Environmental effects on a prion's helix II domain: copper(II) and membrane interactions with PrP180-193 and its analogues.
An abnormal interaction between copper and the prion protein is believed to play a pivotal role in the pathogenesis of prion diseases. Copper binding has been mainly attributed to the N-terminal domain of the prion protein, but this hypothesis has recently been challenged in some papers which suggest that the C-terminal domain might also compete for metal anchoring. In particular, the segment corresponding to the helix II region of the prion protein, namely PrP180-193, has been shown both to bind copper and to exhibit a copper-enhanced cytotoxicity, as well as to interact with artificial membranes. The present work is aimed at extending these results by choosing the most representative model of this domain and by determining its copper affinity. With this aim, the different role played by the electrostatic properties of the C- and N-termini of PrP180-193 (VNITIKQHTVTTTT) in determining its conformational behaviour, copper coordination and ability to perturb model membranes was investigated. Owing to the low solubility of PrP180-193, its copper affinity was evaluated by using the shorter PrPAc184-188NH2 (IKQHT) analogue as a model. ESI-MS, ESR, UV/Vis, and CD measurements were carried out on the copper(II)/PrPAc184-188NH2 and copper(II)/PrP180-193NH2 systems, and showed that PrPAc184-188NH2 is a reliable model for the metal interaction with the helix II domain. The affinity of copper(II) for the helix II fragment is higher than that for the octarepeat and PrP106-126 peptides. Finally, the different ability of PrP180-193 analogues to perturb the DPPC model membrane was assessed by DSC measurements. The possible biological consequences of these findings are also discussed briefly.
Grasso
Domenico
D
Università di Catania, Dipartimento di Scienze Chimiche, Viale Andrea Doria 6, 95125 Catania, Italy.
Grasso
Giulia
G
Guantieri
Valeria
V
Impellizzeri
Giuseppe
G
La Rosa
Carmelo
C
Milardi
Danilo
D
Micera
Giovanni
G
Osz
Katalin
K
Pappalardo
Giuseppe
G
Rizzarelli
Enrico
E
Sanna
Daniele
D
Sóvágó
Imre
I
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D018621:PrPC Proteins / Q000737:chemistry*; D011328:Prions / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013057:Spectrum Analysis
D010446:Peptide Fragments; D018621:PrPC Proteins; D011328:Prions; C521306:prion protein (180-193); D003300:Copper