IscR ( i ron- s ulfur c luster r egulator) is encoded by an ORF located immediately upstream of genes coding for the Escherichia coli Fe-S cluster assembly proteins, IscS, IscU, and IscA. shares amino acid similarity with MarA, a member MarA/SoxS/Rob family transcription factors. In this study, we found that functions as repressor iscRSUA operon, because strains deleted iscR have increased expression operon. addition, in vitro reactions established direct role repression promoter. Analysis...

The transcription factor FNR ( f umarate n itrate r eduction) requires the presence of an iron-sulfur (Fe-S) cluster for its function as a global regulator in Escherichia coli when oxygen becomes scarce. To define oxidation state and type Fe-S present active form FNR, we have studied anaerobically purified with Mössbauer spectroscopy. Our data showed that this contained [4Fe-4S] 2+ (δ = 0.45 mm/s; Δ E Q 1.22 mm/s) was rapidly destroyed on exposure to air. Under these conditions, yellow–green...

The transcription factor FNR from Escherichia coli regulates of genes in response to oxygen deprivation. To determine how the activity is regulated by oxygen, a form had be isolated that properties similar those observed vivo. This was accomplished purification an fraction which exhibited enhanced DNA binding absence oxygen. Iron and sulfide analyses this indicated presence Fe-S cluster. type cluster present, oxygen-stable mutant protein LH28-DA154 also analyzed since purified anoxically...

The cysteine desulfurase, IscS, provides sulfur for Fe-S cluster synthesis in vitro , but a role IscS vivo formation has yet to be established. To study the function of Escherichia coli strain lacking was constructed and characterized. Using this iscS deletion strain, we have observed decreased specific activities proteins containing [4Fe-4S] clusters from soluble (aconitase B, 6-phosphogluconate dehydratase, glutamate synthase, fumarase A, FNR) membrane-bound (NADH dehydrogenase I succinate...

ABSTRACT The major regulator controlling the physiological switch between aerobic and anaerobic growth conditions in Escherichia coli is 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 Δ fnr strains grown glucose minimal media under or conditions. We found that 297 contained within 184 operons were regulated FNR and/or O 2 levels. of many known be involved...

Summary IscR is an iron‐sulphur (Fe‐S) cluster‐containing transcription factor that represses of the operon containing its own gene and iscSUA‐hscBA‐fdx genes, whose products are involved in Fe‐S cluster biogenesis. In this study, global transcriptional profiling Escherichia coli + – strains grown under aerobic anaerobic conditions indicated 40 genes 20 predicted operons were regulated by IscR. DNase I footprinting and/or vitro reactions identified seven new promoters direct control. Among...

In the facultative anaerobe Escherichia coli, transcription factor FNR (fumarate nitrate reduction) regulates gene expression in response to oxygen deprivation. To investigate how activity of is regulated by availability, two mutant proteins, DA154 and LH28-DA154, which have enhanced vivo presence oxygen, were purified compared. Unlike other previously examined preparations, absorption spectrum LH28-DA154 had maxima at 324 nm 419 nm, typical iron-sulfur (Fe-S)-containing proteins. Consistent...

FNR is a well-studied global regulator of anaerobiosis, which widely conserved across bacteria. Despite the importance and anaerobiosis in microbial lifestyles, factors that influence its function on genome-wide scale are poorly understood. Here, we report functional genomic analysis action. We find occupancy at many target sites strongly influenced by nucleoid-associated proteins (NAPs) restrict access to binding sites. At level, only subset predicted were bound under anaerobic fermentative...

The lipopolysaccharide (LPS) from Actinobacillus actinomycetemcomitans strains Y4 and N27 was isolated by the phenol-water procedure. Morphologically, molecule consisted of ribbon branched filaments which comprised 3% cellular dry weight. Chemical analysis purified LPSs both showed them to consist carbohydrate, lipid, 2-keto-3-deoxyoctonate, heptose, hexosamine, phosphate. major fatty acids lipid A moiety were saturated C14 beta-OH compounds. Rhamnose, fucose, galactose, glucose,...

Significance Microbially produced aliphatic alcohols are important biocommodities but exert toxic effects on cells. Understanding the mechanisms by which these inhibit microbial growth and generate resistant microbes will provide insight into physiology improve prospects for biotechnology biofuel production. We find that Escherichia coli ribosomes RNA polymerase mechanistically affected ethanol, identifying ribosome decoding center as a likely target of ethanol-mediated conformational...

Despite the importance of maintaining redox homeostasis for cellular viability, how cells control balance globally is poorly understood. Here we provide new mechanistic insight into between reduced and oxidized electron carriers regulated at level gene expression by mapping regulon response regulator ArcA from Escherichia coli, which responds to quinone/quinol couple via its membrane-bound sensor kinase, ArcB. Our genome-wide analysis reveals that reprograms metabolism under anaerobic...

Summary Fe – S clusters are essential across the biological world, yet how cells regulate expression of cluster biogenesis pathways to cope with changes in demand is not well understood. Here, we describe mechanism by which IscR , a [2 –2 ] cluster‐containing regulator E scherichia coli adjusts synthesis Isc pathway maintain homeostasis. Our data indicate that negative feedback loop operates repress transcription iscRSUA hscBA fdx operon, encoding and machinery, through binding ]– two...

The transcription factor FNR globally regulates gene expression in response to oxygen deprivation Escherichia coli. To understand how activates FNR, a constitutively active FNR* mutant protein, DA154, was studied determine this bypassed the normal regulation pathway. When purified from aerobically grown cells, DA154 protein had larger apparent native molecular mass and an increased affinity for consensus target site as compared with wild-type prepared under identical conditions. These...

IscR is an Fe–S cluster-containing transcription factor involved in a homeostatic mechanism that controls cluster biogenesis Escherichia coli. Although has been proposed to act as sensor of the cellular demands for biogenesis, by which performs this function not known. In study, we investigated biochemical properties gain insight into sensing activity. Mössbauer studies revealed contains predominantly reduced [2Fe-2S]+ vivo. However, upon anaerobic isolation IscR, some clusters became...

Significance Our understanding of how cells regulate intracellular iron pools has been largely shaped by studying grown under aerobic conditions, in which the barrier to acquisition is dominated O 2 -dependent insolubility. However, less known about bacteria meet their demands -limiting or anaerobic environments that are common many ecosystems and reflective ancient atmosphere early Earth. Because transcription factor ferric-uptake regulator (Fur) plays a central role controlling homeostasis...