Roles for intracellular cation transporters in respiratory growth of yeast.

Potassium is involved in copper and iron metabolism in eukaryotic Golgi apparatus, but it is not clear yet whether potassium distributions in other vesicles also affect copper and iron metabolism. Here we show that respiratory growth and iron acquisition by the yeast Saccharomyces cerevisiae relies on potassium (K+) compartmentalization to the mitochondria, as well as the vacuole and late endosome via K+/H+ exchangers Mdm38p, Vnx1p and Nhx1p, respectively. The data indicate that NHX1 and VNX1 knock-out cells grow better than wild type cells on non-fermentable YPEG media, while MDM38 knock-out cells display a growth defect on YPEG media. The over expression of the KHA1 gene located on the Golgi apparatus partially compensates for the growth defect of the MDM38 knock-out strain. The results suggest that the vacuole and late endosome are important potassium storage vesicles and Mdm38p affects the mitochondrial function by regulating copper and iron metabolism. Our study reveals potassium compartmentalization to the subcellular vesicles is relevant for respiratory growth by improving copper utilization and promoting iron absorption.