The structure of LepA, the ribosomal back translocase
The structure of LepA, the ribosomal back translocase
复制标题
DOI：
10.1073/pnas.0801308105
复制
发表时间：
2008-03-25
影响因子：
11.1
通讯作者：
Steitz, Thomas A.
中科院分区：
文献类型：
--
作者：
Evans, Robin N.;Blaha, Gregor;Steitz, Thomas A.
LEPA是一种高度保守的伸长因子，在伸长周期中促进tRNAs在核糖体上的向后移位。我们测定了大肠杆菌LEPA的2.8埃分辨率的晶体结构。LEPA和EF-G之间高度的序列同源性反映在LEPA和EF-G各自同源结构域的结构相似性上。然而，LEPA中III和V结构域的取向与EF-G中的不同。LEPA还包含一个在EF-G中没有发现的C-末端结构域(CTD)，它有一个以前没有观察到的蛋白质折叠。LEPA和EF-G之间的高度结构相似性使我们能够使用EF-G和70年代核糖体之间的复合体的7.3埃冷冻EM结构来推导出LEPA与核糖体结合的同源模型。在这个模型中，LEPA的非常静电阳性的CTD被放置在大的核糖体亚基的A位的直接附近，这表明CTD可能与后移位的tRNA或23S rRNA之间存在相互作用。
LepA is a highly conserved elongation factor that promotes the back translocation of tRNAs on the ribosome during the elongation cycle. We have determined the crystal structure of LepA from Escherichia coli at 2.8-angstrom resolution. The high degree of sequence identity between LepA and EF-G is reflected in the structural similarity between the individual homologous domains of LepA and EF-G. However, the orientation of domains III and V in LepA differs from their orientations in EF-G. LepA also contains a C-terminal domain (CTD) not found in EF-G that has a previously unobserved protein fold. The high structural similarity between LepA and EF-G enabled us to derive a homology model for LepA bound to the ribosome using a 7.3-angstrom cryo-EM structure of a complex between EF-G and the 70S ribosome. In this model, the very electrostatically positive CTD of LepA is placed in the direct vicinity of the A site of the large ribosomal subunit, suggesting a Possible interaction between the CTD and the back translocated tRNA or 23S rRNA.