Ubiquinone accumulates in the mitochondria of yeast mutated in the ubiquinone binding protein, Qcr8p

Biochem Biophys Res Commun. 2006 May 26;344(1):241-5. doi: 10.1016/j.bbrc.2006.03.110. Epub 2006 Mar 29.

Abstract

In Saccharomyces cerevisiae, the trans-membrane helix of Qcr8p, the ubiquinone binding protein of complex III, contributes to the Q binding site. In wild-type cells, residue 62 of the helix is non-polar (proline). Substitution of proline 62 with a polar, uncharged residue does not impair the ability of the cells to respire, complex III assembly is unaffected, ubiquinone occupancy of the Q binding site is unchanged, and mitochondrial ubiquinone levels are in the wild-type range. Substitution with a +1 charged residue is associated with partial respiratory competence, impaired complex III assembly, and loss of cytochrome b. Although ubiquinone occupancy of the Q binding site is similar to wild-type, total mitochondrial ubiquinone doubled in these mutants. Mutants with a +2 charged substitution at position 62 are unable to respire. These results suggest that the accumulation of ubiquinone in the mitochondria may be a compensatory mechanism for impaired electron transport at cytochrome b.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Binding Sites
  • Electron Transport Complex III / genetics*
  • Mitochondria / metabolism*
  • Molecular Sequence Data
  • Mutation
  • Proline / chemistry
  • Proline / genetics
  • Saccharomyces cerevisiae / chemistry
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics*
  • Ubiquinone / analysis
  • Ubiquinone / metabolism*

Substances

  • Saccharomyces cerevisiae Proteins
  • Ubiquinone
  • Proline
  • Qcr8 protein, S cerevisiae
  • Electron Transport Complex III