Regulation of expression of the amino acid transporter gene BAP3 in Saccharomyces cerevisiae.

The BAP3 gene of Saccharomyces cerevisiae encodes a protein with a high similarity to the BAP2 gene product, a high-affinity permease for branched-chain amino acids. In this paper, we show that, like BAP2, the expression of the BAP3 gene in S. cerevisiae is induced by the addition of branched-chain amino acids to the medium. Unexpectedly, most other naturally occurring L-amino acids found in proteins (with the exception of proline, lysine, arginine and histidine) have the same effect on the expression of BAP3. The induction of BAP3 expression appears to be dependent on Stp1p, a nuclear protein, previously shown to be involved in pre-tRNA maturation and also required for the expression of BAP2, as induction is no longer observed in an stp

Organization and expression of a two-gene cluster in the arginine biosynthesis of Saccharomyces cerevisiae

In Saccharomyces cerevisiae, argB and argC define two adjacent and complementing loci, with mutants defective in two consecutive steps of arginine biosynthesis: N-acetylglutamate kinase (AG-kinase) and N-acetylglutamyl-phosphate reductase (AGPreductase). These enzymic activities are readily separated by ammonium sulfate fractionation or Sephadex G-200 chromatography. This suggests that each activity is carried in vivo by a different protein. The synthesis of the two enzymes is coordinately regulated, with an 85-fold difference in specific activities between fully repressed and fully derepressed cells. Missense mutations in the argB locus are defective in AGkinase only. Nonsense mutations in the argB locus are defective in both activities. Missense and nonsense mutations in the argC locus are defective in AGPreductase, with a few alleles also showing a reduced level of AGkinase. These data are best explained by assuming that argB and argC are two genes transcribed as a single messenger from argB to argC. This messenger produces in vivo two distinct proteins corresponding to the argB and argC gene products, either because translation can be initiated at the beginning of both genes, or because a large polypeptide is specifically cut in vivo to yield the gene products of argB and argC. © 1979 Springer-Verlag.SCOPUS: ar.jinfo:eu-repo/semantics/publishe