研究者詳細 - 沈　建仁

論文 - 沈　建仁

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The position and orientation of active carotenoid in photosystem II

Asako Kawamori, Hiroyuki Mino, Jianren Shen

Advanced Topics in Science and Technology in China 64 - 66 2013年

記述言語：英語掲載種別：論文集(書籍)内論文出版者・発行元：Springer

The distances between YD and active carotenoid have been determined in cyanobacterium (synecochoccus vulcanus) and spinach PSII by pulsed electron double resonance (PELDOR). The observed spectra were analyzed taking into spin distribution of over 30 carbon atoms in the carotenoid molecule. The result of simulations based on the recent crystal structure fitted well with the spectra. The observed spectra for spinach PSII was different, showing the crystal structure of spinach PSII is slightly different from that of cyanobacteria. The ELDOR spectra of YD-YZ radical pair were observed in a cyanobacterium. The result showed the different distance from Spinach PSII.

DOI： 10.1007/978-3-642-32034-7_13

Electronic structure of the CaMn4O5 cluster in the PSII system refined to the 1.9 Å X-ray resolution. Possible mechanisms of photosynthetic water splitting

S. Yamanaka, K. Kanda, H. Isobe, K. Nakata, Y. Umena, K. Kawakami, J. R. Shen, N. Kamiya, M. Okumura, T. Takada, H. Nakamura, K. Yamaguchi

Advanced Topics in Science and Technology in China 250 - 254 2013年

記述言語：英語掲載種別：論文集(書籍)内論文出版者・発行元：Springer

Broken-symmetry (BS) UB3LYP calculations have been performed for the CaMn4O5 cluster (1) in the oxygen-evolving complex (OEC) of the PSII system refined to 1.9 Å resolution by Umena, Kawakami, Kamiya, Shen to elucidate its electronic structure that is crucial for consideration of possible mechanisms of photosynthetic water splitting. Our UB3LYP computations have elucidated the position of protonated oxygen of the CaMn(III)2Mn(IV)2O4(OH) cluster (1a) at the S1 stage of Kok cycle. Starting from the newly elucidated S1 structure of 1a, we have calculated the electronic structure of proton and electron released CaMn(IV)4O5 cluster (1b) that mimics the S4 stage of the cycle. The LUMOs of 1b are depicted for pictorial understanding of electrophilic oxygen sites that are responsible for nucleophilic attack of hydroxide anion (or water) for the O-O bond formation. Implications of present computational results are discussed in relation to possible mechanisms of photosynthetic water splitting.

DOI： 10.1007/978-3-642-32034-7_52

Photosystem II and the unique role of bicarbonate: A historical perspective 査読国際誌

Dmitriy Shevela, Julian J. Eaton-Rye, Jian-Ren Shen, Govindjee

BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1817 ( 8 ) 1134 - 1151 2012年8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：ELSEVIER

In photosynthesis, cyanobacteria, algae and plants fix carbon dioxide (CO2) into carbohydrates; this is necessary to support life on Earth. Over 50 years ago, Otto Heinrich Warburg discovered a unique stimulatory role of CO2 in the Hill reaction (i.e., O-2 evolution accompanied by reduction of an artificial electron acceptor), which, obviously, does not include any carbon fixation pathway; Warburg used this discovery to support his idea that O-2 in photosynthesis originates in CO2. During the 1960s, a large number of researchers attempted to decipher this unique phenomenon, with limited success. In the 1970s, Alan Stemler, in Govindjee's lab, perfected methods to get highly reproducible results, and observed, among other things, that the turnover of Photosystem II (PSII) was stimulated by bicarbonate ions (hydrogen carbonate): the effect would, be on the donor or the acceptor, or both sides of PSII. In 1975, Thomas Wydrzynski, also in Govindjee's lab, discovered that there was a definite bicarbonate effect on the electron acceptor (the plastoquinone) side of PSII. The most recent 1.9 angstrom crystal structure of PSII, unequivocally shows HCO3- bound to the non-heme iron that sits in-between the bound primary quinone electron acceptor, Q(A), and the secondary quinone electron acceptor Q(B). In this review, we focus on the historical development of our understanding of this unique bicarbonate effect on the electron acceptor side of PSII, and its mechanism as obtained by biochemical, biophysical and molecular biological approaches in many laboratories around the World. We suggest an atomic level model in which HCO3-/CO32- plays a key role in the protonation of the reduced Q(B). In addition, we make comments on the role of bicarbonate on the donor side of PSII, as has been extensively studied in the labs of Alan Stemler (USA) and Vyacheslav Klimov (Russia). We end this review by discussing the uniqueness of bicarbonate's role in oxygenic photosynthesis and its role in the evolutionary development of O-2-evolving PSII. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.bbabio.2012.04.003

Cationic state distribution over the chlorophyll d-containing P-D1/P-D2 Pair in photosystem II 査読国際誌

Keisuke Saito, Jian-Ren Shen, Hiroshi Ishikita

BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1817 ( 8 ) 1191 - 1195 2012年8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：ELSEVIER SCIENCE BV

Most of the chlorophyll (Chl) cofactors in photosystem II (PSII) from Acaryochloris marina are Chld, although a few Chla molecules are also present. To evaluate the possibility that Chla may participate in the P-D1/P-D2 Chl pair in PSII from A marina, the P-D1(.+)/P-D2(.+) charge ratio was investigated using the PSII crystal structure analyzed at 1.9-angstrom resolution, while considering all possibilities for the Chld-containing P-D1/P-D2 pair, i.e., Chld/Chld, Chla/Chld, and Chld/Chla pairs. Chld/Chld and Chla/Chld pairs resulted in a large P-D1(.+) population relative to P-D2(.+) as identified in Chla/Chla homodimer pairs in PSII from other species. e.g. Thermosynechococcus elongatus PSII. However, the Chld/Chla pair possessed a P-D1(.+)/P-D2(.+) ratio of approximately 50/50, which is in contrast to previous spectroscopic studies on A. marina PSII. The present results strongly exclude the possibility that the Chld/Chla pair serves as P-D1/P-D2 in A marina PSII. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.bbabio.2011.12.003

The structure and activation of substrate water molecules in the S-2 state of photosystem II studied by hyperfine sublevel correlation spectroscopy 査読

Sergey Milikisiyants, Ruchira Chatterjee, Christopher S. Coates, Faisal H. M. Koua, Jian-Ren Shen, K. V. Lakshmi

ENERGY & ENVIRONMENTAL SCIENCE 5 ( 7 ) 7747 - 7756 2012年7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：ROYAL SOC CHEMISTRY

The water-splitting protein, photosystem II, catalyzes the light-driven oxidation of water to dioxygen. The solar water oxidation reaction takes place at the catalytic center, referred to as the oxygen-evolving complex, of photosystem II. During the catalytic cycle, the oxygen-evolving complex cycles through five distinct intermediate states, S-0-S-4. In this study, we trap the oxygen-evolving complex in the S-2 intermediate state by low temperature illumination of photosystem II isolated from three different species, Thermosynechococcus vulcanus, the PsbB variant of Synechocystis PCC 6803 and spinach. We apply two-dimensional hyperfine sublevel correlation spectroscopy to detect weak magnetic interactions between the paramagnetic tetra-nuclear manganese cluster of the S-2 state of the OEC and the surrounding protons. We identify five groups of protons that are interacting with the tetra-nuclear manganese cluster. From the values of hyperfine interactions and using the recently reported 1.9 angstrom resolution X-ray structure of the OEC in the S-1 state [Umena et al., Nature, 2011, 473, 55], we discuss the assignments of the five groups of protons and draw important conclusions on the structure of the oxygen-evolving complex in the S-2 state. In addition, we conclude that the structure of OEC is nearly identical in photosystem II from Thermosynechococcus vulcanus, the PsbB variant of Synechocystis PCC 6803 and spinach.

DOI： 10.1039/c2ee21210b

Influence of the Axial Ligand on the Cationic Properties of the Chlorophyll Pair in Photosystem II from Thermosynechococcus vulcanus 査読国際誌

Keisuke Saito, Jian-Ren Shen, Hiroshi Ishikita

BIOPHYSICAL JOURNAL 102 ( 11 ) 2634 - 2640 2012年6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：CELL PRESS

Influence of the axial ligand of P-D1 chlorophyll (D1-His-198) on the E-m of monomer chlorophylls P-D1 and P-D2, and the P-D1(center dot+)/P-D2(center dot+) charge ratio was investigated by theoretical calculations using the PSII crystal structure of Thermosynechococcus vulcanus analyzed at 1.9-angstrom resolution. It was found that the Em(P-D1)/E-m(P-D2) values and P-D1(center dot+)/P-D2(center dot+) ratio remained unchanged upon D1-H198Q mutation. However, Em(PD1) was increased in the D1-H198A mutant, resulting in a more even distribution of the positive charge over P-D1/P-D2. Introduction of a water molecule as an axial ligand resulted in equal E-m values and P-D1(center dot+)/P-D2(center dot+) ratios between the mutant and wild-type, thus confirming the presence of the water ligand in the mutant.

DOI： 10.1016/j.bpj.2012.04.016

Deformation of Chlorin Rings in the Photosystem II Crystal Structure 査読国際誌

Keisuke Saito, Yasufumi Umena, Keisuke Kawakami, Jian-Ren Shen, Nobuo Kamiya, Hiroshi Ishikita

BIOCHEMISTRY 51 ( 21 ) 4290 - 4299 2012年5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

The crystal structure of Photosystem II (PSII) analyzed at a resolution of 1.9 angstrom revealed deformations of chlorin rings in the chlorophylls for the first time. We investigated the degrees of chlorin ring deformation and factors that contributed to them in the PSII crystal structure, using a normal-coordinate structural decomposition procedure. The out-of-plane distortion of the Pm chlorin ring can be described predominantly by a large "doming mode" arising from the axial ligand, D1-His198, as well as the chlorophyll side chains and PSII protein environment. In contrast, the deformation of P-D2 was caused by a "saddling mode" arising from the D2-Trp191 ring and the doming mode arising from D2-His197. Large ruffling modes, which were reported to lower the redox potential in heme proteins, were observed in P-D1 and Chl(D1), but not in P-D2 and ChlD(2). Furthermore, as P-D1 possessed the largest doming mode among the reaction center chlorophylls, the corresponding bacteriochlorophyll P-L possessed the largest doming mode in bacterial photosynthetic reaction centers. However, the majority of the redox potential shift in the protein environment was determined by the electrostatic environment. The difference in the chlorin ring deformation appears to directly refer to the difference in "the local steric protein environment" rather than the redox potential value in PSII.

DOI： 10.1021/bi300428s

3D0948 光化学系IIコア複合体での非光化学的消光の可能性(光生物-光合成,口頭発表,日本生物物理学会第50回年会(2012年度))

Shibata Yutaka, Nishi Shunsuke, Kawakami Keisuke, Shen Jian-Ren, Renger Thomas

生物物理 52 S62 2012年

3D1022 光化学系II酸素発生系S_2状態におけるMn間磁気的相互作用の解明(光生物-光合成,口頭発表,日本生物物理学会第50回年会(2012年度))

Asada Mizue, Nagashima Hiroki, Koua Faisal Hammad Mekky, Shen Jian-Ren, Mino Hiroyuki

生物物理 52 S63 2012年

Theoretical illumination of water-inserted structures of the CaMn4O5 cluster in the S2 and S3 states of oxygen-evolving complex of photosystem II: full geometry optimizations by B3LYP hybrid density functional 査読

H. Isobe, M. Shoji, S. Yamanaka, Y. Umena, K. Kawakami, N. Kamiya, J.-R. Shen, K. Yamaguchi

Dalton Transactions 41 ( 44 ) 13727 - 13727 2012年

Short Hydrogen Bond between Redox-Active Tyrosine Y-z and D1-His190 in the Photosystem II Crystal Structure 査読国際誌

Keisuke Saito, Jian-Ren Shen, Toyokazu Ishida, Hiroshi Ishikita

BIOCHEMISTRY 50 ( 45 ) 9836 - 9844 2011年11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

The crystal structure of photosystem IT (PSII) analyzed at a resolution of 1.9 A revealed a remarkably short H-bond between redox-active tyrosine Y-z and D1-His190 (2.46 angstrom donor-acceptor distance). Using large-scale quantum mechanical/molecular mechanical (QM/MM) calculations with the explicit PSII protein environment, we were able to reproduce this remarkably short H-bond in the original geometry of the crystal structure in the neutral [YzO center dot center dot center dot H center dot center dot center dot N-e-His-N delta H center dot center dot center dot O=Asn] state, but not in the oxidized states, indicating that the neutral state was the one observed in the crystal structure. In addition to the appropriate redox/protonation state of Y-z and D1-His190, we found that the presence of a cluster of water molecules played a key role in shortening the distance between Y-z and D1-His190. The orientations of the water molecules in the cluster were energetically stabilized by the highly polarized PSII protein environment, where the Ca ion of the oxygen-evolving complex (OEC) and the OEC ligand D1-Glu189 were also involved.

DOI： 10.1021/bi201366j

Distribution of the Cationic State over the Chlorophyll Pair of the Photosystem II Reaction Center 査読国際誌

Keisuke Saito, Toyokazu Ishida, Miwa Sugiura, Keisuke Kawakami, Yasufumi Umena, Nobuo Kamiya, Jian-Ren Shen, Hiroshi Ishikita

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 ( 36 ) 14379 - 14388 2011年9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

The reaction center chlorophylls a (Chla) of photosystem II (PSII) are composed of six Chla molecules including the special pair Chla P-D1/P-D2 harbored by the D1/D2 heterodimer. They serve as the ultimate electron abstractors for water oxidation in the oxygen-evolving Mn4CaO5 cluster. Using the PSII crystal structure analyzed at 1.9 angstrom resolution, the redox potentials of P-D1/center dot P-D2 for one-electron oxidation (E-m) were calculated by considering all PSII subunits and the protonation pattern of all titratable residues. The Em(Chla) values were calculated to be 1015-1132 mV for P-D1 and 1141-1201 mV for P-D2, depending on the protonation state of the Mn4CaO5 cluster. The results showed that Em(P-D1) was lower than E-m(P-D2) P-D2 favoring localization of the charge of the cationic state more on P-D1. The P-D1(center dot+)/P-D2(center dot+) charge ratio determined by the large-scale QM/MM calculations with the explicit PS II protein environment yielded a P-D1(center dot+)/P-D2(center dot+) ratio of similar to 80/similar to 20, which was found to be due to the asymmetry in electrostatic characters of several conserved D1/D2 residue pairs that cause the E-m(P-D1)/E-m(P-D2) difference, e.g., Dl -Asn181/D2-Argl 80, D1-Asn298/D2-Arg294, D1-Asp61/D2-His61, D1-Glu189/D2-Phe188, and D1-Asp170/D2-Phe169. The larger P-D1(center dot+) population than P-D2(center dot+) appears to be an inevitable fate of the intact PSII that possesses water oxidation activity.

DOI： 10.1021/ja203947k

Structure of the catalytic, inorganic core of oxygen-evolving photosystem II at 1.9 angstrom resolution 査読

Keisuke Kawakami, Yasufumi Umena, Nobuo Kamiya, Jian-Ren Shen

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 104 ( 1-2 ) 9 - 18 2011年7月

記述言語：英語出版者・発行元：ELSEVIER SCIENCE SA

The catalytic center for photosynthetic water-splitting consists of 4 Mn atoms and 1 Ca atom and is located near the lumenal surface of photosystem II. So far the structure of the Mn4Ca-cluster has been studied by a variety of techniques including X-ray spectroscopy and diffraction, and various structural models have been proposed. However, its exact structure is still unknown due to the limited resolution of crystal structures of PSII achieved so far, as well as possible radiation damages that might have occurred. Very recently, we have succeeded in solving the structure of photosystem II at 1.9 angstrom. which yielded a detailed picture of the Mn4CaO5-cluster for the first time. In the high resolution structure, the Mn4CaO5-cluster is arranged in a distorted chair form, with a cubane-like structure formed by 3 Mn and 1 Ca, 4 oxygen atoms as the distorted base of the chair, and 1 Mn and 1 oxygen atom outside of the cubane as the back of the chair. In addition, four water molecules were associated with the cluster, among which, two are associated with the terminal Mn atom and two are associated with the Ca atom. Some of these water molecules may therefore serve as the substrates for water-splitting. The high resolution structure of the catalytic center provided a solid basis for elucidation of the mechanism of photosynthetic water splitting. We review here the structural features of the Mn4CaO5-cluster analyzed at 1.9 angstrom resolution, and compare them with the structures reported previously. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jphotobiol.2011.03.017

S-1-State Model of the O-2-Evolving Complex of Photosystem II 査読国際誌

Sandra Luber, Ivan Rivalta, Yasufumi Umena, Keisuke Kawakami, Jian-Ren Shen, Nobuo Kamiya, Gary W. Brudvig, Victor S. Batista

BIOCHEMISTRY 50 ( 29 ) 6308 - 6311 2011年7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

We introduce a quantum mechanics/molecular mechanics model of the oxygen-evolving complex of photosystem II in the S-1 Mn-4(IV,III,IV,III) state, where Ca2+ is bridged to manganese centers by the carboxylate moieties of D170 and A344 on the basis of the new X-ray diffraction (XRD) model recently reported at 1.9 angstrom resolution. The model is also consistent with high-resolution spectroscopic data, including polarized extended X-ray absorption fine structure data of oriented single crystals. Our results provide refined intermetallic distances within the Mn cluster and suggest that the XRD model most likely corresponds to a mixture of oxidation states, including species more reduced than those observed in the catalytic cycle of water splitting.

DOI： 10.1021/bi200681q

Structural-Functional Role of Chloride in Photosystem II 査読国際誌

Ivan Rivalta, Muhamed Amin, Sandra Luber, Serguei Vassiliev, Ravi Pokhrel, Yasufumi Umena, Keisuke Kawakami, Jian-Ren Shen, Nobuo Kamiya, Doug Bruce, Gary W. Brudvig, M. R. Gunner, Victor S. Batista

BIOCHEMISTRY 50 ( 29 ) 6312 - 6315 2011年7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

Chloride binding in photosystem II (PSII) is essential for photosynthetic water oxidation. However, the functional roles of chloride and possible binding sites, during oxygen evolution, remain controversial. This paper examines the functions of chloride based on its binding site revealed in the X-ray crystal structure of PSII at 1.9 angstrom resolution. We find that chloride depletion induces formation of a salt bridge between D2-K317 and D1-D61 that could suppress the transfer of protons to the lumen.

DOI： 10.1021/bi200685w

Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9 angstrom 査読国際誌

Yasufumi Umena, Keisuke Kawakami, Jian-Ren Shen, Nobuo Kamiya

NATURE 473 ( 7345 ) 55 - U65 2011年5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：NATURE PUBLISHING GROUP

Photosystem II is the site of photosynthetic water oxidation and contains 20 subunits with a total molecular mass of 350 kDa. The structure of photosystem II has been reported at resolutions from 3.8 to 2.9 angstrom. These resolutions have provided much information on the arrangement of protein subunits and cofactors but are insufficient to reveal the detailed structure of the catalytic centre of water splitting. Here we report the crystal structure of photosystem II at a resolution of 1.9 angstrom. From our electron density map, we located all of the metal atoms of the Mn4CaO5 cluster, together with all of their ligands. We found that five oxygen atoms served as oxo bridges linking the five metal atoms, and that four water molecules were bound to the Mn4CaO5 cluster; some of them may therefore serve as substrates for dioxygen formation. We identified more than 1,300 water molecules in each photosystem II monomer. Some of them formed extensive hydrogen-bonding networks that may serve as channels for protons, water or oxygen molecules. The determination of the high-resolution structure of photosystem II will allow us to analyse and understand its functions in great detail.

DOI： 10.1038/nature09913

Labile electronic and spin states of the CaMn4O5 cluster in the PSII system refined to the 1.9 angstrom X-ray resolution. UB3LYP computational results 査読

Keita Kanda, Shusuke Yamanaka, Tohru Saito, Yasufumi Umena, Keisuke Kawakami, Jian-Ren Shen, Nobuo Kamiya, Mitsutaka Okumura, Haruki Nakamura, Kizashi Yamaguchi

CHEMICAL PHYSICS LETTERS 506 ( 1-3 ) 98 - 103 2011年4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：ELSEVIER SCIENCE BV

UB3LYP calculations were first performed to elucidate electronic and spin structures of the CaMn4O5 cluster in the oxygen-evolving-complex of the PSII system refined to the 1.9 angstrom X-ray resolution by Kamiya, Shen, and their collaborators. Eight different UB3LYP solutions with axial spin structures were constructed to obtain the energy levels of the cluster on the basis of their X-ray structure. The energy diagrams were analyzed in terms of the Heisenberg model that involves six effective-exchange integrals between manganese ions. Several characteristic features of the electronic states of the cluster are revealed from these theoretical investigations based on the UB3LYP calculations. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2011.02.030

Proton-Coupled Electron-Transfer Processes in Photosystem II Probed by Highly Resolved g-Anisotropy of Redox-Active Tyrosine Y-Z 査読国際誌

Hideto Matsuoka, Jian-Ren Shen, Asako Kawamori, Kei Nishiyama, Yasunori Ohba, Seigo Yamauchi

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 ( 12 ) 4655 - 4660 2011年3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

The oxidation of a redox-active tyrosine residue Y-Z in photosystem II (PSII) is coupled with proton transfer to a hydrogen-bonded D1-His190 residue. Because of the apparent proximity of Y-Z to: the water-oxidizing complex and its redox activity, it is believed that Y-Z plays a significant role in water oxidation in PSII. We investigated the g-anisotropy of the tyrosine radical Y-Z(center dot) to provide insight into the mechanism of Y-Z(center dot) proton-coupled electron transfer in Nth-depleted PSII. The anisotropy was highly resolved by electron paramagnetic resonance spectroscopy at the W-band (94.9 GHz) using PSII single crystals. The g(x)-component along the phenolic C-O bond of Y-Z(center dot) was calculated by density functional theory (DFT). It was concluded from the highly resolved g-anisotropy that Y-Z loses a phenol proton to D1-His190 upon tyrosine oxidation, and D1-His190 redonates the same proton back to Y-Z(center dot) upon reduction.

DOI： 10.1021/ja2000566

Roles of PsbI and PsbM in photosystem II dimer formation and stability studied by deletion mutagenesis and X-ray crystallography 査読国際誌

Keisuke Kawakami, Yasufumi Umena, Masako Iwai, Yousuke Kawabata, Masahiko Ikeuchi, Nobuo Kamiya, Jian-Ren Shen

BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1807 ( 3 ) 319 - 325 2011年3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：ELSEVIER

PsbM and PsbI are two low molecular weight subunits of photosystem II (PSII), with PsbM being located in the center, and PsbI in the periphery, of the PSII dimer. In order to study the functions of these two subunits from a structural point of view, we crystallized and analyzed the crystal structure of PSII dimers from two mutants lacking either PsbM or PsbI. Our results confirmed the location of these two subunits in the current crystal structure, as well as their absence in the respective mutants. The relative contents of PSII dimers were found to be decreased in both mutants, with a concomitant increase in the amount of PSII monomers, suggesting a destabilization of PSII dimers in both of the mutants. On the other hand, the accumulation level of the overall PSII complexes in the two mutants was similar to that in the wild-type strain. Treatment of purified PSII dimers with lauryldimethylamine N-oxide at an elevated temperature preferentially disintegrated the dimers from the PsbM deletion mutant into monomers and CP43-less monomers, whereas no significant degradation of the dimers was observed from the PsbI deletion mutant. These results indicate that although both PsbM and PsbI are required for the efficient formation and stability of PSII dimers in vivo, they have different roles, namely, PsbM is required directly for the formation of dimers and its absence led to the instability of the dimers accumulated. On the other hand, PsbI is required in the assembly process of PSII dimers in vivo: once the dimers are formed. PsbI was no longer required for its stability. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.bbabio.2010.12.013

Photosynthetic Oxygen Evolution in Mesoporous Silica Material: Adsorption of Photosystem II Reaction Center Complex into 23 nm Nanopores in SBA 査読国際誌

Tomoyasu Noji, Chihiro Kamidaki, Keisuke Kawakami, Jian-Ren Shen, Tsutomu Kajino, Yoshiaki Fukushima, Takeshi Sekitoh, Shigeru Itoh

LANGMUIR 27 ( 2 ) 705 - 713 2011年1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

An oxygen-evolving photosynthetic reaction center complex (PSII) was adsorbed into nanopores in SBA, a mesoporous silica compound. We purified the dimer of PSII complex from a thermophilic cyanobacterium, Thermosynechococcus vulcanus, which grows optimally at 57 degrees C. The thermally stable PSII dimeric complex has a diameter of 20 nm and a molecular mass of 756 kDa and binds more than 60 chlorophylls. The SBA particles, with average internal pore diameters of 15 nm (SBA(15)) and 23 nm (SBA(23)), adsorbed 4.7 and 15 mg of PSII/g SBA, respectively. Measurement with a confocal laser-scanning microscope indicated the adsorption of PSII to the surface and the inner space of the SBA(23) particles, indicating the adsorption of PSII into the 23 nm silica nanopores. PSII did not bind to the inner pores of SBA(15). PSII bound to SBA(23) showed the high and stable activity of a photosynthetic oxygen-evolving reaction, indicating the light-driven electron transport from water to the quinone molecules added in the outer medium. The PSII-SBA conjugate can be a new material for photosensors and artificial photosynthetic systems.

DOI： 10.1021/la1032916

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