Hugouvieux-Cotte-Pattat N, Robert-Baudouy J
J Gen Microbiol. 1983 Nov;129(11):3345-53. doi: 10.1099/00221287-129-11-3345.
Gene fusions between the lac structural genes and various genes of the hexuronate system of Escherichia coli K12 were isolated by the technique of Casadaban. Mud(Aprlac) and lambda plac-Mu insertion mutants were constructed in which the lac genes were fused to the regulatory region of the uxu operon. In all the uxu-lac fusion strains, beta-galactosidase expression was shown to be inducible by the natural inducers of the uxu operon (glucuronate and fructuronate) and sensitive to catabolite repression by glucose. In addition we isolated a Mud(Aprlac) fusion where the lac genes were fused to the uxuR regulatory gene. In this fusion the synthesis of beta-galactosidase reflects the regulation of the uxuR gene. In the presence of a wild-type uxuR allele, partial repression of beta-galactosidase expression was found; the repression was removed when inducer was added. This result indicates that while the uxuR gene is subject to autogenous control, the uxuR repressor may have only a low affinity for its own operator.
利用卡萨达班技术分离出了大肠杆菌K12乳糖操纵子结构基因与己糖醛酸系统各种基因之间的基因融合体。构建了Mud（Aprlac）和λplac-Mu插入突变体，其中乳糖操纵子基因与uxu操纵子的调控区域融合。在所有uxu-lac融合菌株中，β-半乳糖苷酶的表达可被uxu操纵子的天然诱导物（葡萄糖醛酸和果糖醛酸）诱导，且对葡萄糖的分解代谢阻遏敏感。此外，我们分离出了一个Mud（Aprlac）融合体，其中乳糖操纵子基因与uxuR调控基因融合。在这种融合体中，β-半乳糖苷酶的合成反映了uxuR基因的调控情况。在存在野生型uxuR等位基因的情况下，发现β-半乳糖苷酶的表达受到部分阻遏；添加诱导物后阻遏作用消除。这一结果表明，虽然uxuR基因受到自身调控，但uxuR阻遏物对其自身操纵子的亲和力可能较低。
