Molecular Features of the Copper Binding Sites in the Octarepeat Domain of the Prion Protein
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- 作者：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
- 刊名：Biochemistry
- 出版年：2002
- 出版时间：March 26, 2002
- 年：2002
- 卷：41
- 期：12
- 页码：3991 - 4001
- 全文大小：293K
- 年卷期：v.41,no.12(March 26, 2002)
- ISSN：1520-4995
文摘
Recent evidence suggests that the prion protein (PrP) is a copper binding protein. The N-terminalregion of human PrP contains four sequential copies of the highly conserved octarepeat sequencePHGGGWGQ spanning residues 60-91. This region selectively binds Cu2+ in vivo. In a previous studyusing peptide design, EPR, and CD spectroscopy, we showed that the HGGGW segment within eachoctarepeat 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 anoctarepeat. The crystal structure of HGGGW in a complex with Cu2+ reveals equatorial coordination bythe histidine imidazole, two deprotonated glycine amides, and a glycine carbonyl, along with an axialwater bridging to the Trp indole. Companion S-band EPR, X-band ESEEM, and HYSCORE experimentsperformed on a library of 15N-labeled peptides indicate that the structure of the copper binding site inHGGGW and PHGGGWGQ in solution is consistent with that of the crystal structure. Moreover, EPRperformed on PrP(23-28, 57-91) and an 15N-labeled analogue demonstrates that the identified structureis 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 molecularmechanism by which PrP detects Cu2+ in the extracellular matrix or releases PrP-bound Cu2+ within theendosome. The structure also reveals an unusual complementary interaction between copper-structuredHGGGW units that may facilitate molecular recognition between prion proteins, thereby suggesting amechanism for transmembrane signaling and perhaps conversion to the pathogenic form.
6.5 and thus suggests a pH-dependent molecularmechanism by which PrP detects Cu2+ in the extracellular matrix or releases PrP-bound Cu2+ within theendosome. The structure also reveals an unusual complementary interaction between copper-structuredHGGGW units that may facilitate molecular recognition between prion proteins, thereby suggesting amechanism for transmembrane signaling and perhaps conversion to the pathogenic form.