Electron paramagnetic resonance blue copper protein

Based on spectroscopic properties, mainly electron paramagnetic resonance (EPR), the active sites of copper proteins have been classified into three groups, types I, II, and III. This nomenclature was originally applied to blue oxidases to distinguish the four copper ions contained in these proteins. The original classification has been extended to the copper sites of other proteins. The recent increase in structural information on the copper sites in proteins has, however, revealed greater diversity in the type of copper site. For instance, the type III and type II sites in ascorbate oxidase are in close proximity, forming a trinuclear site, in which all three copper ions are essential for the reactivity. Some proteins, once believed to contain a copper site with normal spectroscopic properties, and thus referred as type II, have been shown to contain copper coordinated by an unusual side chain. Therefore, in this review, new nomenclature is used to classify the copper sites more precisely with respect to their structural features and spectroscopic properties. The definitions are as follows ... 

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