ジャーナル: Proc Natl Acad Sci U S A / 年: 2014 タイトル: Structural basis for translational surveillance by the large ribosomal subunit-associated protein quality control complex. 著者: Dmitry Lyumkis / Dario Oliveira dos Passos / Erich B Tahara / Kristofor Webb / Eric J Bennett / Staal Vinterbo / Clinton S Potter / Bridget Carragher / Claudio A P Joazeiro / 要旨: All organisms have evolved mechanisms to manage the stalling of ribosomes upon translation of aberrant mRNA. In eukaryotes, the large ribosomal subunit-associated quality control complex (RQC), ...All organisms have evolved mechanisms to manage the stalling of ribosomes upon translation of aberrant mRNA. In eukaryotes, the large ribosomal subunit-associated quality control complex (RQC), composed of the listerin/Ltn1 E3 ubiquitin ligase and cofactors, mediates the ubiquitylation and extraction of ribosome-stalled nascent polypeptide chains for proteasomal degradation. How RQC recognizes stalled ribosomes and performs its functions has not been understood. Using single-particle cryoelectron microscopy, we have determined the structure of the RQC complex bound to stalled 60S ribosomal subunits. The structure establishes how Ltn1 associates with the large ribosomal subunit and properly positions its E3-catalytic RING domain to mediate nascent chain ubiquitylation. The structure also reveals that a distinguishing feature of stalled 60S particles is an exposed, nascent chain-conjugated tRNA, and that the Tae2 subunit of RQC, which facilitates Ltn1 binding, is responsible for selective recognition of stalled 60S subunits. RQC components are engaged in interactions across a large span of the 60S subunit surface, connecting the tRNA in the peptidyl transferase center to the distally located nascent chain tunnel exit. This work provides insights into a mechanism linking translation and protein degradation that targets defective proteins immediately after synthesis, while ignoring nascent chains in normally translating ribosomes.
pH: 6.8 詳細: 50 mM Hepes-KOH, 100 mM KOAc, 5 mM MgOAc, 1 mM EDTA, 2 mM DTT, 2x protease inhibitors, 0.1% Igepal CA-630
グリッド
詳細: freshly plasma-cleaned holey carbon C-flat grid (Protochips) that had been overlaid with 2 nm thin carbon film
凍結
凍結剤: ETHANE / チャンバー内温度: 93 K / 装置: HOMEMADE PLUNGER 手法: specimens were prepared for cryo-EM by applying 3 microliters of sample to a freshly plasma-cleaned holey carbon C-flat grid (Protochips) that had been overlaid with 2 nm thin carbon film, ...手法: specimens were prepared for cryo-EM by applying 3 microliters of sample to a freshly plasma-cleaned holey carbon C-flat grid (Protochips) that had been overlaid with 2 nm thin carbon film, allowing the sample to adsorb to the grid for 30 s, followed by blotting with filter paper and plunge freezing into liquid ethane using a manual cryoplunger in an ambient environment at 4 C.
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電子顕微鏡法
顕微鏡
FEI TECNAI F20
温度
平均: 93 K
アライメント法
Legacy - 非点収差: objective lens astigmatism was corrected by monitoring power spectra of continuously acquired images in leginon