Protein-Protein Interactions in Photosystem II

Louisiana State University, Baton Rouge LA

Investigators

Abstract

This project will elucidate the structural organization of proteins associated with Photosystem II (PS II) in higher plants. Protein-protein interactions among the structural components of the photosystem will be studied using biochemical and molecular approaches. First, the interaction of the manganese-stabilizing protein with the 24 kDa protein will be examined. Chemical modification of the manganese-stabilizing protein when it is associated with PS II membranes dramatically affects the ability of the 24 kDa protein to bind to PS II. It will determined if the binding inhibition of the 24 kDa protein is due to charge neutralization or steric interference. The location of the modified residues will be mapped by mass spectrometry. Second, the effects of chemical modification on the 24 and 17 kDa proteins with respect to protein binding and function will be determined and the location of the modified residues will be mapped. Third, the role of the observed heterogeneity in the extrinsic subunits of PS II with respect to structure and function of the photosystem will be examined. In Arabidopsis, each of the extrinsic proteins of PS II are encoded by two genes. T-DNA insertion lines, which are available for a number of these genes will be examined. For genes, which have no T-DNA insertional lines available (psbO-2 and psbP-1), RNAi constructs will be introduced to suppress the expression of these gene products. The phenotypes of these plants will be examined with respect to PS II function, assembly and stability under control and stress conditions. In addition to this genetic approach, biochemical reconstitution studies examining the function of the two psbO proteins will be performed. These studies will provide important new information concerning the interactions of the extrinsic components of PS II with the intrinsic components of the photosystem and with each other. Additionally, an understanding of the role of extrinsic subunit heterogeneity may provide insights into regulatory "fine tuning" of the photosynthesis. Finally, the Arabidopsis mutants, which we will generate will provide a resource for examining the role of the extrinsic subunits in vivo. Broader Impacts: This project will involve training at different levels. It is anticipated that several undergraduate students will be involved in research related to this project. These students will attend scientific meetings, presenting their research and ultimately publish their results. The graduate students, postdoctoral researchers and research associates are all intimately involved in the training of these undergraduate researchers. Additionally, the project will continue a long-standing association with Dr. Cindy Putnam-Evans at East Carolina University, a female faculty member in a non-Ph.D.-granting department.