Yeast carboxypeptidase Y vacuolar targeting signal is defined by four propeptide amino acids.
The amino-terminal propeptide of carboxypeptidase Y (CPY) is necessary and sufficient for targeting this glycoprotein to the vacuole of Saccharomyces cerevisiae. A 16 amino acid stretch of the propeptide was subjected to region-directed mutagenesis using randomized oligonucleotides. Mutations altering any of four contiguous amino acids, Gln-Arg-Pro-Leu, resulted in secretion of the encoded CPY precursor (proCPY), demonstrating that these residues form the core of the vacuolar targeting signal. Cells that simultaneously synthesize both wild-type and sorting-defective forms of proCPY efficiently sort and deliver only the wild-type molecule to the vacuole. These results indicate that the PRC1 missorting mutations are cis-dominant, implying that the mutant forms of proCPY are secreted as a consequence of failing to interact with the sorting apparatus, rather than a general poisoning of the vacuolar protein targeting system.
Valls
L A
LA
Institute of Molecular Biology, University of Oregon, Eugene 97403.
Winther
J R
JR
Stevens
T H
TH
D000595:Amino Acid Sequence; D001483:Base Sequence; D002268:Carboxypeptidases / Q000235:genetics*; D043402:Cathepsin A; D003001:Cloning, Molecular; D004792:Enzyme Precursors / Q000235:genetics*; D005800:Genes, Fungal; D006023:Glycoproteins / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes; D010641:Phenotype; D011499:Protein Processing, Post-Translational; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D014617:Vacuoles / Q000201:enzymology*
D004792:Enzyme Precursors; D006023:Glycoproteins; D015345:Oligonucleotide Probes; D029701:Saccharomyces cerevisiae Proteins; D002268:Carboxypeptidases; D043402:Cathepsin A; C499283:PRC1 protein, S cerevisiae; C022633:serine carboxypeptidase