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http://dx.doi.org/10.5352/JLS.2009.19.12.1685

Heterologous Expression of Fission Yeast Heavy Metal Transporter, SpHMT-1, Confer Tolerance to Cadmium in Cytosolic Phytochelatin-Deficient Saccharomyces cerevisiae  

Lee, Sang-Man (Division of Applied Biology and Chemistry, School of Applied Biosciences, College of Agriculture and Life Sciences, Kyungpook National University)
Publication Information
Journal of Life Science / v.19, no.12, 2009 , pp. 1685-1689 More about this Journal
Abstract
Phytochelatins (PCs) are small polypeptides synthesized by PC synthase (PCS). They are present in various living organisms including plants, fission yeast, and some animals. The presumed function of PCs is the sequestration of cytosolic toxic heavy metals like cadmium (Cd) into the vacuoles via vacuolar membrane localized heavy metal tolerance factor 1 (HMT-1). HMT-1 was first identified in fission yeast (SpHMT-1), and later in Caenorhabdtis (CeHMT-1). Recently, its homolog has also been found in PC-deficient Drosophila (DmHMT-1), and this homolog has been shown to be involved in Cd detoxification, as confirmed by the heterologous expression of DmHMT-1 in fission yeast. Therefore, the dependence of HMT-1 on PC in Cd detoxification should be re-evaluated. I heterologously expressed SpHMT-1 in cytosolic PC-deficient yeast, Saccharomycea cerevisiae, to understand the dependence of HMT-1 on PC. Yeast cells expressing SpHMT-1 showed increased tolerance to Cd compared with control cells. This result indicates that SpHMT-1 is not strictly correlated with PC production on its function. Moreover, yeast cells expressing SpHMT-1 showed increased tolerance to exogenously applied glutathione (GSH) compared with control cells, and the tolerance to Cd was further increased by exogenously applied GSH, while tolerance in control cells was not. These results indicate that the function of SpHMT-1 in Cd detoxification does not depend on PCs only, and suggest that SpHMT-1 may sequester cytosolic GSH-Cd complexes into the vacuole.
Keywords
Cadmium; glutathione; heavy metal tolerance factor; phytochelatin; vacuole; yeast;
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