1,571 research outputs found
Effects of H-NS and potassium glutamate on σ<SUP>S</SUP>- and σ<SUP>70</SUP>-directed transcription in vitro from osmotically regulated P1 and P2 promoters of proU in Escherichia coli
We have used supercoiled DNA templates in this study to demonstrate that transcription in vitro from the P1 and P2 promoters of the osmoresponsive proU operon of Escherichia coli is preferentially mediated by the σs and σ70-bearing RNA polymerase holoenzymes, respectively. Addition of potassium glutamate resulted in the activation of transcription from both P1 and P2 and also led to a pronounced enhancement of σs selectivity at the P1 promoter. Transcription from P2, and to a lesser extent from P1, was inhibited by the nucleoid protein H-NS but only in the absence of potassium glutamate. This study validates the existence of dual promoters with dual specificities for proU transcription. Our results also support the proposals that potassium, which is known to accumulate in cells grown at high osmolarity, is at least partially responsible for effecting the in vivo induction of proU transcription and that it does so through two mechanisms, directly by the activation of RNA polymerase and indirectly by the relief of repression imposed by H-NS
2. Deep sea drilling at the Amami Sankaku Basin revealed wide distribution of fore-arc basalts across the Izu-Bonin-Mariana Arc: Evidence for spontaneous subduction initiation 52 million years ago
50-Hz plasma treatment of glass fibre reinforced polyester at atmospheric pressure enhanced by ultrasonic irradiation
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