Assembly and Function of Cyanobacterial Photosystem II

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Photosystem II (PSII) is a crucial but complex enzyme that forms the foundation of the photosynthetic machinery that supports all life on earth. This enzyme is responsible for using light energy to extract hydrogen from water. The overall process results in food for life on earth along with the removal of inorganic carbon from the earth's atmosphere and production of oxygen essential for earth's animals and other heterotrophic life forms. From an economic perspective, an understanding of this process is important if successful biomimetic devices are to be developed for such things as solar energy conversion to produce utilizable hydrogen or hydrides as an energy source to power future electric cars. Despite its importance, many aspects of the enzyme's mechanism remain poorly understood. Furthermore, photosystem II sustains very high rates of damage during its normal operation and is, thus, the 'Achilles Heel' of the plant. Many types of plant stress, including drought, result in the rapid and potentially lethal loss of photosystem II because of this damage. Plants must therefore constantly replace the damaged parts of photosystem II and this presents important biosynthetic challenges that are also still not understood.This research project is developing an understanding of the water-splitting mechanism and how the high rates of photosystem II repair are accomplished. The research takes the perspective that photosystem II is a molecular machine and that it is possible to understand how this machine operates by changing its parts using state-of-the-art genetic methods and probing the resultant changes in the machine's operation using a variety of informative biochemical and biophysical techniques. This research takes advantage of the recent crystallization and visualization of the molecular structure of the PSII 'machine'. It combines structure-based mutagenesis to study the assembly and function of the photosystem II complex in a model organism, Synechocystis PCC 6803. Specifically, this project will address hypotheses on the mechanism of photoactivation of photosystem II and will better define the protein factors participating in the repair cycle using microarray experiments.Broader Impacts: These extend beyond the immediate scientific area: 1) The proposed work will provide significant training opportunities for undergraduate students, graduate students, and postdoctoral fellows. 2) The project will have positive impact on the production of Synechocystis microarrays (distributed on a cost-return basis) and the workshops that the Oklahoma Microarray Core Facility conducts. These arrays serve teaching objectives and are being used to teach the principals of microarray production and applications in summer workshops serving the university and surrounding regions. 3) It will allow increased participation in the recently renewed Native Americans in Biological Sciences (NABS) program at Oklahoma State University.