Characterization of a Dominant, Constitutive Mutation, PHOO , for the Repressible Acid Phosphatase Synthesis in Saccharomyces cerevisiae

Abstract

An apparent operator-constitutive mutation was discovered in the repressible acid phosphatase system in Saccharomyces cerevisiae . The site of mutation, designated PHOO , was found to be closely linked to the phoD locus. The mutant allele, PHOO , was semidominant over the wild-type allele and effective for the expression of the phoD gene in cis position. The phoD mutation gave rise to a defective phenotype for the formation of the repressible acid phosphatase. On the other hand, neither the repressible acid phosphatase activity in the cell-free extracts prepared from cells of the temperature-sensitive phoD mutant grown at 25 C, nor that of the revertants from the phoD mutants, could be distinguished from that of the wild-type strain with respect to thermolability and K m value for p -nitrophenylphosphate. These results strongly suggest that the phoD gene is not a structural gene, but a regulatory gene exerting positive control for the formation of repressible acid phosphatase. Close similarity between the apparent role of the phoO-PHOD gene cluster and that of the c-GAL4 gene cluster in the galactose system of S. cerevisiae could be inferred.