Occurrence of Acid-Labile Sulfide in Cadmium-Binding Peptide 1 from Fission Yeast

Abstract

Two kinds of Cd-binding peptides (Cd-BP1 and Cd-BP2) are induced in fission yeast upon addition of CdCl₂ to the culture medium (1). It was also reported that CdBPI and Cd-BP2 consisted of the same components, unit peptides (Cys₃, Glu₃, Gly₁) and Cd atoms, though the respective amounts of components in each molecule were different (1, 2). Now, we have found that Cd-BP1 contains about 1 mol of acidlabile sulfide per mol, and Cd-BP2 contains no labile sulfide. The existence of the labile sulfide explains the unique physicochemical characteristics of Cd-BPI. Since acid-labile sulfide has not been found in metallothioneins or other metallothionein-like metal-binding proteins, the occurrence of labile sulfide in Cd-BPI is the first instance in this field.