In this study we demonstrate that ade9 plays an indirect role in purine biosynthesis as a non-functional allele of SER1 in Saccharomyces cerevisiae. The SER1 locus, encoding 3-phosphoserine aminotransferase required for serine biosynthesis, is located on chromosome XV and resides approximately where ade9 had previously been mapped genetically. A minimal functional construct of SER1 is necessary and sufficient to complement both the adenine- and serine-requiring phenotypes of ade9 strains. In addition, adequate exogenous serine levels mask the adenine phenotype of ade9. A disruption of SER1 behaves in the same manner phenotypically as the original ade9 strain. Therefore, ade9 can be more accurately described as an allele of SER1.
Copyright 1999 John Wiley & Sons, Ltd.