Analysis of the mKir2.1 channel activity in potassium influx defective Saccharomyces cerevisiae strains determined as changes in growth characteristics

Potassium uptake defective Saccharomyces cerevisiae strains (Delta trk1,2 and Delta trk1,2 Delta tok1) were used for the phenotypic analysis of the mouse inward rectifying Kir2.1 channel by growth analysis. Functional expression of both, multi-copy plasmid and chromosomally expressed GFP-mKir2.1 fusion constructs complemented the potassium uptake deficient phenotype in a pH(out) dependent manner. Upon application of Hygromycin B to chromosomally mKir2.1 expressing cells, significantly lower toxin sensitivity (EC50 15.4 mu M) compared to Delta trk1,2 Delta tok1 cells (EC50 2.6 mu M) was observed. Growth determination of mKir2.1 expressing strains upon application of Ag+, Cs+ and Ba2+ as known blockers of mKir2.1 channels revealed significantly decreased channel function. Cells with mKir2.1 were about double sensitive to AgNO3, 350-fold more sensitive to CsCl and 1500-fold more sensitive to BaCl2 in comparison to the respective controls indicating functional expression and correct pharmacology. (c) 2005 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.