Zinc and copper bind to unique sites of histatin 5

Abstract

Metal binding has been suggested to be relevant in the antifungal and antibacterial mechanism of histatin 5, a human salivary protein. Proton nuclear magnetic resonance (NMR) spectra were obtained to investigate the specificity of metal binding to the seven histidyl, one aspartyl and one glutamyl amino acid side-chains of histatin 5 in aqueous solutions. Three C ϵ1–H histidyl and the C γ–H glutamyl resonances of histatin 5 were selectively altered in spectra of solutions containing three equivalents of zinc. Copper binding to histatin 5 resulted in a reduced intensity of C β–H aspartyl resonances, while no evidence for calcium binding was found. These results indicate that zinc binding to histatin 5 involves His-15 present within the –H–E–X–X–H– zinc binding motif, and copper binding occurs within the N-terminal D–S–H–, ATCUN motif.