Identification of histidine residues that act as zinc ligands in β-lactamase II by differential tritium exchange

Abstract

Four histidine-containing peptides were isolated from a tryptic digest of the Zn2+-requiring .beta.-lactamase II from Bacillus cereus. One of these peptides probably contains 2 histidine residues. The presence of 1 equivalent of Zn2+ substantially decreases the rate of exchange of the C-2 proton in at least 2 and probably 3 of the histidine residues of these peptides for solvent 3H. Peptides containing at least 2 of the 3 histidine residues acting as Zn2+ ligands at the tighter Zn2+-binding site of .beta.-lactamase II were identified.