ジャーナル: Nat Commun / 年: 2015 タイトル: Structure of the native Sec61 protein-conducting channel. 著者: Stefan Pfeffer / Laura Burbaum / Pia Unverdorben / Markus Pech / Yuxiang Chen / Richard Zimmermann / Roland Beckmann / Friedrich Förster / 要旨: In mammalian cells, secretory and membrane proteins are translocated across or inserted into the endoplasmic reticulum (ER) membrane by the universally conserved protein-conducting channel Sec61, ...In mammalian cells, secretory and membrane proteins are translocated across or inserted into the endoplasmic reticulum (ER) membrane by the universally conserved protein-conducting channel Sec61, which has been structurally studied in isolated, detergent-solubilized states. Here we structurally and functionally characterize native, non-solubilized ribosome-Sec61 complexes on rough ER vesicles using cryo-electron tomography and ribosome profiling. Surprisingly, the 9-Å resolution subtomogram average reveals Sec61 in a laterally open conformation, even though the channel is not in the process of inserting membrane proteins into the lipid bilayer. In contrast to recent mechanistic models for polypeptide translocation and insertion, our results indicate that the laterally open conformation of Sec61 is the only conformation present in the ribosome-bound translocon complex, independent of its functional state. Consistent with earlier functional studies, our structure suggests that the ribosome alone, even without a nascent chain, is sufficient for lateral opening of Sec61 in a lipid environment.
全体 : Mammalian ribosome bound to the native protein translocon on cani...
全体
名称: Mammalian ribosome bound to the native protein translocon on canine pancreatic ER vesicles
要素
複合体: Mammalian ribosome bound to the native protein translocon on canine pancreatic ER vesicles
-
超分子 #1: Mammalian ribosome bound to the native protein translocon on cani...
超分子
名称: Mammalian ribosome bound to the native protein translocon on canine pancreatic ER vesicles タイプ: complex / ID: 1 / 親要素: 0 / 詳細: The same sample as the one used for EMD-3068 - 72
トモグラム数: 55 / 使用した粒子像数: 64000 / 参照モデル: None / 手法: Template-free, automatic 詳細: Biological density was traced based on discrete Morse theory (DisPerSE software) and topological persistence. Particles were picked on the lumenal side of microsomes based on geometric ...詳細: Biological density was traced based on discrete Morse theory (DisPerSE software) and topological persistence. Particles were picked on the lumenal side of microsomes based on geometric constraints and classified using affinity propagation clustering.