Unoson Cecilia, Wagner E Gerhart H
Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Uppsala, Sweden.
RNA Biol. 2007 Nov;4(3):113-7. doi: 10.4161/rna.4.3.5350. Epub 2007 Nov 29.
Bacterial ribosomes have great difficulties to initiate translation on stable structures within mRNAs. Translational coupling and induced structure changes are strategies to open up inhibitory RNA structures encompassing ribosome binding sites (RBS). There are, however, mRNAs in which stable structures are not unfolded, but that are nevertheless efficiently initiated at high rates. de Smit and van Duin(1) proposed a "ribosome standby" model to theoretically solve this paradox: the 30S ribosome binds nonspecifically to an accessible site on the mRNA (standby site), waiting for a transient opening of a stable RBS hairpin. Upon unfolding, the 30S subunit relocates to form a productive initiation complex. Recent reports have provided experimental support for this model. This review will describe and compare two different flavors of standby sites, their properties, and their likely implications. We also discuss the possibility that ribosome standby may be a more general strategy to obtain high translation rates.
细菌核糖体在mRNA内的稳定结构上起始翻译存在很大困难。翻译偶联和诱导的结构变化是打开包含核糖体结合位点（RBS）的抑制性RNA结构的策略。然而，存在一些mRNA，其稳定结构并未展开，但仍能以高频率高效起始翻译。德·斯密特和范·杜因（1）提出了一个“核糖体备用”模型，从理论上解决这一矛盾：30S核糖体非特异性地结合到mRNA上的一个可及位点（备用位点），等待稳定的RBS发夹结构短暂打开。一旦展开，30S亚基重新定位以形成有活性的起始复合物。最近的报道为该模型提供了实验支持。本综述将描述和比较两种不同类型的备用位点、它们的特性以及可能的影响。我们还讨论了核糖体备用可能是获得高翻译速率的更普遍策略的可能性。
