Fragmentation and dimerization of copper-loaded prion protein by copper-catalysed oxidation

Prion protein consists of an N-terminal domain containing a series of octapeptide repeats with the consensus sequence PHGGGWGQ and a C-terminal domain composed of three a-helices and two short P-strands. Several studies have shown that the N-terminal domain binds five Cu2+ ions. In the present study, we have investigated copper-catalysed oxidation of a recombinant mouse prion protein, PrP23-231. The copper-loaded PrP23-231 was found to be carbonylated by incubation with dopamine. Besides the formation of carboryls, a cross-linked species with the dimeric size and C-terminally truncated species were generated. These reactions were retarded in the presence of Cu+- and Cu2+-specific copper chelators, catalase, and SOD (superoxide dismutase), but not in the presence of various bivalent metal ions. Together, these results indicate that the copper bound to prion protein undergoes catalytic cycling in the presence of catecholamines and causes the oxidation of the protein.