The growth defect in Escherichia coli deficient in peptidyl-tRNA hydrolase is due to starvation for Lys-tRNA(Lys)
The growth defect in Escherichia coli deficient in peptidyl-tRNA hydrolase is due to starvation for Lys-tRNA(Lys)
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DOI：
10.1002/j.1460-2075.1996.tb00643.x
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发表时间：
1996-06-03
期刊：
影响因子：
11.4
通讯作者：
Buckingham, RH
中科院分区：
文献类型：
--
作者：
HeurgueHamard, V;Mora, L;Buckingham, RH
大肠杆菌中存在一种影响肽基-tRNA水解酶的条件性致死温度敏感突变体，表明这种酶对细胞存活是必不可少的，我们在这里报告了这种突变体在编码水解酶的基因PTH中的染色体和多拷贝抑制子的分离。在一种情况下，负责抑制的克隆基因被证明是lysV，这是编码独特赖氨酸受体tRNA的三个基因之一;其他10个克隆的tRNA基因没有影响。lysV的过表达导致tRNA（Lys）浓度增加2至3倍，克服了在非允许温度下细胞中肽基-tRNA水解酶活性的不足。相反，在pth，supN双突变体，其中的tRNA（赖氨酸）的浓度降低，由于转换的lysV的赭石抑制（supN），温度敏感性的初始pth突变体变得加重。因此，携带这两种突变的细胞在39摄氏度下几乎不生长，而在39摄氏度下，pth突变体几乎正常生长。通过从质粒表达lysV恢复双突变体的生长。这些结果表明，限制生长的突变体大肠杆菌缺乏Pth是由于螯合的tRNA（赖氨酸）肽基-tRNA。这与先前的观察结果一致，即这种tRNA特别容易过早地从核糖体解离。
The existence of a conditional lethal temperature-sensitive mutant affecting peptidyl-tRNA hydrolase in Escherichia coli suggests that this enzyme is essential to cell survival, We report here the isolation of both chromosomal and multicopy suppressors of this mutant in pth, the gene encoding the hydrolase. In one case, the cloned gene responsible for suppression is shown to be lysV, one of three genes encoding the unique lysine acceptor tRNA; 10 other cloned tRNA genes are without effect. Overexpression of lysV leading to a 2- to 3-fold increase in tRNA(Lys) concentration overcomes the shortage of peptidyl-tRNA hydrolase activity in the cell at non-permissive temperature. Conversely, in pth, supN double mutants, where the tRNA(Lys) concentration is reduced due to the conversion of lysV to an ochre suppressor (supN), the thermosensitivity of the initial pth mutant becomes accentuated. Thus, cells carrying both mutations show practically no growth at 39 degrees C, a temperature at which the pth mutant grows almost normally. Growth of the double mutant is restored by the expression of lysV from a plasmid. These results indicate that the limitation of growth in mutants of E.coli deficient in Pth is due to the sequestration of tRNA(Lys) peptidyl-tRNA. This is consistent with previous observations that this tRNA is particularly prone to premature dissociation from the ribosome.