Abstract
The histidine‐rich GLFHAIAHFIHGGWHGLIHGWYG peptide (H5WYG) coordinates a Zn^2+^ ion and forms a stable peptide–metal complex promoting membrane fusion at physiologic pH. In our previous article titled ‘Histidine‐rich peptide: evidence for a single zinc‐binding site on H5WYG peptide that promotes membrane fusion at neutral pH’ in Journal of Mass Spectrometry (2009, 44, 81–89), tandem mass spectrometry experiments have provided evidence for the binding of a single Zn^2+^ ion to H5WYG and suggested that this binding is shared between H^11^, H^19^ and probably H^15^ residues. To clarify the involvement of these histidine residues in the binding to the Zn^2+^ ion and especially to remove the doubt about the implication of the H^15^ residue, here we have used three H5WYG mutants termed H5WYGH11A, H5WYGH15A and H5WYGH19A, whose H^11^, H^15^ and H^19^ residues were replaced with an alanine residue. The novelty introduced by these new tandem mass spectrometry experiments performed with the mutants is the demonstration that H^15^ is involved in the binding of the single Zn^2+^ ion and that it may even favour the setting of another Zn^2+^ ion. Thus, the three histidines H^11^, H^15^ and H^19^ could lead to a specific structuring of H5WYG that can promote membrane fusion upon the binding of zinc. Copyright © 2009 John Wiley & Sons, Ltd.