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9.A.9 The Low Affinity Fe2+ Transporter (FeT) Family

The FeT family consists of a single iron-deprivation inducible protein, Fet4p of Saccharomyces cerevisiae as no homologues are currently present in the databases. S. cerevisiae reduces Fe3+ to Fe2+ by an Fe3+ reductase localized to the external surface of the plasma membrane. The Fet4p permease then takes up Fe2+ into the cytoplasm with low affinity (Km = 30 µM). It may also transport Co2+ and Cd2+. The protein has 552 amino acyl residues and six putative transmembrane α-helical spanners. It presumably uses the pmf across the cytoplasmic membrane, but the energy-coupling mechanism is not established. A proton symport mechanism may or may not drive uptake.

The generalized transport reaction catalyzed by the Fet4p permease of S. cerevisiae is:

Fe2+ (out) Æ Fe2+ (in).

References associated with 9.A.9 family:

Ahmad, F., Y. Luo, H. Yin, Y. Zhang, and Y. Huang. (2022). Identification and analysis of iron transporters from the fission yeast Schizosaccharomyces pombe. Arch. Microbiol. 204: 152. 35079912
Dix, D., J. Bridgham, M. Broderius and D. Eide (1997) Characterization of the FET4 protein of yeast. Evidence for a direct role in the transport of iron. J. Biol. Chem. 272: 11770-11777. 9115232
Dix, D.R., J.T. Bridgham, M.A. Broderius, C.A. Byersdorfer and D.J. Eide (1994). The FET4 gene encodes the low affinity Fe(II) transport protein of Saccharomyces cerevisiae. J. Biol. Chem. 269: 26092-26099. 7929320
Eide, D. and M. Guerinot (1997). Metal ion uptake in eukaryotes. ASM News 63: 199-205.