MOLECULAR CHARACTERIZATION OF 2 HIGH-AFFINITY SULFATE TRANSPORTERS INSACCHAROMYCES-CEREVISIAE

Strains resistant to the toxic analogues of sulfate, selenate and chro mate have been isolated. Their genetic analysis allowed us to identify four genes. One, called MET28, encodes a transcriptional factor. The three other genes, called SUL1, SUL2 and SUL3, encode proteins involve d in sulfate transport. The sequence of Sul1p and Sul2p indicate that they are integral membrane proteins exhibiting, respectively, 11 and 1 0 transmembrane domains. Moreover, Sul1p and Sul2p share a high degree of similarity. Sulfate transport kinetic studies made with parental a nd mutant strains show that, as expected from genetic results, Sacchar omyces cerevisiae has two high affinity sulfate transport systems. Sul 3p has been shown to be involved in the transcriptional regulation of the SUL2 gene.