Design and use of photoactive ruthenium complexes to study electron transfer within cytochrome bc(1) and from cytochrome bc(1) to cytochrome c
by Millett, Francis; Havens, Jeffrey; Rajagukguk, Sany; Durham, Bill
The cytochrome bc(1) complex (ubiquinone:cytochrome c oxidoreductase) is the central integral membrane protein in the mitochondrial respiratory chain as well as the electron-transfer chains of many respiratory and photosynthetic prokaryotes. Based on X-ray crystallographic studies of cytochrome bc(1), a mechanism has been proposed in which the extrinsic domain of the iron-sulfur protein first binds to cytochrome b where it accepts an electron from ubiquinol in the Q(o) site, and then rotates by 57 degrees to a position close to cytochrome c(1) where it transfers an electron to cytochrome c(1). This review describes the development of a ruthenium photooxidation technique to measure key electron transfer steps in cytochrome bc(1), including rapid electron transfer from the iron-sulfur protein to cytochrome c(1). It was discovered that this reaction is rate-limited by the rotational dynamics of the iron-sulfur protein rather than true electron transfer. A conformational linkage between the occupant of the Q(o) ubiquinol binding site and the rotational dynamics of the iron-sulfur protein was discovered which could play a role in the bifurcated oxidation of ubiquinol. A ruthenium photoexcitation method is also described for the measurement of electron transfer from cytochrome c(1) to cytochrome c. This article is part of a Special Issue entitled: Respiratory Complex III and related bc complexes.
- Journal
- Biochimica et Biophysica Acta-Bioenergetics
- Volume
- 1827
- Issue
- 11-12
- Year
- 2013
- Start Page
- 1309-1319
- URL
- https://dx.doi.org/10.1016/j.bbabio.2012.09.002
- ISBN/ISSN
- 0005-2728
- DOI
- 10.1016/j.bbabio.2012.09.002