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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Dual targeting of a single tRNA(Trp) requires two different tryptophanyl-tRNA synthetases in Trypanosoma brucei
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Dual targeting of a single tRNA(Trp) requires two different tryptophanyl-tRNA synthetases in Trypanosoma brucei

机译：单一tRNA（Trp）的双重靶向需要布鲁氏锥虫中两个不同的色氨酸-tRNA合成酶

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摘要

The mitochondrion of Trypanosoma brucei does not encode any tRNAs. This deficiency is compensated for by the import of a small fraction of nearly all of its cytosolic tRNAs. Most trypanosomal aminoacyl-tRNA synthetases are encoded by single-copy genes, suggesting the use of the same enzyme in the cytosol and mitochondrion. However, the T. brucei genome contains two distinct genes for eukaryotic tryptophanyl-tRNA synthetase (TrpRS). RNA interference analysis established that both TrpRS1 and TrpRS2 are essential for growth and required for cytosolic and mitochondrial tryptophanyl-tRNA formation, respectively. Decoding the mitochondrial tryptophan codon UGA requires mitochondria-specific C -> U RNA editing in the anticodon of the imported tRNA(Trp). In vitro charging assays with recombinant TrpRS enzymes demonstrated that the edited anticodon and the mitochondria-specific thiolation of U33 in the imported tRNA(Trp) act as antideterminants for the cytosolic TrpRS1. The existence of two TrpRS enzymes, therefore, can be explained by the need for a mitochondrial synthetase with extended substrate specificity to achieve aminoacylation of the imported thiolated and edited tRNA(Trp). Thus, the notion that, in an organism, all nuclear-encoded tRNAs assigned to a given amino acid are charged by a single aminoacyl-tRNA synthetase, is not universally valid.
机译：布氏锥虫的线粒体不编码任何tRNA。通过导入几乎所有其胞质tRNA的一小部分，可以弥补这种不足。大多数锥虫氨酰基-tRNA合成酶由单拷贝基因编码，这表明在细胞质和线粒体中使用相同的酶。但是，布鲁氏杆菌基因组包含两个不同的真核生物色氨酸-tRNA合成酶（TrpRS）基因。 RNA干扰分析确定，TrpRS1和TrpRS2都是生长所必需的，分别是胞质和线粒体色氨酸-tRNA形成所必需的。解码线粒体色氨酸密码子UGA需要在导入的tRNA（Trp）的反密码子中编辑线粒体特异的C-> U RNA。重组TrpRS酶的体外充电分析表明，导入的tRNA（Trp）中编辑的反密码子和U33的线粒体特异性硫醇化作用作为胞质TrpRS1的抗决定剂。因此，可以通过需要具有延长的底物特异性的线粒体合成酶来实现导入的硫醇化和编辑的tRNA（Trp）的氨酰化，来解释两种TrpRS酶的存在。因此，在生物体中，分配给给定氨基酸的所有核编码tRNA都由单个氨酰基-tRNA合成酶带电的观点并不是普遍有效的。

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