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Conformational changes of Aβ peptide result in its transformation from native monomeric state to the toxic soluble dimers, oligomers and insoluble aggregates that are hallmarks of Alzheimer’s disease (AD). Interactions of zinc ions with Aβ are mediated by the N-terminal Aβ1–16 domain and appear to play a key role in AD progression. There is a range of results indicating that these interactions trigger the Aβ plaque formation. We have determined structure and functional characteristics of the metal binding domains derived from several Aβ variants and found that their zinc-induced oligomerization is governed by conformational changes in the minimal zinc binding site 6HDSGYEVHH14. The residue H6 and segment 11EVHH14, which are part of this site are crucial for formation of the two zinc-mediated interaction interfaces in Aβ. These structural determinants can be considered as promising targets for rational design of the AD-modifying drugs aimed at blocking pathological Aβ aggregation.

Zinc-induced aggregation of the amyloid-β peptide (Aβ) is a hallmark molecular feature of Alzheimer's disease (AD). Recently it was shown that phosphorylation of Aβ at Ser8 promotes the formation of toxic aggregates. In this work, we have studied the impact of Ser8 phosphorylation on the mode of zinc interaction with the Aβ metal-binding domain 1-16 using isothermal titration calorimetry, electrospray ionization mass spectrometry and NMR spectroscopy. We have discovered a novel zinc binding site ((6)HDpS(8)) in the phosphorylated peptide, in which the zinc ion is coordinated by the imidazole ring of His6, the phosphate group attached to Ser8 and a backbone carbonyl group of His6 or Asp7. Interaction of the zinc ion with this site involves His6, thereby withdrawing it from the interaction pattern observed in the non-modified peptide. This event was found to stimulate dimerization of peptide chains through the (11)EVHH(14) site, where the zinc ion is coordinated by the two pairs of Glu11 and His14 in the two peptide subunits. The proposed molecular mechanism of zinc-induced dimerization could contribute to the understanding of initiation of pathological Aβ aggregation, and the (11)EVHH(14) tetrapeptide can be considered as a promising drug target for the prevention of amyloidogenesis.