Dusha I, Austin S, Dixon R
Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 521, H-6701, Szeged, Hungary.
FEMS Microbiol Lett. 1999 Oct 15;179(2):491-9. doi: 10.1111/j.1574-6968.1999.tb08768.x.
In Sinorhizobium meliloti the expression of the nodulation genes nodABC is regulated in response to the level of fixed nitrogen (ammonia). Previous results suggested that the response to the nitrogen status is mediated by the two-component NtrB/NtrC system which controls transcription of the nodD3 gene, encoding a positive regulatory protein for the activation of nodABC transcription. Here we confirm by DNase I footprinting and gel shift assays that NtrC, when phosphorylated by NtrB, is able to interact with the enhancer sequences present upstream of nodD3. A model is proposed whereby NtrC functions to control the transcription from the two promoters in the upstream region of nodD3 in response to nitrogen status.
在苜蓿中华根瘤菌中，结瘤基因nodABC的表达受固定氮（氨）水平的调控。先前的结果表明，对氮状态的响应是由双组分NtrB/NtrC系统介导的，该系统控制nodD3基因的转录，nodD3基因编码一种用于激活nodABC转录的正调控蛋白。在这里，我们通过DNA酶I足迹法和凝胶迁移试验证实，当被NtrB磷酸化时，NtrC能够与nodD3上游存在的增强子序列相互作用。我们提出了一个模型，即NtrC发挥作用，以响应氮状态控制nodD3上游区域两个启动子的转录。
