RNA determinants for translational editing - Mischarging a minihelix substrate by a tRNA synthetase
RNA determinants for translational editing - Mischarging a minihelix substrate by a tRNA synthetase
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DOI：
10.1074/jbc.274.11.6835
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发表时间：
1999-03-12
影响因子：
4.8
通讯作者：
Schimmel, P
中科院分区：
文献类型：
--
作者：
Nordin, BE;Schimmel, P
蛋白质合成的保真度需要氨基酰基-tRNA合成酶对氨基酸底物的有效识别，异亮氨酰-tRNA合成酶(IILS)对结构相似的氨基酸、缬氨酸和异亮氨酸的准确区分，部分结果是水解性编辑反应，这阻止了错误激活的valine稳定地连接到tRNA(ILE)。编辑反应依赖于tRNA(ILE)的存在，tRNA(ILE)含有促进错误激活的Valine编辑所必需的离散D-环核苷酸，由tRNA(ILE)的受体-T Psi C螺旋组成的RNA小螺旋是ILS特异性氨基酰化的底物，这些底物缺乏上述D-环核苷酸。由于微型螺旋包含氨基酰化的决定因素，我们认为它们可能还在编辑中发挥先前未被认识到的作用，在这里我们表明，与tRNA(ILE)微型螺旋(ILE)不能触发失活的Valine的水解，事实上，与Valine误充电，此外，MiniHelix(ILE)中增强或抑制异亮氨酸充电的突变对Valine也起到同样的作用，因此，MiniHelix(ILE)包含独立于氨基酸的充电信号，本身也不提供编辑的决定因素。模仿tRNA(ILE)的D-茎/环的RNA发夹也不能单独或与微型螺旋(ILE)结合诱导失活的Valine的水解。因此，需要tRNA的天然三倍体(ILE)来促进有效的编辑。考虑到微型螺旋被认为是tRNA结构的更古老的部分，这些结果与以下观点一致：在遗传密码的发展过程中，编辑RNA决定因素是在氨基酰化系统建立之后添加的。
The fidelity of protein synthesis requires efficient discrimination of amino acid substrates by aminoacyl-tRNA synthetases, Accurate discrimination of the structurally similar amino acids, valine and isoleucine, by isoleucyl-tRNA synthetase (IleRS) results, in part, from a hydrolytic editing reaction, which prevents misactivated valine from being stably joined to tRNA(Ile). The editing reaction is dependent on the presence of tRNA(Ile), which contains discrete D-loop nucleotides that are necessary to promote editing of misactivated valine, RNA minihelices comprised of just the acceptor-T Psi C helix of tRNA(Ile) are substrates for specific aminoacylation by IleRS, These substrates lack the aforementioned D-loop nucleotides. Because minihelices contain determinants for aminoacylation, we thought that they might also play a role in editing that has not previously been recognized, Here we show that, in contrast to tRNA(Ile) minihelix(Ile) is unable to trigger the hydrolysis of misactivated valine and, in fact, is mischarged with valine, In addition, mutations in minihelix(Ile) that enhance or suppress charging with isoleucine do the same with valine, Thus, minihelix(Ile) contains signals for charging (by Il-eRS) that are independent of the amino acid and, by itself, minihelix(Ile) provides no determinants for editing. An RNA hairpin that mimics the D-stem/loop of tRNA(Ile) is also unable to induce the hydrolysis of misactivated valine, both by itself and in combination with minihelix(Ile). Thus, the native tertiary fold of tRNA(Ile) is required to promote efficient editing. Considering that the minihelix is thought to be the more ancestral part of the tRNA structure, these results are consistent with the idea that, during the development of the genetic code, RNA determinants for editing were added after the establishment of an aminoacylation system.