Metal binding to alpha-synuclein peptides and its contribution to toxicity.

Recent studies have suggested that alpha-synuclein (AS) is a metal binding protein. Metals also induce protein aggregation. In order to clarify controversy over the location of the metal binding sites six peptide fragments spanning the full length of the protein were analysed to identify metal binding domains. Our results indicated that both the C-terminus of the protein and a region around histidine 50 play a role in copper binding. We suggest that the true binding domain is a nonlinear site composed of both areas acting together to bind copper. The toxicity of these peptides to SH-SY5Y cells was also studied. There was a copper-independent component associated with the NAC domain of the protein and a copper-dependent component associated with the C-terminus of the protein and potentiated by involvement of the N-terminus. We hypothesise that copper binding can cause conversion of AS to a neurotoxic form via inter-protein interactions.