Table 3.
Transporters involved in homeostasis of iron
| Family | Organism | Transporter | Function | Representative structurea |
|---|---|---|---|---|
| Nramp | Plants | NRAMPXb [10,47,137,138,174] | Fe2+ import into cytosol at PM, vacuole, and chloroplast | 8E60c |
| Fungid | Smf1/3 [2,34,136] | Fe2+ import into cytosol at PM (Smf1) and vacuole (Smf3) | 8E60c | |
| Mammals | NRAMP1 [34,136,154,175] | Import of Fe2+ from phagosomes into cytosol | 8E60c | |
| Mammals | NRAMP2 [34,136,154,175,176] | Fe2+ import into cytosol at PM, endosomes, and lysosomes | 8E60c | |
| ABC transporter | Gram-negative bacteriae | YbtPQ [177], YfeABCD [97,132,178], Irp6/7 [33,179], SfaABC [94,140,180], ViuPDGC [125,131], FhuCDB [131,181], FbpABC [27,182] | Fe2+ import and virulence | 1Y4T |
| Gram-positive bacteriae | Pit1/2 [183,184], IrtAB [185,186], PiaABC [131,187], FeuABC [124,131], MtsABC [133] | Complexed Fe2+ import and virulence | 3HH8 | |
| Plants | IDI7 [47,107,109] | Fe2+ import into cytosol from vacuolar tonoplast of leaves, stem, and flower | 6G7P | |
| Plants | ATM3 [105,188,189] STA1 [106,190,191] | Fe2+ import into cytosol from mitochondria and biogenesis of Fe-S cluster | 7N58f | |
| Fungid | Abc3 [110,192,193] | Heme import into cytosol from vacuole | 3HH8 | |
| Mammals | ABCB7 [120,154,188,194,195] | Complexed Fe2+ export from mitochondrial matrix | 7VGFf | |
| Mammals | ABCG2 [120,196,197] | Complexed Fe2+ export at PM | 6VXFf | |
| CDF | Bacteria | YiiP [102], EmfA [103] | Fe2+ export | 2QFIg |
| ZIP | Plants | IRT1/2 [47,105,109] | Fe2+ import at PM (IRT1 and IRT2) and vacuole (IRT2) | 5TSBg |
| Mammals | ZIP8, ZIP14 [15,17,119] | Import of free Fe2+ at PM | 5TSBg | |
| CCC1 | Plants | VIT1 [49,50,138,198] | Fe2+ export from cytosol into vacuoles | 6IU9 |
| Fungid | Ccc1, Pcl1 [2,110,113] | Fe2+ export from cytosol into vacuoles | 6IU9 | |
| MFS transporter | Fungid | Arn1-4, Sit1, Enb1, Taf1, Str1/3 [2,94,110-112,199] | Internalization of Fe3+-siderophore (Arn1-4, Sit1, Enb1, Taf1, Str1) / Fe2+-heme (Str3) | 5AYM |
| Mammals | FLVCR1a/1b/2 [16,21,120,154,200] | Export out of (FLVCR1a) and import into (FLVCR1b/2) cytosol of heme bound Fe2+ at PM (FLVCR1a/2) and mitochondria (FLVCR1b) | 5AYM | |
| Plants | FPN2 [105,108] | Fe2+ import into vacuole from cytosol | 5AYM | |
| Mammals, bacteria | FPN [15,41,77,100,101,116,154,175,201] | Fe2+ export out of cytosol across PM and regulation of hepcidin | 5AYM | |
| Mammals | HCP1 [21,22,94,202,203] | Import of Fe2+-heme into cytosol at PM | 5AYM | |
| Calcium channel | Mammals | LTCC [28,118,204,205] | Import of free Fe2+ into cytosol across PM | 3JBRg |
| Porin | Gram-negative bacteria | Fe2+ porin [27,95] | Import of Fe2+ across OM | 2PORh |
| Oligopeptide transportere | Plants | YSL [26,206] | Complexed-iron transport across chloroplast, vacuole, ER and PM | - |
| Permease | Plants | PIC1 [25,105] | Fe2+ export from cytosol into chloroplast | 6C9Wg |
| Fungid | Ftr1, Fip1 [2,94,110], Fet4 [2,94,110,207] | Fe3+ (Ftr1, Fip1) or Fe2+ (Fet4) import into cytosol across PM | 6C9Wg | |
| Fungid | Fth1, Ftr2 [2,110] | Fe3+ import into cytosol from vacuole | 6C9Wg | |
| Mammals | HRG1 [16,17,94,208,209] | Transport of Fe2+-heme into cytosol from PM, endosomes, and lysosomes | 6C9Wg | |
| Transferrin/Lactoferrin receptor | Gram-negative bacteria | TbpA/TbpB [94,210,211] | Import of Fe3+-transferrin into periplasm across OM | 3V89 |
| Mammals | TfR1/2 [65,119,154,212], LfR [95,213-215] | Internalization of Fe3+-transferrin (TfR1/2), H-ferritin (TfR1/2) and lactoferrin (LfR) | 3S9L | |
| Gram-negative bacteria | LbpA/LbpB [94,210,211] | Import of Fe3+-lactoferrin into periplasm across OM | 7JRD | |
| Heme receptor | Bacteriae | IsdABCH [94,126,216], HmuTUV [131,217], PhuTUV [127,131], TBUT heme receptors [218-221] | Import of Fe2+-heme into periplasm across OM | 2Q8Q |
| Fungid | Shu1 [110,192,222] | Import of Fe2+-heme into cytosol | 2Q8Q | |
| Mammals | CD91 [17,223,224] | Import of Fe2+-heme in complex with hemopexin into cytosol across PM | 2Q8Q | |
| Hemoglobin receptor | Mammals | CD163 [17,223,225,226] | Import of hemoglobin bound Fe2+ in complex with haptoglobin into cytosol across PM | 6K0Lg |
| Siderophore receptor | Bacteriae | Fe3+-siderophore receptors [123,131,227-230] | Internalization of Fe3+-siderophore across OM | 4HMQ |
| Mammals | 24p3 [120,231,232] | Fe3+- siderophore import into cytosol across PM | 3K3Lg | |
| Ferritin receptor | Mammals | Tim-2 [120,154,233,234] | H-ferritin import into cytosol across PM | 2OR7 |
| Mammals | Scara-5 [120,154,233,234] | L-ferritin import into cytosol across PM | 7BZZ | |
| Mammals | SFT [154,173,235,236] | Tf-dependent and independent iron uptake into cytosol across PM in the intestine | - | |
| G-protein coupled transporter | Gram-negative bacteria | FeoB [94,98,99,237-239] | Fe2+ import into cytosol across IM | 3K53g |
| TonB | Gram-negative bacteria | TonB-ExbB-ExbD [94,96,240] | Energizes transport of iron-complexes from OM to IM (TonB) | 2GSK |
| Energizes transport of iron-complexes from OM to IM (ExbB-ExbD) | 5ZFP | |||
| Mitochondrial carrier family transporter | Fungid | Mrs3/4 [2,110,114,115] | Fe2+ export from cytosol into mitochondria | 1OKCg |
| Mammals | MFRN1/2 [16,154,241-243] | Fe2+ export from cytosol into mitochondria | 1OKCg | |
| TRP channel | Mammals | TRPML1 [119,120,244,245] | Fe2+ export from endosomes and lysosomes into cytosol | 5WJ5g |
a
The most relevant representative structure, prioritizing high-resolution structures with bound iron, then ones with other metal ions, then ones with no bound metal.
b
X is a number; plants generally have 5-7 numbered NRAMP homologs.
c
Structures with bound Mn2+.
d
Fungi transporters are best characterized in yeasts, so yeast proteins are generally listed in this table.
e
Non-exhaustive list.
f
Structures with no bound divalent ions at sites for transition metal transport.
g
Structures with bound Zn2+.
h
Structures with bound Ca2+.