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首页> 外文期刊>Journal of bacteriology >Gratuitous overexpression of genes in Escherichia coli leads to growth inhibition and ribosome destruction.
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Gratuitous overexpression of genes in Escherichia coli leads to growth inhibition and ribosome destruction.

机译：大肠杆菌中基因的过度表达会导致生长抑制和核糖体破坏。

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We attempted to test the idea that the relative abundance of each individual tRNA isoacceptor in Escherichia coli can be altered by varying its cognate codon concentration. In order to change the overall codon composition of the messenger pool, we have expressed in E. coli lacZ with the aid of T7 RNA polymerase so that their respective gene products individually accounted for 30% of the total bacterial protein. Unexpectedly, the maximum expression of either test gene has no specific effect on the relative rates of synthesis of the tRNA species that we studied. Instead, we find that there is a cumulative breakdown of rRNAs, which results in a loss of ribosomes and protein synthetic capacity. After either of the test genes is maximally induced, there is a growing fraction of protein synthesis invested in beta-galactosidase or delta tufB that is matched by a comparable decrease of the fraction of normal protein synthesis. We have also observed enhanced accumulation of two heat shock proteins during overexpression. Finally, after several hours of overexpression of either test protein, the bacteria are no longer viable. These results are relevant to the practical problems of obtaining high expression levels for cloned proteins.
机译：我们试图检验这样的想法，即通过改变其同源密码子浓度可以改变大肠杆菌中每个单独的tRNA异构体的相对丰度。为了改变信使库的整体密码子组成，我们借助T7 RNA聚合酶在大肠杆菌lacZ中表达了蛋白质，因此它们各自的基因产物分别占细菌蛋白质总量的30％。出乎意料的是，这两个测试基因的最大表达对我们研究的tRNA物种的相对合成速率没有特异性影响。取而代之的是，我们发现rRNA的累积分解，导致核糖体和蛋白质合成能力的丧失。在最大程度地诱导了两个测试基因后，在β-半乳糖苷酶或delta tufB中投入的蛋白质合成比例不断增加，而正常蛋白质合成比例则相应下降。我们还观察到过表达过程中两种热激蛋白的积累增加。最终，在任一测试蛋白过表达数小时后，细菌不再存活。这些结果与获得高表达水平的克隆蛋白的实际问题有关。

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