The FET3 gene product required for high affinity iron transport in yeast is a cell surface ferroxidase.
The yeast FET3 gene is required for high affinity iron transport (Askwith, C., Eide, D., Ho, A. V., Bernard, P. S., Li, L., Davis-Kaplan, S., Sipe, D. M., and Kaplan, J. (1994) Cell 76, 403-410). The gene has extensive sequence homology to the family of multi-copper oxidases. In this communication, we demonstrate that the gene product is a cell surface ferroxidase involved in iron transport. Cells that contain a functional FET3 gene product exhibited an iron-dependent non-mitochondrial increase in oxygen consumption. Comparison of the rate of iron oxidation to O2 consumption yielded an approximate value of 4:1, as predicted for a ferroxidase. Spheroplasts obtained from cells grown under low iron conditions also displayed an iron-dependent increase in O2 consumption. Treatment of spheroplasts with trypsin or affinity-purified antibodies directed against the putative external ferroxidase domain of Fet3 had no effect on basal O2 consumption but inhibited the iron-dependent increase in O2 consumption. Anti-peptide antibodies directed against the cytosolic domain of Fet3 had no effect on O2 consumption. These studies indicate that Fet3 is a plasma membrane ferroxidase required for high affinity iron uptake, in which the ferroxidase-containing domain is localized on the external cell surface.
Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84132.
D M
DM
De Silva
C C
CC
Askwith
D
D
Eide
J
J
Kaplan
D000595:Amino Acid Sequence; D001692:Biological Transport; D002462:Cell Membrane / Q000201:enzymology; D002570:Ceruloplasmin / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins
D029701:Saccharomyces cerevisiae Proteins; D007501:Iron; D010088:Oxidoreductases; D002570:Ceruloplasmin; C085513:FET3 protein, S cerevisiae; D010100:Oxygen