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Journal of Bacteriology, October 2003, p. 5993-6004, Vol. 185, No. 20
0021-9193/03/$08.00+0 DOI: 10.1128/JB.185.20.5993-6004.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT,1 Department of Molecular Biology and Biotechnology, Western Bank, University of Sheffield, Sheffield S10 2TN, United Kingdom2
Received 13 May 2003/ Accepted 30 July 2003
FNR is an Escherichia coli transcription factor that regulates the transcription of many genes in response to anaerobiosis. We have constructed a series of artificial FNR-dependent promoters, based on the melR promoter, in which a consensus FNR binding site was centered at position -41.5 relative to the transcription start site. A second consensus FNR binding site was introduced at different upstream locations, and promoter activity was assayed in vivo. FNR can activate transcription from these promoters when the upstream FNR binding site is located at many different positions. However, sharp repression is observed when the upstream-bound FNR is located near positions -85 or -95. This repression is relieved by the FNR G74C substitution mutant, previously identified as being defective in transcription repression at the yfiD promoter. A parallel series of artificial FNR-dependent promoters, carrying a consensus FNR binding site at position -61.5 and a second upstream DNA site for FNR, was also constructed. Again, promoter activity was repressed by FNR when the upstream-bound FNR was located at particular positions.
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