Assembly and Function of the Cyanobacterial Photosystem II Complex

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Intellectual Merit: If carbon-neutral energy and chemical feedstock solutions are to be developed, these will likely include natural or engineered photosynthetic organisms that manufacture valuable products and/or engineered devices that mimic the principals of natural photosynthesis by coupling of light capture to charge separation and then to endergonic chemical bond rearrangement. An understanding of oxygenic photosynthesis is important on both counts. Despite much progress, there are many important facets of the photosynthetic mechanism that remain to be understood. Of central importance is the water oxidation mechanism catalyzed by photosystem II (PSII), which utilizes water as the source of reductant to fix inorganic carbon. Many aspects of the enzyme's oxygen-yielding water oxidation mechanism remain poorly understood. This includes the repair processes necessitated by incessant photodamage sustained by PSII. These photodamage processes are due to the extraordinary high-potential multi-electron redox reactions that PSII catalyzes; also an important consideration for natural and biomimetic solar energy applications. This proposal addresses two major questions: First, is there a signal conveying the occurrence of damage to an individual PSII complex thereby targeting it for repair or is the repair process a generalized response randomly operating on the population of PSII in response to photodamage-inducing conditions? Second, how are the active site metals, manganese and calcium, assembled into a catalytically active complex? The project will combine molecular genetic, biochemical and biophysical approaches to understand the D1 protein repair process and the assembly and function of the catalytically active complex and also the role of the proteins that tune its reactivity and organize its structure.Broader Impacts: Immersing high school science teachers in a research environment that will be combined with professional development activities will help educators gain an explicit view of how scientific knowledge is generated and will also help with their own curriculum development. Teacher participants will be trained to conduct research and mentor students. They will perpetuate this acquired knowledge with their students by implementing new content knowledge and pedagogical skills into their existing curriculum, mentoring students in student research projects and coaching students in science fair competitions. During state and national conferences teachers will share their developed curriculum and mentoring skills with other educators. The PI and Co-PI will disseminate the science research findings and the educational outreach experience at science and education conference, presenting at the OSU National Lab Day, and through research and practitioner journals.