THE MENKES-WILSON-DISEASE GENE HOMOLOG IN YEAST PROVIDES COPPER TO A CERULOPLASMIN-LIKE OXIDASE REQUIRED FOR IRON UPTAKE

The CCC2 gene of the yeast Saccharomyces cerevisiae is homologous to t he human genes defective in Wilson disease and Menkes disease. A bioch emical hallmark of these diseases is a deficiency of copper in cerulop lasmin and other copper proteins found in extracytosolic compartments. Here we demonstrate that disruption of the yeast CCC2 gene results in defects in respiration and iron uptake. These defects could be revers ed by supplementing cells with copper. suggesting that CCC2 mutant cel ls were copper deficient, However, cytosolic copper levels and copper uptake were normal. Instead, CCC2 mutant cells lacked a copper-depende nt oxidase activity associated with the estracytosolic domain of the F ET3-encoded protein, a ceruloplasmin homologue previously shown to be necessary for high-affinity iron uptake in yeast. Copper restored oxid ase activity both in vitro and in vivo, paralleling the ability of cop per to restore respiration and iron uptake. These results suggest that the CCC2-encoded protein is required for the export of copper from th e cytosol into an estracytosolic compartment, supporting the proposal that intracellular copper transport is impaired in Wilson disease and Menkes disease.