US-Switzerland Cooperative Research: Photosynthetic Electron Transfer Reactions

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This award provides modest support to Dr. David B. Knaff of Texas Tech University to facilitate a long term research visit to the University of Zurich, Switzerland. There he will collaborate in two lines of research with Professor Hans R. Bosshard of the Biochemistry Institute and Professor Reinhard Bachofen of the Plant Biology Institute. Both collaborative projects represent logical extensions of Dr. Knaff's current research; however, his laboratory is not adequately equipped to carry out certain aspects of the work alone. Collaboration with Professor Bosshard centers on elucidating the details of an electrostatically stabilized complex between two plant electron transfer proteins, ferredoxin and ferredoxin:NADP+ oxidoreductase (FNR). FNR is a key enzyme of the photosynthetic electron transfer chain of all oxygen-evolving photosynthetic organisms. Chemical modification of specific amino acid groups will be employed to identify the charged groups that are involved in holding the two proteins together. Antibodies prepared against different sites on FNR will be used to identify the specific roles of different domains on FNR in catalyzing electron transfer from ferredoxin to NADP+. Characterization of the detailed geometry of the ferrodoxin:FNR complex may provide clues to the likely configuration of other ferrodoxin:enzyme complexes. It may also provide insights into the functioning of related protein complexes in mammalian metabolism. Professor Bosshard has state-of-the-art facilities for protein sequencing and he is an acknowledged world-leader in using the technique of differential chemical modification to identify specific amino acid residues involved in the formation of protein complexes. Collaboration with Professor Bachofen will focus on identifying changes in electron-carrying protein constituents in one region of the electron transfer chain of Rhodopseudomonas viridis that occur when the bacterium is grown under aerobic versus photosynthetic conditions. The electron transfer chains of such photosynthetic purple non-sulfur bacteria have become increasingly better understood in recent years. However, much less is known about the respiratory chain than about its photosynthetic electron transfer chain. Resemblances between electron flow in photosynthetic purple bacteria and in mitochondria, chloroplasts and cyanobacteria increase the potential relevance and significance of this work. Professor Bachofen's group offers valuable state-of-the-art computer-controlled apparatus for growing photosynthetic bacteria and expertise in the molecular biology of such bacteria.