Copper²⁺ Binding to α-Synuclein. Histidine50 Can Form a Ternary Complex with Cu²⁺ at the N-Terminus but Not a Macrochelate

Abstract

Alpha-synuclein (αSyn) forms amyloid fibrils in the neurons of Parkinson's disease (PD) patients'. Despite a role for Cu 2+ in accelerating αSyn fibril formation, coupled with reports of copper dishomeostasis in Parkinson's disease (PD), there remain controversies surrounding the coordination geometry of Cu 2+ with αSyn. Here we compare visible circular dichroism (CD) spectra of Cu 2+ loaded on to full-length αSyn together with four peptides that model aspects of Cu 2+ binding to the N-terminus and Histidine50 of αSyn. Using glycine as a competitive ligand, the affinity of Cu 2+ for full-length αSyn is determined to have a conditional dissociation constant, at pH 7.4, of 0.1 nM. A similar affinity of 0.3 nM is determined for the tri-peptide MDV that mimics the N-terminus of αSyn, while the incorporation of a putative histidine side-chain in the Nterminal complex facilitates the formation of a macrochelate with the histidine, which results in an increase in

Acetylation Rather than H50Q Mutation Impacts the Kinetics of Cu(II) Binding to α‐Synuclein

“…Consequently, the pathological H50Q mutation has no impact on the kinetics of Cu 2+ binding to the high‐affinity site of αSyn. Such observation is in good agreement with the result obtained by Tian et al ., [23] but contradictory to that of De Ricco and co‐workers [20] . The reason could be that the experimental concentration of αSyn in the latter study was so high that a Cu 2+ bridged ternary complex was generated [23] …”

“…[20] The reason could be that the experimental concentration of αSyn in the latter study was so high that a Cu 2 + bridged ternary complex was generated. [23] In contrast, using an analogous method, the Cu 2 + binding affinity of NAc-αSyn (K d = 23(3) μM) was determined to be around four orders of magnitude weaker than that of WT-αSyn (K d = 3.0(7) nM). So far, K d values reported for Cu 2 + binding to WT-αSyn as determined by different techniques vary between 0.1 nM and 0.7 μM.…”

Amyloid Oligomers: A Joint Experimental/Computational Perspective on Alzheimer’s Disease, Parkinson’s Disease, Type II Diabetes, and Amyotrophic Lateral Sclerosis

“…However, it can also involve H50 depending on pH and concentration. 735,736 Copper has been shown to be one of the most potent modulators of αS structure as well as a very effective accelerator of αS fibrillation in vitro. 732 AFM-based experiments revealed that the presence of Cu(II) significantly enhanced the relative abundance of the β-sheet like structure in the otherwise conformationally heterogeneous monomeric αS.…”

“…In site 1, which has the highest affinity for Cu­(II), the cation is coordinated by the N-terminal NH2 group of M1, the deprotonated backbone amide, the carboxylic groups of D2, and a water molecule. However, it can also involve H50 depending on pH and concentration. , Copper has been shown to be one of the most potent modulators of αS structure as well as a very effective accelerator of αS fibrillation in vitro . AFM-based experiments revealed that the presence of Cu­(II) significantly enhanced the relative abundance of the β-sheetlike structure in the otherwise conformationally heterogeneous monomeric αS .…”

Differential effects of Cu2+ and Fe3+ ions on in vitro amyloid formation of biologically-relevant α-synuclein variants

“…However, if Cu 2? would bind around His50, such an interaction should give rise to a CD signal (Tian et al 2019) and thus we conclude that for our acetylated aSyn variants at our conditions, the affinity of Cu 2? must be less than 100 lM.…”