Mechanism for the disassembly of the posttermination complex inferred from cryo-EM studies
Mechanism for the disassembly of the posttermination complex inferred from cryo-EM studies
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DOI：
10.1016/j.molcel.2005.05.005
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发表时间：
2005-06-10
期刊：
影响因子：
16
通讯作者：
Frank, J
中科院分区：
文献类型：
--
作者：
Gao, N;Zavialov, AV;Frank, J
核糖体再循环，即每一轮蛋白质合成后终止后复合物的分解，是mRNA翻译的重要步骤，但其机制仍不清楚。在真细菌中，再循环由RRF（核糖体再循环因子）和EF-G（延伸因子G）催化。通过使用冷冻电子显微镜，我们已经获得了两个密度图，一个RRF绑定终止后复合物和一个50 S亚基绑定EF-G和RRF。比较这两个地图，我们发现域I的RRF是在相同的方向，而域II的EF-G含有50 S亚基是广泛旋转（类似于60度）相比，其在70 S复合体的方向。将RRF的50 S构象映射到70 S终止后复合物上表明，它可以破坏亚基间桥B2 a和B3，从而影响两个亚基的分离。这些观察结果提供了结构基础的机制，其中终止后复合物被分裂成亚基的RRF和EF-G的联合行动。
Ribosome recycling, the disassembly of the posttermination complex after each round of protein synthesis, is an essential step in mRNA translation, but its mechanism has remained obscure. In eubacteria, recycling is catalyzed by RRF (ribosome recycling factor) and EF-G (elongation factor G). By using cryoelectron microscopy, we have obtained two density maps, one of the RRF bound posttermination complex and one of the 50S subunit bound with both EF-G and RRF. Comparing the two maps, we found domain I of RRF to be in the same orientation, while domain II in the EF-G-containing 50S subunit is extensively rotated (similar to 60 degrees) compared to its orientation in the 70S complex. Mapping the 50S conformation of RRF onto the 70S posttermination complex suggests that it can disrupt the intersubunit bridges B2a and B3, and thus effect a separation of the two subunits. These observations provide the structural basis for the mechanism by which the posttermination complex is split into subunits by the joint action of RRF and EF-G.