Cytochrome C Oxidation by the Bacterial Photosynthetic Reaction Center From Rhodobacter Sphaeroides

179 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2000.The interaction of the photosynthetic reaction center (RC) from Rhodobacter sphaeroides and soluble c-type cytochromes has been studied by redox potentiometry and kinetic absorbance spectroscopy. Under intense continuous illumination, in the presence of excess reactants, the RC turnover rate was seen to depend strongly on the bulk ionic strength. Results from both horse-heart cytochrome c (Cyt c), and native bacterial cytochrome c2, are presented as a demonstration that, at neutral pH and low ionic strength, RC turnover is rate-limited by the slow release of the bound reaction product, photooxidized cytochrome. Double flash studies confirm the basic result, but also suggest that slower parallel pathways of electron transfer from the soluble cytochrome pool may exist that circumvent the canonical electron transfer mechanism under conditions of strong product inhibition. Ground state redox titration of Cyt c, in the presence of varying RC concentrations, and redox titration of single flash-induced Cyt c-to-RC electron transfer kinetics, demonstrates redox state-sensitive formation of electron transfer-active RC-Cyt c complexes. Discovery of preferential ferricytochrome binding sheds some light on the diversity of kinetic behavior reported for this system.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD