title: Ectopic potassium uptake in trk1 trk2 mutants of Saccharomyces cerevisiae correlates with a highly hyperpolarized membrane potential.
abstract: Null trk1 trk2 mutants of Saccharomyces cerevisiae exhibit a low-affinity uptake of K+ and Rb+. We show that this low-affinity Rb+ uptake is mediated by several independent transporters, and that trk1Delta cells and especially trk1Delta trk2Delta cells are highly hyperpolarized. Differences in the membrane potentials were assessed for sensitivity to hygromycin B and by flow cytometric analyses of cellular DiOC6(3) fluorescence. On the basis of the latter analyses, it is proposed that Trk1p and Trk2p are involved in the control of the membrane potential, preventing excessive hyperpolarizations. K+ starvation and nitrogen starvation hyperpolarize both TRK1 TRK2 and trk1Delta trk2Delta cells, thus suggesting that other proteins, in addition to Trk1p and Trk2p, participate in the control of the membrane potential. The HAK1 K+ transporter from Schwanniomyces occidentalis suppresses the K+-defective transport of trk1Delta trk2Delta cells but not the high hyperpolarization, and the HKT1 K+ transporter from wheat suppresses both defects, in the presence of Na+. We discuss the mechanism involved in the control of the membrane potential by Trk1p and Trk2p and the causal relationship between the high membrane potential (negative inside) of trk1Delta trk2Delta cells and its ectopic transport of alkali cations.
authors.affiliation: Departamento de Biotecnología, Escuela Técnica Superior de Ingenieros Agrónomos, Universidad Politécnica de Madrid, 28040 Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Madrid
authors.forename: M J
authors.initials: MJ
authors.lastname: Gómez
authors.forename: J
authors.initials: J
authors.lastname: Ramos
authors.forename: A
authors.initials: A
authors.lastname: Rodríguez-Navarro
mesh_terms: D001692:Biological Transport / Q000502:physiology; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D027682:Cation Transport Proteins; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D006921:Hygromycin B / Q000494:pharmacology; D007473:Ion Channels; D008564:Membrane Potentials / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics; D024101:Mitochondrial Proteins; D011188:Potassium / Q000493:pharmacokinetics*; D012413:Rubidium / Q000493:pharmacokinetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D000071256:Uncoupling Protein 1
chemical_list: D002352:Carrier Proteins; D027682:Cation Transport Proteins; D005456:Fluorescent Dyes; D005656:Fungal Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; C085258:TRK2 protein, S cerevisiae; D000071256:Uncoupling Protein 1; C068664:TRK1 protein, S cerevisiae; D006921:Hygromycin B; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D012413:Rubidium; D011188:Potassium