Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Korea.
FEMS Microbiol Lett. 2010 Mar;304(2):107-15. doi: 10.1111/j.1574-6968.2009.01884.x.
Recently, a cyclic AMP receptor protein homologue, GlxR, was reported to bind to the upstream regions of several genes involved in the regulation of diverse physiological processes in Corynebacterium glutamicum. However, the function of GlxR has not yet been explored in C. glutamicum in vivo using a glxR deletion mutant. Therefore, this study examines the role of GlxR as a repressor in glyoxylate bypass and carbon catabolite repression (CCR) using a deletion mutant. The disruption of glxR resulted in a severe growth defect, but growth was restored by complementation with the glxR and crp genes from C. glutamicum and Streptomyces coelicolor, respectively. The production of isocitrate lyase (ICL) and malate synthase (MS) was significantly increased in the glxR mutant. The specific activities of both enzymes were increased in the glxR mutant, regardless of the carbon source. In accordance, the promoter activities of ICL and MS using lacZ fusion were derepressed in the glxR mutant. In addition, the glxR mutant exhibited derepression of the gluA gene for glutamate uptake in the presence of glucose, thereby relieving CCR by glucose. These results indicate that GlxR plays an important role in CCR as well as in acetate metabolism.
最近，有报道称环磷酸腺苷受体蛋白同源物 GlxR 与参与棒状杆菌属谷氨酸多种生理过程调节的几个基因的上游区域结合。然而，在体内使用 glxR 缺失突变体尚未探索 GlxR 在谷氨酸棒状杆菌中的功能。因此，本研究使用缺失突变体研究 GlxR 作为乙醛酸旁路和碳分解代谢阻遏（CCR）的阻遏物的作用。glxR 的破坏导致严重的生长缺陷，但通过分别从谷氨酸棒状杆菌和链霉菌属共青霉中补充 glxR 和 crp 基因，生长得到恢复。在 glxR 突变体中，异柠檬酸裂解酶（ICL）和苹果酸合酶（MS）的产量显著增加。无论碳源如何，两种酶的比活性在 glxR 突变体中均增加。相应地，ICL 和 MS 的启动子活性在 glxR 突变体中被去阻遏，使用 lacZ 融合。此外，glxR 突变体在葡萄糖存在时表现出对谷氨酸摄取的 gluA 基因的去阻遏，从而通过葡萄糖缓解 CCR。这些结果表明 GlxR 在 CCR 以及乙酸盐代谢中起重要作用。
