Pouwels P H, Scholten H J
J Bacteriol. 1979 Aug;139(2):393-7. doi: 10.1128/jb.139.2.393-397.1979.
From a strain of Escherichia coli with two copies of the tryptophan (trp) operon and one copy of the lactose (lac) operon, under control of one of the trp regulatory elements, we have isolated a mutant which does not grow in a medium containing 19 amino acids, unless tryptophan is added, and which cannot ferment lactose. The apparent pleiotropic nature of the mutation(s) is indicated by the very slow growth of mutant bacteria on minimal-medium agar supplemented with glucose and tryptophan. The amount of the trp enzymes (anthranilate synthetase and tryptophan synthetase) and trp messenger ribonucleic acid is reduced several-fold in the mutant compared to the isogenic wild-type strain, whereas the enzymes tryptophanyl-transfer ribonucleic acid synthetase and glucose 6-phosphate dehydrogenase remain the same. The incorporation of radioactive label into pulse-labeled but not into stable ribonucleic acid is significantly lower. Our results suggest that in the mutant organism the control of transcription of some operons, including the trp operon, is modified. An alternative explanation is that mutant bacteria contain a ribonuclease with increased activity for some messenger ribonucleic acid species.
从一株含有两个色氨酸（trp）操纵子拷贝和一个乳糖（lac）操纵子拷贝、且受其中一个trp调控元件控制的大肠杆菌中，我们分离出了一个突变体。该突变体在含有19种氨基酸的培养基中无法生长，除非添加色氨酸，并且不能发酵乳糖。突变细菌在添加了葡萄糖和色氨酸的基本培养基琼脂上生长非常缓慢，这表明突变具有明显的多效性。与同基因野生型菌株相比，突变体中trp酶（邻氨基苯甲酸合成酶和色氨酸合成酶）以及trp信使核糖核酸的量减少了几倍，而色氨酸转移核糖核酸合成酶和葡萄糖6-磷酸脱氢酶的量保持不变。放射性标记掺入脉冲标记的核糖核酸而非稳定核糖核酸中的量显著降低。我们的结果表明，在突变生物体中，包括trp操纵子在内的一些操纵子的转录调控发生了改变。另一种解释是，突变细菌含有一种对某些信使核糖核酸种类活性增强的核糖核酸酶。
