CATABOLITE INACTIVATION OF HETEROLOGOUS FRUCTOSE-1,6-BISPHOSPHATASES AND FRUCTOSE-1,6-BISPHOSPHATASE-BETA-GALACTOSIDASE FUSION PROTEINS IN SACCHAROMYCES-CEREVISIAE

Fructose-1,6-bisphosphatase (FruP(2)ase) from Saccharomyces cerevisiae is rapidly inactivated upon addition of glucose to a culture growing on non-sugar carbon sources. Under the same conditions the FruP(2)ases from Schizosaccharomyces pombe or Escherichia coli expressed in S. ce revisiae were not affected. A chimaeric protein containing the first 1 78 amino acids from the N-terminal half of S. cerevisiae FruP(2)ase fu sed to E. coli beta-galactosidase was susceptible to catabolite inacti vation. Elimination of a putative destruction box, RAELVNLVG...KK....K ., beginning at amino acid 60 did not prevent catabolite inactivation. Similarly a change of the vacuole-targeting sequence QKKLD, amino aci ds 80-84, to QKNSD did not affect significantly the course of inactiva tion of beta-galactosidase. A fusion protein carrying only the first 1 38 amino acids from FruP(2)ase was inactivated at a higher rate than t he one carrying the first 178, suggesting the existence of a protectiv e region between amino acids 138 and 178. A fusion protein carrying th e first 81 amino acids from FruP(2)ase was inactivated by glucose at a similar rate to the one carrying the 178 amino acids, but one with on ly the first 18 amino acids was resistant to catabolite inactivation. Inactivation of FruP(2)ase in mutants ubr1 that lack a protein require d for ubiquitin-dependent proteolysis, or pra1 that lack vacuolar prot ease A, proceeded as in a wild type. Our results suggest that at least two domains of FruP(2)ase may mark beta-galactosidase for catabolite inactivation and that FruP(2)ase can be inactivated by a mechanism ind ependent of transfer to the vacuole.