title: Near-atomic resolution structural model of the yeast 26S proteasome.
abstract: The 26S proteasome operates at the executive end of the ubiquitin-proteasome pathway. Here, we present a cryo-EM structure of the Saccharomyces cerevisiae 26S proteasome at a resolution of 7.4 Å or 6.7 Å (Fourier-Shell Correlation of 0.5 or 0.3, respectively). We used this map in conjunction with molecular dynamics-based flexible fitting to build a near-atomic resolution model of the holocomplex. The quality of the map allowed us to assign α-helices, the predominant secondary structure element of the regulatory particle subunits, throughout the entire map. We were able to determine the architecture of the Rpn8/Rpn11 heterodimer, which had hitherto remained elusive. The MPN domain of Rpn11 is positioned directly above the AAA-ATPase N-ring suggesting that Rpn11 deubiquitylates substrates immediately following commitment and prior to their unfolding by the AAA-ATPase module. The MPN domain of Rpn11 dimerizes with that of Rpn8 and the C-termini of both subunits form long helices, which are integral parts of a coiled-coil module. Together with the C-terminal helices of the six PCI-domain subunits they form a very large coiled-coil bundle, which appears to serve as a flexible anchoring device for all the lid subunits.
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Beck
authors.forename: Pia
authors.initials: P
authors.lastname: Unverdorben
authors.forename: Stefan
authors.initials: S
authors.lastname: Bohn
authors.forename: Andreas
authors.initials: A
authors.lastname: Schweitzer
authors.forename: Günter
authors.initials: G
authors.lastname: Pfeifer
authors.forename: Eri
authors.initials: E
authors.lastname: Sakata
authors.forename: Stephan
authors.initials: S
authors.lastname: Nickell
authors.forename: Jürgen M
authors.initials: JM
authors.lastname: Plitzko
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Villa
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baumeister
authors.forename: Friedrich
authors.initials: F
authors.lastname: Förster
mesh_terms: D020285:Cryoelectron Microscopy; D010450:Endopeptidases / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*
chemical_list: C115451:RPN11 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D010450:Endopeptidases; D046988:Proteasome Endopeptidase Complex; C573321:Rpn8 protein, S cerevisiae; C061553:ATP dependent 26S protease