A new bacterial promoter type has been identified in the last few years. Originally designated as nif (= nitrogen fixation) or ntr (= nitrogen regulation) consensus promoter, it is now evident that this promoter occurs in many different bacterial species and is used not only for genes involved in nitrogen assimilation but also for genes determining many other unrelated metabolic functions. The general features of this type of promoter are (i) the conserved -24(GG)/-12(GC) consensus sequence, (ii) its recognition by a specific RNA polymerase sigma factor, sigma 54, which is encoded by the ntrA gene (synonyms: glnF, rpoN, rpoE), and (iii) the requirement for a transcriptional regulatory protein to activate the expression of the associated genes. In addition, many (but not all) of these genes possess a promoter-upstream activator sequence (enhancer) which is the target site for the binding of the activating protein and is required for maximal expression. In some cases, in which gene expression does not appear to be dependent on the presence of upstream binding sites, the activating protein may interact directly with the RNA polymerase-promoter complex. In conclusion, the expression from all -24/-12 consensus promoters known to date is positively controlled.

中文翻译：

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-24 / -12启动子已经成熟。

在最近几年中已经确定了一种新的细菌启动子类型。最初被指定为nif（=氮固定）或ntr（=氮调节）共有启动子，现在很明显，该启动子出现在许多不同的细菌物种中，不仅用于涉及氮同化的基因，而且还用于确定许多其他同化基因。不相关的代谢功能。这种类型的启动子的一般特征是（i）保守的-24（GG）/-12（GC）共有序列，（ii）被ntrA编码的特定RNA聚合酶sigma因子sigma 54识别。基因（同义词：glnF，rpoN，rpoE），以及（iii）需要转录调节蛋白来激活相关基因的表达。此外，这些基因中的许多（但不是全部）具有启动子上游激活序列（增强子），该序列是激活蛋白结合的目标位点，是最大表达所必需的。在某些情况下，基因表达似乎不依赖于上游结合位点的存在，活化蛋白可以直接与RNA聚合酶-启动子复合体相互作用。总之，迄今为止已知的所有-24 / -12共有启动子的表达都受到了积极控制。