A discriminator code-based DTD surveillance ensures faithful glycine delivery for protein biosynthesis in bacteria
A discriminator code-based DTD surveillance ensures faithful glycine delivery for protein biosynthesis in bacteria
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DOI：
10.7554/elife.38232
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发表时间：
2018-08-09
期刊：
影响因子：
7.7
通讯作者：
Sankaranarayanan, Rajan
中科院分区：
文献类型：
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作者：
Kuncha, Santosh Kumar;Suma, Katta;Sankaranarayanan, Rajan
D-氨基酰基-tRNA脱酰酶(DTD)除作用于D-氨基酸外，还作用于tRNA上的无手性甘氨酸。我们最近发现，这一活性使DTD能够清除非同源的Gly-tRNA(ALA)，效率是其对Gly-tRNA(Gly)的1000倍，表明tRNA对DTD的调节(Pawar等人，2017)。在这里，我们证明了tRNA的鉴别基主要解释了这种活性差异，并且是通过DTD进行选择的关键。因此，尿嘧啶鉴别子碱基作为负决定因素，防止Gly-tRNA(Gly)被DTD误编辑，这种保护被EF-Tu增强。有趣的是，真核生物DTD具有反向鉴别碱基特异性，仅使用G3.U70识别tRNA(Gly/Ala)。此外，DTD防止蛋白质中丙氨酸到甘氨酸的错误结合，而不仅仅是回收错误充电的tRNA(ALA)。总体而言，本研究揭示了DTD与识别基座的独特协同进化，并提示DTD对细菌tRNA(Gly)S具有较强的选择压力，要求其保留一个嘧啶识别码子。
D-aminoacyl-tRNA deacylase (DTD) acts on achiral glycine, in addition to D-amino acids, attached to tRNA. We have recently shown that this activity enables DTD to clear noncognate Gly-tRNA(Ala) with 1000-fold higher efficiency than its activity on Gly-tRNA(Gly), indicating tRNA-based modulation of DTD (Pawar et al., 2017). Here, we show that tRNA's discriminator base predominantly accounts for this activity difference and is the key to selection by DTD. Accordingly, the uracil discriminator base, serving as a negative determinant, prevents Gly-tRNA(Gly) misediting by DTD and this protection is augmented by EF-Tu. Intriguingly, eukaryotic DTD has inverted discriminator base specificity and uses only G3.U70 for tRNA(Gly/Ala) discrimination. Moreover, DTD prevents alanine-to-glycine misincorporation in proteins rather than only recycling mischarged tRNA(Ala). Overall, the study reveals the unique co-evolution of DTD and discriminator base, and suggests DTD's strong selection pressure on bacterial tRNA(Gly)s to retain a pyrimidine discriminator code.