Yeast genes controlling responses to topogenic signals in a model transmembrane protein.
Yeast protein insertion orientation (PIO) mutants were isolated by selecting for growth on sucrose in cells in which the only source of invertase is a C-terminal fusion to a transmembrane protein. Only the fraction with an exocellular C terminus can be processed to secreted invertase and this fraction is constrained to 2-3% by a strong charge difference signal. Identified pio mutants increased this to 9-12%. PIO1 is SPF1, encoding a P-type ATPase located in the endoplasmic reticulum (ER) or Golgi. spf1-null mutants are modestly sensitive to EGTA. Sensitivity is considerably greater in an spf1 pmr1 double mutant, although PIO is not further disturbed. Pmr1p is the Golgi Ca(2+) ATPase and Spf1p may be the equivalent ER pump. PIO2 is STE24, a metalloprotease anchored in the ER membrane. Like Spf1p, Ste24p is expressed in all yeast cell types and belongs to a highly conserved protein family. The effects of ste24- and spf1-null mutations on invertase secretion are additive, cell generation time is increased 60%, and cells become sensitive to cold and to heat shock. Ste24p and Rce1p cleave the C-AAX bond of farnesylated CAAX box proteins. The closest paralog of SPF1 is YOR291w. Neither rce1-null nor yor291w-null mutations affected PIO or the phenotype of spf1- or ste24-null mutants. Mutations in PIO3 (unidentified) cause a weaker Pio phenotype, enhanced by a null mutation in BMH1, one of two yeast 14-3-3 proteins.
Tipper
Donald J
DJ
Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA. donald.tipper@umassmed.edu
Harley
Carol A
CA
D000251:Adenosine Triphosphatases / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D005656:Fungal Proteins / Q000378:metabolism; D015723:Gene Library; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D005822:Genetic Vectors; D006026:Glycoside Hydrolases / Q000378:metabolism; D008025:Ligases / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism; D008954:Models, Biological; D016296:Mutagenesis; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D010641:Phenotype; D010940:Plant Proteins / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013997:Time Factors; D044763:Ubiquitin-Conjugating Enzymes; D043324:beta-Fructofuranosidase; D001616:beta-Galactosidase / Q000378:metabolism; D001618:beta-Lactamases / Q000378:metabolism
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D008565:Membrane Proteins; D009153:Mutagens; D010940:Plant Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; C090109:SPF1 protein, plant; D029701:Saccharomyces cerevisiae Proteins; D005020:Ethyl Methanesulfonate; C079437:UBE2L3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D006026:Glycoside Hydrolases; D001616:beta-Galactosidase; D043324:beta-Fructofuranosidase; D008666:Metalloendopeptidases; C491251:STE24 protein, S cerevisiae; D001618:beta-Lactamases; D000251:Adenosine Triphosphatases; D008025:Ligases