title: Autocatalytic subunit processing couples active site formation in the 20S proteasome to completion of assembly.
abstract: The eukaryotic 20S proteasome is responsible for the degradation of many cellular proteins, but how it is assembled and how its distinct active sites are formed are not understood. Like other proteasome subunits, the yeast Doa3 protein is synthesized in precursor form. We show that the N-terminal propeptide is required for Doa3 incorporation into the proteasome and, remarkably, that the propeptide functions in trans, suggesting it serves a chaperone-like function in proteasome biogenesis. Propeptide processing is not required for proteasome assembly but is needed for maturation of a specific subset of active sites. The likely nucleophile for these sites is provided by the N-terminal threonine of mature Doa3. Additional data indicate that precursor processing is autocatalytic and requires association of the two halves of the proteasome particle, thereby preventing formation of proteolytic sites until the central hydrolytic chamber has been sealed off from the rest of the cell.
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Chicago, Illinois 60637, USA.
authors.forename: P
authors.initials: P
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Hochstrasser
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D002918:Chymotrypsin / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D011498:Protein Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D005656:Fungal Proteins; D009097:Multienzyme Complexes; D011498:Protein Precursors; D029701:Saccharomyces cerevisiae Proteins; D002918:Chymotrypsin; D003546:Cysteine Endopeptidases; C083706:PRE1 protein, S cerevisiae; D046988:Proteasome Endopeptidase Complex