Molecular aspects of photosystem I |
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Authors: | Henrik Vibe Scheller Helle Naver Birger Lindberg Møller |
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Institution: | Plant Biochemistry Laboratory, Dept of Plant Biology, Royal Veterinary and Agricultural Univ., 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Copenhagen, Denmark. |
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Abstract: | Photosystem I (PSI) in higher plants consists of 17 polypeptide subunits. Cofactors are chlorophyll a and b , β-carotene, phylloquinone and iron-sulfur clusters. Eight subunits are specific for higher plants while the remaining ones are also present in cyanobacteria. Two 80-kDa subunits (PSI-A and -B) constitute the major part of PSI and bind most of the pigments and electron donors and acceptors. The 9-kDa PSI-C carries the remaining electron acceptors which are 4Fe-4S] iron sulfur clusters. PSI-D, -E and -H have importance for integrity and function at the stromal face of PSI while PSI-F has importance for function at the lumenal face. PSI-N is localized at the lumenal side, but its function is unknown. Four subunits are light-harvesting chlorophyll a/b -binding proteins. The remaining subunits are integral membrane proteins with poorly understood function. Subunit interactions have been studied in reconstitution experiments and by cross-linking studies. Based on these data, it is concluded that iron-sulfur cluster FB is proximal to FX and that FA is the terminal acceptor in PSI. Similarities between PSI and the reaction center from green sulfur bacteria are discussed. |
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Keywords: | Electron transport green sulfur bacteria iron sulfur clusters photosystem I |
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