Structure of the E-coli protein-conducting channel bound to a translating ribosome
Structure of the E-coli protein-conducting channel bound to a translating ribosome
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DOI：
10.1038/nature04133
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发表时间：
2005-11-17
期刊：
影响因子：
64.8
通讯作者：
Frank, J
中科院分区：
文献类型：
--
作者：
Mitra, K;Schaffitzel, C;Frank, J
分泌的和膜上的蛋白质通过蛋白质传导通道(PCC)跨细胞膜转运或进入细胞膜。在这里，我们提出了一个冷冻电子显微镜重建的大肠杆菌PCC，SecYEG，与核糖体和一个新生的链包含一个信号锚。这个重建显示了一个信使RNA，三个转移RNA，新生的链，以及与mRNA发夹结合的一个易位的PCC和第二个非易位的PCC的详细特征。移位的PCC与两侧的核糖体RNA发夹和背部的核糖体蛋白形成连接，留下一个正面开口。基于正常模式的古细菌SecYEβ结构与PCC电子显微镜密度的灵活匹配有利于PCC中两个SecYEG复合体从前到前的排列，并支持在多肽转运过程中通过打开两个连接的SecY一半形成通道。基于我们在两个分离的孔道中观察到的PCC的移位，我们提出了一个共翻译蛋白移位的模型。
Secreted and membrane proteins are translocated across or into cell membranes through a protein-conducting channel (PCC). Here we present a cryo-electron microscopy reconstruction of the Escherichia coli PCC, SecYEG, complexed with the ribosome and a nascent chain containing a signal anchor. This reconstruction shows a messenger RNA, three transfer RNAs, the nascent chain, and detailed features of both a translocating PCC and a second, non-translocating PCC bound to mRNA hairpins. The translocating PCC forms connections with ribosomal RNA hairpins on two sides and ribosomal proteins at the back, leaving a frontal opening. Normal mode-based flexible fitting of the archaeal SecYE beta structure into the PCC electron microscopy densities favours a front-to-front arrangement of two SecYEG complexes in the PCC, and supports channel formation by the opening of two linked SecY halves during polypeptide translocation. On the basis of our observation in the translocating PCC of two segregated pores with different degrees of access to bulk lipid, we propose a model for co-translational protein translocation.