A SYNTHETIC PEPTIDE ENCOMPASSING THE BINDING-SITE OF THE 2ND ZINC ATOM (THE STRUCTURAL ZINC) OF ALCOHOL-DEHYDROGENASE

A 23-residue peptide was synthesized that incorporates the loop which binds the structural zinc atom of mammalian alcohol dehydrogenases and contributes, in part, to subunit interactions in the native enzyme. Neither the amino acid composition nor the sequence of the peptide resemble those of zinc fingers. The reduced peptide stoichiometrically binds zinc or cobalt to form stable complexes with a dissociation constant for the peptide/Co2+ complex of 2.1-mu-M at pH 7.5. EDTA disrupts the complex. The absorption and magnetic circular dichroic spectra of the cobalt-peptide are indicative of a tetrahedral coordination geometry, and are similar to those of the cobalt-substituted structural site of horse and human (beta-1-beta-1) liver alcohol dehydrogenases. Consequently, the synthetic peptide can serve as a model for the metal-binding segment of alcohol dehydrogenase and for studies of fundamental problems concerning protein/metal interactions.