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The sigma subunit of RNA polymerase orchestrates basal transcription by first binding to core RNA polymerase and then recognizing promoters. Using a series of 16 alanine-substitution mutations, we show that residues in a narrow region of Escherichia coli sigma70 (590 to 603) are involved in transcription activation by a mutationally altered CRP derivative,(More)
IscR (iron-sulfur cluster regulator) is encoded by an ORF located immediately upstream of genes coding for the Escherichia coli Fe-S cluster assembly proteins, IscS, IscU, and IscA. IscR shares amino acid similarity with MarA, a member of the MarA/SoxS/Rob family of transcription factors. In this study, we found that IscR functions as a repressor of the(More)
Fe-S clusters are key to the sensing and transcription functions of three transcription factors, FNR, IscR and SoxR. All three proteins were discovered in Escherichia coli but experimental data and bioinformatic predictions suggest that homologs of these proteins exist in other bacterial species, highlighting the widespread nature of Fe-S-dependent(More)
The expression of several Escherichia coli operons is activated by the Fnr protein during anaerobic growth and is further controlled in response to nitrate and nitrite by the homologous response regulators, NarL and NarP. Among these operons, the napF operon, encoding a periplasmic nitrate reductase, has unique features with respect to its Fnr-, NarL-, and(More)
The cysteine desulfurase, IscS, provides sulfur for Fe-S cluster synthesis in vitro, but a role for IscS in in vivo Fe-S cluster formation has yet to be established. To study the in vivo function of IscS in Escherichia coli, a strain lacking IscS was constructed and characterized. Using this iscS deletion strain, we have observed decreased specific(More)
The transcription factor FNR (fumarate nitrate reduction) requires the presence of an iron-sulfur (Fe-S) cluster for its function as a global transcription regulator in Escherichia coli when oxygen becomes scarce. To define the oxidation state and type of Fe-S cluster present in the active form of FNR, we have studied anaerobically purified FNR with(More)
The major regulator controlling the physiological switch between aerobic and anaerobic growth conditions in Escherichia coli is the DNA binding protein FNR. To identify genes controlled by FNR, we used Affymetrix Antisense GeneChips to compare global gene expression profiles from isogenic MG1655 wild-type and Deltafnr strains grown in glucose minimal media(More)
In the facultative anaerobe Escherichia coli, the transcription factor FNR (fumarate nitrate reduction) regulates gene expression in response to oxygen deprivation. To investigate how the activity of FNR is regulated by oxygen availability, two mutant proteins, DA154 and LH28-DA154, which have enhanced in vivo activity in the presence of oxygen, were(More)
The puc operon of Rhodobacter sphaeroides comprises the pucBA structural genes which encode B800-850 light-harvesting beta and alpha polypeptides, respectively. Northern (RNA) blot hybridization analysis of puc operon expression has identified two pucBA-specific transcripts. The small (0.5-kilobase [kb]) transcript encodes the beta and alpha polypeptides(More)
FNR is a global regulator that controls transcription of genes whose functions facilitate adaptation to growth under O2 limiting conditions. It has long been appreciated that the activity of FNR must be regulated by O2 availability, since FNR dependent gene expression is observed in vivo only under anaerobic conditions, while similar levels of this protein(More)