Induced structural changes of 7SL RNA during the assembly of human signal recognition particle
Induced structural changes of 7SL RNA during the assembly of human signal recognition particle
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DOI：
10.1038/nsb843
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发表时间：
2002-10-01
期刊：
影响因子：
--
通讯作者：
Nagai, K
中科院分区：
文献类型：
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作者：
Kuglstatter, A;Oubridge, C;Nagai, K
真核细胞信号识别颗粒（SRP）是一种细胞质核糖核蛋白颗粒，其将分泌蛋白和膜蛋白靶向内质网。SRP 54与7SL RNA的S结构域的结合高度依赖于SRP 19。在这里，我们提出的晶体结构的人SRP三元复合物组成的SRP 19，M结构域的SRP 54和S结构域的7SL RNA。当SRP 54的M结构域与7SL RNA-SRP 19复合物结合时，7SL RNA中螺旋8的不对称环塌陷。不对称环的长链中的四个核苷酸的碱基连续堆叠并与M结构域相互作用，而短链中的两个腺嘌呤翻转并与螺旋6形成两个A-次要基序。这种稳定的相互作用只有在螺旋6通过SRP 19与螺旋6和8的四环的预先结合而平行于螺旋8定位时才可能。因此，三元复合物的晶体结构表明了为什么SRP 19对于SRP 54与S结构域RNA的稳定结合是必需的。
The eukaryotic signal recognition particle (SRP) is a cytoplasmic ribonucleoprotein particle that targets secretory and membrane proteins to the endoplasmic reticulum. The binding of SRP54 to the S domain of 7SL RNA is highly dependent on SRP19. Here we present the crystal structure of a human SRP ternary complex consisting of SRP19, the M domain of SRP54 and the S domain of 7SL RNA. Upon binding of the M domain of SRP54 to the 7SL RNA-SRP19 complex, the asymmetric loop of helix 8 in 7SL RNA collapses. The bases of the four nucleotides in the long strand of the asymmetric loop continuously stack and interact with the M domain, whereas the two adenines in the short strand flip out and form two A-minor motifs with helix 6. This stabilizing interaction is only possible when helix 6 has been positioned parallel to helix 8 by the prior binding of SRP19 to the tetraloops of helices 6 and 8. Hence, the crystal structure of the ternary complex suggests why SRP19 is necessary for the stable binding of SRP54 to the S domain RNA.