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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Substrate recognition by class I lysyl-tRNA synthetases: A molecular basis for gene displacement
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Substrate recognition by class I lysyl-tRNA synthetases: A molecular basis for gene displacement

机译：I类赖氨酰-tRNA合成酶对底物的识别：基因置换的分子基础

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摘要

Lysyl-tRNA synthetases (LysRSs) are unique amongst the aminoacyl-tRNA synthetases in being composed of unrelated class I and class II enzymes. To allow direct compar- ison between the two types of LysRS, substrate recognition by class I LysRSs was examined. Genes encoding both an archaeal and a bacterial class I enzyme were able to rescue an Escherichia coli strain deficient in LysRS, indicating their ability to func- tionally substitute for a class II LysRS in vivo. In vitro charac- terization showed lysine activation and recognition to be tRNA- dependent, an attribute of several class I, but not class II, aminoacyl-tRNA synthetases. Examination of tRNA recognition showed that class I LysRSs recognize the same elements in tRNA~(Lys) as their class II counterparts, namely the discriminator base (N73) and the anticodon. This sequence-specific recognition of the same nucleotides in tRNA~(Lys) by the two unrelated types of enzyme suggests that tRNA~(Lys) predates at least one of the LysRSs in the evolution of the translational apparatus. The only observed variation in recognition was that the G2.U71 wobble pair of spirochete tRNA~(Lys) acts as antideterminant for class II LysRS but does not alter class I enzyme recognition. This difference in tRNA recognition strongly favors the use of a class I-type enzyme to aininoacylate particular tRNA~(Lys) species and provides a molecular basis for the observed displacement of class II by class I LysRSs in certain bacteria.
机译：赖氨酰-tRNA合成酶（LysRSs）在氨酰基-tRNA合成酶中是独特的，由不相关的I类和II类酶组成。为了直接比较两种类型的LysRS，我们检查了I类LysRS的底物识别。既编码古细菌又编码细菌I类酶的基因能够拯救缺乏LysRS的大肠杆菌菌株，这表明它们具有在体内功能上替代II类LysRS的能力。体外鉴定显示赖氨酸的激活和识别是依赖于tRNA的，这是几种I类而非II类氨酰基tRNA合成酶的属性。对tRNA识别的检查表明，I类LysRSs识别tRNA_（Lys）中与它们的II类对应物相同的元件，即鉴别基（N73）和反密码子。两种无关类型的酶对tRNA_（Lys）中相同核苷酸的序列特异性识别表明，在翻译装置的进化中，tRNA_（Lys）至少早于LysRS之一。唯一观察到的识别差异是螺旋体tRNA〜（Lys）的G2.U71摆动对充当II类LysRS的抗决定剂，但不会改变I类酶的识别。 tRNA识别的这种差异强烈支持使用I类酶对特定的tRNA_（Lys）物种进行氨基酰化，并为某些细菌中I类LysRS取代II类提供分子基础。

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