Ruthenium flash initiated studies of electron transfer between cytochrome c and the b hemes of cytochrome b5 and sulfite oxidase, and electron transfer within cytochrome bc1.

摘要

Electron transfer within and between biological protein complexes comprises the predominant means of cellular energy production via the coupling of electronic events to the establishment of an electrochemical membrane gradient used to drive the synthesis of high energetic compounds such as ATP. Research undertaken and described herein pursues an elucidation of the specifics of redox events in three separate protein systems, as well as a more general understanding of the nature biological electron transfer, for which the current experiments are relevant and augment. Specifically, the kinetics of electron transfer between cytochromes c and b5, cytochrome c and sulfite oxidase, and cytochromes c and bc 1 (complex III) were studied using a method of rapid flash oxidation of an attached ruthenium reagent to cytochrome c. In addition, redox events within cytochrome bc1 were studied using the binuclear ruthenium reagent, Ru2D, as a cytochrome c surrogate to rapidly initiate oxidant-induced-turnover of the enzyme. Evidence provided below reveals the rate of intracomplex electron transfer between cytochrome c and the b hemes of sulfite oxidase and cytochrome b5 in the physiological direction and redox state for the first time. For the redox events within cytochrome bc1, the effects of several different experimental conditions---including temperature, viscosity, inhibitors, substrates and mutants---are provided and suggest a level of allosteric communication between distal quinone active sites and electronic equilibration across the dimeric interface.