Amyloid plaques associated to Alzheimer's disease present a high content of zinc ions. We previously showed that the N-terminal region of the amyloid peptide Abeta constitutes an autonomous zinc-binding domain. This region encompasses the previously identified epitope Abeta(4-10) targeted by antibodies capable to reduce amyloid deposition, but the influence of Abeta/Zn binding on the epitope recognition remains unknown. We demonstrate here the effect of Zn2+ ions on the recognition of peptides sharing the sequence of the Abeta N-terminal domain, by two monoclonal antibodies recognizing the beta-amyloid(4-10) epitope. The presence of Zn2+, but not of other cations, increased the recognition of the (1-16) peptide, while it was without effect on the recognition of the (1-10) peptide. These findings show a zinc-induced conformational change of the (1-16)-N-terminal region of AP3, which results in a better accessibility of the Abeta(4-10) epitope to the anti-Abeta antibodies, and suggest a role of zinc in epitope-based vaccination approaches.