Stereo diagrams (parallel eyes) depicting the copper-binding sites. Electron-density maps (2Fo − Fc, contoured at 1.5σ; blue) are shown for the type I Cu-binding site (a) and the type II and III Cu-binding sites (b). Anomalous maps (contoured at 6σ; red) were calculated using the diffraction data used for the SAD method and phases calculated using a final model. The final model is superimposed in a stick representation with atoms in standard colours for the Cu-coordinating residues and a water molecule (red spheres). Cu atoms are shown as small spheres coloured in the same colours as in Fig. 1. The figures were prepared with BobScript (Esnouf, 1999) and Raster3D.