Evidence for only one iron-sulfur cluster in center X of photosystem I from higher plants.
In the photosystem I of thylakoid membranes, the photoinduced electron transfer involves three iron-sulfur centers, A, B, and X. Among them, center X is characterized by very unusual spectroscopic and redox properties. Recent arguments have been presented in favor of a [2Fe-2S] structure for the clusters implicated in this center, but the number of these clusters is still a controversial question. By using an original EPR method, based on the differences in the relaxation properties of A, B, and X, we have determined the stoichiometry for the iron-sulfur clusters in photosystem I. Our measurements indicate that center X is composed of a single iron-sulfur cluster per P700. The possible implications of this result for the polypeptide composition of the core reaction center are discussed.
Guigliarelli
B
B
Laboratoire d'Electronique des Milieux Condensés, UA-784, Centre National de la Recherche Scientifique, Université de Provence, Marseille, France.
Guillaussier
J
J
Bertrand
P
P
Gayda
J P
JP
Setif
P
P
D002734:Chlorophyll / Q000032:analysis*; D002736:Chloroplasts / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D007506:Iron-Sulfur Proteins / Q000032:analysis*; D045342:Light-Harvesting Protein Complexes; D008667:Metalloproteins / Q000032:analysis*; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins / Q000032:analysis*; D010944:Plants
D007506:Iron-Sulfur Proteins; D045342:Light-Harvesting Protein Complexes; D008667:Metalloproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll