Characterization of potassium transport in wild-type and isogenic yeast strains carrying all combinations of trk1, trk2 and tok1 null mutations

Mol Microbiol. 2003 Feb;47(3):767-80. doi: 10.1046/j.1365-2958.2003.03335.x.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport*
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism
  • Cations / metabolism
  • Culture Media
  • Electrophysiology
  • Genes, Fungal
  • Mutation*
  • Potassium / metabolism*
  • Potassium Channels / genetics
  • Potassium Channels / metabolism
  • Rubidium / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism*


  • Cation Transport Proteins
  • Cations
  • Culture Media
  • Potassium Channels
  • Saccharomyces cerevisiae Proteins
  • TOK1 protein, S cerevisiae
  • TRK2 protein, S cerevisiae
  • TRK1 protein, S cerevisiae
  • Rubidium
  • Potassium