Yeast aconitase in two locations and two metabolic pathways: seeing small amounts is believing

Mol Biol Cell. 2005 Sep;16(9):4163-71. doi: 10.1091/mbc.e04-11-1028. Epub 2005 Jun 22.


The distribution of identical enzymatic activities between different subcellular compartments is a fundamental process of living cells. At present, the Saccharomyces cerevisiae aconitase enzyme has been detected only in mitochondria, where it functions in the tricarboxylic acid (TCA) cycle and is considered a mitochondrial matrix marker. We developed two strategies for physical and functional detection of aconitase in the yeast cytosol: 1) we fused the alpha peptide of the beta-galactosidase enzyme to aconitase and observed alpha complementation in the cytosol; and 2) we created an ACO1-URA3 hybrid gene, which allowed isolation of strains in which the hybrid protein is exclusively targeted to mitochondria. These strains display a specific phenotype consistent with glyoxylate shunt elimination. Together, our data indicate that yeast aconitase isoenzymes distribute between two distinct subcellular compartments and participate in two separate metabolic pathways; the glyoxylate shunt in the cytosol and the TCA cycle in mitochondria. We maintain that such dual distribution phenomena have a wider occurrence than recorded currently, the reason being that in certain cases there is a small fraction of one of the isoenzymes, in one of the locations, making its detection very difficult. We term this phenomenon of highly uneven isoenzyme distribution "eclipsed distribution."

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetates
  • Aconitate Hydratase / deficiency
  • Aconitate Hydratase / genetics
  • Aconitate Hydratase / metabolism*
  • Amino Acid Sequence
  • Cytosol / enzymology
  • Ethanol
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Iron Regulatory Protein 1 / genetics
  • Iron Regulatory Protein 1 / metabolism
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Mitochondria / metabolism
  • Molecular Sequence Data
  • Mutation
  • Organisms, Genetically Modified
  • Protein Transport / physiology
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Signal Transduction / genetics
  • Signal Transduction / physiology*
  • beta-Galactosidase / metabolism


  • Acetates
  • Fungal Proteins
  • Isoenzymes
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae Proteins
  • Ethanol
  • beta-Galactosidase
  • Aconitate Hydratase
  • Iron Regulatory Protein 1