Ubc8p functions in catabolite degradation of fructose-1, 6-bisphosphatase in yeast.
The key gluconeogenic enzyme fructose-1,6-bisphosphatase (FBPase) is synthesized when cells of the yeast Saccharomyces cerevisiae are grown on a non-fermentable carbon source. After shifting the cells to glucose-containing medium, in a process called catabolite degradation, FBPase is selectively and rapidly broken down. We have isolated gid mutants, which are defective in this glucose-induced degradation process. When complementing the defect in catabolite degradation of FBPase in gid3-1 mutant cells with a yeast genomic library, we identified the GID3 gene and found it to be identical to UBC8 encoding the ubiquitin-conjugating enzyme Ubc8p. The in vivo function of Ubc8p (Gid3p) has remained a mystery so far. Here we demonstrate the involvement of Ubc8p in the glucose-induced ubiquitylation of FBPase as a prerequisite for catabolite degradation of the enzyme via the proteasome. Like FBPase, Ubc8p is found in the cytoplasmic fraction of the cell. We demonstrate cytoplasmic degradation of FBPase.
Schüle
T
T
Institut für Biochemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart and Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität Frankfurt, Marie-Curie-Strabetae 9, 60439 Frankfurt, Germany.
Rose
M
M
Entian
K D
KD
Thumm
M
M
Wolf
D H
DH
D001673:Biodegradation, Environmental; D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D008025:Ligases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes; D014452:Ubiquitins / Q000378:metabolism*
D005656:Fungal Proteins; D014452:Ubiquitins; D044763:Ubiquitin-Conjugating Enzymes; C409686:ubiquitin-conjugating enzyme UBC8; D006597:Fructose-Bisphosphatase; D008025:Ligases