Role of the Nha1 antiporter in regulating K+ influx in Saccharomyces cerevisiae

NHA1 encodes a K+ (Na+)/H+ antiporter in the plasma membrane of Saccharomyces cerevisiae. We report that cells expressing the NHA1 gene contained less K+ than the mutant lacking the gene when grown without K+ limitation. They also grew better at low K+ and showed higher affinity of transport than the nha1 strain. In agreement with the function of an electroneutral cation/H+ antiporter, the effect was only observed at acidic pH. The improved growth and transport depended on the presence of Trk1p (the main K+ influx system) and did not require the product of TRK2. We propose that Nha1p regulates the potassium content of the cell and, as a consequence, can affect the activity of the main K+ influx system (Trk1p). Copyright (C) 2002 John Wiley Sons, Ltd.