RELEASE FACTOR-DEPENDENT FALSE STOPS ARE INFREQUENT IN ESCHERICHIA-COLI
RELEASE FACTOR-DEPENDENT FALSE STOPS ARE INFREQUENT IN ESCHERICHIA-COLI
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DOI：
10.1006/jmbi.1993.1124
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发表时间：
1993-03-05
影响因子：
5.6
通讯作者：
KURLAND, CG
中科院分区：
文献类型：
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作者：
JORGENSEN, F;ADAMSKI, FM;KURLAND, CG
我们已经估计了释放因子依赖性事件的频率，其中有义密码子被错误地翻译为终止密码子。我们将此事件称为“错误停止”。为了便于测量假终止频率，我们使用质粒表达系统来单独增加释放因子（RF）1和释放因子（RF）2的细胞水平。然后，我们能够在不同浓度的释放因子下，借助于alacZ持续合成能力测定来测量翻译持续合成能力的损失。我们发现，RF 1浓度增加30- 40倍会使lacZ的合成能力从0.6降低到0.3。假设持续合成能力的丧失仅仅是由于错误终止，并且RF 1过量产生的数据可以线性地外推回到细胞中正常的RF 1浓度，这对应于在正常量的RF 1存在下每个密码子接近10- 5的错误终止频率。此外，RF 2浓度增加三倍对lacZ基因的持续合成能力没有可测量的影响。我们的数据表明，与其他翻译错误的发生率相比，错误停顿相对较少。
We have estimated the frequency of release factor dependent events in which a sense codon is mistakenly translated as a stop codon. We refer to this event as a "false stop". In order to facilitate the measurement of false stop frequencies we have used a plasmid expression system to increase individually the cellular levels of release factor (RF) 1 and of release factor (RF) 2. We were then able to measure the loss of translational processivity with the aid of alacZprocessivity assay at different concentrations of the release factors. We find that a 30- to 40-fold increase of the RF1 concentration reduceslacZprocessivity from 0·6 to 0·3. Assuming that the processivity loss is due only to false stops and that the RF1 overproduction data can be extrapolated back linearly to the normal RF1 concentration in the cell, this corresponds to a false stop frequency close to 10-5per codon in the presence of normal amounts of RF1. Furthermore, a threefold increase of the RF2 concentrations had no measurable effect on the processivity of thelacZgene. Our data suggest that false stops are relatively infrequent compared to the incidence of other translation errors.