title: Specific Interactions between the ferredoxin and terminal oxygenase components of a class IIB Rieske nonheme iron oxygenase, carbazole 1,9a-dioxygenase.
abstract: Carbazole 1,9a-dioxygenase (CARDO) consists of terminal oxygenase (Oxy), ferredoxin (Fd), and ferredoxin reductase (Red) components and is a member of the Rieske nonheme iron oxygenases. Rieske nonheme iron oxygenases are divided into five subclasses (IA, IB, IIA, IIB, and III) based on the number of constituents and the nature of their redox centers. Each component of a class IIB CARDO from Nocardioides aromaticivorans IC177 was purified, and the interchangeability of the electron transfer reactions with each component from the class III CARDOs was investigated. Despite the fact that the Fds of both classes are Rieske-type, strict specificities between the Oxy and Fd components were observed. On the other hand, the Fd and Red components were interchangeable, even though the Red components differ in cofactor composition; the class IIB Red contains flavin-adenine-dinucleotide (FAD)- and NADH-binding domains, whereas the class III Red has a chloroplast-type [2Fe-2S] cluster in addition to the FAD- and NADH-binding domains. The crystal structures of the class IIB Oxy and Fd components were compared to the previously reported Fd:Oxy complex structure of class III CARDO. This comparison suggested residues in common between class IIB and class III CARDOs that are important for interactions between Fd and Oxy. In the class IIB CARDOs, these included His75 and Glu71 in Fd and Lys20 and Glu357 in Oxy for electrostatic interactions, and Phe74 and Pro90 in Fd and Trp21, Leu359, and Val367 in Oxy for hydrophobic interactions. The residues that formed the interacting surface but were not conserved between classes were thought to be necessary to form the appropriate geometry and to determine electron transfer specificity between Fd and Oxy.
authors.affiliation: Biotechnology Research Center, The University of Tokyo, Tokyo, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Inoue
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ashikawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Umeda
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Abo
authors.forename: Junichi
authors.initials: J
authors.lastname: Katsuki
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Usami
authors.forename: Haruko
authors.initials: H
authors.lastname: Noguchi
authors.forename: Zui
authors.initials: Z
authors.lastname: Fujimoto
authors.forename: Tohru
authors.initials: T
authors.lastname: Terada
authors.forename: Hisakazu
authors.initials: H
authors.lastname: Yamane
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nojiri
mesh_terms: D000192:Actinomycetales / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D018360:Crystallography, X-Ray; D049308:Dioxygenases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D005288:Ferredoxins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D010105:Oxygenases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005288:Ferredoxins; D021122:Protein Subunits; D010105:Oxygenases; D049308:Dioxygenases; C108434:carbazole 1,9a-dioxygenase