Prion protein binds copper within the physiological concentration range.
The prion protein is known to be a copper-binding protein, but affinity and stoichiometry data for the full-length protein at a physiological pH of 7 were lacking. Furthermore, it was unknown whether only the highly flexible N-terminal segment with its octarepeat region is involved in copper binding or whether the structured C-terminal domain is also involved. Therefore we systematically investigated the stoichiometry and affinity of copper binding to full-length prion protein PrP(23-231) and to different N- and C-terminal fragments using electrospray ionization mass spectrometry and fluorescence spectroscopy. Our data indicate that the unstructured N-terminal segment is the cooperative copper-binding domain of the prion protein. The prion protein binds up to five copper(II) ions with half-maximal binding at approximately 2 microm. This argues strongly for a direct role of the prion protein in copper metabolism, since it is almost saturated at about 5 microm, and the exchangeable copper pool concentration in blood is about 8 microm.
Department of Neuropathology, Georg August University of Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany. mkramer@med.uni-goettingen.de
M L
ML
Kramer
H D
HD
Kratzin
B
B
Schmidt
A
A
Römer
O
O
Windl
S
S
Liemann
S
S
Hornemann
H
H
Kretzschmar
D000818:Animals; D001665:Binding Sites; D003300:Copper / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D051379:Mice; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D011328:Prions / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D021241:Spectrometry, Mass, Electrospray Ionization
D010446:Peptide Fragments; D011328:Prions; D003300:Copper