title: Localization and function of the yeast multidrug transporter Tpo1p.
abstract: In Saccharomyces cerevisiae four transporters, Tpo1p-Tpo4p, all members of the major facilitator superfamily, have been shown to confer resistance to polyamines. It was suggested that they act by pumping their respective substrate into the lumen of the vacuole depending on the proton gradient generated by the V-ATPase. Using sucrose gradient ultracentrifugation we found that an hemagglutinin (HA)-tagged Tpo1p as well as its HA-tagged Tpo2p-4p homologues co-localize with plasma membrane markers. Because the HA-tagged Tpo1p carrier protein proved to be functional in conferring resistance to polyamines in TPO1 knockouts, a function of Tpo1p in transport of polyamines across the plasma membrane seemed to be likely. The polyamine transport activity of wild type cells was compared with the respective activity of a TPO1 knockout strain. The results obtained strongly suggest that Tpo1p is a plasma membrane-bound exporter, involved in the detoxification of excess spermidine in yeast. When studying polyamine transport of wild type cells, we furthermore found that S. cerevisiae is excreting putrescine during the fermentative growth phase.
authors.affiliation: Institut für Biochemie, Universität zu Köln, Zülpicher Strasse 47, 50674 Köln, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Albertsen
authors.forename: Inga
authors.initials: I
authors.lastname: Bellahn
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krämer
authors.forename: Sabine
authors.initials: S
authors.lastname: Waffenschmidt
mesh_terms: D017920:Antiporters; D001692:Biological Transport; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D017931:DNA Primers; D018432:Drug Resistance, Multiple; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D027701:Organic Cation Transport Proteins; D011073:Polyamines / Q000493:pharmacokinetics*; D016133:Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D013095:Spermidine / Q000493:pharmacokinetics; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D017920:Antiporters; D002352:Carrier Proteins; D017931:DNA Primers; D026901:Membrane Transport Proteins; D027701:Organic Cation Transport Proteins; D011073:Polyamines; D029701:Saccharomyces cerevisiae Proteins; C475058:TPO1 protein, S cerevisiae; D013095:Spermidine