Visualization of elongation factor G on the Escherichia coli 70S ribosome:: The mechanism of translocation
Visualization of elongation factor G on the Escherichia coli 70S ribosome:: The mechanism of translocation
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DOI：
10.1073/pnas.95.11.6134
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发表时间：
1998-05-26
影响因子：
11.1
通讯作者：
Frank, J
中科院分区：
文献类型：
--
作者：
Agrawal, RK;Penczek, P;Frank, J
在蛋白质合成过程中，延伸因子 G (EF-G) 与核糖体结合并促进易位步骤，即 tRNA 从核糖体的 A 位点移动到 P 位点的过程，并且 mRNA 通过一个密码子前进。通过使用三维冷冻电子显微镜，我们在核糖体-EF-G-GDP-夫西地酸复合物中可视化了 EF-G，将 EF-G-GDP 的晶体结构拟合到冷冻密度图显示主要与结构域 IV 相关的大构象变化，该结构域模仿 Phe-tRNA（Phe）、EF-Tu 和 GTP 类似物结构同源三元复合物中 tRNA 反密码子臂的形状。该结构域的尖端部分位于与 A 位 tRNA 的反密码子臂重叠的位置，其在核糖体中的位置是通过对易位前复合物的研究得知的，这意味着 EF-G 通过与反密码子臂的物理相互作用将 A 位 tRNA 置换到 P 位点。
During protein synthesis, elongation factor G (EF-G) binds to the ribosome and promotes the step of translocation, a process in which tRNA moves from the A to the P site of the ribosome and the mRNA is advanced by one codon, By using three-dimensional cryo-electron microscopy, we have visualized EF-G in a ribosome-EF-G-GDP-fusidic acid complex, Fitting the crystal structure of EF-G-GDP into the cryo density map reveals a large conformational change mainly associated with domain IV, the domain that mimics the shape of the anticodon arm of the tRNA in the structurally homologous ternary complex of Phe-tRNA(Phe), EF-Tu, and a GTP analog. The tip portion of this domain is found in a position that overlaps the anticodon arm of the A-site tRNA, whose position in the ribosome is known from a study of the pretranslocational complex, implying that EF-G displaces the A-site tRNA to the P site by physical interaction with the anticodon arm.