Molecular evidence for the coordination of nitrogen and carbon metabolisms, revealed by a study on the transcriptional regulation of the agl3EFG operon that encodes a putative carbohydrate transporter in Streptomyces coelicolor
Molecular evidence for the coordination of nitrogen and carbon metabolisms, revealed by a study on the transcriptional regulation of the agl3EFG operon that encodes a putative carbohydrate transporter in Streptomyces coelicolor
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对天蓝色链霉菌中编码假定碳水化合物转运蛋白的 agl3EFG 操纵子的转录调控的研究揭示了氮和碳代谢协调的分子证据
DOI：
10.1016/j.bbrc.2016.02.044
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发表时间：
2016-03-18
影响因子：
3.1
通讯作者：
Wang, Jin
中科院分区：
文献类型：
--
作者：
Cen, Xu-Feng;Wang, Jing-Zhi;Wang, Jin
在链霉菌冷色M145的agl3EFGXYZ操纵子（SCO7167-SCO7162，缩写为agl3操纵子）中，agl3EFG基因编码一种假定的abc型碳水化合物转运蛋白。该操纵子的转录已被邻近的gntr家族调控因子AglR （SCO7168）抑制，这种抑制可以通过在低碳源上生长而释放。在这项研究中，我们证明了agl3操纵子的转录也直接受到GlnR的抑制，GlnR是油菜中调控氮代谢的中心调节因子。采用agl3启动子和纯化的重组GlnR和Agl3R的混合物进行的电泳迁移试验（EMSA）表明，GlnR和Agl3R结合agl3操纵子启动子区域内不同的DNA序列，DNase I足迹试验进一步证实了这一点。由于已经证明Agl3R和GlnR分别感知细胞外碳和氮的供应，因此假设agl3操纵子的转录严格受细胞外碳和氮源的可用性的控制。与假设一致，进一步发现agl3操纵子仅在贫碳和富氮供应条件下才会被抑制，当两个调节因子都失活时。研究认为，激活agl3操纵子的表达可能促进细胞外碳水化合物的吸收，从而平衡细胞内碳氮比。(C) 2016 Elsevier Inc.版权所有。
In the agl3EFGXYZ operon (SCO7167-SCO7162, abbreviated as agl3 operon) of Streptomyces coelicolor M145, agl3EFG genes encode a putative ABC-type carbohydrate transporter. The transcription of this operon has been proved to be repressed by AglR (SCO7168), a neighboring GntR-family regulator, and this repression can be released by growth on poor carbon sources. Here in this study, we prove that the transcription of agl3 operon is also directly repressed by GlnR, a central regulator governing the nitrogen metabolism in S. coelicolor. The electrophoretic mobility shift assay (EMSA) employing the agl3 promoter and mixtures of purified recombinant GlnR and Agl3R indicates that GlnR and Agl3R bind to different DNA sequences within the promoter region of agl3 operon, which is further confirmed by the DNase I footprinting assay. As Agl3R and GlnR have been demonstrated to sense the extracellular carbon and nitrogen supplies, respectively, it is hypothesized that the transcription of agl3 operon is stringently governed by the availabilities of extracellular carbon and nitrogen sources. Consistent with the hypothesis, the agl3 operon is further found to be derepressed only under the condition of poor carbon and rich nitrogen supplies, when both regulators are inactivated. It is believed that activation of the expression of agl3 operon may facilitate the absorption of extracellular carbohydrates to balance the ratio of intracellular carbon to nitrogen. (C) 2016 Elsevier Inc. All rights reserved.