Evidence for the existence of [2Fe-2S] as well as [4Fe-4S] clusters among FA,FB and FX. Implications for the structure of the Photosystem I reaction center |
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| Institution: | 1. Department of Chemistry, Portland State University, Portland, OR U.S.A.;2. Laboratory of Chemical Biodynamics, University of California, Berkeley, CA, U.S.A.;3. Department of Chemistry, Iowa State University, Ames, IA U.S.A.;4. Department of Chemistry, University of Georgia, Athens, GA U.S.A.;1. State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;2. LipidALL Technologies Company Limited, Changzhou 213022, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;3. Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia;4. Department of Biochemistry and Molecular Biology, The Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Melbourne, Australia;1. Laboratory of Functional Neurochemistry, IRCCS Mondino Foundation, via Mondino 2, 27100, Pavia. Italy;2. Department of Molecular Genetics, Erasmus University Medical Center Rotterdam, the Netherlands;3. Department of Life, Health and Environmental Sciences, University of L’Aquila, L''Aquila, Italy;1. Department of Biochemistry, University of Wisconsin-Madison, Wisconsin, USA;2. Department of Biostatistics and Medical Informatics, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Wisconsin, USA;3. Division of Endocrinology, Department of Internal Medicine, Carver College of Medicine, Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa, USA |
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| Abstract: | Core extrusion of the bound iron-sulfur centers from spinach Photosystem I showed the presence of 2Fe-2S] clusters as well as 4Fe-4S] clusters among FA, FB and FX. Extrusion of the iron-sulfur ensemble was not quantitative; however, the presence of 2Fe-2S] clusters correlated with higher concentration of unfolding solvent. Since FX is highly resistant to denaturation, and since FA and FB are known to contain 4Fe-4S] clusters, the 2Fe-2S] clusters are assigned to FX. The presence of 2Fe-2S] clusters in Photosystem I has significance in the structure and organization of FX on the reaction center. Since four cysteinyl ligands are assumed to hold an iron-sulfur cluster, a Photosystem I subunit may consist of two approx. 64-kDa proteins bridged by a single 2Fe-2S] cluster. The complete reaction center would consist of two subunits positioned so that two 2Fe-2S] clusters are in magnetic interaction, thereby constituting FX. |
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