Peculiarities of copper binding to alpha-synuclein.

Heavy metals have been implicated as the causative agents for the pathogenesis of the most prevalent neurodegenerative disease. Various mechanisms have been proposed to explain the toxic effects of metals ranging from metal-induced oxidation of protein to metal-induced changes in the protein conformation. Aggregation of alpha-synuclein is implicated in Parkinson's disease (PD), and various metals, including copper, constitute a prominent group of a-synuclein aggregation enhancers. In this study, we have systematically characterized the alpha-synuclein-Cu2+ binding sites and analyzed the possible role of metal binding in a-synuclein fibrillation using a set of biophysical techniques, such as electron paramagnetic resonance (EPR), electron spin-echo envelope modulation (ESEEM), circular dichroism (CD), and size exclusion chromatography (SEC). Our analyses indicated that a-synuclein possesses at least two binding sites for Cu2+. We have been able to locate one of the binding sites in the N-terminal region. Furthermore, based on the EPR studies of model peptides and beta-synuclein, we concluded that the suspected His residue did not appear to participate in strong Cu2+ binding.