The proton pumping pathway of bovine heart cytochrome c oxidase

Kunitoshi Shimokata, Yukie Katayama, Haruka Murayama, Makoto Suematsu, Tomitake Tsukihara, Kazumasa Muramoto, Hiroshi Aoyama, Shinya Yoshikawa, Hideo Shimada

Research output: Contribution to journalArticlepeer-review

114 Citations (Scopus)


X-ray structures of bovine heart cytochrome c oxidase have suggested that the enzyme, which reduces O2 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 O2 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.

Original languageEnglish
Pages (from-to)4200-4205
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number10
Publication statusPublished - 2007 Mar 6


  • HeLa cell
  • Keto-enol tautomerism
  • Mitochondrial import
  • Mutagenesis
  • Peptide bond

ASJC Scopus subject areas

  • General


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