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Electron Transfer Complex Formation between Oxygenase and Ferredoxin Components in Rieske Nonheme Iron Oxygenase System

2006; Elsevier BV; Volume: 14; Issue: 12 Linguagem: Inglês

10.1016/j.str.2006.10.004

1878-4186

Yuji Ashikawa, Zui Fujimoto, Haruko Noguchi, Hiroshi Habe, Toshio Omori, Hisakazu Yamane, Hideaki Nojiri,

Photosynthetic Processes and Mechanisms

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 Å 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.