Carboxypeptidase yscS: gene structure and function of the vacuolar enzyme

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Abstract
The gene encoding carboxypeptidase yscS in Saccharomyces cerevisiae, CPS1, was cloned by complementation of the cps1‐3 mutation. The cloned CPS1 gene, which again enabled a leucine auxotrophic cps1‐3 mutant to grow on the modified dipeptide Cbz‐Gly‐Leu (Cbz, benzyloxycarbonyl) as sole leucine source, was sequenced and found to consist of an open reading frame of 1728 bp encoding a protein of 576 amino acids. The putative protein contains a hydrophobic stretch of 20 amino acids and a putative signal sequence cleavage site. Five putative N‐glycosylation sites are also in the protein sequence. This data is consistent with the previous finding of carboxypeptidase yscS being a vacuolar peptidase. Chromosomal disruption of the CPS1 gene completely abolishes carboxypeptidase yscS activity. This protein is yet another member of the peptidases in S. cerevisiae involved in nitrogen metabolism.