This work presents the further purification of a Cd-linking protein in Oxytricha granulifera by reverse-phase chromatography. This protein contains 25% cysteine and no aromatic amino acid. It may be considered as a chelatin with some similarity to metallothioneins. During the purification of another Cd-linking compound, we were able to demonstrate that the H protein precursor of glycine cleavage is present in Oxytricha. This is the first finding of the presence of this system in Protozoa.