title: Structure of the human 26S proteasome at a resolution of 3.9 Å.
abstract: Protein degradation in eukaryotic cells is performed by the Ubiquitin-Proteasome System (UPS). The 26S proteasome holocomplex consists of a core particle (CP) that proteolytically degrades polyubiquitylated proteins, and a regulatory particle (RP) containing the AAA-ATPase module. This module controls access to the proteolytic chamber inside the CP and is surrounded by non-ATPase subunits (Rpns) that recognize substrates and deubiquitylate them before unfolding and degradation. The architecture of the 26S holocomplex is highly conserved between yeast and humans. The structure of the human 26S holocomplex described here reveals previously unidentified features of the AAA-ATPase heterohexamer. One subunit, Rpt6, has ADP bound, whereas the other five have ATP in their binding pockets. Rpt6 is structurally distinct from the other five Rpt subunits, most notably in its pore loop region. For Rpns, the map reveals two main, previously undetected, features: the C terminus of Rpn3 protrudes into the mouth of the ATPase ring; and Rpn1 and Rpn2, the largest proteasome subunits, are linked by an extended connection. The structural features of the 26S proteasome observed in this study are likely to be important for coordinating the proteasomal subunits during substrate processing.
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany;
authors.forename: Andreas
authors.initials: A
authors.lastname: Schweitzer
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany;
authors.forename: Antje
authors.initials: A
authors.lastname: Aufderheide
authors.affiliation: Beckman Institute, University of Illinois, Urbana-Champaign, Urbana, IL 61801;
authors.forename: Till
authors.initials: T
authors.lastname: Rudack
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany;
authors.forename: Florian
authors.initials: F
authors.lastname: Beck
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany;
authors.forename: Günter
authors.initials: G
authors.lastname: Pfeifer
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany;
authors.forename: Jürgen M
authors.initials: JM
authors.lastname: Plitzko
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany;
authors.forename: Eri
authors.initials: E
authors.lastname: Sakata
authors.affiliation: Beckman Institute, Department of Physics, Energy Biosciences Institute, Center for the Physics of Living Cells, University of Illinois, Urbana-Champaign, Urbana, IL 61801; Center for Biophysics and Quantitative Biology, University of Illinois, Urbana-Champaign, Urbana, IL 61801;
authors.forename: Klaus
authors.initials: K
authors.lastname: Schulten
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany; Cryo-electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands f.g.forster@uu.nl baumeist@biochem.mpg.de.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Förster
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany; f.g.forster@uu.nl baumeist@biochem.mpg.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baumeister
mesh_terms: D006801:Humans; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D011487:Protein Conformation; D015003:Yeasts
chemical_list: D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease
keywords: AAA-ATPase; cryo-electron microscopy; integrative modeling; proteostasis