Involvement of histidines 11, 15 and 19 in the binding of zinc to the fusogenic H5WYG peptide

Abstract

The histidine-rich GLFHAIAHFIHGGWHGLIHGWYG peptide (H5WYG) coordinates a Zn2+ 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 Zn2+ ion to H5WYG and suggested that this binding is shared between H11, H19 and probably H15 residues. To clarify the involvement of these histidine residues in the binding to the Zn2+ ion and especially to remove the doubt about the implication of the H15 residue, here we have used three H5WYG mutants termed H5WYGH11A, H5WYGH15A and H5WYGH19A, whose H11, H15 and H19 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 H15 is involved in the binding of the single Zn2+ ion and that it may even favour the setting of another Zn2+ ion. Thus, the three histidines H11, H15 and H19 could lead to a specific structuring of H5WYG that can promote membrane fusion upon the binding of zinc.