Copper Coordination to the Prion Fragment (95-126): Implications for Neurodegenerative Diseases

The causative event in transmissible spongiform encephalopathies is the misfolding of the prion protein (PrP), a process influenced, in a way that is not yet fully understood, by transition metal ions, particularly copper, which modulate folding, aggregation, and redox activity. In this study, we investigated the interaction of copper(II) ions with the prion fragment PrP(95-126), which includes the non-octarepeat high-affinity sites His96 and His111, as well as an amyloidogenic tail involved in PrP misfolding and membrane interaction. UV-vis and circular dichroism analyses revealed the predominant formation of a 1:1 Cu/PrP(95-126) complex, accompanied by modest restructuring, consistent with an increased aggregation propensity upon copper binding. The Cu/PrP(95-126) complexes exhibited limited redox activity toward catechol substrates, which was further reduced in membrane-mimetic systems such as SDS micelles and large unilamellar vesicles (LUVs). His96 appears not to play a critical role in copper coordination or redox activation. This study explores the coordination modes and reactivity of copper(II) with PrP, as well as employing a membrane mimic, aspects that are still highly controversial in the literature, providing insights for further in vitro studies.