Regulation of yeast H+-ATPase by protein kinases belonging to a family dedicated to activation of plasma membrane transporters

The regulation of electrical membrane potential is a fundamental property o f living cells. This biophysical parameter determines nutrient uptake, intr acellular potassium and turgor, uptake of toxic cations, and stress respons es. In fungi and plants, an important determinant of membrane potential is the electrogenic proton-pumping ATPase, but the systems that modulate its a ctivity remain largely unknown. We have characterized two genes from Saccha romyces cerevisiae, PTK2 and HRK1 (YOR267c), that Encode protein kinases im plicated in activation of the yeast plasma membrane H+-ATPase (Pma1) in res ponse to glucose metabolism. These kinases mediate, directly or indirectly, an increase in affinity of Pma1 for ATP, which probably involves Ser-899 p hosphorylation, Ptk2 has the strongest effect on Pma1, and ptk2 mutants exh ibit a pleiotropic phenotype of tolerance to toxic cations, including sodiu m, lithium, manganese, tetramethylammonium, hygromycin B, and norspermidine , A plausible interpretation is that ptk2 mutants have a decreased membrane potential and that diverse cation transporters are voltage dependent. Acco rdingly, ptk2 mutants exhibited reduced uptake of lithium and methylammoniu m, Ptk2 and Hrk1 belong to a subgroup of yeast protein kinases dedicated to the regulation of plasma membrane transporters, which include Npr1 (regula tor of Gap1 and Tat2 amino acid transporters) and Ha14 and Ha15 (regulators of Trkl and Trk2 potassium transporters),