Molecular features of the copper binding sites in the octarepeat domain of the prion protein

Colin S. Burns, Eliah Aronoff-Spencer, Christine M. Dunham, Paula Lario, Nikolai I. Avdievich, William E. Antholine, Marilyn M. Olmstead, Alice Vrielink, Gary J. Gerfen, Jack Peisach, William G. Scott, Glenn L. Millhauser

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346 Scopus citations

Abstract

Recent evidence suggests that the prion protein (PrP) is a copper binding protein. The N-terminal region of human PrP contains four sequential copies of the highly conserved octarepeat sequence PHGGGWGQ spanning residues 60-91. This region selectively binds Cu2+ in vivo. In a previous study using peptide design, EPR, and CD spectroscopy, we showed that the HGGGW segment within each octarepeat comprises the fundamental Cu2+ binding unit [Aronoff-Spencer et al. (2000) Biochemistry 40, 13760-13771]. Here we present the first atomic resolution view of the copper binding site within an octarepeat. The crystal structure of HGGGW in a complex with Cu2+ reveals equatorial coordination by the histidine imidazole, two deprotonated glycine amides, and a glycine carbonyl, along with an axial water bridging to the Trp indole. Companion S-band EPR, X-band ESEEM, and HYSCORE experiments performed on a library of 15N-labeled peptides indicate that the structure of the copper binding site in HGGGW and PHGGGWGQ in solution is consistent with that of the crystal structure. Moreover, EPR performed on PrP(23-28, 57-91) and an l5N-labeled analogue demonstrates that the identified structure is maintained in the full PrP octarepeat domain. It has been shown that copper stimulates PrP endocytosis. The identified Gly-Cu linkage is unstable below pH ≈6.5 and thus suggests a pH-dependent molecular mechanism by which PrP detects Cu2+ in the extracellular matrix or releases PrP-bound Cu2+ within the endosome. The structure also reveals an unusual complementary interaction between copper-structured HGGGW units that may facilitate molecular recognition between prion proteins, thereby suggesting a mechanism for transmembrane signaling and perhaps conversion to the pathogenic form.

Original languageEnglish (US)
Pages (from-to)3991-4001
Number of pages11
JournalBiochemistry
Volume41
Issue number12
DOIs
StatePublished - Mar 26 2002

ASJC Scopus subject areas

  • Biochemistry

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    Burns, C. S., Aronoff-Spencer, E., Dunham, C. M., Lario, P., Avdievich, N. I., Antholine, W. E., Olmstead, M. M., Vrielink, A., Gerfen, G. J., Peisach, J., Scott, W. G., & Millhauser, G. L. (2002). Molecular features of the copper binding sites in the octarepeat domain of the prion protein. Biochemistry, 41(12), 3991-4001. https://doi.org/10.1021/bi011922x