Kinetic parameters for tmRNA binding to alanyl-tRNA synthetase and elongation factor Tu from Escherichia coli
Kinetic parameters for tmRNA binding to alanyl-tRNA synthetase and elongation factor Tu from Escherichia coli
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DOI：
10.1021/bi992439d
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发表时间：
2000-03-14
期刊：
影响因子：
2.9
通讯作者：
Kraal, B
中科院分区：
文献类型：
--
作者：
Barends, S;Wower, J;Kraal, B
氨酰化和转运tmRNA到停滞的核糖体构成了反式翻译的先决条件，这是一个促进停滞的核糖体从截短的mRNA的3'端释放和降解不完全合成的蛋白质的过程。氨酰化的tmRNA的动力学分析表明，tmRNA具有较低的亲和力和较低的周转数比同源tRNA（Ala）的丙氨酰-tRNA合成酶，导致75倍低的k（猫）/K-M值。Ala-tmRNA与延伸因子Tu和GTP复合的结合速率常数比Ala-tRNA（Ala）低约150倍，而其解离速率常数则低约5倍。这些观察结果可以被解释为表明，其他因素促进tmRNA结合到核糖体。
Aminoacylation and transportation of tmRNA to stalled ribosomes constitute prerequisite steps for trans-translation, a process facilitating the release of stalled ribosomes from 3' ends of truncated mRNAs and the degradation of incompletely synthesized proteins. Kinetic analysis of the aminoacylation of tmRNA indicates that tmRNA has both a lower affinity and a lower turnover number than cognate tRNA(Ala) for alanyl-tRNA synthetase, resulting in a 75-fold lower k(cat)/K-M value. The association rate constant of Ala-tmRNA for elongation factor Tu in complex with GTP is about 150-fold lower than that of Ala-tRNA(Ala), whereas its dissocation rate constant is about 5-fold lower. These observations can be interpreted to suggest that additional factors facilitate tmRNA binding to ribosomes.