Novel types of two-domain multi-copper oxidases: possible missing links in the evolution

An analysis of the genome sequence database revealed novel types of two-domain multi-copper oxidases. The two-domain proteins have the conspicuous combination of blue-copper and inter-domain trinuclear copper binding residues, which is common in ceruloplasmin and ascorbate oxidase but not in nitrite reductase, and therefore are considered to retain the characteristics of the plausible ancestral form of ceruloplasmin and ascorbate oxidase. A possible evolutionary relationship of these proteins is proposed. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.