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Characterization of potassium transport in wild‐type and isogenic yeast strains carrying all combinations of trk1 , trk2 and tok1 null mutations
Author(s) -
Bertl Adam,
Ramos José,
Ludwig Jost,
LichtenbergFraté Hella,
Reid John,
Bihler Hermann,
Calero Fernando,
Martínez Paula,
Ljungdahl Per O.
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03335.x
Subject(s) - biology , yeast , saccharomyces cerevisiae , mutant , potassium , biochemistry , strain (injury) , in vivo , function (biology) , in vitro , wild type , microbiology and biotechnology , biophysics , gene , genetics , chemistry , organic chemistry , anatomy
Summary Saccharomyces cerevisiaecells express three defined potassium‐specific transport systems en‐coded byTRK1,TRK2andTOK1. 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 oftrk1Δ,trk2Δ andtok1Δ null mutations. Thein vivoK+transport characteristics of each strain have been documented using growth‐based assays, and thein vitrobiochemical 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 ofTRK1andTRK2, strains lack the ability specifically to take up K+, andtrk1Δtrk2Δ 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 thein vivo activity of Tok1p.