Copper(II) Sequentially Loads onto the N?Terminal Amino Group of the Cellular Prion Protein before the Individual Octarepeats

摘要

The cellular prion protein (PrP~C) binds to Cu~(2+) ions in vivo, and a misfolded form of PrP~C is responsible for a range of transmissible spongiform encephalopathies. Recently, disruption of Cu~(2+) homeostasis in mice has been shown to impart resistance to scrapie infection. Using full-length PrP~C and model peptide fragments, we monitor the sequential loading of Cu~(2+) ions onto PrP~C using visible circular dichroism. We show the N-terminal amino group of PrP~C is not the principal binding site for Cu~(2+); however, surprisingly, it has an affinity for Cu~(2+) tighter than that of the individual octarepeat binding sites present within PrP~C. We re-evaluate what is understood about the sequential loading of Cu~(2+) onto the full-length protein and show for the first time that Cu~(2+) loads onto the N-terminal amino group before the single octarepeat binding sites.