title: Electron transfer complex formation between oxygenase and ferredoxin components in Rieske nonheme iron oxygenase system.
abstract: Carbazole 1,9a-dioxygenase (CARDO), a member of the Rieske nonheme iron oxygenase system (ROS), consists of a terminal oxygenase (CARDO-O) and electron transfer components (ferredoxin [CARDO-F] and ferredoxin reductase [CARDO-R]). We determined the crystal structures of the nonreduced, reduced, and substrate-bound binary complexes of CARDO-O with its electron donor, CARDO-F, at 1.9, 1.8, and 2.0 A resolutions, respectively. These structures provide the first structure-based interpretation of intercomponent electron transfer between two Rieske [2Fe-2S] clusters of ferredoxin and oxygenase in ROS. Three molecules of CARDO-F bind to the subunit boundary of one CARDO-O trimeric molecule, and specific binding created by electrostatic and hydrophobic interactions with conformational changes suitably aligns the two Rieske clusters for electron transfer. Additionally, conformational changes upon binding carbazole resulted in the closure of a lid over the substrate-binding pocket, thereby seemingly trapping carbazole at the substrate-binding site.
authors.affiliation: Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ashikawa
authors.forename: Zui
authors.initials: Z
authors.lastname: Fujimoto
authors.forename: Haruko
authors.initials: H
authors.lastname: Noguchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Habe
authors.forename: Toshio
authors.initials: T
authors.lastname: Omori
authors.forename: Hisakazu
authors.initials: H
authors.lastname: Yamane
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nojiri
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002227:Carbazoles / Q000737:chemistry; D019281:Dimerization; D049308:Dioxygenases / Q000737:chemistry* / Q000378:metabolism; D014450:Electron Transport Complex III / Q000737:chemistry*; D004583:Electrons; D005288:Ferredoxins / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010100:Oxygen / Q000737:chemistry; D010105:Oxygenases / Q000737:chemistry*; D011549:Pseudomonas / Q000201:enzymology; D017382:Reactive Oxygen Species; D013056:Spectrophotometry, Ultraviolet; D055672:Static Electricity; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D002227:Carbazoles; D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D017382:Reactive Oxygen Species; C037989:Rieske iron-sulfur protein; C041514:carbazole; D010105:Oxygenases; D049308:Dioxygenases; C108434:carbazole 1,9a-dioxygenase; D014450:Electron Transport Complex III; D010100:Oxygen