Cis and trans-acting regulatory elements required for regulation of the CPS1 gene in Saccharomyces cerevisiae

Aminopeptidase yscCo-II: a new cobalt-dependent aminopeptidase from yeast-purification and biochemical characterization

Saccharomyces cerevisiae aminopeptidase yscCo-II (APCo-II) was purified to apparent homogeneity by gel filtration, affinity chromatography and anion-exchange chromatography. APCo-II is an hexameric cobalt-dependent metallo-enzyme with an estimated native molecular mass of 290 kDa. Enzyme activity is only detected in the presence of cobalt ions at pH 7.0. Substrate specificity studies indicate that aminopeptidase yscCo-II cleaves only basic N-terminal residues. PMSF, Cu(2+), 1,10-phenanthroline and bestatin were found to be very strong inhibitors of aminopeptidase yscCo-II activity. Kinetic studies indicated that the enzyme has a similar K(m) and Ka(Co )(activation constant of cobalt) and, following extraction of cobalt from the enzyme, activity was recovered only after cobalt addition.

Nitrogen catabolite repression in Saccharomyces cerevisiae

In Saccharomyces cerevisiae the expression of all known nitrogen catabolite pathways are regulated by four regulators known as Gln3, Gat1, Dal80, and Deh1. This is known as nitrogen catabolite repression (NCR). They bind to motifs in the promoter region to the consensus sequence 5'GATAA 3'. Gln3 and Gat1 act positively on gene expression whereas Dal80 and Deh1 act negatively. Expression of nitrogen catabolite pathway genes known to be regulated by these four regulators are glutamine, glutamate, proline, urea, arginine. GABA, and allantonie. In addition, the expression of the genes encoding the general amino acid permease and the ammonium permease are also regulated by these four regulatory proteins. Another group of genes whose expression is also regulated by Gln3, Gat1, Dal80, and Deh1 are some proteases, CPS1, PRB1, LAP1, and PEP4, responsible for the degradation of proteins into amino acids thereby providing a nitrogen source to the cell. In this review, all known promoter sequences related to expression of nitrogen catabolite pathways are discussed as well as other regulatory proteins. Overview of metabolic pathways and promotors are presented.

Review: biosynthesis and function of yeast vacuolar proteases

The yeast vacuole, which is equivalent to the lysosome of higher eukaryotes, is one of the best characterized degradative organelles. This review describes the biosynthesis and function of yeast vacuolar proteases. Most of these enzymes are delivered to the vacuole via the early compartments of the secretory pathway and the endosome, while one of them is directly imported from the cytoplasm. The proteases are synthesized as precursors which undergo many post-translational modifications before the final active form is generated. Proteolytic activation by developments in the analysis of the functions of vacuolar proteolysis are described. Substrates of the vacuolar proteases are mostly imported via endocytosis or autophagocytosis, and vacuolar proteolysis appears to be mainly important under nutritional stress conditions and sporulation.

Identification of regulatory proteins that might be involved in carbon catabolite repression of the aminopeptidase I gene of the yeast Saccharomyces cerevisiae

Transcription of the vacuolar aminopeptidase yscI (APE1) gene in Saccharomyces cerevisiae has previously been suggested to require the participation of a cis upstream activation sequence (UAS) involved in carbon catabolite repression that responds to glucose. To determine the structure of the APE1 UAS element, we used the 18-bp sequence 5'-ATGAATTAGTCAGCTTCT-3' as the DNA-binding site. Using gel mobility shift assays, we have identified a 78 kDa protein from yeast that binds specifically to both single and double-stranded forms of the UAS DNA-binding site. We have also identified a 48 kDa heterodimer from yeast that binds specifically to the single-stranded form of the UAS and whose DNA binding activity is remarkably heat stable. Even though the APE1 UAS contains a consensus sequence for the binding of the yeast activator protein yAP1, the two DNA-protein complexes could still be detected in a strain bearing a deletion in the YAP1 gene.