A pathogenic mutation in cytochrome c oxidase results in impaired proton pumping while retaining O2-reduction activity

Ida Namslauer, Hyun Ju Lee, Robert B. Gennis, Peter Brzezinski

Research output: Contribution to journalArticle

Abstract

In this work we have investigated the effect of a pathogenic mitochondrial DNA mutation found in human colon cells, at a functional-molecular level. The mutation results in the amino-acid substitution Tyr19His in subunit I of the human CytcO and it is associated with respiratory deficiency. It was introduced into Rhodobacter sphaeroides, which carries a cytochrome c oxidase (cytochrome aa3) that serves as a model of the mitochondrial counterpart. The residue is situated in the middle of a pathway that is used to transfer substrate protons as well as protons that are pumped across the membrane. The Tyr33His (equivalent residue in the bacterial CytcO) structural variant of the enzyme was purified and its function was investigated. The results show that in the structurally altered CytcO the activity decreased due to slowed proton transfer; proton transfer from an internal proton donor, the highly-conserved Glu286, to the catalytic site was slowed by a factor of ~5, while reprotonation of the Glu from solution was slowed by a factor of ~40. In addition, in the structural variant proton pumping was completely impaired. These results are explained in terms of introduction of a barrier for proton transfer through the D pathway and changes in the coordination of water molecules surrounding the Glu286 residue. The study offers an explanation, at the molecular level, to the link between a specific amino-acid substitution and a pathogenic phenotype identified in human colon cells.

Original languageEnglish (US)
Pages (from-to)550-556
Number of pages7
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1797
Issue number5
DOIs
StatePublished - May 1 2010

    Fingerprint

Keywords

  • Cytochrome aa
  • Deficiency
  • Electron transfer
  • Mitochondria
  • Mitochondrial disease
  • MtDNA
  • Respiratory chain

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

Cite this