Crystal structure of the Ffh and EF-G binding sites in the conserved domain IV of Escherichia coli 4.5S RNA
Crystal structure of the Ffh and EF-G binding sites in the conserved domain IV of Escherichia coli 4.5S RNA
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DOI：
10.1016/s0969-2126(00)00137-4
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发表时间：
2000-05-15
期刊：
影响因子：
5.7
通讯作者：
Nagai, K
中科院分区：
文献类型：
--
作者：
Jovine, L;Hainzl, T;Nagai, K
背景：细菌信号识别颗粒（signal recognition particle， SRP）由4.5S RNA和Ffh蛋白组成，在将含信号肽的蛋白靶向到细胞膜分泌器官中起着至关重要的作用。4.5S RNA增加了Ffh对信号肽的亲和力，是SRP与其受体蛋白FtsY相互作用的必要条件。4.5S RNA还与核糖体中的延伸因子G （EF-G）相互作用，这种相互作用是有效翻译所必需的。结果：我们用Lu3+多次异常色散（MAD）测定了含有Ffh和EF-G结合位点的4.5S RNA片段的2.7埃晶体结构。这个碎片由三个螺旋组成，由一个对称的和一个不对称的内部环连接。与之前报道的核磁共振衍生结构相反，对称环完全由非规范碱基对组成。这些氢键对不断堆叠，并将不寻常的氢键供体和受体组合投射到浅的小槽中。因此，结构可以被看作是两个双螺旋杆，由从一条链伸出的不对称环铰接。结论：基于我们的晶体结构和之前报道的化学保护实验结果，我们预测Ffh结合在对称环的小凹槽上。在4.5S RNA和23S rRNA的EF-G结合位点上发现了相同的十核核苷酸序列。4.5S RNA和核糖体蛋白L11-RNA复合体晶体中的十核核苷酸结构提示4.5S RNA和23S rRNA如何与EF-G相互作用并在翻译核糖体中发挥作用。
Background: Bacterial signal recognition particle (SRP), consisting of 4.5S RNA and Ffh protein, plays an essential role in targeting signal-peptide-containing proteins to the secretory apparatus in the cell membrane. The 4.5S RNA increases the affinity of Ffh for signal peptides and is essential for the interaction between SRP and its receptor, protein FtsY. The 4.5S RNA also interacts with elongation factor G (EF-G) in the ribosome and this interaction is required for efficient translation.Results: We have determined by multiple anomalous dispersion (MAD) with Lu3+ the 2.7 Angstrom crystal structure of a 4.5S RNA fragment containing binding sites for both Ffh and EF-G. This fragment consists of three helices connected by a symmetric and an asymmetric internal loop. In contrast to NMR-derived structures reported previously, the symmetric loop is entirely constituted by non-canonical base pairs. These pairs continuously stack and project unusual sets of hydrogen-bond donors and accepters into the shallow minor groove. The structure can therefore be regarded as two double helical rods hinged by the asymmetric loop that protrudes from one strand.Conclusions: Based on our crystal structure and results of chemical protection experiments reported previously, we predicted that Ffh binds to the minor groove of the symmetric loop. An identical decanucleotide sequence is found in the EF-G binding sites of both 4.5S RNA and 23S rRNA. The decanucleotide structure in the 4.5S RNA and the ribosomal protein L11-RNA complex crystals suggests how 4.5S RNA and 23S rRNA might interact with EF-G and function in translating ribosomes.