Effects on translation pausing of alterations in protein and RNA components of the ribosome exit tunnel
Effects on translation pausing of alterations in protein and RNA components of the ribosome exit tunnel
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DOI：
10.1128/jb.00632-08
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发表时间：
2008-09-01
影响因子：
3.2
通讯作者：
Zengel, Janice M.
中科院分区：
文献类型：
--
作者：
Lawrence, Marlon G.;Lindahl, Lasse;Zengel, Janice M.
氨基酸在核糖体的肽基转移酶中心聚合成肽。新生肽然后在它们到达核糖体外环境之前通过出口通道。许多新生肽与出口通道相互作用，并在其肽链内的特定位点停止延伸。核糖体的RNA和蛋白质成分中的几种突变变化先前已被证明会干扰暂停。这些变化位于隧道的最西侧区域，靠近核糖体蛋白L4和L22形成的收缩。为了扩展我们对肽诱导的暂停的了解，我们对两种肽SecM和一种短肽Crb（CmlA）诱导的暂停进行了比较研究，该肽需要氯霉素作为暂停的共诱导剂。我们分析了L4和L22中15个突变变化的影响，以及23 S rRNA的甲基化核苷酸A2058的影响，该核苷酸先前涉及暂停并位于L4-L22收缩附近。我们的研究结果表明，A2058的甲基化和L4和L22中的大多数突变变化对响应CrbCmlA和SecM的暂停具有不同的影响。只有一个变化，即L4中氨基酸72后的6个氨基酸插入，会影响两种肽的暂停。我们得出结论，这两种肽相互作用的出口隧道的不同区域。我们的研究结果表明，这两种肽使用不同的暂停机制，或者它们的相互作用不同，但在核糖体的功能重要区域诱导类似的抑制性构象变化。
Amino acids are polymerized into peptides in the peptidyl transferase center of the ribosome. The nascent peptides then pass through the exit tunnel before they reach the extraribosomal environment. A number of nascent peptides interact with the exit tunnel and stall elongation at specific sites within their peptide chain. Several mutational changes in RNA and protein components of the ribosome have previously been shown to interfere with pausing. These changes are localized in the narrowest region of the tunnel, near a constriction formed by ribosomal proteins L4 and L22. To expand our knowledge about peptide-induced pausing, we performed a comparative study of pausing induced by two peptides, SecM and a short peptide, Crb(CmlA), that requires chloramphenicol as a coinducer of pausing. We analyzed the effects of 15 mutational changes in L4 and L22, as well as the effects of methylating nucleotide A2058 of 23S rRNA, a nucleotide previously implicated in pausing and located close to the L4-L22 constriction. Our results show that methylation of A2058 and most mutational changes in L4 and L22 have differential effects on pausing in response to CrbCmlA and SecM. Only one change, a 6-amino-acid insertion after amino acid 72 in L4, affects pausing in both peptides. We conclude that the two peptides interact with different regions of the exit tunnel. Our results suggest that either the two peptides use different mechanisms of pausing or they interact differently but induce similar inhibitory conformational changes in functionally important regions of the ribosome.