Characterization of copper binding to the peptide amyloid-beta(1-16) associated with Alzheimer's disease.
Amyloid-beta peptide (Abeta) is the principal constituent of plaques associated with Alzheimer's disease (AD) and is thought to be responsible for the neurotoxicity associated with the disease. Copper binding to Abeta has been hypothesized to play an important role in the neruotoxicity of Abeta and free radical damage, and Cu2+ chelators represent a possible therapy for AD. However, many properties of copper binding to Abeta have not been elucidated clearly, and the location of copper binding sites on Abeta is also in controversy. Here we have used a range of spectroscopic techniques to characterize the coordination of Cu2+ to Abeta(1-16) in solution. Electrospray ionization mass spectrometry shows that copper binds to Abeta(1-16) at pH 6.0 and 7.0. The mode of copper binding is highly pH dependent. Circular dichroism results indicate that copper chelation causes a structural transition of Abeta(1-16). UV-visible absorption spectra suggest that three nitrogen donor ligands and one oxygen donor ligand (3N1O) in Abeta(1-16) may form a type II square-planar coordination geometry with Cu2+. By means of fluorescence spectroscopy, competition studies with glycine and L-histidine show that copper binds to Abeta(1-16) with an affinity of Ka approximately 10(7) M(-1) at pH 7.8. Besides His6, His13, and His14, Tyr10 is also involved in the coordination of Abeta(1-16) with Cu2+, which is supported by 1H NMR and UV-visible absorption spectra. Evidence for the link between Cu2+ and AD is growing, and this work has made a significant contribution to understanding the mode of copper binding to Abeta(1-16) in solution.
Ma
Qing-Feng
QF
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, 100084 Beijing, China.
Hu
Jia
J
Wu
Wei-Hui
WH
Liu
Hua-Dong
HD
Du
Jin-Tang
JT
Fu
Yuan
Y
Wu
Yong-Wei
YW
Lei
Peng
P
Zhao
Yu-Fen
YF
Li
Yan-Mei
YM
D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism; D002942:Circular Dichroism; D003300:Copper / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D021241:Spectrometry, Mass, Electrospray Ionization; D013053:Spectrophotometry
D016229:Amyloid beta-Peptides; D001704:Biopolymers; D010446:Peptide Fragments; C433241:amyloid beta-protein (1-16); D003300:Copper