Elaborate transcription regulation of the Bacillus subtilis ilv‐leu operon involved in the biosynthesis of branched‐chain amino acids through global regulators of CcpA, CodY and TnrA
Elaborate transcription regulation of the Bacillus subtilis ilv‐leu operon involved in the biosynthesis of branched‐chain amino acids through global regulators of CcpA, CodY and TnrA
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DOI：
10.1111/j.1365-2958.2005.04635.x
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发表时间：
2005-06
影响因子：
3.6
通讯作者：
Shigeo Tojo;T. Satomura;K. Morisaki;J. Deutscher;K. Hirooka;Y. Fujita
中科院分区：
文献类型：
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作者：
Shigeo Tojo;T. Satomura;K. Morisaki;J. Deutscher;K. Hirooka;Y. Fujita
参与支链氨基酸生物合成的枯草芽孢杆菌ilv‐leu操纵子受TnrA和CodY介导的负调控，TnrA和CodY识别并结合位于ilv‐leu启动子上游的各自顺式元件。已知该操纵子受CcpA依赖性正调控。我们目前已经通过体外DNA酶I足迹法以及cre的缺失和碱基取代分析，确定了这种正调控的分解代谢物反应元件（cre）（碱基−96至−82; +1是ilv‐leu转录起始碱基）。在添加谷氨酰胺和氨基酸的葡萄糖基本培养基中的富氮生长条件下，CcpA和CodY分别对ilv‐leu产生正和负调节，但TnrA不起作用。此外，CcpA和CodY能够在没有相互抵消调节的情况下发挥作用，尽管CcpA依赖的正调节不能克服CodY依赖的负调节。此外，在以谷氨酸作为唯一氮源的葡萄糖基本培养基中的氮限制条件下，CcpA和TnrA分别发挥正和负调节作用，但CodY不起作用。这种CcpA依赖性的正调节在没有TnrA依赖性的负调节的情况下发生。然而，在没有CcpA依赖性正调控的情况下，TnrA依赖性负调控不会发生，这增加了这种负调控可能会减少CcpA依赖性正调控的可能性。这种对B的精细转录调控的生理作用。讨论了枯草杆菌ilv‐leu操纵子在该生物体整体代谢调节中的作用。
The Bacillus subtilis ilv‐leu operon involved in the biosynthesis of branched‐chain amino acids is under negative regulation mediated by TnrA and CodY, which recognize and bind to their respective cis‐elements located upstream of the ilv‐leu promoter. This operon is known to be under CcpA‐dependent positive regulation. We have currently identified a catabolite‐responsive element (cre) for this positive regulation (bases −96 to −82; +1 is the ilv‐leu transcription initiation base) by means of DNase I‐footprinting in vitro, and deletion and base‐substitution analyses of cre. Under nitrogen‐rich growth conditions in glucose‐minimal medium supplemented with glutamine and amino acids, CcpA and CodY exerted positive and negative regulation of ilv‐leu, respectively, but TnrA did not function. Moreover, CcpA and CodY were able to function without their counteracting regulation of each other, although the CcpA‐dependent positive regulation did not overcome the CodY‐dependent negative regulation. Furthermore, under nitrogen‐limited conditions in glucose‐minimal medium with glutamate as the sole nitrogen source, CcpA and TnrA exerted positive and negative regulation, respectively, but CodY did not function. This CcpA‐dependent positive regulation occurred without the TnrA‐dependent negative regulation. However, the TnrA‐dependent negative regulation did not occur without the CcpA‐dependent positive regulation, raising the possibility that this negative regulation might decrease the CcpA‐dependent positive regulation. The physiological role of this elaborate transcription regulation of the B. subtilis ilv‐leu operon in overall metabolic regulation in this organism is discussed.