title: Proteasome assembly from 15S precursors involves major conformational changes and recycling of the Pba1-Pba2 chaperone.
abstract: The chaperones Ump1 and Pba1-Pba2 promote efficient biogenesis of 20S proteasome core particles from its subunits via 15S intermediates containing alpha and beta subunits, except beta7. Here we elucidate the structural role of these chaperones in late steps of core particle biogenesis using biochemical, electron microscopy, cross-linking and mass spectrometry analyses. In 15S precursor complexes, Ump1 is largely unstructured, lining the inner cavity of the complex along the interface between alpha and beta subunits. The alpha and beta subunits form loosely packed rings with a wider alpha ring opening than in the 20S core particle, allowing for the Pba1-Pba2 heterodimer to be partially embedded in the central alpha ring cavity. During biogenesis, the heterodimer is expelled from the alpha ring by a restructuring event that organizes the beta ring and leads to tightening of the alpha ring opening. In this way, the Pba1-Pba2 chaperone is recycled for a new round of proteasome assembly.
authors.affiliation: Gene Center Munich, Ludwig-Maximilians-Universität München, Feodor-Lynen Strasse 25, D-81377 Munich, Germany.
authors.forename: Malte
authors.initials: M
authors.lastname: Kock
authors.affiliation: Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, D-50674 Cologne, Germany.
authors.forename: Maria M
authors.initials: MM
authors.lastname: Nunes
authors.affiliation: Gene Center Munich, Ludwig-Maximilians-Universität München, Feodor-Lynen Strasse 25, D-81377 Munich, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Hemann
authors.affiliation: Gene Center Munich, Ludwig-Maximilians-Universität München, Feodor-Lynen Strasse 25, D-81377 Munich, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kube
authors.affiliation: Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, D-50674 Cologne, Germany.
authors.forename: R Jürgen
authors.initials: RJ
authors.lastname: Dohmen
authors.affiliation: Gene Center Munich, Ludwig-Maximilians-Universität München, Feodor-Lynen Strasse 25, D-81377 Munich, Germany.
authors.forename: Franz
authors.initials: F
authors.lastname: Herzog
authors.affiliation: Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, D-50674 Cologne, Germany.
authors.forename: Paula C
authors.initials: PC
authors.lastname: Ramos
authors.affiliation: Gene Center Munich, Ludwig-Maximilians-Universität München, Feodor-Lynen Strasse 25, D-81377 Munich, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Wendler
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry; D019281:Dimerization; D013058:Mass Spectrometry; D008854:Microscopy, Electron; D018832:Molecular Chaperones / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D018832:Molecular Chaperones; C559194:Pba1 protein, S cerevisiae; C559196:Pba2 protein, S cerevisiae; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; C110856:proteasome maturation protein; D046988:Proteasome Endopeptidase Complex