Cross‐Talk Between the Octarepeat Domain and the Fifth Binding Site of Prion Protein Driven by the Interaction of Copper(II) with the N‐terminus

Abstract

Prion diseases are a group of neurodegenerative diseases based on the conformational conversion of the normal form of the prion protein (PrP(C)) to the disease-related scrapie isoform (PrP(Sc)). Copper(II) coordination to PrP(C) has attracted considerable interest for almost 20 years, mainly due to the possibility that such an interaction would be an important event for the physiological function of PrP(C). In this work, we report the copper(II) coordination features of the peptide fragment Ac(PEG11)3PrP(60-114) [Ac = acetyl] as a model for the whole N-terminus of the PrP(C) metal-binding domain. We studied the complexation properties of the peptide by means of potentiometric, UV/Vis, circular dichroism and electrospray ionisation mass spectrometry techniques. The results revealed that the preferred histidyl binding sites largely depend on the pH and copper(II)/peptide ratio. Formation of macrochelate species occurs up to a 2:1 metal/peptide ratio in the physiological pH range and simultaneously involves the histidyl residues present both inside and outside the octarepeat domain. However, at increased copper(II)/peptide ratios amide-bound species form, especially within the octarepeat domain. On the contrary, at basic pH the amide-bound species predominate at any copper/peptide ratio and are formed preferably with the binding sites of His96 and His111, which is similar to the metal-binding-affinity order observed in our previous studies.

Copper(II) Coordination Abilities of the Tau Protein's N‐Terminus Peptide Fragments: A Combined Potentiometric, Spectroscopic and Mass Spectrometric Study

“…Interestingly, the different spectra obtained at pH 5 and pH 6 (Figure S9, Inset) appear quite different from those observed in Cu(II)−Tau(9‐16) and Cu(II)−Tau(26‐33) systems, when the (N im ,N − ,N − ) binding mode is favoured as suggested by potentiometric and spectroscopic results, revealing a different coordination mode of copper(II). The observed CD profiles are reminiscent of those reported for copper(II) complexes of prion peptide fragments when macrochelate complex species form …”

“…The observed CD profiles are reminiscent of those reported for copper(II) complexes of prion peptide fragments when macrochelate complex species form. [39] Moreover, the far-UV CD spectra of Cu(II)À Tau(12-16)(30-34), recorded at higher pH values ( Figure S9a, pH range 7-10) revealed the presence of a growing negative band around λ = 220 nm and a small positive band centred at λ = 250 nm. Similar variations in the CD-band profiles were also found for the copper(II) complexes of the peptide fragments Tau (26)(27)(28)(29)(30)(31)(32)(33) suggesting the preference for copper(II) binding at His32 sites at 1 : 1 metal to peptide ratio and basic pH values.…”

Interaction between Hemin and Prion Peptides: Binding, Oxidative Reactivity and Aggregation

“…In particular, four histidines are present in four highly conserved octa-repeats (OR) within its N-terminal domain in the portion between residues 57 and 90 and can form complexes ranging from OR-Cu 2+ to OR-(Cu 2+ ) 4 [ 26 ] where the metal is bound with very different affinity. Moreover, the N-terminal amino group [ 24 ] and the region between 90–114, that contains two histidines (His111 and His96) [ 27 ] can bind copper (II) ions with high affinity. In particular, copper (II) binding affinity follows the order His111 > His96 >> His77 ≈ His85 [ 27 ].…”

“…Moreover, the N-terminal amino group [ 24 ] and the region between 90–114, that contains two histidines (His111 and His96) [ 27 ] can bind copper (II) ions with high affinity. In particular, copper (II) binding affinity follows the order His111 > His96 >> His77 ≈ His85 [ 27 ].…”

Investigation on the conformational conversion of human prion protein by molecular dynamics simulation

“…The N-terminus of prion protein contains a signal peptide that directs its intracellular trafficking to Golgi (residues 1-22 in huPrP) 181 , four octarepeat regions associated with copper binding (residues 60-91 in huPrP), a hydrophobic region (residues 106-126 in huPrP), and the non-octarepeat copper binding site (His96 and His111 in huPrP) 68,182 .…”