Characterization of the FET4 protein of yeast. Evidence for a direct role in the transport of iron.
The low affinity Fe2+ uptake system of Saccharomyces cerevisiae requires the FET4 gene. In this report, we present evidence that FET4 encodes the Fe2+ transporter protein of this system. Antibodies prepared against FET4 detected two distinct proteins with molecular masses of 63 and 68 kDa. In vitro synthesis of FET4 suggested that the 68-kDa form is the primary translation product, and the 63-kDa form may be generated by proteolytic cleavage of the full-length protein. Consistent with its role as an Fe2+ transporter, FET4 is an integral membrane protein present in the plasma membrane. The level of FET4 closely correlated with uptake activity over a broad range of expression levels and is itself regulated by iron. Furthermore, mutations in FET4 can alter the kinetic properties of the low affinity uptake system, suggesting a direct interaction between FET4 and its Fe2+ substrate. Mutations affecting potential Fe2+ ligands located in the predicted transmembrane domains of FET4 significantly altered the apparent Km and/or Vmax of the low affinity system. These mutations may identify residues involved in Fe2+ binding during transport.
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Department of Biochemistry and Molecular Biology, University of Minnesota, Duluth, Minnesota 55812, USA.
Bridgham
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Broderius
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Eide
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D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D000079922:Copper Transport Proteins; D019084:Fluorescent Antibody Technique, Indirect; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D033862:Iron-Binding Proteins; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008961:Models, Structural; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
D002352:Carrier Proteins; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; C105847:FET4 protein, S cerevisiae; D033862:Iron-Binding Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D007501:Iron