Structure of the mammalian ribosome-channel complex at 17 Å resolution
Structure of the mammalian ribosome-channel complex at 17 Å resolution
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DOI：
10.1016/s0022-2836(02)01111-7
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发表时间：
2002-12-06
影响因子：
5.6
通讯作者：
Akey, CW
中科院分区：
文献类型：
--
作者：
Morgan, DG;Ménétret, JF;Akey, CW
蛋白质共翻译易位到内质网 (ER) 腔和膜蛋白的生物合成需要核糖体与 Sec61p 复合物形成的膜通道结合。我们现在报道了源自内质网膜的哺乳动物核糖体通道复合物的 17 埃结构。核糖体亚基的原子模型与来自嗜热栖热菌的编程核糖体对齐，以提供共同的参考框架。然后将嗜热嗜热菌核糖体以及所有已知的高分辨率亚基模型停靠在我们的核糖体通道复合体图谱中。该结构显示核糖体在出口位点含有假定的 tRNA，与非编程酵母核糖体的比较表明 L1 茎可能充当 tRNA 出口路径中的门。我们在包括 ES27 在内的脊椎动物核糖体大亚基中定位了 6 个主要的扩展片段，并提出了 ES30 的功能。大核糖体亚基通过四个连接与通道相连。我们确定了大亚基 rRNA 中的区域和四种可能有助于形成连接的蛋白质。核糖体的这些区域可能充当指导不对称易位通道组装的模板。其中三个连接形成栅栏，将假定的易位分开。来自附加膜组件的附着位点的孔。核糖体通道连接还形成开放连接，允许新生链进入细胞质。在适合整个复合体的阈值下，通道相当坚固，并且假定的易位孔的管腔一半是关闭的。这些数据表明小分子跨膜流动可能受到通道本身的阻碍，而不是核糖体通道连接处的阻碍。 (C) 2002 Elsevier Science Ltd. 保留所有权利。
The co-translational translocation of proteins into the endoplasmic reticulum (ER) lumen and the biogenesis of membrane proteins require ribosome binding to a membrane channel formed by the Sec61p complex. We now report the 17 Angstrom structure of a mammalian ribosome-channel complex derived from ER membranes. Atomic models of the ribosomal subunits were aligned to the programmed ribosome from Thermus thermophilus, to provide a common reference frame. The T. thermophilus ribosome, and by extension all known high resolution subunit models, were then docked within our map of the ribosome-channel complex. The structure shows that the ribosome contains a putative tRNA in the exit site, and a comparison with a non-programmed, yeast ribosome suggests that the L1 stalk may function as a gate in the tRNA exit path. We have localized six major expansion segments in the large subunit of the vertebrate ribosome including ES27, and suggest a function for ES30.The large ribosomal subunit is linked to the channel by four connections. We identified regions in the large subunit rRNA and four proteins that may help form the connections. These regions of the ribosome probably serve as a template to guide the assembly of the asymmetric translocation channel. Three of the connections form a picket fence that separates the putative translocation. pore from the attachment site of an additional membrane component. The ribosome-channel connections also create an open junction that would allow egress of a nascent chain into the cytosol. At a threshold that is appropriate for the entire complex, the channel is rather solid and the lumenal half of the putative translocation pore is closed. These data suggest that the flow of small molecules across the membrane may be impeded by the channel itself, rather than the ribosome-channel junction. (C) 2002 Elsevier Science Ltd. All rights reserved.