title: The proton pumping pathway of bovine heart cytochrome c oxidase.
abstract: X-ray structures of bovine heart cytochrome c oxidase have suggested that the enzyme, which reduces O(2) in a process coupled with a proton pumping process, contains a proton pumping pathway (H-pathway) composed of a hydrogen bond network and a water channel located in tandem across the enzyme. The hydrogen bond network includes the peptide bond between Tyr-440 and Ser-441, which could facilitate unidirectional proton transfer. Replacement of a possible proton-ejecting aspartate (Asp-51) at one end of the H-pathway with asparagine, using a stable bovine gene expression system, abolishes the proton pumping activity without influencing the O(2) reduction function. Blockage of either the water channel by a double mutation (Val386Leu and Met390Trp) or proton transfer through the peptide by a Ser441Pro mutation was found to abolish the proton pumping activity without impairment of the O(2) reduction activity. These results significantly strengthen the proposal that H-pathway is involved in proton pumping.
authors.affiliation: Department of Biochemistry and Integrative Medical Biology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Kunitoshi
authors.initials: K
authors.lastname: Shimokata
authors.forename: Yukie
authors.initials: Y
authors.lastname: Katayama
authors.forename: Haruka
authors.initials: H
authors.lastname: Murayama
authors.forename: Makoto
authors.initials: M
authors.lastname: Suematsu
authors.forename: Tomitake
authors.initials: T
authors.lastname: Tsukihara
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Muramoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Aoyama
authors.forename: Shinya
authors.initials: S
authors.lastname: Yoshikawa
authors.forename: Hideo
authors.initials: H
authors.lastname: Shimada
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D002417:Cattle; D003576:Electron Transport Complex IV / Q000378:metabolism / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D008956:Models, Chemical; D016296:Mutagenesis; D009206:Myocardium / Q000201:enzymology*; D010100:Oxygen / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D011522:Protons; D012694:Serine / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
chemical_list: D010455:Peptides; D011522:Protons; D001224:Aspartic Acid; D014443:Tyrosine; D012694:Serine; D003576:Electron Transport Complex IV; D010100:Oxygen