Identification of Subunit G of Yeast Mitochondrial F1F0-ATP Synthase, a Protein Required for Maximal Activity of Cytochrome C Oxidase

Eur J Biochem. 1999 Jun;262(2):315-23. doi: 10.1046/j.1432-1327.1999.00345.x.

Abstract

By means of a yeast genome database search, we have identified an open reading frame located on chromosome XVI of Saccharomyces cerevisiae that encodes a protein with 53% amino acid similarity to the 11.3-kDa subunit g of bovine mitochondrial F1F0-ATP synthase. We have designated this ORF ATP20, and its product subunit g. A null mutant strain, constructed by insertion of the HIS3 gene into the coding region of ATP20, retained oxidative phosphorylation function. Assembly of F1F0-ATP synthase in the atp20-null strain was not affected in the absence of subunit g and levels of oligomycin-sensitive ATP hydrolase activity in mitochondria were normal. Immunoprecipitation of F1F0-ATP synthase from mitochondrial lysates prepared from atp20-null cells expressing a variant of subunit g with a hexahistidine motif indicated that this polypeptide was associated with other well-characterized subunits of the yeast complex. Whilst mitochondria isolated from the atp20-null strain had the same oxidative phosphorylation efficiency (ATP : O) as that of the control strain, the atp20-null strain displayed approximately a 30% reduction in both respiratory capacity and ATP synthetic rate. The absence of subunit g also reduced the activity of cytochrome c oxidase, and altered the kinetic control of this complex as demonstrated by experiments titrating ATP synthetic activity with cyanide. These results indicate that subunit g is associated with F1F0-ATP synthase and is required for maximal levels of respiration, ATP synthesis and cytochrome c oxidase activity in yeast.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cattle
  • DNA Primers
  • Electron Transport Complex IV / chemistry
  • Electron Transport Complex IV / metabolism*
  • Membrane Proteins / chemistry
  • Membrane Proteins / metabolism
  • Molecular Sequence Data
  • Oxidative Phosphorylation
  • Proton-Translocating ATPases / chemistry
  • Proton-Translocating ATPases / metabolism*
  • Saccharomyces cerevisiae / enzymology*
  • Sequence Homology, Amino Acid

Substances

  • DNA Primers
  • Membrane Proteins
  • Electron Transport Complex IV
  • Proton-Translocating ATPases