ISOLATION OF PHOSPHORIBOSYLPYROPHOSPHATE SYNTHETASE (PRS1) GENE FROM CANDIDA-ALBICANS

We have isolated a 3.7 kb EcoR1 fragment from a genomic library of Can dida albicans which displayed a 65% level of identity with the PRS gen e family (PRS) of Saccharomyces cerevisiae. The PRS gene encodes a pho sphoribosylpyrophosphate (PRPP) synthetase of S. cerevisiae, which cat alyses the synthesis of purines, pyrimidines, and amino acids such as histidine and tryptophan. By Northern analyses, we observed that the e ntire 3.7 kb EcoR1 fragment as well as a 1.1 kb KpnI-SacI internal fra gment of the 3.7 kb EcoR1 fragment hybridized to the same 1.4 kb trans cript. An internal 2.6 kb KpnI fragment was subcloned and sequenced. A deduced sequence of 321 amino acids representing a polypeptide of 35. 2 kDa was determined. A FASTA search indicated that the C albicans PRS (Ca PRS1) had an overall homology at the amino acid level of 91% with the S. cerevisiae PRS3. Putative transcriptional start and terminatio n sequences as well as a cation-binding, PRPP synthetase signature seq uence were identified. Ca PRS1 was localized to chromosome 2 of the C. albicans genome. Low stringency hybridizations indicates that the org anism may possess multiple PRS genes. The function of these genes in n itrogen signaling is discussed. The Ca PRS1 sequence submitted to the EMBL data library is available under Accession Number U23934.