The Hsp70 chaperone Ssa1 is essential for catabolite induced degradation of the gluconeogenic enzyme fructose-1,6-bisphosphatase.
Fructose-1,6-bisphosphatase (FBPase) is a key regulatory enzyme of gluconeogenesis. In the yeast Saccharomyces cerevisiae, it is only expressed when cells are grown in medium with nonfermentable carbon sources. Addition of glucose to cells leads to inactivation of FBPase and degradation via the ubiquitin-proteasome system. Polyubiquitination of FBPase is carried out by the Gid complex, a multi-subunit ubiquitin ligase. Using tandem affinity purification and subsequent mass spectrometry we identified the Hsp70 chaperone Ssa1 as a novel interaction partner of FBPase. Studies with the temperature-sensitive mutant ssa1-45(ts) showed that Ssa1 is essential for polyubiquitination of FBPase by the Gid complex. Moreover, we show that degradation of an additional gluconeogenic enzyme, phosphoenolpyruvate carboxykinase, is also affected in ssa1-45(ts) cells demonstrating that Ssa1 plays a general role in elimination of gluconeogenic enzymes.
Institut für Biochemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
Jeannette
J
Juretschke
Ruth
R
Menssen
Albert
A
Sickmann
Dieter H
DH
Wolf
D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D005943:Gluconeogenesis; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
D018840:HSP70 Heat-Shock Proteins; C090869:SSA3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D006597:Fructose-Bisphosphatase