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Proc Natl Acad Sci U S A. 2012 Sep 11;109(37):14870-5. doi: 10.1073/pnas.1213333109. Epub 2012 Aug 27.

Near-atomic resolution structural model of the yeast 26S proteasome.

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  • 1Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany.

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.

PMID:
22927375
[PubMed - indexed for MEDLINE]
PMCID:
PMC3443124
Free PMC Article

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