title: Biogenesis of the yeast vacuole (lysosome). Proteinase yscB contributes molecularly and kinetically to vacuolar hydrolase-precursor maturation.
abstract: The vacuolar proteinase yscB (PrB) has been implicated in the final maturation of procarboxypeptidase yscY (pro-CpY) to the mature wild-type form CpYb of 61 kDa. In PrB-deficient mutants, only the proteinase yscA processed form CpYa of 62 kDa is found [Mechler, B., Müller, H. & Wolf, D. H. (1987) EMBO J. 6, 2157-2163]. We report now that, akin to CpY, two forms of mature proteinase yscA (PrA) can be distinguished. In PrB-deficient mutant cells, PrAa, migrating at about 43 kDa in SDS/PAGE, is found, whereas PrAb, found in wild-type cells, had the known molecular mass of 42 kDa. In the PrB-deficient strain, pro-PrA and pro-CpY matured only to the higher-molecular-mass forms, PrAa and CpYa, and the maturation of both precursors was slower than in the isogenic wild-type strain. Pulse-labeling experiments indicated that the mature forms, PrAb or CpYb, are generated directly in the PrB-containing wild-type strain in vivo. In vitro experiments showed that PrB is able to trigger maturation of its 42-kDa pro-PrB precursor to mature PrB in the absence of PrA. Mature PrB and its proteolytic activity, however, shows a higher stability in the presence of mature PrA. The data indicate a molecular and kinetic participation of proteinase yscB in vacuolar hydrolase precursor maturation.
authors.affiliation: Institut für Medizinische Mikrobiologie, Universität Basel, Switzerland.
authors.forename: H H
authors.initials: HH
authors.lastname: Hirsch
authors.forename: H H
authors.initials: HH
authors.lastname: Schiffer
authors.forename: D H
authors.initials: DH
authors.lastname: Wolf
mesh_terms: D015153:Blotting, Western; D016521:Electrophoresis, Gel, Pulsed-Field; D004792:Enzyme Precursors / Q000378:metabolism*; D004795:Enzyme Stability; D006867:Hydrolases / Q000378:metabolism*; D007700:Kinetics; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000648:ultrastructure*; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D004792:Enzyme Precursors; D006867:Hydrolases; D012697:Serine Endopeptidases; C023302:yeast proteinase B; D029701:Saccharomyces cerevisiae Proteins