Visualization of release factor 3 on the ribosome during termination of protein synthesis
Visualization of release factor 3 on the ribosome during termination of protein synthesis
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DOI：
10.1038/nature02332
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发表时间：
2004-02-26
期刊：
影响因子：
64.8
通讯作者：
van Heel, M
中科院分区：
文献类型：
--
作者：
Klaholz, BP;Myasnikov, AG;van Heel, M
核糖体终止蛋白质合成需要两类释放因子（RF）。II类RF3是一种GTPase，在新生多肽释放后从核糖体中去除I类RFs (RF1或RF2)（1-3）。GDP状态下的RF3与核糖体I类RF复合物结合，随后GDP交换GTP并释放I类RF。由于GTP水解触发RF3的释放（参考文献4），我们使用不可水解的GTP类似物将RF3捕获在大肠杆菌核糖体上。在低温电子显微镜下，我们发现配合物可以有两种不同的构象状态。在“状态1”中，RF3与核糖体预结合，而在“状态2”中，RF3与核糖体GTPase中心接触。转运RNA分子从状态1的肽基位点转移到状态2的出口位点。这种易位与核糖体的大构象重排有关。由于状态1似乎可以同时容纳RF3和RF2，其位置从先前的研究中已知（5,6），我们可以推断第I类RFs的释放机制。
Termination of protein synthesis by the ribosome requires two release factor (RF) classes. The class II RF3 is a GTPase that removes class I RFs (RF1 or RF2) from the ribosome after release of the nascent polypeptide(1-3). RF3 in the GDP state binds to the ribosomal class I RF complex, followed by an exchange of GDP for GTP and release of the class I RF. As GTP hydrolysis triggers release of RF3 (ref. 4), we trapped RF3 on Escherichia coli ribosomes using a nonhydrolysable GTP analogue. Here we show by cryo-electron microscopy that the complex can adopt two different conformational states. In 'state 1', RF3 is pre-bound to the ribosome, whereas in 'state 2' RF3 contacts the ribosome GTPase centre. The transfer RNA molecule translocates from the peptidyl site in state 1 to the exit site in state 2. This translocation is associated with a large conformational rearrangement of the ribosome. Because state 1 seems able to accommodate simultaneously both RF3 and RF2, whose position is known from previous studies(5,6), we can infer the release mechanism of class I RFs.