title: The yeast STE6 gene encodes a homologue of the mammalian multidrug resistance P-glycoprotein.
abstract: Mammalian tumours displaying multidrug resistance overexpress a plasma membrane protein (P-glycoprotein), which is encoded by the MDR1 gene and apparently functions as an energy-dependent drug efflux pump. Tissue-specific expression of MDR1 and other members of the MDR gene family has been observed in normal cells, suggesting a role for P-glycoproteins in secretion. We have isolated a gene from the yeast Saccharomyces cerevisiae that encodes a protein very similar to mammalian P-glycoproteins. Deletion of this gene resulted in sterility of MATa, but not of MAT alpha cells. Subsequent analysis revealed that the yeast P-glycoprotein is the product of the STE6 gene, a locus previously shown to be required in MATa cells for production of a-factor pheromone. Our findings suggest that the STE6 protein functions to export the hydrophobic a-factor lipopeptide in a manner analogous to the efflux of hydrophobic cytotoxic drugs catalysed by the related mammalian P-glycoprotein. Thus, the evolutionarily conserved family of MDR-like genes, including the hlyB gene of Escherichia coli and the STE6 gene of S. cerevisiae, encodes components of secretory pathways distinct from the classical, signal sequence-dependent protein translocation system.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
authors.forename: J P
authors.initials: JP
authors.lastname: McGrath
authors.forename: A
authors.initials: A
authors.lastname: Varshavsky
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000595:Amino Acid Sequence; D001483:Base Sequence; D004351:Drug Resistance / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D005800:Genes, Fungal; D006023:Glycoproteins; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D010675:Pheromones / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D005656:Fungal Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D010675:Pheromones; C489277:STE6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins