The possible role of Gly residues in prion octarepeat region in coordination of Cu2+ ions

Spectroscopic and potentiometric data have shown that insertion of tripeptides other than the Gly3 peptide fragment, Ala3 or Lys3, into the prion octarepeat region destabilizes the biologically relevant Cu2+ complex with the metal ion bound equatorially through the {Nimid,2N-} donor set. The other likely role of the high glycine content could be enforcement of the high flexibility of the N-terminal prion region resulting in the unstructured protein organization. However, the insertion of bulkier amino acid residues does not change the basic coordination mode at physiological pH which involves imidazole nitrogen and two amide nitrogen donors from the third and fourth residues.