Evidence that the intermediate electron acceptor,A2, in Photosystem I is a bound iron-sulfur protein |
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Authors: | JH Golbeck BR Velthuys B Kok |
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Institution: | Martin Marietta Laboratories, 1450 South Rolling Road, Baltimore, Md. 21227 U.S.A. |
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Abstract: | Absorption changes accompanying the formation of light-induced P-700+ were investigated in a highly enriched Photosystem I preparation where an intermediate electron acceptor preceding P-430 could be detected. In an enriched Photosystem I particle, light-induced reversible absorption changes observed at 700 nm in the presence of dithionite resembled those previously seen at 703 nm and 820 nm 9], thus indicating the presence of a backreaction between P-700+ and A?2. After this same Photosystem I particle was treated to denature the bound iron-sulfur centers, the photochemical changes that could be attributed to P-700 A2 were completely lost. These results provide evidence that the intermediate electron acceptor, A2, is a bound iron-sulfur protein. Additional studies in the 400–500 nm region with Photosystem I particles prepared by sonication indicate that the spectrum of A2 is different from that of P-430. |
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Keywords: | DPIP 2 6-dichlorophenolindophenol |
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