Signal Recognition Particle-ribosome Binding Is Sensitive to Nascent Chain Length
Signal Recognition Particle-ribosome Binding Is Sensitive to Nascent Chain Length
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DOI：
10.1074/jbc.m114.563239
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发表时间：
2014-07-11
影响因子：
4.8
通讯作者：
Walter, Peter
中科院分区：
文献类型：
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作者：
Noriega, Thomas R.;Tsai, Albert;Walter, Peter
信号识别颗粒（SRP）将显示信号序列的核糖体-新生链复合物（RNCs）引导至原核生物质膜和真核生物内质网中的蛋白质转运通道。最初提出，当信号序列从RNC出现时，SRP结合信号序列，并且当翻译延伸新生链时，成功的结合变得受损，从而将信号序列从核糖体表面上的SRP移开。后来的研究对这个简单的模型提出了质疑，提出SRP结合不受新生链长度的影响。在这里，我们重新调查这个问题，使用两种新的和独立的荧光共振能量转移测定。我们发现，SRP结合到RNC的到达和解离速率根据新生链长度而变化，导致在功能信号序列从核糖体中出现后不久亲和力最高。此外，我们发现，SRP结合RNCs在多个和相互转换的构象，相反，RNCs存在于两个构象区分SRP相互作用动力学。
The signal recognition particle (SRP) directs ribosome-nascent chain complexes (RNCs) displaying signal sequences to protein translocation channels in the plasma membrane of prokaryotes and endoplasmic reticulum of eukaryotes. It was initially proposed that SRP binds the signal sequence when it emerges from an RNC and that successful binding becomes impaired as translation extends the nascent chain, moving the signal sequence away from SRP on the ribosomal surface. Later studies drew this simple model into question, proposing that SRP binding is unaffected by nascent chain length. Here, we reinvestigate this issue using two novel and independent fluorescence resonance energy transfer assays. We show that the arrival and dissociation rates of SRP binding to RNCs vary according to nascent chain length, resulting in the highest affinity shortly after a functional signal sequence emerges from the ribosome. Moreover, we show that SRP binds RNCs in multiple and interconverting conformations, and that conversely, RNCs exist in two conformations distinguished by SRP interaction kinetics.