Bell A, Busby S
School of Biochemistry, University of Birmingham, UK.
Mol Microbiol. 1994 Jan;11(2):383-90. doi: 10.1111/j.1365-2958.1994.tb00318.x.
We have characterized a number of mutations in fnr that interfere with FNR-dependent transcription activation at two promoters where the FNR-binding site is centred around 41 1/2 bp upstream from the transcription start site. The substituted residues in all but one of these FNR mutants are clustered around a presumed surface-exposed beta-turn containing G85 which, we suggest, forms an activating region that contacts RNA polymerase at these promoters. Using the 'oriented heterodimers' method described elsewhere, we show that this activating region on the promoter-proximal subunit of the FNR dimer is sufficient to activate transcription initiation. In contrast, this region is not essential for activation of a third FNR-dependent promoter where the FNR-binding site is centred at 61 1/2 bp upstream from the transcription start site. However, a substitution at S73 interferes with FNR-dependent activation at both this promoter and promoters in which the FNR site is located at 41 1/2 bp from the transcript start, suggesting that FNR may contain a second activating region.
我们已经鉴定出fnr中的一些突变，这些突变会干扰两个启动子处FNR依赖的转录激活，在这两个启动子中，FNR结合位点位于转录起始位点上游约41.5 bp处的中心位置。除了一个FNR突变体之外，所有这些突变体中被取代的残基都聚集在一个推测的表面暴露的β-转角周围，该β-转角包含G85，我们认为它形成了一个在这些启动子处与RNA聚合酶接触的激活区域。使用在其他地方描述的“定向异二聚体”方法，我们表明FNR二聚体的启动子近端亚基上的这个激活区域足以激活转录起始。相比之下，该区域对于激活第三个FNR依赖的启动子不是必需的，在这个启动子中，FNR结合位点位于转录起始位点上游61.5 bp处的中心位置。然而，S73处的取代会干扰该启动子以及FNR位点位于距转录起始41.5 bp处的启动子的FNR依赖的激活，这表明FNR可能包含第二个激活区域。
