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大肠杆菌K12中己糖醇转运系统合成的调控机制分析。

Analysis of the regulatory mechanisms controlling the synthesis of the hexitol transport systems in Escherichia coli K12.

作者信息

Lengeler J, Steinberger H

出版信息

Mol Gen Genet. 1978 Aug 17;164(2):163-9. doi: 10.1007/BF00267381.

Abstract

The synthesis of the transport systems (enzymeII-complexes) coded for in the mtl and in the gut (srl) operon was found to be induced by unphosphorylated D-mannitol and D-glucitol respectively. Induction from the outside however is only possible if these polyols are taken up into the cells. Induction of the D-mannitol system is immediate, resistant against catabolite repression, relatively insensitive towards transient repression and starts from a high uninduced level (5--30%). By contrast, the induction of the D-glucitol system starts at a low basal level (0.5--2.5%), does show a pronounced lag from 25 to 90 min, and is hypersensitive towards catabolite and transient repression. These differences apparently reflect primarely differences in the corresponding operator-promotor genes mtl (P,O) and gut (P,O) as well as differences in the uptake of the first, inducing hexitol molecules. For each operon additional regulatory genes exist, called mtlR and gutR respectively, in which transrecessive, temperature sensitive mutations leading to a constitutive expression of the corresponding operon can be found. The influence of these regulatory mechanisms in diauxie experiments and their importance for the differentiation of the three operons during evolution from apparently one common ancestor operon will be discussed.

摘要

已发现,mtl操纵子和gut(srl)操纵子中编码的转运系统(酶II复合物)的合成分别由未磷酸化的D-甘露糖醇和D-葡糖醇诱导。然而,只有当这些多元醇被细胞吸收时,才能从外部进行诱导。D-甘露糖醇系统的诱导是即时的,抗分解代谢物阻遏,对瞬时阻遏相对不敏感,且从较高的未诱导水平(5%-30%)开始。相比之下,D-葡糖醇系统的诱导从较低的基础水平(0.5%-2.5%)开始,在25至90分钟内有明显的延迟,并且对分解代谢物和瞬时阻遏高度敏感。这些差异显然主要反映了相应的操纵基因启动子基因mtl(P,O)和gut(P,O)的差异,以及第一种诱导己糖醇分子摄取的差异。每个操纵子都存在额外的调控基因,分别称为mtlR和gutR,在其中可以发现导致相应操纵子组成型表达的反式隐性、温度敏感突变。将讨论这些调控机制在二次生长实验中的影响,以及它们在从一个明显的共同祖先操纵子进化过程中对三个操纵子分化的重要性。

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