ジャーナル: Structure / 年: 2012 タイトル: Structure and 3D arrangement of endoplasmic reticulum membrane-associated ribosomes. 著者: Stefan Pfeffer / Florian Brandt / Thomas Hrabe / Sven Lang / Matthias Eibauer / Richard Zimmermann / Friedrich Förster / 要旨: In eukaryotic cells, cotranslational protein translocation across the endoplasmic reticulum (ER) membrane requires an elaborate macromolecular machinery. While structural details of ribosomes bound ...In eukaryotic cells, cotranslational protein translocation across the endoplasmic reticulum (ER) membrane requires an elaborate macromolecular machinery. While structural details of ribosomes bound to purified and solubilized constituents of the translocon have been elucidated in recent years, little structural knowledge of ribosomes bound to the complete ER protein translocation machinery in a native membrane environment exists. Here, we used cryoelectron tomography to provide a three-dimensional reconstruction of 80S ribosomes attached to functional canine pancreatic ER microsomes in situ. In the resulting subtomogram average at 31 Å resolution, we observe direct contact of ribosomal expansion segment ES27L and the membrane and distinguish several membrane-embedded and lumenal complexes, including Sec61, the TRAP complex and another large complex protruding 90 Å into the lumen. Membrane-associated ribosomes adopt a preferred three-dimensional arrangement that is likely specific for ER-associated polyribosomes and may explain the high translation efficiency of ER-associated ribosomes compared to their cytosolic counterparts.
名称: ER membrane associated ribosome / タイプ: sample / ID: 1000 / 詳細: The sample is embedded into its native membrane / 集合状態: ER membrane associated ribosome / Number unique components: 1
分子量
理論値: 4.5 MDa
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超分子 #1: Membrane-bound 80S ribosome
超分子
名称: Membrane-bound 80S ribosome / タイプ: complex / ID: 1 / 組換発現: No / データベース: NCBI / Ribosome-details: ribosome-eukaryote: ALL
試料ホルダーモデル: OTHER / Tilt series - Axis1 - Min angle: -60 ° / Tilt series - Axis1 - Max angle: 60 °
実験機器
モデル: Tecnai Polara / 画像提供: FEI Company
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画像解析
詳細
The particles were selected using PyTom and classified by constrained principal component analysis. Average number of projections used in the 3D reconstructions: 1000. Average number of class averages: 1.
最終 再構成
アルゴリズム: OTHER / 解像度のタイプ: BY AUTHOR / 解像度: 31.0 Å / 解像度の算出法: FSC 0.5 CUT-OFF / ソフトウェア - 名称: PyTom