title: Isolation and characterization of S. cerevisiae mutants defective in somatostatin expression: cloning and functional role of a yeast gene encoding an aspartyl protease in precursor processing at monobasic cleavage sites.
abstract: The peptide somatostatin exists as two different molecular species. In addition to the most common form, somatostatin-14, there is also a fourteen amino acid N-terminally extended form of the tetradecapeptide, somatostatin-28. Both peptides are synthesized as larger precursors containing paired basic and monobasic amino acids at their processing sites, which upon cleavage generate either somatostatin-14 or -28, respectively. In some species of fish two distinct, but homologous, precursors (prosomatostatin-I and -II) give rise to somatostatin-14 and -28, respectively. Whereas anglerfish prosomatostatin-II was previously shown to release exclusively somatostatin-28, the yeast Saccharomyces cerevisiae proteolytically matures the homologous prosomatostatin-I precursor to somatostatin-28 and -14 as well as to a lysine-extended form of somatostatin-14. The Kex2 endoprotease appears to be essential for the formation of lysine somatostatin-14 and is involved either directly or indirectly in the release of mature somatostatin-14. The isolation of yeast mutants defective in somatostatin-28 expression (sex mutant) allowed the cloning of a non-essential gene, which encodes an aspartyl protease, whose disruption severely affects the cleavage of mature somatostatin-28 from both somatostatin precursors. We conclude that two distinct endoproteases, which demonstrate some cross specificity in vivo, are involved in the proteolytic maturation of prosomatostatin at mono- and dibasic processing sites in yeast.
authors.affiliation: National Research Council of Canada, Biotechnology Research Institute, Montréal, Québec.
authors.forename: Y
authors.initials: Y
authors.lastname: Bourbonnais
authors.forename: J
authors.initials: J
authors.lastname: Ash
authors.forename: M
authors.initials: M
authors.lastname: Daigle
authors.forename: D Y
authors.initials: DY
authors.lastname: Thomas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D005399:Fishes; D005800:Genes, Fungal; D000072235:Mating Factor; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D010452:Peptide Biosynthesis; D010455:Peptides / Q000235:genetics; D010675:Pheromones / Q000235:genetics; D010957:Plasmids; D043484:Proprotein Convertases; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D013004:Somatostatin / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D013381:Subtilisins
chemical_list: D010455:Peptides; D010675:Pheromones; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D013004:Somatostatin; D000072235:Mating Factor; C028456:prosomatostatin; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; D013381:Subtilisins; C058751:KEX2 protein, S cerevisiae; D016282:Aspartic Acid Endopeptidases