title: Characterization of the ubiquinol oxidation sites in cytochromes bo and bd from Escherichia coli using aurachin C analogues.
abstract: Natural aurachin C is the most potent inhibitor of oxidation of ubiquinols by cytochromes bo and bd from Escherichia coli. To probe the structural properties of the substrate oxidation site in the ubiquinol oxidases, we synthesized a systematic set of aurachin C analogues (N-hydroxy-4-quinolone derivatives) and examined how their structure affects their activity towards cytochromes bo and bd, which are structurally unrelated. We found that the presence of the 3-methyl group of the 2-n-decyl and 2-n-undecyl derivatives increased the inhibitory potency towards both enzymes, probably due to a local steric congestion that allows favorable interaction of the alkyl tail with the enzyme. Increase in the chain length of the 3-alkyl tail of the 2-n-undecyl derivatives decreased the inhibitory potency only in cytochrome bo, indicating that the binding site for the alkyl tails of cytochrome bo is smaller than that of cytochrome bd. Based on these findings, we discuss the differences in the molecular mechanism of substrate oxidation by these two terminal ubiquinol oxidases.
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan. miyoshi@kais. kyoto-u.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Miyoshi
authors.forename: K
authors.initials: K
authors.lastname: Takegami
authors.forename: K
authors.initials: K
authors.lastname: Sakamoto
authors.forename: T
authors.initials: T
authors.lastname: Mogi
authors.forename: H
authors.initials: H
authors.lastname: Iwamura
mesh_terms: D001665:Binding Sites; D003573:Cytochrome b Group; D003580:Cytochromes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D045222:Electron Transport Chain Complex Proteins; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D009154:Mutation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015363:Quinolones / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D015363:Quinolones; C052096:aurachin C; D014451:Ubiquinone; C017168:cytochrome bo, E coli; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli; C003741:ubiquinol