named Low1 and Low2, respectively. Low2 is missing in some cyanobacterial and eukaryotic PSIs, whereas Low1 is absent only in Gloeobacter. These findings provide insights into not only the identity of low-energy Chls in PSI, but also the evolutionary changes of low-energy Chls in oxyphototrophs.

DOI： 10.7554/elife.73990

その他リンク： https://cdn.elifesciences.org/articles/73990/elife-73990-v1.xml

Structure, Function, and Variations of the Photosystem I-Antenna Supercomplex from Different Photosynthetic Organisms. 査読国際誌

Jian-Ren Shen

Sub-cellular biochemistry 99 351 - 377 2022年

記述言語：英語掲載種別：研究論文（学術雑誌）

Photosystem I (PSI) is a protein complex functioning in light-induced charge separation, electron transfer, and reduction reactions of ferredoxin in photosynthesis, which finally results in the reduction of NAD(P)- to NAD(P)H required for the fixation of carbon dioxide. In eukaryotic algae, PSI is associated with light-harvesting complex I (LHCI) subunits, forming a PSI-LHCI supercomplex. LHCI harvests and transfers light energy to the PSI core, where charge separation and electron transfer reactions occur. During the course of evolution, the number and sequences of protein subunits and the pigments they bind in LHCI change dramatically depending on the species of organisms, which is a result of adaptation of organisms to various light environments. In this chapter, I will describe the structure of various PSI-LHCI supercomplexes from different organisms solved so far either by X-ray crystallography or by cryo-electron microscopy, with emphasis on the differences in the number, structures, and association patterns of LHCI subunits associated with the PSI core found in different organisms.

DOI： 10.1007/978-3-031-00793-4_11

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