THE YEAST PLASMA-MEMBRANE URACIL PERMEASE IS STABILIZED AGAINST STRESS-INDUCED DEGRADATION BY A POINT MUTATION IN A CYCLIN-LIKE DESTRUCTION BOX

Yeast uracil permease appears to be fairly stable in exponentially growing cells, but it; undergoes rapid endocytosis followed by degradation when cells are submitted to adverse conditions, such as nutrient starvation or inhibition of protein synthesis. Uracil permease has a sequence (RIALGSLTD) that is very similar to the ''destruction box'' of mitotic cyclins. This box is required for the ubiquitin-dependent proteolysis of cyclins. We replaced the invariant arginine residue of the putative ''destruction box'' in uracil permease by an alanine. The mutation significantly protected the permease against stress-induced degradation. This result suggests that ligation to ubiquitin could be a signal for uracil permease degradation. (C) 1994 Academic Press, Inc.