ABSTRACT
The multi-copper oxidase family is comprised of structural domains, all of which are based on the cupredoxin fold [6]. This folding pattern is typified by the structures of the small blue copper proteins, plastocyanin and azurin, and comprises two (3 sheets arranged in a sandwich configuration. Fig. 1 shows the (3 sheet topology and hydrogen bonding pattern observed in plastocyanin [7] (PDB code lplc); each sheet comprises essentially four strands. In azurin [4] (PDB code 2aza) there is an extra strand, 5, in the sheet involving strands 2b, 8, 7, and 4. Ribbon diagrams of plastocyanin and azurin are shown in Fig. 2. Whereas other common p sheet structures, such as super oxide dismutase, the immunoglobulins, and the fibronectin domains contain only anti-parallel strands, the cupredoxin fold has two parallel strands-1 and 3 in the first sheet and 2b and 8 in the second. In addition, strand 2 participates in both sheets, crossing over from one sheet to the other.
