The second cupredoxin domain of multicopper oxidase McoP and similar proteins
This family includes archaeal and bacterial multicopper oxidases (MCOs), represented by the extremely thermostable McoP from the hyperthermophilic archaeon Pyrobaculum aerophilum. McoP is an efficient metallo-oxidase that catalyzes the oxidation of cuprous and ferrous ions. It is noteworthy that McoP has three-fold higher catalytic efficiency when using nitrous oxide as electron acceptor than when using dioxygen, the typical oxidizing substrate of multicopper oxidases. McoP may function as a novel archaeal nitrous oxide reductase that is probably involved in the denitrification pathway in archaea. Although MCOs have diverse functions, majority of them have three cupredoxin domain repeats 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 2 of 3-domain MCOs has lost the ability to bind copper.
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