title: Probing molecular structure of dioxygen reduction site of bacterial quinol oxidases through ligand binding to the redox metal centers.
abstract: Cytochromes bo and bd are structurally unrelated terminal ubiquinol oxidases in the aerobic respiratory chain of Escherichia coli. The high-spin heme o-CuB binuclear center serves as the dioxygen reduction site for cytochrome bo, and the heme b595-heme d binuclear center for cytochrome bd. CuB coordinates three histidine ligands and serves as a transient ligand binding site en route to high-spin heme o one-electron donor to the oxy intermediate, and a binding site for bridging ligands like cyanide. In addition, it can protect the dioxygen reduction site through binding of a peroxide ion in the resting state, and connects directly or indirectly Tyr288 and Glu286 to carry out redox-driven proton pumping in the catalytic cycle. Contrary, heme b595 of cytochrome bd participate a similar role to CuB in ligand binding and dioxygen reduction but cannot perform such versatile roles because of its rigid structure.
authors.affiliation: Department of Life Science, Faculty of Science, Himeji Institute of Technology, Akou-gun, Hyogo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tsubaki
authors.forename: H
authors.initials: H
authors.lastname: Hori
authors.forename: T
authors.initials: T
authors.lastname: Mogi
mesh_terms: D001665:Binding Sites; D003573:Cytochrome b Group; D003580:Cytochromes / Q000737:chemistry* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D045222:Electron Transport Chain Complex Proteins; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D008024:Ligands; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D020836:Protein Structure, Quaternary
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV