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【9.9】the mechanism of photosynthetic water-splitting

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Posted at 2013-9-9 07:11:39 | All floors |Read mode

讲座主标题:Atomic structure of photosystem II membrane-protein complex and the mechanism of photosynthetic water-splitting     
讲座人:Jian-Ren Shen (沈建仁教授)
讲座开始时间:2013-09-09 15:00:00
讲座结束时间:2013-09-09 17:00:00
讲座内容介绍: Photosystem II (PSII) is a multi-subunit membrane protein complex consisting of 20 subunits with a total molecular mass of 350 kDa, which catalyzes the light-induced water-splitting reaction, resulting in the generation of electrons, protons and molecular oxygen. This reaction is extremely important to all oxygenic life forms on the earth as it provides oxygen to the atmosphere and convert light energy into biologically useful chemical energy, both indispensible for sustaining life on the earth. In order to reveal the molecular mechanisms of water-splitting, we have analyzed the structure of PSII at 1.9 Å resolution (1), making PSII the largest membrane-protein complex whose structure has been solved beyond 2.0 Å resolution. Our analysis revealed not only the detailed structure of the whole PSII dimer complex including nearly 2,800 water molecules (Fig. 1), but also elucidated for the first time the detailed structure of a Mn4CaO5-cluster, the catalytic center for water-splitting (Fig. 2). Our results showed that the Mn4CaO5-cluster is organized in a distorted chair form, implying that it has a high structural flexibility, enabling it easier to undergo structural changes occurring in the water-splitting reaction. Based on these and our related studies (2, 3), I will discuss the mechanism of light-induced water-splitting that may have important implications for synthesis of artificial catalysts for water-splitting, an important task in the studies of artificial photosynthesis. In view of the importance of light-induced water-splitting, the structural analysis of PSII has been selected as one of the "Breakthroughs of the year 2011" by Science (4).
(1) Umena Y., Kawakami K., Shen J.-R. and Kamiya N. (2011) Nature, 473, 55-60.
(2) Kawakami, K., Umena, Y., Kamiya, N. & Shen, J.-R. (2009) Proc. Natl. Acad. Sci. USA. 106, 8567–8572.
(3) Koua F. H. M., Umena Y., Kawakami K., Shen J.-R. (2013) Proc. Natl. Acad. Sci. USA. 110, 3889-3894.
(4) "Breakthrough of the Year 2011", Science, 334, 1630.

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