title: Multiple forms of copper (II) co-ordination occur throughout the disordered N-terminal region of the prion protein at pH 7.4.
abstract: Although the physiological function of the prion protein remains unknown, in vitro experiments suggest that the protein may bind copper (II) ions and play a role in copper transport or homoeostasis in vivo. The unstructured N-terminal region of the prion protein has been shown to bind up to six copper (II) ions, with each of these ions co-ordinated by a single histidine imidazole and nearby backbone amide nitrogen atoms. Individually, these sites have micromolar affinities, which is weaker than would be expected of a true cuproprotein. In the present study, we show that with subsaturating levels of copper, different forms of co-ordination will occur, which have higher affinity. We have investigated the copper-binding properties of two peptides representing the known copper-binding regions of the prion protein: residues 57-91, which contains four tandem repeats of the octapeptide GGGWGQPH, and residues 91-115. Using equilibrium dialysis and spectroscopic methods, we unambiguously demonstrate that the mode of copper co-ordination in both of these peptides depends on the number of copper ions bound and that, at low copper occupancy, copper ions are co-ordinated with sub-micromolar affinity by multiple histidine imidazole groups. At pH 7.4, three different modes of copper co-ordination are accessible within the octapeptide repeats and two within the peptide comprising residues 91-115. The highest affinity copper (II)-binding modes cause self-association of both peptides, suggesting a role for copper (II) in controlling prion protein self-association in vivo.
authors.affiliation: Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wells
authors.forename: Clare
authors.initials: C
authors.lastname: Jelinska
authors.forename: Laszlo L P
authors.initials: LL
authors.lastname: Hosszu
authors.forename: C Jeremy
authors.initials: CJ
authors.lastname: Craven
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Clarke
authors.forename: John
authors.initials: J
authors.lastname: Collinge
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Waltho
authors.forename: Graham S
authors.initials: GS
authors.lastname: Jackson
mesh_terms: D001665:Binding Sites; D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D011328:Prions / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D011328:Prions; D003300:Copper