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Characterization of potassium cation transport systems in the yeast Zygosaccharomyces rouxii Potassium has become absolutely necessary cation for living cells, including yeasts, because it plays several important roles in physiological processes. Intracellular concentration of K+ in yeasts is usually between 200 mM and 300 mM, while the external K+ concentration is ranging from molar to micromolar. To adapt to environments with low K+ content, yeast cells employ various K+ high-affinity uptake systems, e.g. Trk, Hak and K+ -ATPase, that provide cells with the sufficient amount of potassium. The recent release of the complete sequence of the osmotolerant yeast Zygosaccharomyces rouxii genome allowed us to search homologues of the known yeast potassium uptake systems. We have found just one gene encoding a putative potassium transporter homologous to the S. cerevisie TRK1. For the characterisation of transport properties and physiological roles of the product of this gene, named ZrTRK1, three approaches have been used. First, the IT tools serve to analyse sequence characteristics, phylogenetic relationships etc. The second approach involves cloning of the gene and its expression in a S. cerevisiae mutant strain lacking its own two Trk systems, characterisation of transformants' growth phenotypes and... |
