Buck M, Cannon W, Woodcock J
AFRC IPSR, University of Sussex, Brighton, UK.
Nucleic Acids Res. 1987 Dec 10;15(23):9945-56. doi: 10.1093/nar/15.23.9945.
Upstream sequences of the Klebsiella pneumoniae nifH promoter were mutagenised and activation of the mutated promoters by the nif-specific transcriptional activator protein NifA examined in vivo. Of the sixteen mutations analysed, only those within the nifH upstream activator sequence (UAS), characterised by a TGT-N10-ACA motif, influenced nifH promoter activity. Mutations altering the two-fold rotational symmetry of the UAS or the spacing between the TGT and ACA motifs reduced promoter activity, consistent with the UAS functioning as a NifA binding site. The bases flanking the TGT-ACA motif of the UAS also appear to influence activation by NifA. Substituting the nifH UAS with a binding site for the transcriptional activator NtrC resulted in improved NtrC-dependent activation of the nifH promoter demonstrating that the activator specificity of the nifH promoter is dependent upon the presence of the appropriate upstream sequences to which the activator binds.
对肺炎克雷伯菌nifH启动子的上游序列进行诱变，并在体内检测nif特异性转录激活蛋白NifA对突变启动子的激活作用。在分析的16个突变中，只有那些位于以TGT-N10-ACA基序为特征的nifH上游激活序列（UAS）内的突变影响nifH启动子活性。改变UAS的二重旋转对称性或TGT与ACA基序之间间距的突变会降低启动子活性，这与UAS作为NifA结合位点的功能一致。UAS的TGT-ACA基序两侧的碱基似乎也影响NifA的激活作用。用转录激活因子NtrC的结合位点替换nifH UAS导致nifH启动子的NtrC依赖性激活得到改善，这表明nifH启动子的激活因子特异性取决于激活因子结合的适当上游序列的存在。
