Transcriptional regulation of the uptake [NiFe]hydrogenase genes in Rhodobacter capsulatus

2005 ◽  
Vol 33 (1) ◽  
pp. 28-32 ◽  
Author(s):  
P.M. Vignais ◽  
S. Elsen ◽  
A. Colbeau
Keyword(s):  
Gene Expression ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Regulatory System ◽  
Integration Host Factor ◽  
Host Factor ◽  
Promoter Recognition ◽  
The Stability ◽  
A Site

Transcription of the hupSL genes, which encode the uptake [NiFe]hydrogenase of Rhodobacter capsulatus, is specifically activated by H2. Three proteins are involved, namely the H2-sensor HupUV, the histidine kinase HupT and the transcriptional activator HupR. hupT and hupUV mutants have the same phenotype, i.e. an increased level of hupSL expression (assayed by phupS::lacZ fusion) in the absence of H2; they negatively control hupSL gene expression. HupT can autophosphorylate its conserved His217, and in vitro phosphotransfer to Asp54 of its cognate response regulator, HupR, was demonstrated. The non-phosphorylated form of HupR binds to an enhancer site (5′-TTG-N5-CAA) of phupS localized at −162/−152 nt and requires integration host factor to activate fully hupSL transcription. HupUV is an O2-insensitive [NiFe]hydrogenase, which interacts with HupT to regulate the phosphorylation state of HupT in response to H2 availability. The N-terminal domain of HupT, encompassing the PAS domain, is required for interaction with HupUV. This interaction with HupT, leading to the formation of a (HupT)2–(HupUV)2 complex, is weakened in the presence of H2, but incubation of HupUV with H2 has no effect on the stability of the heterodimer/tetramer, HupUV–(HupUV)2, equilibrium. HupSL biosynthesis is also under the control of the global two-component regulatory system RegB/RegA, which controls gene expression in response to redox. RegA binds to a site close to the −35 promoter recognition site and to a site overlapping the integration host factor DNA-binding site (5′-TCACACACCATTG, centred at −87 nt) and acts as a repressor.

scholarly journals Regulation and Characterization of Two Nitroreductase Genes, nprA and nprB, of Rhodobacter capsulatus

2005 ◽  
Vol 71 (12) ◽  
pp. 7643-7649 ◽  
Author(s):  
Eva Pérez-Reinado ◽  
Rafael Blasco ◽  
Francisco Castillo ◽  
Conrado Moreno-Vivián ◽  
M. Dolores Roldán
Keyword(s):  
Gene Expression ◽  
Salicylic Acid ◽  
Rhodobacter Capsulatus ◽  
Sequence Data ◽  
Regulatory System ◽  
Wide Range ◽  
Nitrofuran Derivatives ◽  
Response To Stress

ABSTRACT Among photosynthetic bacteria, strains B10 and E1F1 of Rhodobacter capsulatus photoreduce 2,4-dinitrophenol (DNP), which is stoichiometrically converted into 2-amino-4-nitrophenol by a nitroreductase activity. The reduction of DNP is inhibited in vivo by ammonium, which probably acts at the level of the DNP transport system and/or physiological electron transport to the nitroreductase, since this enzyme is not inhibited by ammonium in vitro. Using the complete genome sequence data for strain SB1003 of R. capsulatus, two putative genes coding for possible nitroreductases were isolated from R. capsulatus B10 and disrupted. The phenotypes of these mutant strains revealed that both genes are involved in the reduction of DNP and code for two major nitroreductases, NprA and NprB. Both enzymes use NAD(P)H as the main physiological electron donor. The nitroreductase NprA is under ammonium control, whereas the nitroreductase NprB is not. In addition, the expression of the nprB gene seems to be constitutive, whereas nprA gene expression is inducible by a wide range of nitroaromatic and heterocyclic compounds, including several dinitroaromatics, nitrofuran derivatives, CB1954, 2-aminofluorene, benzo[a]pyrene, salicylic acid, and paraquat. The identification of two putative mar/sox boxes in the possible promoter region of the nprA gene and the induction of nprA gene expression by salicylic acid and 2,4-dinitrophenol suggest a role in the control of the nprA gene for the two-component MarRA regulatory system, which in Escherichia coli controls the response to some antibiotics and environmental contaminants. In addition, upregulation of the nprA gene by paraquat indicates that this gene is probably a member of the SoxRS regulon, which is involved in the response to stress conditions in other bacteria.

scholarly journals Regulated Expression of a Highly Conserved Regulatory Gene Cluster Is Necessary for Controlling Photosynthesis Gene Expression in Response to Anaerobiosis in Rhodobacter capsulatus

1999 ◽  
Vol 181 (14) ◽  
pp. 4334-4341 ◽  
Author(s):  
Shouying Du ◽  
Jean-Louis K. Kouadio ◽  
Carl E. Bauer
Keyword(s):  
Gene Expression ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Expression Patterns ◽  
Regulatory Gene ◽  
Global Response ◽  
Promoter Recognition ◽  
In Vivo Analysis ◽  
Extension Analysis

ABSTRACT We utilized primer extension analysis to demonstrate that the divergently transcribed regB and senC-regA-hvrAtranscripts contain stable 5′ ends 43 nucleotides apart within theregB-senC intergenic region. DNA sequence analysis indicates that this region contains two divergent promoters with overlapping ς70 type −35 and −10 promoter recognition sequences. In vivo analysis of expression patterns ofregB::lacZ andsenC-regA-hvrA::lacZ reporter gene fusions demonstrates that the regB andsenC-regA-hvrA transcripts are both negatively regulated by the phosphorylated form of the global response regulator RegA. DNase I protection assays with a constitutively active variant of RegA indicate that RegA binds between regB and senCoverlapping −10 and −35 promoter recognition sequences. Two mutations were also isolated in a regB-deficient background that increased expression of the senC-regA-hvrA operon 10- and 5-fold, respectively. As a consequence of increased RegA expression, these mutants exhibited elevated aerobic and anaerobic photosynthesis (puf) gene expression, even in the absence of the sensor kinase RegB. These results indicate that autoregulation by RegA is a factor contributing to the maintenance of an optimal low level of RegA expression that allows responsiveness to activation by phosphorylation.

scholarly journals Differential Expression of the CO2 Fixation Operons of Rhodobacter sphaeroides by the Prr/Reg Two-Component System during Chemoautotrophic Growth

2002 ◽  
Vol 184 (23) ◽  
pp. 6654-6664 ◽  
Author(s):  
Janet L. Gibson ◽  
James M. Dubbs ◽  
F. Robert Tabita
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Cytochrome Oxidase ◽  
Rhodobacter Sphaeroides ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Signal Transduction Pathway ◽  
Pentose Phosphate ◽  
Bisphosphate Carboxylase

ABSTRACT In Rhodobacter sphaeroides, the two cbb operons encoding duplicated Calvin-Benson Bassham (CBB) CO2 fixation reductive pentose phosphate cycle structural genes are differentially controlled. In attempts to define the molecular basis for the differential regulation, the effects of mutations in genes encoding a subunit of Cbb3 cytochrome oxidase, ccoP, and a global response regulator, prrA (regA), were characterized with respect to CO2 fixation (cbb) gene expression by using translational lac fusions to the R. sphaeroides cbb I and cbbII promoters. Inactivation of the ccoP gene resulted in derepression of both promoters during chemoheterotophic growth, where cbb expression is normally repressed; expression was also enhanced over normal levels during phototrophic growth. The prrA mutation effected reduced expression of cbbI and cbbII promoters during chemoheterotrophic growth, whereas intermediate levels of expression were observed in a double ccoP prrA mutant. PrrA and ccoP1 prrA strains cannot grow phototrophically, so it is impossible to examine cbb expression in these backgrounds under this growth mode. In this study, however, we found that PrrA mutants of R. sphaeroides were capable of chemoautotrophic growth, allowing, for the first time, an opportunity to directly examine the requirement of PrrA for cbb gene expression in vivo under growth conditions where the CBB cycle and CO2 fixation are required. Expression from the cbbII promoter was severely reduced in the PrrA mutants during chemoautotrophic growth, whereas cbbI expression was either unaffected or enhanced. Mutations in ccoQ had no effect on expression from either promoter. These observations suggest that the Prr signal transduction pathway is not always directly linked to Cbb3 cytochrome oxidase activity, at least with respect to cbb gene expression. In addition, lac fusions containing various lengths of the cbbI promoter demonstrated distinct sequences involved in positive regulation during photoautotrophic versus chemoautotrophic growth, suggesting that different regulatory proteins may be involved. In Rhodobacter capsulatus, ribulose 1,5-bisphosphate carboxylase-oxygenase (RubisCO) expression was not affected by cco mutations during photoheterotrophic growth, suggesting that differences exist in signal transduction pathways regulating cbb genes in the related organisms.

scholarly journals The Escherichia coli K-12 NarL and NarP Proteins Insulate the nrf Promoter from the Effects of Integration Host Factor

2006 ◽  
Vol 188 (21) ◽  
pp. 7449-7456 ◽  
Author(s):  
Douglas F. Browning ◽  
David J. Lee ◽  
Alan J. Wolfe ◽  
Jeffrey A. Cole ◽  
Stephen J. W. Busby
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Regulatory Region ◽  
Enteric Bacteria ◽  
Integration Host Factor ◽  
Host Factor ◽  
Receptor Protein ◽  
E Coli ◽  
Serovar Typhimurium ◽  
K 12

ABSTRACT The Escherichia coli K-12 nrf operon promoter can be activated fully by the FNR protein (regulator of fumarate and nitrate reduction) binding to a site centered at position −41.5. FNR-dependent transcription is suppressed by integration host factor (IHF) binding at position −54, and this suppression is counteracted by binding of the NarL or NarP response regulator at position −74.5. The E. coli acs gene is transcribed from a divergent promoter upstream from the nrf operon promoter. Transcription from the major acsP2 promoter is dependent on the cyclic AMP receptor protein and is modulated by IHF and Fis binding at multiple sites. We show that IHF binding to one of these sites, located at position −127 with respect to the nrf promoter, has a positive effect on nrf promoter activity. This activation is dependent on the face of the DNA helix, independent of IHF binding at other locations, and found only when NarL/NarP are not bound at position −74.5. Binding of NarL/NarP appears to insulate the nrf promoter from the effects of IHF. The acs-nrf regulatory region is conserved in other pathogenic E. coli strains and related enteric bacteria but differs in Salmonella enterica serovar Typhimurium.

scholarly journals Multiple Factors Independently RegulatehilA and Invasion Gene Expression in Salmonella enterica Serovar Typhimurium

2000 ◽  
Vol 182 (7) ◽  
pp. 1872-1882 ◽  
Author(s):  
Robin L. Lucas ◽  
C. Phoebe Lostroh ◽  
Concetta C. DiRusso ◽  
Michael P. Spector ◽  
Barry L. Wanner ◽  
...  
Keyword(s):  
Gene Expression ◽  
Salmonella Enterica ◽  
Inorganic Phosphate ◽  
Response Regulator ◽  
Regulatory System ◽  
Negative Control ◽  
Host Cells ◽  
Uptake System ◽  
Intracellular Signals ◽  
Serovar Typhimurium

HilA activates the expression of Salmonella entericaserovar Typhimurium invasion genes. To learn more about regulation ofhilA, we isolated Tn5 mutants exhibiting reduced hilA and/or invasion gene expression. In addition to expected mutations, we identified Tn5 insertions inpstS, fadD, flhD, flhC, and fliA. Analysis of the pstS mutant indicates that hilA and invasion genes are repressed by the response regulator PhoB in the absence of the Pst high-affinity inorganic phosphate uptake system. This system is required for negative control of the PhoR-PhoB two-component regulatory system, suggesting thathilA expression may be repressed by PhoR-PhoB under low extracellular inorganic phosphate conditions. FadD is required for uptake and degradation of long-chain fatty acids, and our analysis of the fadD mutant indicates that hilA is regulated by a FadD-dependent, FadR-independent mechanism. Thus, fatty acid derivatives may act as intracellular signals to regulatehilA expression. flhDC and fliAencode transcription factors required for flagellum production, motility, and chemotaxis. Complementation studies with flhCand fliA mutants indicate that FliZ, which is encoded in an operon with fliA, activates expression of hilA, linking regulation of hilA with motility. Finally, epistasis tests showed that PhoB, FadD, FliZ, SirA, and EnvZ act independently to regulate hilA expression and invasion. In summary, our screen has identified several distinct pathways that can modulate S. enterica serovar Typhimurium's ability to express hilA and invade host cells. Integration of signals from these different pathways may help restrict invasion gene expression during infection.

scholarly journals Purification of the integration host factor homolog of Rhodobacter capsulatus: cloning and sequencing of the hip gene, which encodes the beta subunit.

1993 ◽  
Vol 175 (20) ◽  
pp. 6499-6504 ◽  
Author(s):  
B Toussaint ◽  
I Delic-Attree ◽  
R De Sury D'Aspremont ◽  
L David ◽  
M Vinçon ◽  
...  
Keyword(s):  
Rhodobacter Capsulatus ◽  
Integration Host Factor ◽  
Host Factor ◽  
Beta Subunit ◽  
Cloning And Sequencing

scholarly journals Integration Host Factor Positively Regulates Virulence Gene Expression in Vibrio cholerae

2008 ◽  
Vol 190 (13) ◽  
pp. 4736-4748 ◽  
Author(s):  
Emily Stonehouse ◽  
Gabriela Kovacikova ◽  
Ronald K. Taylor ◽  
Karen Skorupski
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Gene ◽  
Toxin Production ◽  
Dnase I ◽  
Integration Host Factor ◽  
Host Factor ◽  
Mobility Shift ◽  
Virulence Gene Expression ◽  
Dnase I Footprinting

ABSTRACT Virulence gene expression in Vibrio cholerae is dependent upon a complex transcriptional cascade that is influenced by both specific and global regulators in response to environmental stimuli. Here, we report that the global regulator integration host factor (IHF) positively affects virulence gene expression in V. cholerae. Inactivation of ihfA and ihfB, the genes encoding the IHF subunits, decreased the expression levels of the two main virulence factors tcpA and ctx and prevented toxin-coregulated pilus and cholera toxin production. IHF was found to directly bind to and bend the tcpA promoter region at an IHF consensus site centered at position −162 by using gel mobility shift assays and DNase I footprinting experiments. Deletion or mutation of the tcpA IHF consensus site resulted in the loss of IHF binding and additionally disrupted the binding of the repressor H-NS. DNase I footprinting revealed that H-NS protection overlaps with both the IHF and the ToxT binding sites at the tcpA promoter. In addition, disruption of ihfA in an hns or toxT mutant background had no effect on tcpA expression. These results suggest that IHF may function at the tcpA promoter to alleviate H-NS repression.

Sign in / Sign up

Export Citation Format

Share Document