Demonstration of a multistep mechanism for assembly of the SRP.SRP receptor complex: Implications for the catalytic role of SRP RNA
Demonstration of a multistep mechanism for assembly of the SRP.SRP receptor complex: Implications for the catalytic role of SRP RNA
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DOI：
10.1016/j.jmb.2008.05.049
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发表时间：
2008-09-05
影响因子：
5.6
通讯作者：
Shan, Shu-ou
中科院分区：
文献类型：
--
作者：
Zhang, Xin;Kung, Simon;Shan, Shu-ou
信号识别颗粒（SRP）及其受体（SR）中的两个GTP酶控制新合成的蛋白质向内质网或质膜的递送。在蛋白质靶向反应期间，4.5S SRP RNA将两种GTPases之间的结合加速了400倍。利用荧光共振能量转移，我们证明了一个稳定的SRP.SR复合物的形成涉及两个不同的步骤：SRP和SR之间的快速初始缔合，形成一个GTP独立的早期复合物，然后GTP依赖的构象重排，形成稳定的最终复合物。我们还发现，4.5S SRP RNA显着稳定的早期GTP非依赖性中间体。此外，突变分析表明，突变体SRP RNA稳定早期中间体的能力与它们加速SRP.SR复合物形成的能力之间存在强相关性。我们建议，SRP RNA，通过稳定的早期中间体，可以给这个短暂的中间体更长的寿命，因此更高的概率重新排列到稳定的最终复合物。这提供了解释4.5S RNA如何在SRP.SR复合物组装中发挥其催化作用的连贯模型。(C)2008爱思唯尔有限公司保留所有权利。
Two GTPases in the signal recognition particle (SRP) and its receptor (SR) control the delivery of newly synthesized proteins to the endoplasmic reticulum or plasma membrane. During the protein targeting reaction, the 4.5S SRP RNA accelerates the association between the two GTPases by 400-fold. Using fluorescence resonance energy transfer, we demonstrate here that formation of a stable SRP.SR complex involves two distinct steps: a fast initial association between SRP and SR to form a GTP-independent early complex and then a GTP-dependent conformational rearrangement to form the stable final complex. We also found that the 4.5S SRP RNA significantly stabilizes the early GTP-independent intermediate. Furthermore, mutational analyses show that there is a strong correlation between the ability of the mutant SRP RNAs to stabilize the early intermediate and their ability to accelerate SRP.SR complex formation. We propose that the SRP RNA, by stabilizing the early intermediate, can give this transient intermediate a longer life time and therefore a higher probability to rearrange to the stable final complex. This provides a coherent model that explains how the 4.5S RNA exerts its catalytic role in SRP.SR complex assembly. (C) 2008 Elsevier Ltd. All rights reserved.