Figure 4. The Cu²⁺-bound N-terminal domain contacts the C-terminal domain.

The reductions in the heights of backbone [N,H^N] signals in the C-terminal domain of PrP, induced by proximity to the Cu²⁺ bound to the N-terminal domain, are illustrated on the backbone structure by a colour scale, ranging from dark blue to cyan (0–30% peak height reduction) and cyan to green (30–60% reduction). Data is shown for the full-length prion protein loaded with two Cu²⁺ ions (A) and the truncated PrP^91–231 construct, loaded with one Cu²⁺ ion (B). Residues for which there are no data are coloured grey. Signals from the area of the C-terminal domain that contacts the unfolded N-terminal domain see the largest reductions (coloured green) because they are closer to the Cu²⁺ ion bound to the unfolded domain. The unfolded domain of the protein and the Cu²⁺ ion bound to it are omitted for clarity.