FET3/YMR058W Summary Help

Standard Name FET3 1
Systematic Name YMR058W
Feature Type ORF, Verified
Description Ferro-O2-oxidoreductase; multicopper oxidase that oxidizes ferrous (Fe2+) to ferric iron (Fe3+) for subsequent cellular uptake by transmembrane permease Ftr1p; required for high-affinity iron uptake and involved in mediating resistance to copper ion toxicity, belongs to class of integral membrane multicopper oxidases; protein abundance increases in response to DNA replication stress (2, 3, 4, 5 and see Summary Paragraph)
Name Description FErrous Transport 1
Chromosomal Location
ChrXIII:388822 to 390732 | ORF Map | GBrowse
Gene Ontology Annotations All FET3 GO evidence and references
  View Computational GO annotations for FET3
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 22 genes
Classical genetics
reduction of function
Large-scale survey
110 total interaction(s) for 93 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 9
  • Affinity Capture-RNA: 2
  • Affinity Capture-Western: 1
  • FRET: 1
  • PCA: 30
  • Two-hybrid: 1

Genetic Interactions
  • Dosage Growth Defect: 2
  • Dosage Lethality: 1
  • Dosage Rescue: 3
  • Negative Genetic: 25
  • Phenotypic Enhancement: 3
  • Positive Genetic: 3
  • Synthetic Growth Defect: 19
  • Synthetic Lethality: 7
  • Synthetic Rescue: 3

Expression Summary
Length (a.a.) 636
Molecular Weight (Da) 72,360
Isoelectric Point (pI) 4.45
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXIII:388822 to 390732 | ORF Map | GBrowse
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1911 388822..390732 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | E.C. | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000004662

Fet3p and Ftr1p comprise the cell-surface (6, 7, 1) high-affinity iron uptake system (8, 9) which imports iron when it is present in low concentrations. Fet3p is a multicopper ferroxidase (6, 7, 1, 10) that receives iron(II) ions from cell-surface iron reductases such as Fre1p and Fre2p and passes iron(III) ions to the iron permease Ftr1p (9). S. cerevisiae is also capable of acquiring iron via a low-affinity uptake system (Fet4p) or via bacterial siderophores.

For proper cell-surface targeting, the Fet3p-Ftr1p complex must be assembled in the endoplasmic reticulum (11). Without Fet3p, Ftr1p is retained in the ER (9). Without Ftr1p, Fet3p proceeds as far as the Golgi apparatus, but is misglycosylated and recycled back to the ER (12). Fet3p acquires copper, which is necessary for its oxidase activity (7, 1), from Ccc2p in a post-Golgi compartment (7, 13, 14, 15). Copper acquisition requires genes involved in vacuolar assembly (15) (including TFP1 (16) and VPS41 (14)) and the presence of chloride as an allosteric effector, not as a counter-charge (17).

The Fet3p ferroxidase site is also capable of oxidizing copper(I) (3, 18) and is inhibited by azide (10). Holo-Fet3p contains four copper(I) ions (10).

Transcription of FET3 and FTR1 is inhibited by high iron and induced under conditions of low iron (7, 1, 19, 20) or low oxygen (20, 21, 22). FET3 and FTR1 are induced by Aft1p (9, 13, 20, 23, 24, 25, 26, 27) and Aft2p (27), which are inhibited by a signal from mitochondrial iron-sulfur clusters, not cytosolic iron (28, 29). In mutants lacking the yeast frataxin homolog Yfh1p, iron accumulates in the mitochondria and FET3 and FTR1 are induced 10- to 50-fold (30). Independent of iron levels, FET3 and FTR1 are induced under glucose depletion by Aft1p (31); Snf4p and Snf1p are required. Copper also induces transcription of FET3 and FTR1 via Aft1p (26), and FET3 is induced by chloroquine (32).

Exposure to high iron initiates the degradation of the Fet3p-Ftr1p complex. In high iron, Ftr1p becomes hyperubiquitinated, and the complex is targeted to the vacuole via endocytosis. Degradation requires iron to be transported through Ftr1p; the presence of iron in the cytosol is not sufficient (33).

fet3 mutants exhibit several phenotypes which can be suppressed by growing the cells in high iron. Among them are: deficient growth in low iron (1), on ethanol (indicating a defect in respiration) (7), on galactose/raffinose (34), at alkaline pH (35), or at pH7 in minimal media (16). fet3 mutants are sensitive to copper (3, 36, 37) and other transition metals (37); the cell compensates for deletion of FET3 by increasing expression of FET4, which imports other transition metals promiscuously (37).

Fet3p is homologous to two human proteins. Ceruloplasmin (CP) (OMIM) is a soluble protein highly expressed in liver and found in serum; deficiency of CP causes a pleiotropic condition called aceruloplasminemia (OMIM). Hephaestin (OMIM) is an X-linked gene found primarily at the tips of intestinal villi. Human hephaestin complements deletion of FET3 (38), as does C. albicans FET3 (39). A truncated, soluble form of Fet3p is blue in color (2) and complements deletion of ceruloplasmin in mice (40). Coordinate expression in S. cerevisiae of both fio1+ and fip1+ from S. pombe, the homologs of FET3 and FTR1, respectively, complements deletion of FET3, indicating that fio1+ is a functional homolog of Fet3p but is incapable of interacting with Ftr1p (19).

Last updated: 2005-07-27 Contact SGD

References cited on this page View Complete Literature Guide for FET3
1) Askwith C, et al.  (1994) The FET3 gene of S. cerevisiae encodes a multicopper oxidase required for ferrous iron uptake. Cell 76(2):403-10
2) Hassett RF, et al.  (1998) Spectral and kinetic properties of the Fet3 protein from Saccharomyces cerevisiae, a multinuclear copper ferroxidase enzyme. J Biol Chem 273(36):23274-82
3) Shi X, et al.  (2003) Fre1p Cu2+ reduction and Fet3p Cu1+ oxidation modulate copper toxicity in Saccharomyces cerevisiae. J Biol Chem 278(50):50309-15
4) Tkach JM, et al.  (2012) Dissecting DNA damage response pathways by analysing protein localization and abundance changes during DNA replication stress. Nat Cell Biol 14(9):966-76
5) Batista-Nascimento L, et al.  (2013) Yeast protective response to arsenate involves the repression of the high affinity iron uptake system. Biochim Biophys Acta 1833(5):997-1005
6) De Silva DM, et al.  (1995) The FET3 gene product required for high affinity iron transport in yeast is a cell surface ferroxidase. J Biol Chem 270(3):1098-101
7) Yuan DS, et al.  (1995) The Menkes/Wilson disease gene homologue in yeast provides copper to a ceruloplasmin-like oxidase required for iron uptake. Proc Natl Acad Sci U S A 92(7):2632-6
8) Dix DR, et al.  (1994) The FET4 gene encodes the low affinity Fe(II) transport protein of Saccharomyces cerevisiae. J Biol Chem 269(42):26092-9
9) Stearman R, et al.  (1996) A permease-oxidase complex involved in high-affinity iron uptake in yeast. Science 271(5255):1552-7
10) de Silva D, et al.  (1997) Purification and characterization of Fet3 protein, a yeast homologue of ceruloplasmin. J Biol Chem 272(22):14208-13
11) Wang TP, et al.  (2003) Targeted suppression of the ferroxidase and iron trafficking activities of the multicopper oxidase Fet3p from Saccharomyces cerevisiae. J Biol Inorg Chem 8(6):611-20
12) Sato M, et al.  (2004) Endoplasmic reticulum quality control of unassembled iron transporter depends on Rer1p-mediated retrieval from the golgi. Mol Biol Cell 15(3):1417-24
13) Lin SJ, et al.  (1997) A role for the Saccharomyces cerevisiae ATX1 gene in copper trafficking and iron transport. J Biol Chem 272(14):9215-20
14) Radisky DC, et al.  (1997) Characterization of VPS41, a gene required for vacuolar trafficking and high-affinity iron transport in yeast. Proc Natl Acad Sci U S A 94(11):5662-6
15) Yuan DS, et al.  (1997) Restriction of copper export in Saccharomyces cerevisiae to a late Golgi or post-Golgi compartment in the secretory pathway. J Biol Chem 272(41):25787-93
16) Gaxiola RA, et al.  (1998) The yeast CLC chloride channel functions in cation homeostasis. Proc Natl Acad Sci U S A 95(7):4046-50
17) Davis-Kaplan SR, et al.  (1998) Chloride is an allosteric effector of copper assembly for the yeast multicopper oxidase Fet3p: an unexpected role for intracellular chloride channels. Proc Natl Acad Sci U S A 95(23):13641-5
18) Stoj C and Kosman DJ  (2003) Cuprous oxidase activity of yeast Fet3p and human ceruloplasmin: implication for function. FEBS Lett 554(3):422-6
19) Askwith C and Kaplan J  (1997) An oxidase-permease-based iron transport system in Schizosaccharomyces pombe and its expression in Saccharomyces cerevisiae. J Biol Chem 272(1):401-5
20) Hassett RF, et al.  (1998) Regulation of high affinity iron uptake in the yeast Saccharomyces cerevisiae. Role of dioxygen and Fe. J Biol Chem 273(13):7628-36
21) Vasconcelles MJ, et al.  (2001) Identification and characterization of a low oxygen response element involved in the hypoxic induction of a family of Saccharomyces cerevisiae genes. Implications for the conservation of oxygen sensing in eukaryotes. J Biol Chem 276(17):14374-84
22) Jensen LT and Culotta VC  (2002) Regulation of Saccharomyces cerevisiae FET4 by oxygen and iron. J Mol Biol 318(2):251-60
23) Yamaguchi-Iwai Y, et al.  (1995) AFT1: a mediator of iron regulated transcriptional control in Saccharomyces cerevisiae. EMBO J 14(6):1231-9
24) Yamaguchi-Iwai Y, et al.  (1996) Iron-regulated DNA binding by the AFT1 protein controls the iron regulon in yeast. EMBO J 15(13):3377-84
25) Casas C, et al.  (1997) The AFT1 transcriptional factor is differentially required for expression of high-affinity iron uptake genes in Saccharomyces cerevisiae. Yeast 13(7):621-37
26) Gross C, et al.  (2000) Identification of the copper regulon in Saccharomyces cerevisiae by DNA microarrays. J Biol Chem 275(41):32310-6
27) Rutherford JC, et al.  (2003) Aft1p and Aft2p mediate iron-responsive gene expression in yeast through related promoter elements. J Biol Chem 278(30):27636-43
28) Chen OS, et al.  (2004) Transcription of the yeast iron regulon does not respond directly to iron but rather to iron-sulfur cluster biosynthesis. J Biol Chem 279(28):29513-8
29) Rutherford JC, et al.  (2005) Activation of the iron regulon by the yeast Aft1/Aft2 transcription factors depends on mitochondrial but not cytosolic iron-sulfur protein biogenesis. J Biol Chem 280(11):10135-40
30) Babcock M, et al.  (1997) Regulation of mitochondrial iron accumulation by Yfh1p, a putative homolog of frataxin. Science 276(5319):1709-12
31) Haurie V, et al.  (2003) The Snf1 protein kinase controls the induction of genes of the iron uptake pathway at the diauxic shift in Saccharomyces cerevisiae. J Biol Chem 278(46):45391-6
32) Emerson LR, et al.  (2002) Relationship between chloroquine toxicity and iron acquisition in Saccharomyces cerevisiae. Antimicrob Agents Chemother 46(3):787-96
33) Felice MR, et al.  (2005) Post-transcriptional regulation of the yeast high affinity iron transport system. J Biol Chem 280(23):22181-90
34) Southron JL, et al.  (2004) Complementation of Saccharomyces cerevisiae ccc2 mutant by a putative P1B-ATPase from Brassica napus supports a copper-transporting function. FEBS Lett 566(1-3):218-22
35) Serrano R, et al.  (2004) Copper and iron are the limiting factors for growth of the yeast Saccharomyces cerevisiae in an alkaline environment. J Biol Chem 279(19):19698-704
36) Szczypka MS, et al.  (1997) Saccharomyces cerevisiae mutants altered in vacuole function are defective in copper detoxification and iron-responsive gene transcription. Yeast 13(15):1423-35
37) Li L and Kaplan J  (1998) Defects in the yeast high affinity iron transport system result in increased metal sensitivity because of the increased expression of transporters with a broad transition metal specificity. J Biol Chem 273(35):22181-7
38) Li L, et al.  (2003) Functional studies of hephaestin in yeast: evidence for multicopper oxidase activity in the endocytic pathway. Biochem J 375(Pt 3):793-8
39) Eck R, et al.  (1999) A multicopper oxidase gene from Candida albicans: cloning, characterization and disruption. Microbiology 145 ( Pt 9)():2415-22
40) Harris ZL, et al.  (2004) A fungal multicopper oxidase restores iron homeostasis in aceruloplasminemia. Blood 103(12):4672-3