title: Light-induced reduction of bovine adrenodoxin via the covalently bound ruthenium(II) bipyridyl complex: intramolecular electron transfer and crystal structure.
abstract: Bovine adrenodoxin (Adx) plays an important role in the electron-transfer process in the mitochondrial steroid hydroxylase system of the bovine adrenal cortex. Using electron paramagnetic resonance (EPR) spectroscopy, we showed that photoreduction of the [2Fe-2S] cluster of Adx via (4'-methyl-2,2'-bipyridine)bis(2,2'-bipyridine)ruthenium(II) [Ru(bpy)2(mbpy)] covalently attached to the protein surface can be used as a new approach to probe the "shuttle" hypothesis for the electron transfer by Adx. The 1.5 A resolution crystal structure of a 1:1 Ru(bpy)2(mbpy)-Adx(1-108) complex reveals the site of modification, Cys95, and allows to predict the possible intramolecular electron-transfer pathways within the complex. Photoreduction of uncoupled Adx, mutant Adx(1-108), and Ru(bpy)2(mbpy)-Adx(1-108) using safranin T as the mediating electron donor suggests that two electrons are transferred from the dye to Adx. The intramolecular photoreduction rate constant for the ruthenated Adx has been determined and is discussed according to the predicted pathways.
authors.affiliation: Crystallography Group, Max-Delbrück-Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, D-13125 Berlin-Buch, Germany.
authors.forename: Andrei
authors.initials: A
authors.lastname: Halavaty
authors.forename: Jürgen J
authors.initials: JJ
authors.lastname: Müller
authors.forename: Jörg
authors.initials: J
authors.lastname: Contzen
authors.forename: Christiane
authors.initials: C
authors.lastname: Jung
authors.forename: Frank
authors.initials: F
authors.lastname: Hannemann
authors.forename: Rita
authors.initials: R
authors.lastname: Bernhardt
authors.forename: Marcus
authors.initials: M
authors.lastname: Galander
authors.forename: Friedhelm
authors.initials: F
authors.lastname: Lendzian
authors.forename: Udo
authors.initials: U
authors.lastname: Heinemann
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D000325:Adrenodoxin / Q000737:chemistry* / Q000528:radiation effects*; D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D007700:Kinetics; D008027:Light; D008958:Models, Molecular; D010084:Oxidation-Reduction / Q000528:radiation effects; D011487:Protein Conformation; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D000325:Adrenodoxin; D015082:2,2'-Dipyridyl; D012428:Ruthenium