Research Institute of Innovative Technology for the Earth (RITE), 9-2 Kizugawadai, Kizugawa, Kyoto, 619-0292, Japan.
Microbiology (Reading). 2011 Jan;157(Pt 1):21-28. doi: 10.1099/mic.0.044552-0. Epub 2010 Sep 23.
The Corynebacterium glutamicum anaerobic nitrate reductase operon narKGHJI is repressed by a transcriptional regulator, ArnR, under aerobic conditions. A consensus binding site of the cAMP receptor protein (CRP)-type regulator, GlxR, was recently found upstream of the ArnR binding site in the narK promoter region. Here we investigated the involvement of GlxR and cAMP in expression of the narKGHJI operon in vivo. Electrophoretic mobility shift assays showed that the putative GlxR binding motif in the narK promoter region is essential for the cAMP-dependent binding of GlxR. Promoter-reporter assays showed that mutation in the GlxR binding site resulted in significant reduction of narK promoter activity. Furthermore, a deletion mutant of the adenylate cyclase gene cyaB, which is involved in cAMP synthesis, exhibited a decrease in both narK promoter activity and nitrate reductase activity. These results demonstrated that C. glutamicum GlxR positively regulates narKGHJI expression in a cAMP-dependent manner.
谷氨酸棒杆菌厌氧硝酸盐还原酶操纵子 narKGHJI 在有氧条件下受转录调节因子 ArnR 抑制。最近在 ArnR 结合位点的 narK 启动子区域上游发现了 cAMP 受体蛋白 (CRP) 型调节剂 GlxR 的一个共识结合位点。在这里，我们研究了 GlxR 和 cAMP 在体内 narKGHJI 操纵子表达中的参与。电泳迁移率变动分析显示，narK 启动子区域中假定的 GlxR 结合基序对于 cAMP 依赖性 GlxR 结合是必需的。启动子报告基因分析表明，GlxR 结合位点的突变导致 narK 启动子活性显著降低。此外，参与 cAMP 合成的腺苷酸环化酶基因 cyaB 的缺失突变体表现出 narK 启动子活性和硝酸盐还原酶活性的降低。这些结果表明，C. glutamicum GlxR 以 cAMP 依赖性方式正向调节 narKGHJI 的表达。
