Zinc(II) modulates specifically amyloid formation and structure in model peptides
Résumé
Metal ions such as zinc and copper can have dramatic effects on the aggregation kinetics of and the structures formed by several amyloidogenic peptides/proteins. Depending on the identity of the amyloidogenic peptide/protein and the conditions, Zn(II) and Cu(II) can promote or inhibit fibril formation, and in some cases these metal ions have opposite effects. To better understand this modulation of peptide aggregation by metal ions, the impact of Zn(II) binding to three amyloidogenic peptides (Aβ14-23, Aβ11-23, and Aβ11-28) on the formation and structure of amyloid-type fibrils was investigated. Zn(II) was able to accelerate fibril formation for all three peptides as measured by thioflavin T fluorescence and transmission electron microscopy. The effects of Zn(II) on Aβ11-23 and Aβ11-28 aggregation were very different compared with the effects of Cu(II), showing that these promoting effects were metal-specific. X-ray absorption spectroscopy suggested that the Zn(II) binding to Aβ11-23 and Aβ11-28 is very different from Cu(II) binding, but that the binding is similar in the case of Aβ14-23. A model is proposed in which the different coordination chemistry of Zn(II) compared with Cu(II) explains the metal-specific effect on aggregation and the difference between peptides Aβ14-23 and Aβ11-23/Aβ11-28.