Miozzari G, Yanofsky C
Proc Natl Acad Sci U S A. 1978 Nov;75(11):5580-4. doi: 10.1073/pnas.75.11.5580.
The promoter/operator/leader region of the trp operon of Shigella dysenteriae 16 has single base pair differences from the corresponding region of Escherichia coli at positions -24 and -13. The difference at -13 was shown to be responsible for the 90% reduction in promoter function characteristic of the trp operon of S. dysenteriae. The base pair difference at position -13 also renders the operator partially constitutive. This allows the organism to maintain relatively high repressed levels of the trp enzymes and increases the relative importance of attenuation as a transcription control mechanism. These findings and the earlier observation that the trpE protein of S. dysenteriae is only slightly active explain the low in vivo expression of the trp operon of this organism. Nutritional studies suggest that operons involved in other amino acid biosynthetic pathways in S. dysenteriae 16 may be similarly partially inactivated.
痢疾志贺氏菌16型色氨酸操纵子的启动子/操纵基因/前导区在-24和-13位与大肠杆菌的相应区域存在单碱基对差异。已证明-13位的差异导致痢疾志贺氏菌色氨酸操纵子启动子功能降低90%。-13位的碱基对差异还使操纵基因部分组成型表达。这使该生物体能够维持色氨酸酶相对较高的阻遏水平，并增加了衰减作为转录控制机制的相对重要性。这些发现以及早期观察到的痢疾志贺氏菌色氨酸E蛋白活性较低，解释了该生物体色氨酸操纵子在体内表达水平较低的原因。营养研究表明，痢疾志贺氏菌16型中参与其他氨基酸生物合成途径的操纵子可能同样部分失活。
