Bacterial Reaction Centers With New Photochemical Properties

Project: Research project

Description

The research of Professor James Allen, along with Dr. JoAnn Williams and their team, focuses on elucidating the factors that give photosynthetic organisms the ability to convert light into chemical energy. The overall objective of this project is to engineer novel metal clusters that can catalyze light-induced oxidation reactions. Their research builds on a solid base of NSF-supported work in adding functions to a model photosynthetic system, the bacterial reaction center. Previously, they have constructed reaction centers that contain a metal-binding site where manganese is oxidized in a high-potential light-driven reaction. This project will be taken to a new level by protein designs using two complementary approaches to achieve the goal of introducing multinuclear manganese clusters to the reaction center. One method combines reaction centers with small synthetic proteins containing dinuclear manganese centers, allowing tests of electron transfer between the synthetic and natural proteins. A second strategy takes advantage of the structural similarity between the reaction centers and photosystem II. In these designs, reaction centers will be modified to add domains that in photosystem II interact with the tetranuclear manganese cluster where water oxidation occurs. A variety of experimental techniques are available in their laboratory and those of their collaborators to probe the activity of multi-nuclear manganese clusters in reaction centers. The ability of the cofactors to perform specific light-induced reactions will be correlated with critical properties such as the binding, oxidation states, electron transfer rates, and structures. The studies should yield insight into the requirements needed for metal clusters to perform complex multi-electron reactions.

In all photosynthetic systems, the primary energy transduction event is the light-induced generation of a charge-separated state in a pigment-protein complex. Detailed spectroscopic studies and three-dimensional structures of these complexes form a firm foundation for understanding many of their functions. However, the mechanism by which the manganese cluster of photosystem II catalyzes the essential biological process of water oxidation is a major outstanding question in the field. Thus this project is directed towards dissecting this capacity. The bacterial reaction center will serve as a platform to recreate features of the manganese cluster of photosystem II in a well-defined protein environment. Characterization of key properties of a variety of manganese clusters should reveal common motifs in metal clusters that facilitate oxidation reactions. Overall, the insight gained from these studies should help establish molecular concepts that explain how manganese cofactors in proteins efficiently perform intricate chemical reactions, as well as lead to the development of novel biological systems that can accomplish beneficial light-directed catalytic processes.

The research of Professor Allen and Dr. Williams in using protein design to answer fundamental scientific questions about photosynthetic reactions serves as a springboard towards achieving diverse participation in scientific research, fresh perspectives in undergraduate education, and a well-prepared science workforce. The means of achieving these ends are multifaceted. To overcome traditional low graduation rates and limited participation in science degree programs, they provide students from a local community college with a personal research experience in a supportive environment that encourages their continuation in science. The PI and a graduate student are taking part in a program to increase the number of underrepresented students who earn a PhD. To integrate reseach and education, an undergraduate textbook emphasizing problem solving is under development. To improve preparation for the broader scientific research enterprise, they will initiate instruction in career planning for graduate students and create an infrastructure to facilitate access to professional development resources.
StatusFinished
Effective start/end date8/1/157/31/19

Funding

  • National Science Foundation (NSF): $658,512.00

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Manganese
Photosystem II Protein Complex
Oxidation
Metals
Proteins
Students
Education
Electrons
Water
Textbooks
Biological systems
Pigments
Electron energy levels
Chemical reactions
Binding Sites
Engineers
Planning