Plumbridge J
Institut de Biologie Physico-chimique, Paris, France.
J Bacteriol. 1996 May;178(9):2629-36. doi: 10.1128/jb.178.9.2629-2636.1996.
The nagC gene, encoding the NagC repressor/activator of the nag regulon, is part of the nagBACD operon. When the promoter-proximal nagB and nagA genes are induced 20- to 40-fold, the nagC gene is induced only two- to threefold. In addition to being transcribed as part of the polycistronic nagBACD mRNA, nagC is also expressed from two promoters located within the upstream nagA gene. These promoters are comparable in strength to the induced nagB promoter, resulting in a high basal level of the nagC mRNA. This means that when the nagBA genes are induced, there is a much smaller effect on the amount of nagC mRNA. The nagC gene is subject to low-level translation so that the amount of NagC protein is kept low despite the relatively high transcription levels.
编码Nag调控子的NagC阻遏物/激活剂的nagC基因是nagBACD操纵子的一部分。当启动子近端的nagB和nagA基因被诱导20至40倍时,nagC基因仅被诱导两至三倍。除了作为多顺反子nagBACD mRNA的一部分被转录外,nagC还从上游nagA基因内的两个启动子表达。这些启动子的强度与被诱导的nagB启动子相当,导致nagC mRNA的基础水平较高。这意味着当nagBA基因被诱导时,对nagC mRNA量的影响要小得多。nagC基因进行低水平翻译,因此尽管转录水平相对较高,但NagC蛋白的量仍保持较低。