title: Influence of altered plasma membrane fatty acid composition on cesium transport characteristics and toxicity in Saccharomyces cerevisiae.
abstract: The influence of altered plasma membrane fatty acid composition on cesium uptake and toxicity was investigated in Saccharomyces cerevisiae. Detailed kinetic studies revealed that both the Vmax and Km values for Cs+ transport increased (by approximately twofold in the latter case) when S. cerevisiae was grown in medium supplemented with the polyunsaturated fatty acid linoleate. In addition, Cs+ uptake by linoleate-enriched cells was considerably less sensitive to the competitive effects of other monovalent cations (K+, Rb+, and NH4+) than that by unsupplemented cells. Stimulation of Cs+ uptake in the presence of certain K+ and Rb+ concentrations was only evident in linoleate-enriched S. cerevisiae. At 100 mM CsCl, the initial rate of Cs+ uptake was greater in linoleate-supplemented cells than in unsupplemented cells and this was reflected in a more rapid displacement of cellular K+. However, little difference in net Cs+ accumulation between linoleate-supplemented and unsupplemented cells was evident during prolonged incubation in buffer or during growth. Thus, Cs+ toxicity was similar in linoleate-supplemented and unsupplemented cells. The results were consistent with the Cs+ (K+) transport mechanism adopting an altered conformational state in linoleate-enriched S. cerevisiae.
authors.affiliation: Department of Biology, Georgia State University, Atlanta 30303, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hoptroff
authors.forename: S
authors.initials: S
authors.lastname: Thomas
authors.forename: S V
authors.initials: SV
authors.lastname: Avery
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002414:Cations, Monovalent / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002586:Cesium / Q000378:metabolism* / Q000633:toxicity; D003470:Culture Media; D005227:Fatty Acids; D019787:Linoleic Acid / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012413:Rubidium / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D002414:Cations, Monovalent; D003470:Culture Media; D005227:Fatty Acids; D000644:Quaternary Ammonium Compounds; D002586:Cesium; D019787:Linoleic Acid; D012413:Rubidium; D011188:Potassium