title: Design and use of photoactive ruthenium complexes to study electron transfer within cytochrome bc1 and from cytochrome bc1 to cytochrome c.
abstract: The cytochrome bc1 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 bc1, 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 Qo site, and then rotates by 57° to a position close to cytochrome c1 where it transfers an electron to cytochrome c1. This review describes the development of a ruthenium photooxidation technique to measure key electron transfer steps in cytochrome bc1, including rapid electron transfer from the iron-sulfur protein to cytochrome c1. 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 Qo 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 c1 to cytochrome c. This article is part of a Special Issue entitled: Respiratory Complex III and related bc complexes.
authors.affiliation: Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA. Electronic address: millett@uark.edu.
authors.forename: Francis
authors.initials: F
authors.lastname: Millett
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Havens
authors.forename: Sany
authors.initials: S
authors.lastname: Rajagukguk
authors.forename: Bill
authors.initials: B
authors.lastname: Durham
mesh_terms: D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism; D003575:Cytochromes c1 / Q000378:metabolism; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction / Q000528:radiation effects; D011487:Protein Conformation; D012428:Ruthenium / Q000737:chemistry* / Q000378:metabolism; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
chemical_list: D009942:Organometallic Compounds; D014451:Ubiquinone; D012428:Ruthenium; D045304:Cytochromes c; D003575:Cytochromes c1; D014450:Electron Transport Complex III; C003741:ubiquinol