The third Cupredoxin domain of multicopper oxidase Fet3p
Fet3p catalyzes the ferroxidase reaction, which couples the oxidation of Fe(II) to Fe(III) with the four-electron reduction of molecular oxygen to water. Fet3p is a type I membrane protein with the amino-terminal oxidase domain in the extracellular space and the carboxyl terminus in the cytoplasm. The periplasmic produced Fe(III) is transferred to the permease Ftr1p for import into the cytosol. The four copper ions are inserted post-translationally and are essential for catalytic activity, thus linking copper and iron homeostasis. Like other related multicopper oxidases (MCOs), Fet3p is composed of three cupredoxin domains that include one mononuclear and one trinuclear copper center. The copper ions are bound in several sites: Type 1, Type 2, and/or Type 3. The ensemble of types 2 and 3 copper is called a trinuclear cluster. MCOs oxidize their substrate by accepting electrons at a mononuclear copper center and transferring them to the active site trinuclear copper center. The cupredoxin domain 3 of 3-domain MCOs contains the Type 1 (T1) copper binding site and part the trinuclear copper binding site, which is located at the interface of domains 1 and 3.
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