title: Cytochrome d axial ligand of the bd-type terminal quinol oxidase from Escherichia coli.
abstract: Using various spectroscopic techniques, we studied the structure of the dioxygen reduction site of the bd-type terminal quinol oxidase in the aerobic respiratory chain of Escherichia coli. Resonance Raman and FT-IR spectroscopies identified the v(Fe(2+)-CO) and v(C-O) stretching frequencies at 471 and 1980.7 cm-1, respectively, at the cytochrome d center of the dithionite-reduced CO-bound enzyme. The CO ligation in the cytochrome bd complex is considerably different from those of the heme-copper terminal oxidases. Anaerobic addition of NO to the air-oxidized enzyme caused an exchange of cytochrome d-bound dioxygen with NO leading to an appearance of cytochrome d-NO EPR signal. But there is no superhyperfine structure originating from the cytochrome d proximal 14N ligand in the central resonance of the NO EPR signal. These results suggest that cytochrome d axial ligand of the cytochrome bd complex is likely a histidine residue in an anomalous condition or other than a histidine residue and, therefore, the molecular structure around the dioxygen-binding site is different from that of the heme-copper terminal oxidases.
authors.affiliation: Department of Life Science, Faculty of Science, Himeji Institute of Technology, Hyogo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tsubaki
authors.forename: T
authors.initials: T
authors.lastname: Uno
authors.forename: H
authors.initials: H
authors.lastname: Hori
authors.forename: T
authors.initials: T
authors.lastname: Mogi
authors.forename: Y
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Y
authors.initials: Y
authors.lastname: Anraku
mesh_terms: D001665:Binding Sites; D002248:Carbon Monoxide / Q000378:metabolism; D003573:Cytochrome b Group; D017937:Cytochrome d Group / Q000737:chemistry* / Q000378:metabolism; D003580:Cytochromes / Q000378:metabolism; D004227:Dithionite / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D045222:Electron Transport Chain Complex Proteins; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006639:Histidine / Q000378:metabolism; D006860:Hydrogen Bonding; D009569:Nitric Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D004227:Dithionite; D009569:Nitric Oxide; D006639:Histidine; D002248:Carbon Monoxide; D017937:Cytochrome d Group; D010088:Oxidoreductases; C020094:duroquinol oxidase; C040077:cytochrome bd terminal oxidase complex, E coli