MET16 encodes phosphoadenosine-phosphosulfate reductase (3'-phosphoadenylylsulfate reductase; PAPS reductase) (3), an enzyme involved in the sulfate assimilation pathway in yeast (1, 4, 5). MET16 was first identified in a screen for methionine auxotrophs (1), as sulfate assimilation is required for methionine biosynthesis in yeast (4, 3) Transcription of MET16 and other genes required for sulfate assimilation is activated in the absence of methionine. A complex comprising Cbf1p, the transcriptional activator Met4p, and Met28p binds to a UAS in the MET16 promoter (6, 7, 8, 9, 10). Mutations in MET4 abolish transcription of MET16, while mutations in MET1, MET8, and MET17, which encode other sulfate assimilation enzymes, abolish PAPS reductase activity but do not affect transcription of MET16 (3). It has been suggested that the enzymes involved in sulfate assimilation form a complex (3). Met16p is similar to the PAPS reductases from E. coli (3) and Aspergillus nidulans (11).

Last updated: 1999-09-23