Minor but key chlorophylls in Photosystem II |
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| Authors: | Masami Kobayashi Satoru Watanabe Takanori Gotoh Hajime Koizumi Yuka Itoh Machiko Akiyama Yoshihiro Shiraiwa Tohru Tsuchiya Hideaki Miyashita Mamoru Mimuro Takashi Yamashita Tadashi Watanabe |
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| Affiliation: | (1) Institute of Materials Science, University of Tsukuba, Tsukuba 305-8573, Japan;(2) Institute of Biological Sciences, University of Tsukuba, Tsukuba 305-8572, Japan;(3) Department of Technology and Ecology, Hall of Global Environmental Research, and Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan;(4) Department of Pure and Applied Chemistry, Tokyo University Science, Noda 278-8510, Japan;(5) Institute of Industrial Science, University of Tokyo, Komaba 153-8505, Japan |
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| Abstract: | A ‘metal-free’ chlorophyll (Chl) a, pheophytin (Phe) a, functions as the primary electron acceptor in PS II. On the basis of Phe a/PS II = 2, Phe a content is postulated as an index for estimation of the stoichiometry of pigments and photosystems. We found Phe a in a Chl d-dominant cyanobacterium Acaryochloris marina, whereas Phe d was absent. The minimum Chl a:Phe a ratio was 2:2, indicating that the primary electron donor is Chl a, accessory is Chl d, and the primary electron acceptor is Phe a in PS II of A. marina. Chl d was artificially formed by the treatment of Chl a with papain in aqueous organic solvents. Further, we will raise a key question on the mechanisms of water oxidation in PS II. |
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| Keywords: | Acaryochloris marina chlorophyll chlorophyll a chlorophyll d cyanobacteria oxygen evolution pheophytin a Photosystem II P680 |
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