Molecular Model of the Human 26S Proteasome

Division of Structural Biology, The Institute of Cancer Research, Chester Beatty Laboratories, London SW3 6JB, UK.
Molecular cell (Impact Factor: 14.02). 04/2012; 46(1):54-66. DOI: 10.1016/j.molcel.2012.03.026
Source: PubMed

ABSTRACT The 26S proteasome plays a fundamental role in eukaryotic homeostasis by undertaking the highly controlled degradation of a wide range of proteins, including key cellular regulators such as those controlling cell-cycle progression and apoptosis. Here we report the structure of the human 26S proteasome determined by cryo-electron microscopy and single-particle analysis, with secondary structure elements identified both in the 20S proteolytic core region and in the 19S regulatory particle. We have used this information together with crystal structures, homology models, and other biochemical information to construct a molecular model of the complete 26S proteasome. This model allows for a detailed description of the 20S core within the 26S proteasome and redefines the overall assignment of subunits within the 19S regulatory particle. The information presented here provides a strong basis for a mechanistic understanding of the 26S proteasome.

17 Reads
  • Source
    • "Structurally, the PCI-containing subunits arrange in a horseshoe-like shape, juxtaposed with the two MPN subunits. This architecture is strikingly similar to that of the 26S proteasome lid and the eukaryotic translation initiation factor eIF3 [8], [9], [10], [11], [12], [13]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Cop9 signalosome complex (CSN) regulates the functional cycle of the major E3 ubiquitin ligase family, the cullin RING E3 ubiquitin ligases (CRLs). Activated CRLs are covalently modified by the ubiquitin-like protein Nedd8 (neural precursor cell expressed developmentally down-regulated protein 8). CSN serves an essential role in myriad cellular processes by reversing this modification through the isopeptidase activity of its CSN5 subunit. CSN5 alone is inactive due to an auto-inhibited conformation of its catalytic domain. Here we report the molecular basis of CSN5 catalytic domain activation and unravel a molecular hierarchy in CSN deneddylation activity. The association of CSN5 and CSN6 MPN (for Mpr1/Pad1 N-terminal) domains activates its isopeptidase activity. The CSN5/CSN6 module, however, is inefficient in CRL deneddylation, indicating a requirement of further elements in this reaction such as other CSN subunits. A hybrid molecular model of CSN5/CSN6 provides a structural framework to explain these functional observations. Docking this model into a published CSN electron density map and using distance constraints obtained from cross-linking coupled to mass-spectrometry, we find that the C-termini of the CSN subunits could form a helical bundle in the centre of the structure. They likely play a key scaffolding role in the spatial organization of CSN and precise positioning of the dimeric MPN catalytic core.
    PLoS ONE 08/2014; 9(8):e105688. DOI:10.1371/journal.pone.0105688 · 3.23 Impact Factor
  • Source
    • "This was in according with the expression pattern of Ac larvae fed with RJM. 26S proteasome (Rpn9) plays a fundamental role in eukaryotic homeostasis [71], [72]. The ubiquitin-proteasome system mediated viral protein degradation constitutes a host defense process against some RNA viral infections [73]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Chinese honeybee Apis cerana (Ac) is one of the major Asian honeybee species for local apiculture. However, Ac is frequently damaged by Chinese sacbrood virus (CSBV), whereas Apis mellifera (Am) is usually resistant to it. Heterospecific royal jelly (RJ) breeding in two honeybee species may result in morphological and genetic modification. Nevertheless, knowledge on the resistant mechanism of Am to this deadly disease is still unknown. In the present study, heterospecific RJ breeding was conducted to determine the effects of food change on the larval mortality after CSBV infection at early larval stage. 2-DE and MALDI-TOF/TOF MS proteomic technology was employed to unravel the molecular event of the bees under heterospecific RJ breeding and CSBV challenge. The change of Ac larval food from RJC to RJM could enhance the bee resistance to CSBV. The mortality rate of Ac larvae after CSBV infection was much higher when the larvae were fed with RJC compared with the larvae fed with RJM. There were 101 proteins with altered expressions after heterospecific RJ breeding and viral infection. In Ac larvae, 6 differential expression proteins were identified from heterospecific RJ breeding only, 21 differential expression proteins from CSBV challenge only and 7 differential expression proteins from heterospecific RJ breeding plus CSBV challenge. In Am larvae, 17 differential expression proteins were identified from heterospecific RJ breeding only, 26 differential expression proteins from CSBV challenge only and 24 differential expression proteins from heterospecific RJ breeding plus CSBV challenge. The RJM may protect Ac larvae from CSBV infection, probably by activating the genes in energy metabolism pathways, antioxidation and ubiquitin-proteasome system. The present results, for the first time, comprehensively descript the molecular events of the viral infection of Ac and Am after heterospecific RJ breeding and are potentially useful for establishing CSBV resistant populations of Ac for apiculture.
    PLoS ONE 08/2014; 9(8):e102663. DOI:10.1371/journal.pone.0102663 · 3.23 Impact Factor
  • Source
    • "How the highly related Rpt subunits assemble with their cognate partner in the complex cellular environment remains to be elucidated. Since Adc17 binds to the amino-terminal region of Rpt6, and since structural analyses of the proteasome have revealed that Rpt dimers are held together by the amino-terminal regions of each Rpt (Beck et al., 2012; da Fonseca et al., 2012; Lander et al., 2012), we wondered whether Adc17 played a role in the Rpt6- Rpt3 heterodimer formation. We therefore designed assays to test this possibility. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The proteasome is essential for the selective degradation of most cellular proteins. To survive overwhelming demands on the proteasome arising during environmental stresses, cells increase proteasome abundance. Proteasome assembly is known to be complex. How stressed cells overcome this vital challenge is unknown. In an unbiased suppressor screen aimed at rescuing the defects of a yeast Rpt6 thermosensitive proteasome mutant, we identified a protein, hereafter named Adc17, as it functions as an ATPase dedicated chaperone. Adc17 interacts with the amino terminus of Rpt6 to assist formation of the Rpt6-Rpt3 ATPase pair, an early step in proteasome assembly. Adc17 is important for cell fitness, and its absence aggravates proteasome defects. The abundance of Adc17 increases upon proteasome stresses, and its function is crucial to maintain homeostatic proteasome levels. Thus, cells have mechanisms to adjust proteasome assembly when demands increase, and Adc17 is a critical effector of this process.
    Molecular Cell 08/2014; 55(4). DOI:10.1016/j.molcel.2014.06.017 · 14.02 Impact Factor
Show more


17 Reads
Available from