2.A.108.1.5
High-affinity oxidase-dependent plasma membrane Fe²⁺-Fe³⁺ uptake transporter, Fio1/Fip1 (Frp1) (Singh et al., 2006). Metalloreductase responsible for reducing extracellular iron and copper prior to import. It catalyzes the reductive uptake of Fe³⁺-salts and Fe³⁺ bound to catecholate or hydroxamate siderophores. Fe³⁺ is reduced to Fe²⁺, which then dissociates from the siderophore and can be imported by the high-affinity Fe²⁺ transport complex in the plasma membrane. Fio1 is a multicopper oxidase that contains three cupredoxin domains with eleven candidate iron-binding ligands, whereas Frp1 harbors a ferric reductase domain with three-candidate heme-binding ligands. The complex also participates in Cu²⁺ reduction and Cu⁺ uptake (Ahmad et al. 2022).