CuII binding sites located at His-96 and His-111 of the human prion protein: thermodynamic and spectroscopic studies on model peptides.
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.
Gralka
Ewa
E
Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, Wroclaw, Poland.
Valensin
Daniela
D
Porciatti
Elena
E
Gajda
Carolina
C
Gaggelli
Elena
E
Valensin
Gianni
G
Kamysz
Wojciech
W
Nadolny
Rafał
R
Guerrini
Remo
R
Bacco
Dimitri
D
Remelli
Maurizio
M
Kozlowski
Henryk
H
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
D008024:Ligands; D010455:Peptides; D011328:Prions; D011522:Protons; D006639:Histidine; D003300:Copper