relation: http://d-scholarship-dev.library.pitt.edu/8694/
title: Electron Spin Resonance Analysis of Cu(II) Coordination in Alzheimer's Disease-Related Peptides
creator: Shin, Byong-kyu
description: We exploit electron spin resonance (ESR) to understand the Cu(II) coordination of Alzheimer's disease-related peptides. It has been observed that at a low level of Cu(II), the amyloid-β (Aβ) peptide forms fibrillar aggregates, whereas amorphous aggregates are dominant at a high level of Cu(II). Three histidine residues, His6, His13, and His14, are believed to be important to the interaction between Aâ and the metal ion. The role of each histidine residue in binding to Cu(II) has been controversial mainly due to the difficulty in elucidating the coordination environment of Cu(II) at physiological pH. Using pulsed ESR, we precisely examine the multiple histidine coordination in the Cu(II)-Aβ complex. For the first time, we provide direct evidence that all the three histidine residues coordinate to Cu(II) at physiological pH. Also, the relative contribution of the imidazole ring of each histidine residue to the Cu(II) coordination is quantified. To establish the relative contribution, we have developed a method that examines the effects of multiple histidine coordination on electron spin-echo modulation. The ESR results reveal that His13 and His14 simultaneously coordinate to Cu(II) in a significant fraction of the Cu(II)-Aβ complex at physiological pH. A broad interpretation of this result leads to the hypothesis that the simultaneous Cu(II)-coordination by the two adjacent residues retards the formation of the β-sheet structure and enables a substantial amount of amorphous aggregates to form.Next, we propose potential Cu(II)-binding motifs in tau protein based on the ESR spectra of some tau fragments. In tau protein, there are four pseudorepeats, each of which has a highly conserved 18-amino-acid segment. The ESR results show that the 18-amino-acid sequence in each pseudorepeat has a good binding affinity for Cu(II). In particular, pulsed ESR spectra reveal that a histidine residue and a backbone amide group are involved in the Cu(II) coordination and the presence of the intact N-terminus is essential for the stability of the complex. Also, given that the reported dissociation constants of some Cu(II)-peptide complexes vary by several orders of magnitude, we have developed a simple method to precisely compare the dissociation constants at physiological pH.
date: 2011-09-30
type: University of Pittsburgh ETD
type: PeerReviewed
format: application/pdf
language: en
identifier: http://d-scholarship-dev.library.pitt.edu/8694/1/Byong-kyuShinRevised080511.pdf
identifier:   Shin, Byong-kyu  (2011) Electron Spin Resonance Analysis of Cu(II) Coordination in Alzheimer's Disease-Related Peptides.  Doctoral Dissertation, University of Pittsburgh.    (Unpublished)