Activation of Human Mitochondrial Lysyl-tRNA Synthetase upon Maturation of Its Premitochondrial Precursor
Activation of Human Mitochondrial Lysyl-tRNA Synthetase upon Maturation of Its Premitochondrial Precursor
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DOI：
10.1021/bi201337b
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发表时间：
2012-01-31
期刊：
影响因子：
2.9
通讯作者：
Mirande, Marc
中科院分区：
文献类型：
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作者：
Dias, Jose;Octobre, Guillaume;Mirande, Marc
人赖氨酰-tRNA合成酶的细胞质和线粒体种类通过KARS 1基因的选择性剪接由单个基因编码。胞质酶具有真核生物特异性的N-末端多肽延伸，其赋予天然酶有效的tRNA结合特性，所述tRNA结合特性是真核生物翻译机器内tRNA从合成酶向延伸因子EF 1A载体转移所需的。线粒体酶在靶向该细胞器时从其前体成熟。为了了解细胞溶质和线粒体酶是如何适应参与两个不同的翻译机器，真核生物或细菌的起源，我们的特点是线粒体LysRS物种。在这里，我们报告说，线粒体LysRS的前体裂解导致一个成熟的酶减少tRNA结合性能相比，那些细胞质的对应物。这种适应机制可以防止抑制翻译通过螯合的赖氨酰-tRNA的合成酶在一个隔室中的细菌样延伸因子EF-Tu不能帮助其从合成酶的解离。我们还观察到RxxxKRxxK。线粒体LysRS的tRNA结合基序在该酶的前体形式中不起作用，并且在线粒体靶向序列裂解后起作用。需要前体的成熟来揭示这种酶的有效tRNA结合特性的发现对于其活性的时空调节具有强烈的影响，并且与先前的研究一致，该研究表明能够促进tRNA（Lys）包装成HIV-1病毒颗粒的唯一LysRS种类是线粒体酶的成熟形式。
The cytoplasmic and mitochondrial species of human lysyl-tRNA synthetase are encoded by a single gene by means of alternative splicing of the KARS1 gene. The cytosolic enzyme possesses a eukaryote-specific N-terminal polypeptide extension that confers on the native enzyme potent tRNA binding properties required for the vectorial transfer of tRNA from the synthetase to elongation factor EF1A within the eukaryotic translation machinery. The mitochondrial enzyme matures from its precursor upon being targeted to that organelle. To understand how the cytosolic and mitochondrial enzymes are adapted to participate in two distinct translation machineries, of eukaryotic or bacterial origin, we characterized the mitochondrial LysRS species. Here we report that cleavage of the precursor of mitochondrial LysRS leads to a mature enzyme with reduced tRNA binding properties compared to those of the cytoplasmic counterpart. This adaptation mechanism may prevent inhibition of translation through sequestration of lysyl-tRNA on the synthetase in a compartment where the bacterial-like elongation factor EF-Tu could not assist in its dissociation from the synthetase. We also observed that the RxxxKRxxK. tRNA-binding motif of mitochondrial LysRS is not functional in the precursor form of that enzyme and becomes operational after cleavage of the mitochondrial targeting sequence. The finding that maturation of the precursor is needed to reveal the potent tRNA binding properties of this enzyme has strong implications for the spatiotemporal regulation of its activities and is consistent with previous studies suggesting that the only LysRS species able to promote packaging of tRNA(Lys) into HIV-1 viral particles is the mature form of the mitochondrial enzyme.