U.S.-Japan Cooperative Research: Analysis of the Photosystem I Reaction Center by Resolution-Reconstitution Methods

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This award will facilitate continued cooperation between Professor John H. Golbeck, Department of Chemistry, Portland State University; Professor Isamu Ikegami, Teikyo University, Sagamiko, Japan; and Professor Shigeru Itoh, National Institute of Basic Biology, Okazaki, Japan. The scientists are collaborating in a study of some of the basic processes occurring when photosynthesis takes place in green plants and cyanobacteria. They are focusing on the lower- potential system (Photosystem I) of two photochemical systems involved sequentially in the overall photosynthetic process. This cooperative project is based on the combined individual abilities of the U.S. and Japanese researchers to remove and then put back, selectively, the chlorophyll molecules, the phylloquinone molecules, and the iron-sulfur clusters that make up the reaction center. This newly developed, selective resolution and reconstitution protocol, combined with the scientists' ability to effect polypeptide - protein rebinding, offers new opportunities to address longstanding questions regarding the pathways of electron flow in Photosystem I. By leaving some of the components out when reconstructing the complex, the function of these subunits may become better understood. Some of the components may also be chemically altered or exchanged before the complex is reconstituted, in order to synthesize artificial or modified centers, and the effect determined. In addition, use of certain iron and sulfur isotopes will permit various spectroscopic studies to be carried out, yielding structural information regarding the complex.