Role of Pex21p for Piggyback Import of Gpd1p and Pnc1p into Peroxisomes of Saccharomyces cerevisiae.
Proteins designated for peroxisomal protein import harbor one of two common peroxisomal targeting signals (PTS). In the yeast Saccharomyces cerevisiae, the oleate-induced PTS2-dependent import of the thiolase Fox3p into peroxisomes is conducted by the soluble import receptor Pex7p in cooperation with the auxiliary Pex18p, one of two supposedly redundant PTS2 co-receptors. Here, we report on a novel function for the co-receptor Pex21p, which cannot be fulfilled by Pex18p. The data establish Pex21p as a general co-receptor in PTS2-dependent protein import, whereas Pex18p is especially important for oleate-induced import of PTS2 proteins. The glycerol-producing PTS2 protein glycerol-3-phosphate dehydrogenase Gpd1p shows a tripartite localization in peroxisomes, in the cytosol, and in the nucleus under osmotic stress conditions. We show the following: (i) Pex21p is required for peroxisomal import of Gpd1p as well as a key enzyme of the NAD(+) salvage pathway, Pnc1p; (ii) Pnc1p, a nicotinamidase without functional PTS2, is co-imported into peroxisomes by piggyback transport via Gpd1p. Moreover, the specific transport of these two enzymes into peroxisomes suggests a novel regulatory role for peroxisomes under various stress conditions.
From the Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, and.
Daniel
D
Effelsberg
From the Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, and.
Luis Daniel
LD
Cruz-Zaragoza
Medizinisches Proteom-Center, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Jason
J
Tonillo
From the Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, and.
Wolfgang
W
Schliebs
From the Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, and ralf.erdmann@rub.de.
Ralf
R
Erdmann
D002352:Carrier Proteins / Q000502:physiology*; D019281:Dimerization; D050536:Glycerol-3-Phosphate Dehydrogenase (NAD+) / Q000378:metabolism*; D009535:Nicotinamidase / Q000378:metabolism*; D020675:Peroxisomes / Q000378:metabolism*; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology*; D013312:Stress, Physiological
D002352:Carrier Proteins; C116846:PEX21 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C568531:GPD1 protein, S cerevisiae; D050536:Glycerol-3-Phosphate Dehydrogenase (NAD+); D009535:Nicotinamidase; C474330:PNC1 protein, S cerevisiae
Gpd1p; PTS2; Pex21p; Pex7p; Pnc1p; organelle; peroxisome; protein targeting; protein translocation; protein-protein interaction