title: CuII binding sites located at His-96 and His-111 of the human prion protein: thermodynamic and spectroscopic studies on model peptides.
abstract: The prion protein (PrP) is a Cu(2+)-binding cell-surface glycoprotein. Using PrP peptide fragments, by means of potentiometric, spectroscopic and thermodynamic techniques, we have shown that Cu(2+) ions bind to the region comprising His-96, His-111 and the octarepeat domain within residues 60-91. Cu(2+) may bind in different modes, which strongly depend both on His position within the peptide sequence and on the adjacent residues. We have used a series of protected oligopeptides having His at the C- or the N-terminus, inducing different binding modes to amide nitrogens around the His residue, either towards the N- or C-terminus. His imidazole acts as an anchoring site for Cu(2+) and then binding to ionized amide nitrogens follows. When it is directed towards the C-terminus the formation of a less stable seven-membered chelate ring with a {N(im), N(-)} binding mode occurs. When coordination goes towards the N-terminus the thermodynamically more stable six-membered chelate ring is formed. NMR data suggest that both the coordination modes are possible for the model peptides; however, the thermodynamic measurements show that they only slightly differ in energy and the influence of the adjacent amino acid residues can address the coordination toward the C- or the N-terminus.
authors.affiliation: Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, Wroclaw, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Gralka
authors.forename: Daniela
authors.initials: D
authors.lastname: Valensin
authors.forename: Elena
authors.initials: E
authors.lastname: Porciatti
authors.forename: Carolina
authors.initials: C
authors.lastname: Gajda
authors.forename: Elena
authors.initials: E
authors.lastname: Gaggelli
authors.forename: Gianni
authors.initials: G
authors.lastname: Valensin
authors.forename: Wojciech
authors.initials: W
authors.lastname: Kamysz
authors.forename: Rafał
authors.initials: R
authors.lastname: Nadolny
authors.forename: Remo
authors.initials: R
authors.lastname: Guerrini
authors.forename: Dimitri
authors.initials: D
authors.lastname: Bacco
authors.forename: Maurizio
authors.initials: M
authors.lastname: Remelli
authors.forename: Henryk
authors.initials: H
authors.lastname: Kozlowski
mesh_terms: D001665:Binding Sites; D002151:Calorimetry; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006639:Histidine / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011199:Potentiometry; D011328:Prions / Q000737:chemistry*; D011522:Protons; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D008024:Ligands; D010455:Peptides; D011328:Prions; D011522:Protons; D006639:Histidine; D003300:Copper