Functional analysis of phytochelatin synthase from Arabidopsis thaliana and its expression in Escherichia coli and Saccharomyces cerevisiae

Plants, like other organisms, have adaptive mechanisms whereby they are able to respond to both nutrient deficiencies and toxicities. Phytochelatins (PCs) play an essential role in heavy-metal detoxification in plants, fungi and worms. PCs chelate heavy metals and then PCmetal complexes are translocated across the tonoplast and sequestered in vacuoles. PCs are synthesized from glutathione by the enzyme PC synthase (PCS). Comparison of the deduced amino acid sequences of PCS suggests that the C-terminal domain may be important for activation of the enzyme. We established the method for purification of PCS from Arabidopsis thaliana to perform enzymatic characterization. Moreover, the PCS gene was expressed in E. coli and S. cerevisiae to enhance tolerance to toxicity of cadmium ion. The obtained results implied that the some regions of the PCS may serve as regulatory region through interaction with cadmium ion and/or oxygen related compounds. Moreover, PCS expression dramatically enhanced cadmium ion tolerance of different organisms. Based on our findings, functional mechanism for PCS activation was hypothesized. q 2004 Elsevier Ltd. All rights reserved.