title: Modifications on the hydrogen bond network by mutations of Escherichia coli copper efflux oxidase affect the process of proton transfer to dioxygen leading to alterations of enzymatic activities.
abstract: CueO has a branched hydrogen bond network leading from the exterior of the protein molecule to the trinuclear copper center. This network transports protons in the four-electron reduction of dioxygen. We replaced the acidic Glu506 and Asp507 residues with the charged and uncharged amino acid residues. Peculiar changes in the enzyme activity of the mutants relative to the native enzyme indicate that an acidic amino acid residue at position 506 is essential for effective proton transport. The Ala mutation resulted in the formation of a compensatory hydrogen bond network with one or two extra water molecules. On the other hand, the Ile mutation resulted in the complete shutdown of the hydrogen bond network leading to loss of enzymatic activities of CueO. In contrast, the hydrogen bond network without the proton transport function was constructed by the Gln mutation. These results exerted on the hydrogen bond network in CueO are discussed in comparison with proton transfers in cytochrome oxidase.
authors.affiliation: Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Kajikawa
authors.forename: Kunishige
authors.initials: K
authors.lastname: Kataoka
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakurai
mesh_terms: D019943:Amino Acid Substitution; D001224:Aspartic Acid / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D003300:Copper / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism; D006860:Hydrogen Bonding; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D011522:Protons
chemical_list: D029968:Escherichia coli Proteins; D011522:Protons; D001224:Aspartic Acid; D018698:Glutamic Acid; D003300:Copper; D010088:Oxidoreductases; C499679:cueO protein, E coli; D003576:Electron Transport Complex IV; D010100:Oxygen