Copper-induced structural changes in the ovine prion protein are influenced by a polymorphism at codon 112

Prion diseases are associated with conformational change in the copper-binding protein PrP. The copper-binding sites in PrP are located in the N-terminal region of the molecule and comprise a series of tandem repeats of the sequence PHGGGWGQ together with two histidines at residues 96 and 111 (human PrP numbering). The co-ordination of copper ions within the non-octapeptide repeat metal ion-binding site involves Met109 (human numbering, which corresponds with Met112 in ovine PrP) and the binding of copper to this site leads to an increase in β-sheet formation in PrP. Here we have investigated the influence of the M112T polymorphism on copper-induced structural changes in ovine recombinant PrP. M112ARQ and T112ARQ ovine PrP show similar secondary structure although M112ARQ appears more thermostable than T112ARQ. Following treatment with copper, M112ARQ showed a greater increase in β-sheet content than did T112ARQ when measured by CD spectroscopy and by ELISA using anti-PrP monoclonal antibodies. These biochemical and biophysical differences between M112ARQ and T112ARQ correlate with similar differences seen between allelic variants of ovine PrP associated with susceptibility and resistance to classical scrapie. These observations suggest that T112ARQ may provide a measure of resistance to classical scrapie pathogenesis compared to M112ARQ.