Characterization of potassium transport in wild-type and isogenic yeast strains carrying all combinations of trk1, trk2 and tok1 null mutations.
Saccharomyces cerevisiae cells express three defined potassium-specific transport systems en-coded by TRK1, TRK2 and TOK1. To gain a more complete understanding of the physiological function of these transport proteins, we have constructed a set of isogenic yeast strains carrying all combinations of trk1delta, trk2delta and tok1delta null mutations. The in ... vivo K+ transport characteristics of each strain have been documented using growth-based assays, and the in vitro biochemical and electrophysiological properties associated with K+ transport have been determined. As has been reported previously, Trk1p and Trk2p facilitate high-affinity potassium uptake and appear to be functionally redundant under a wide range of environmental conditions. In the absence of TRK1 and TRK2, strains lack the ability specifically to take up K+, and trk1deltatrk2delta double mutant cells depend upon poorly understood non-specific cation uptake mechanisms for growth. Under conditions that impair the activity of the non-specific uptake system, termed NSC1, we have found that the presence of functional Tok1p renders cells sensitive to Cs+. Based on this finding, we have established a growth-based assay that monitors the in vivo activity of Tok1p.
Mesh Terms:
Biological Transport, Cation Transport Proteins, Cations, Culture Media, Electrophysiology, Genes, Fungal, Mutation, Potassium, Potassium Channels, Rubidium, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Biological Transport, Cation Transport Proteins, Cations, Culture Media, Electrophysiology, Genes, Fungal, Mutation, Potassium, Potassium Channels, Rubidium, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Mol. Microbiol.
Date: Feb. 01, 2003
PubMed ID: 12535075
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