Evidence for different cadmium detoxification system in Saccharomyces Cerevisiae.

The yeast genome contains 30 ABC proteins. Of these proteins 22 are predicted to contain multiple membrane spans and are thus considered to be true ABC transporters, while the remaining 8 presumably carry out non-transport functions in the cell. Phylogenetic analyses established the existence of six ABC subfamilies. Member of ABCC subfamily also called MRP are involved in the efflux of xenobiotics in eukaryotic cells. Five members of the ABCC subfamily are full length (Ycf1p, Bpt1p, Ybt1, Nft1p, and Vmr1p), one is short (Yor1p). While Yor1p localizes to the plasma membrane the others localized to the vacuolar membrane (1). In many cases yeast ABCCs exhibit overlapping substrate specificity. There is not a critical functional distinction between full-length and short ABCCs. On glucose medium the main transporter of cadmium-GS conjugates into the vacuole is the Yeast Cadmium Factor, Ycf1p (2), while on ethanol/glycerol medium Vmr1p mediates cadmium detoxification (3). In this study, experiments carried out in presence of L-Buthionine-sulfoximine (BSO), a specific inhibitor of γglutamylcysteine synthetase, on Saccharomyces Cerevisiae wild type and Vmr1p- deleted strain, suggested that on ethanol/glycerol medium the Vmr1p mediates cadmium detoxification but not through formation of Cd[GS]2 complexes. 1. Paumi C, et al. (2009) Microbiol.Mol.Biol.Rev 73, 577 2. Li Z, Szczypka M, Lu Y, Thiele D & Rea P. J Biol Chem (1996) 271: 6509–6517. 3. D Wawrzycka, I Sobczak, G Bartosz, T Bocer, S Ułaszewski1 & Andr´e Goffeau. FEMS Yeast Res. 2010;10(7):828-38.