Transformation of cadmium-binding complexes during cadmium sequestration in fission yeast

Fission yeast responded to environmental cadmium by producing a family of small Cd-binding peptides, phytochelatins (PCn). A low molecular weight (LMW) complex essentially composed of PC2, and PC3 was produced and then disappeared gradually in 24 hrs after Cd treatment, which served as a transient form for a temporary but quick relief of Cd in the cytosoL It had been reported that the LMW complex was further transported into the vacuole by an ABC-type protein (HMT1), and a higher molecular weight (HMW) complex was formed in the vacuole. Results from gel filtration chromatography and HPLC analysis showed that the transformation of the LMW to the HMW complex was accompanied with a rearrangement of its PCn component. Besides, the molecular conformation of the HMW complex changed from a relaxed form in the early stage to a more condensed conformation during cell aging. And the transformation of the LMW into the HMW complex by the addition of sulfide in the test tube was demonstrated.