RATES OF AMINOACYL-TRANS-RNA SELECTION AT 29 SENSE CODONS INVIVO
RATES OF AMINOACYL-TRANS-RNA SELECTION AT 29 SENSE CODONS INVIVO
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DOI：
10.1016/0022-2836(89)90170-8
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发表时间：
1989-09-05
影响因子：
5.6
通讯作者：
YARUS, M
中科院分区：
文献类型：
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作者：
CURRAN, JF;YARUS, M
我们已经将氨酰-tRNA选择放置在单个密码子上，与假定具有统一速率的移码竞争。通过分析移位框架中的报告，获得了29个YNN密码子与它们的同源氨基酰tRNA在大肠杆菌对数生长过程中的相对结合速率。对于五个密码子，三个以C开头，两个以U开头，这些相对速率与延伸因子Tu介导的核糖体中氨酰tRNA结合和随后的GTP水解的相对速率一致。因此，移码试验可能在体内测量了这一过程。观察到的氨酰-tRNA选择率跨越25倍的范围。因此，在体内转运不同密码子所需的时间可能有很大不同。在高表达基因中经常使用的密码子通常比很少使用的密码子更快地选择氨基酰tRNA。这表明，氨酰-tRNA选择的速度是决定偏向使用同义密码子的一个重要因素。然而，优先使用密码子似乎只对氨基酰-tRNA选择率最高的密码子有标记。体内的快速选择通常是通过提高具有中等固有速度(速率常数)的密码子的tRNA浓度来实现的，而不是通过选择固有的快速密码子来实现的。尽管倾向于高速率，但也有一些快速翻译的密码子并不常用，还有一些常见的密码子翻译得相对较慢。因此，对于一些密码子来说，其他因素比速度更重要。在弱表达的基因中没有观察到强烈的快速选择氨酰-tRNA的偏好。取而代之的是，人们稍微倾向于选择较慢的氨基酰tRNA。即使在许多ync/U对中，两个密码子都与相同的延伸因子Tu/GTP/氨酰-tRNA复合体反应，但ync密码子选择氨酰-tRNA的速率总是大于相应YNU密码子的速率。因此，对于这些tRNAs，tRNAs体内速率常数之间的差异取决于反密码子碱基配对的性质。然而，密码子/反密码子组成与氨酰tRNA选择率之间没有明显的一般关系。移码方法可以推广到所有密码子。
We have placed aminoacyl-tRNA selection at individual codons in competition with a frameshift that is assumed to have a uniform rate. By assaying a reporter in the shifted frame, relative rates for association of the 29 YNN codons and their cognate aminoacyl-tRNAs were obtained during logarithmic growth in Escherichia coli. For five codons, three beginning with C and two with U, these relative rates agree with relative in vitro rates for elongation factor Tu-mediated aminoacyl-tRNA binding in ribosomes and subsequent GTP hydrolysis. Therefore, the frameshift assay probably measures this process in vivo. Observed rates for aminoacyl-tRNA selection span a 25-fold range. Therefore, the time required to transit different codons in vivo probably differs substantially. Codons very frequently used in highly expressed genes generally select aminoacyl-tRNAs more quickly than do rarely used codons. This suggests that speed of aminoacyl-tRNA selection is a significant factor determining biased use of synonymous codons. However, the preferential use of codons appears to be marked only for codons with the highest rates of aminoacyl-tRNA selection. Rapid selection in vivo is usually effected by elevation of the tRNA concentration for codons with moderate intrinsic speed (rate constant), not by choosing intrinsically fast codons. Despite a preference for high rate, there are quickly translated codons that are not commonly used, and common codons that are translated relatively slowly. Other factors are therefore more important than speed for some codons. Strong preference for rapid aminoacyl-tRNA selection is not observed in weakly expressed genes. Instead, there is a slight preference for slower aminoacyl-tRNA selection. The rate of aminoacyl-tRNA selection by a YNC codon is always greater than the rate of the corresponding YNU codon even though in many YNC/U pairs both codons react with the same elongation factor Tu/GTP/aminoacyl-tRNA complex. Thus, for these tRNAs, the differences between in vivo rate constants of tRNAs are dependent of the nature of anticodon base-pairing. However, no more general relationship is evident between codon/anticodon composition and rate of aminoacyl-tRNA selection. The frameshift method can be extended to all codons.