Zn– and Cd–Metallothionein Recombinant Species from the Most Diverse Phyla May Contain Sulfide (S2−) Ligands

A sulfide surprise: The analysis of ZnII–, CdII–, and CuI–MT recombinant preparations of metallothioneins (MTs) from many organisms provides clear evidence that sulfide ions are present in nearly all their physiologically stable ZnII–MT and CdII–MT complexes (see picture), but in none of the CuI–MT species. The features of the MT complexes are in good correlation with those reported for plant and yeast ZnII–or CdII–γ-glutamyl peptides.