Pleomorphic Copper Coordination by Alzheimer’s Disease Amyloid-β Peptide

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• 作者：Simon C. Drew ; Christopher J. Noble ; Colin L. Masters ; Graeme R. Hanson ; Kevin J. Barnham
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：January 28, 2009
• 年：2009
• 卷：131
• 期：3
• 页码：1195-1207
• 全文大小：583K
• 年卷期：v.131,no.3(January 28, 2009)
• ISSN：1520-5126

文摘

Numerous conflicting models have been proposed regarding the nature of the Cu²⁺ coordination environment of the amyloid β (Aβ) peptide, the causative agent of Alzheimer’s disease. This study used multifrequency CW-EPR spectroscopy to directly resolve the superhyperfine interactions between Cu²⁺ and the ligand nuclei of Aβ, thereby avoiding ambiguities associated with introducing point mutations. Using a library of Aβ16 analogues with site-specific ¹⁵N-labeling at Asp1, His6, His13, and His14, numerical simulations of the superhyperfine resonances delineated two independent 3N1O Cu²⁺ coordination modes, {N_a^D1, O, N_ε^H6, N_ε^H13} (component Ia) and {N_a^D1, O, N_ε^H6, N_ε^H14} (component Ib), between pH 6−7. A third coordination mode (component II) was identified at pH 8.0, and simulation of the superhyperfine resonances indicated a 3N1O coordination sphere involving nitrogen ligation by His6, His13, and His14. No differences were observed upon ¹⁷O-labeling of the phenolic oxygen of Tyr10, confirming it is not a key oxygen ligand in the physiological pH range. Hyperfine sublevel correlation (HYSCORE) spectroscopy, in conjunction with site-specific ¹⁵N-labeling, provided additional support for the common role of His6 in components Ia and Ib, and for the assignment of a {O, N_ε^H6, N_ε^H13, N_ε^H14} coordination sphere to component II. HYSCORE studies of a peptide analogue with selective ¹³C-labeling of Asp1 revealed ¹³C cross-peaks characteristic of equatorial coordination by the carboxylate oxygen of Asp1 in component Ia/b coordination. The direct resolution of Cu²⁺ ligand interactions, together with the key finding that component I is composed of two distinct coordination modes, provides valuable insight into a range of conflicting ligand assignments and highlights the complexity of Cu²⁺/Aβ interactions.