Dr. Toivo Kallas investigates the molecular biochemistry of photosynthetic reaction mechanisms and stress responses of microalgae and cyanobacteria. A central focus is the cytochrome (Cyt) bf complex, which transfers electrons between the two photochemical reaction centers, establishes a transmembrane proton gradient for ATP synthesis, and serves in redox sensing and regulation of photosynthesis. Current NSF research involves in vitro and in vivo strategies to investigate the Chlamydomonas chloroplast Rieske iron-sulfur protein of the bf complex, its unique domain movement in catalysis and signaling , and electron transfer mechanisms in cyanobacteria. A new NSF proposal has been submitted to investigate redox signaling mechanisms and the enigmatic Cyt bf quinone-reductase (Qi) domain, which has important implications for cyclic electron flow (thus ATP/NAD(P)H balance), signaling, and oxygen radical production. This research relies on the cyanobacterium Synechocystis PCC 6803, an available genomic microarray, and recently solved 3D structures of algal (Stroebel et al., 2003) and cyanobacterial Cyt bf complexes. Dr. Kallas has mentored some 35 undergraduate and 10 Master's students. His own interest in science was stimulated by an NSF summer institute for high school students.
Options for REU projects include: (a) chemical or random-targeted mutagenesis, fluorescence screening, and complementation to identify sites in the bf complex or elsewhere involved in redox sensing/signaling, (b) analysis of available Cyt bf mutants by low temperature fluorescence to assess photosystem ratios, time-resolved spectroscopy to assess electron transfer kinetics, and microarray and 2D gel electrophoresis and mass spectrometry (MS) studies to evaluate gene/protein regulation and possible modifications, and (c) structure-based, site-directed mutagenesis of the Cyt bf Qi domain to evaluate the role and impacts of quinone-reductase site turnover. Such projects would provide excellent experiences for REU students and would make full use of the UW Oshkosh Proteomics and Functional Genomics Core Facility.
