InterPro domain: IPR034271

The proteins in this subfamily share homology to ascorbate oxidase and other members of the blue copper oxidase family. Expression of protein NTP303 from Nicotiana tabacum is detected during germination and pollen tube growth [ 1 ]. Ascorbate oxidase is a member of the multicopper oxidase (MCO) family that couples oxidation of substrates with reduction of dioxygen to water.

Although MCOs have diverse functions, majority of them have three cupredoxin domain repeats that include one mononuclear and one trinuclear copper centre. 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 centre and transferring them to the active site trinuclear copper centre. The cupredoxin domain 2 of 3-domain MCOs has lost the ability to bind copper [ 2 ].

1. Characterization of a pollen-specific cDNA clone from Nicotiana tabacum expressed during microgametogenesis and germination. Plant Mol. Biol. 18, 1101-11
2. Refined crystal structure of ascorbate oxidase at 1.9 A resolution. J. Mol. Biol. 224, 179-205