Zhang Xiaoxiao, Yan Kaige, Zhang Yixiao, Li Ningning, Ma Chengying, Li Zhifei, Zhang Yanqing, Feng Boya, Liu Jing, Sun Yadong, Xu Yanji, Lei Jianlin, Gao Ning
Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
Nucleic Acids Res. 2014 Dec 1;42(21):13430-9. doi: 10.1093/nar/gku1135. Epub 2014 Nov 11.
Many ribosome-interacting GTPases, with proposed functions in ribosome biogenesis, are also implicated in the cellular regulatory coupling between ribosome assembly process and various growth control pathways. EngA is an essential GTPase in bacteria, and intriguingly, it contains two consecutive GTPase domains (GD), being one-of-a-kind among all known GTPases. EngA is required for the 50S subunit maturation. However, its molecular role remains elusive. Here, we present the structure of EngA bound to the 50S subunit. Our data show that EngA binds to the peptidyl transferase center (PTC) and induces dramatic conformational changes on the 50S subunit, which virtually returns the 50S subunit to a state similar to that of the late-stage 50S assembly intermediates. Very interestingly, our data show that the two GDs exhibit a pseudo-two-fold symmetry in the 50S-bound conformation. Our results indicate that EngA recognizes certain forms of the 50S assembly intermediates, and likely facilitates the conformational maturation of the PTC of the 23S rRNA in a direct manner. Furthermore, in a broad context, our data also suggest that EngA might be a sensor of the cellular GTP/GDP ratio, endowed with multiple conformational states, in response to fluctuations in cellular nucleotide pool, to facilitate and regulate ribosome assembly.
许多与核糖体相互作用的GTP酶在核糖体生物合成中具有特定功能，同时也参与核糖体组装过程与各种生长控制途径之间的细胞调节偶联。EngA是细菌中一种必需的GTP酶，有趣的是，它包含两个连续的GTP酶结构域（GD），这在所有已知的GTP酶中是独一无二的。EngA是50S亚基成熟所必需的。然而，其分子作用仍然难以捉摸。在此，我们展示了与50S亚基结合的EngA的结构。我们的数据表明，EngA与肽基转移酶中心（PTC）结合，并在50S亚基上诱导显著的构象变化，这实际上使50S亚基回到类似于后期50S组装中间体的状态。非常有趣的是，我们的数据表明，在与50S结合的构象中，两个GD呈现出假二重对称。我们的结果表明，EngA识别50S组装中间体的某些形式，并可能直接促进23S rRNA的PTC的构象成熟。此外，在更广泛的背景下，我们的数据还表明，EngA可能是细胞GTP/GDP比率的传感器，具有多种构象状态，以响应细胞核苷酸池的波动，促进和调节核糖体组装。
