scholarly journals The AppA and PpsR Proteins from Rhodobacter sphaeroides Can Establish a Redox-Dependent Signal Chain but Fail To Transmit Blue-Light Signals in Other Bacteria

2007 ◽  
Vol 189 (6) ◽  
pp. 2274-2282 ◽  
Author(s):  
Andreas Jäger ◽  
Stephan Braatsch ◽  
Kerstin Haberzettl ◽  
Sebastian Metz ◽  
Lisa Osterloh ◽  
...  
Keyword(s):  
Gene Expression ◽  
Blue Light ◽  
Rhodobacter Sphaeroides ◽  
Rhodobacter Capsulatus ◽  
Paracoccus Denitrificans ◽  
Response Regulator ◽  
Bacterial Species ◽  
Protein Protein Interaction ◽  
Dependent Signal ◽  
Light Signals

ABSTRACT The AppA protein of Rhodobacter sphaeroides has the unique ability to sense and transmit redox and light signals. In response to decreasing oxygen tension, AppA antagonizes the transcriptional regulator PpsR, which represses the expression of photosynthesis genes, including the puc operon. This mechanism, which is based on direct protein-protein interaction, is prevented by blue-light absorption of the BLUF domain located in the N-terminal part of AppA. In order to test whether AppA and PpsR are sufficient to transmit redox and light signals, we expressed these proteins in three different bacterial species and monitored oxygen- and blue-light-dependent puc expression either directly or by using a luciferase-based reporter construct. The AppA/PpsR system could mediate redox-dependent gene expression in the alphaproteobacteria Rhodobacter capsulatus and Paracoccus denitrificans but not in the gammaproteobacterium Escherichia coli. Analysis of a prrA mutant strain of R. sphaeroides strongly suggests that light-dependent gene expression requires a balanced interplay of the AppA/PpsR system with the PrrA response regulator. Therefore, the AppA/PpsR system was unable to establish light signaling in other bacteria. Based on our data, we present a model for the interdependence of AppA/PpsR signaling and the PrrA transcriptional activator.

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 ChiS is a noncanonical DNA-binding hybrid sensor kinase that directly regulates the chitin utilization program in Vibrio cholerae

2020 ◽  
Author(s):  
Catherine A. Klancher ◽  
Shouji Yamamoto ◽  
Triana N. Dalia ◽  
Ankur B. Dalia
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Dna Binding ◽  
Vibrio Cholerae ◽  
Response Regulator ◽  
Bacterial Species ◽  
Dependent Manner ◽  
Major Mechanism ◽  
Dependent Signal ◽  
Sense And Respond

AbstractTwo-component signal transduction systems (TCSs) represent a major mechanism that bacteria use to sense and respond to their environment. Prototypical TCSs are composed of a membrane-embedded histidine kinase (HK), which senses an environmental stimulus and subsequently phosphorylates a cognate partner protein called a response regulator (RR) that regulates gene expression in a phosphorylation-dependent manner. Vibrio cholerae uses the hybrid HK ChiS to activate the expression of the chitin utilization program, which is critical for the survival of this facultative pathogen in its aquatic reservoir. A cognate RR for ChiS has not been identified and the mechanism of ChiS-dependent signal transduction remains unclear. Here, we show that ChiS is a noncanonical membrane-embedded one-component system that can both sense chitin and directly regulate gene expression via a cryptic DNA binding domain. Unlike prototypical TCSs, we find that ChiS DNA binding is diminished, rather than stimulated, by phosphorylation. Finally, we provide evidence that ChiS likely activates gene expression by directly recruiting RNA polymerase. Together, this work addresses the mechanism of action for a major transcription factor in V. cholerae and highlights the versatility of signal transduction systems in bacterial species.Significance StatementFrom bacteria to humans, the ability to properly respond to environmental cues is critical for survival. The cholera pathogen Vibrio cholerae uses one protein, ChiS, to sense chitin in its environmental reservoir to regulate the expression of genes that are critical for the survival and evolution of this pathogen in this niche. Here, we study how the chitin sensor ChiS works, and discover that it regulates gene expression in an unexpected and unorthodox manner. Thus, this study uncovers how the major regulator ChiS works in this important human pathogen and highlights the versatile mechanisms that living systems use to respond to their environment.

scholarly journals Redox and light regulation of gene expression in photosynthetic prokaryotes

2003 ◽  
Vol 358 (1429) ◽  
pp. 147-154 ◽  
Author(s):  
Carl Bauer ◽  
Sylvie Elsen ◽  
Lee R. Swem ◽  
Danielle L. Swem ◽  
Shinji Masuda
Keyword(s):  
Gene Expression ◽  
Blue Light ◽  
Carbon Fixation ◽  
Rhodobacter Capsulatus ◽  
Bacterial Species ◽  
Regulation Of Gene Expression ◽  
Light Regulation ◽  
Disulphide Bond ◽  
Control Synthesis ◽  
Cellular Redox

All photosynthetic organisms control expression of photosynthesis genes in response to alterations in light intensity as well as to changes in cellular redox potential. Light regulation in plants involves a well–defined set of red– and blue–light absorbing photoreceptors called phytochrome and cryptochrome. Less understood are the factors that control synthesis of the plant photosystem in response to changes in cellular redox. Among a diverse set of photosynthetic bacteria the best understood regulatory systems are those synthesized by the photosynthetic bacterium Rhodobacter capsulatus . This species uses the global two–component signal transduction cascade, RegB and RegA, to anaerobically de–repress anaerobic gene expression. Under reducing conditions, the phosphate on RegB is transferred to RegA, which then activates genes involved in photosynthesis, nitrogen fixation, carbon fixation, respiration and electron transport. In the presence of oxygen, there is a second regulator known as CrtJ, which is responsible for repressing photosynthesis gene expression. CrtJ responds to redox by forming an intramolecular disulphide bond under oxidizing, but not reducing, growth conditions. The presence of the disulphide bond stimulates DNA binding activity of the repressor. There is also a flavoprotein that functions as a blue–light absorbing anti–repressor of CrtJ in the related bacterial species Rhodobacter sphaeroides called AppA. AppA exhibits a novel long–lived photocycle that is initiated by blue–light absorption by the flavin. Once excited, AppA binds to CrtJ thereby inhibiting the repressor activity of CrtJ. Various mechanistic aspects of this photocycle will be discussed.

Control of dimethylsulfoxide reductase expression in Rhodobacter capsulatus: the role of carbon metabolites and the response regulators DorR and RegA

Microbiology ◽  
2002 ◽  
Vol 148 (2) ◽  
pp. 605-614 ◽  
Author(s):  
Ulrike Kappler ◽  
Wilhelmina M Huston ◽  
Alastair G McEwan
Keyword(s):  
Gene Expression ◽  
Carbon Source ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Reductase Activity ◽  
Negative Regulator ◽  
Wild Type ◽  
Dmso Reductase ◽  
Dimethylsulfoxide Reductase ◽  
Operon Expression

Regulation of the expression of dimethylsulfoxide (DMSO) reductase was investigated in the purple phototrophic bacterium Rhodobacter capsulatus. Under phototrophic, anaerobic conditions with malate as carbon source, DMSO caused an approximately 150-fold induction of DMSO reductase activity. The response regulator DorR was required for DMSO-dependent induction and also appeared to slightly repress DMSO reductase expression in the absence of substrate. Likewise, when pyruvate replaced malate as carbon source there was an induction of DMSO reductase activity in cells grown at low light intensity (16 W m−2) and again this induction was dependent on DorR. The level of DMSO reductase activity in aerobically grown cells was elevated when pyruvate replaced malate as carbon source. One possible explanation for this is that acetyl phosphate, produced from pyruvate, may activate expression of DMSO reductase by direct phosphorylation of DorR, leading to low levels of induction of dor gene expression in the absence of DMSO. A mutant lacking the global response regulator of photosynthesis gene expression, RegA, exhibited high levels of DMSO reductase in the absence of DMSO, when grown phototrophically with malate as carbon source. This suggests that phosphorylated RegA acts as a repressor of dor operon expression under these conditions. It has been proposed elsewhere that RegA-dependent expression is negatively regulated by the cytochrome cbb 3 oxidase. A cco mutant lacking cytochrome cbb 3 exhibited significantly higher levels of Φ[dorA::lacZ] activity in the presence of DMSO compared to wild-type cells and this is consistent with the above model. Pyruvate restored DMSO reductase expression in the regA mutant to the same pattern as found in wild-type cells. These data suggest that R. capsulatus contains a regulator of DMSO respiration that is distinct from DorR and RegA, is activated in the presence of pyruvate, and acts as a negative regulator of DMSO reductase expression.

scholarly journals RegB/RegA, a Highly Conserved Redox-Responding Global Two-Component Regulatory System

2004 ◽  
Vol 68 (2) ◽  
pp. 263-279 ◽  
Author(s):  
Sylvie Elsen ◽  
Lee R. Swem ◽  
Danielle L. Swem ◽  
Carl E. Bauer
Keyword(s):  
Carbon Fixation ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Bacterial Species ◽  
Anaerobic Respiration ◽  
Regulatory System ◽  
Redox Active ◽  
Membrane Bound ◽  
Cognate Response Regulator ◽  
Aerobic And Anaerobic

SUMMARY The Reg regulon from Rhodobacter capsulatus and Rhodobacter sphaeroides encodes proteins involved in numerous energy-generating and energy-utilizing processes such as photosynthesis, carbon fixation, nitrogen fixation, hydrogen utilization, aerobic and anaerobic respiration, denitrification, electron transport, and aerotaxis. The redox signal that is detected by the membrane-bound sensor kinase, RegB, appears to originate from the aerobic respiratory chain, given that mutations in cytochrome c oxidase result in constitutive RegB autophosphorylation. Regulation of RegB autophosphorylation also involves a redox-active cysteine that is present in the cytosolic region of RegB. Both phosphorylated and unphosphorylated forms of the cognate response regulator RegA are capable of activating or repressing a variety of genes in the regulon. Highly conserved homologues of RegB and RegA have been found in a wide number of photosynthetic and nonphotosynthetic bacteria, with evidence suggesting that RegB/RegA plays a fundamental role in the transcription of redox-regulated genes in many bacterial species.

scholarly journals Isolation and Characterization of Rhodobacter capsulatus Mutants Affected in Cytochromecbb3 Oxidase Activity

1998 ◽  
Vol 180 (4) ◽  
pp. 969-978 ◽  
Author(s):  
Hans-Georg Koch ◽  
Olivia Hwang ◽  
Fevzi Daldal
Keyword(s):  
Oxidase Activity ◽  
Rhodobacter Capsulatus ◽  
Paracoccus Denitrificans ◽  
Response Regulator ◽  
Pleiotropic Effect ◽  
Chromosomal Dna ◽  
Reading Frame ◽  
Isolation And Characterization ◽  
Wild Type Phenotype ◽  
Additional Group

ABSTRACT The facultative phototrophic bacterium Rhodobacter capsulatus contains only one form of cytochrome (cyt)c oxidase, which has recently been identified as acbb3 -type cyt c oxidase. This is unlike other related species, such as Rhodobacter sphaeroides and Paracoccus denitrificans, which contain an additional mitochondrial-likeaa 3-type cyt c oxidase. An extensive search for mutants affected in cyt c oxidase activity in R. capsulatus led to the isolation of at least five classes of mutants. Plasmids complementing them to a wild-type phenotype were obtained for all but one of these classes from a chromosomal DNA library. The first class of mutants contained mutations within the structural genes (ccoNOQP) of the cytcbb 3 oxidase. Sequence analysis of these mutants and of the plasmids complementing them revealed thatccoNOQP in R. capsulatus is not flanked by the oxygen response regulator fnr, which is located upstream of these genes in other species. Genetic and biochemical characterizations of mutants belonging to this group indicated that the subunits CcoN, CcoO, and CcoP are required for the presence of an active cytcbb 3 oxidase, and unlike inBradyrhizobium japonicum, no active CcoN-CcoO subcomplex was found in R. capsulatus. In addition, mutagenesis experiments indicated that the highly conserved open reading frame 277 located adjacent to ccoNOQP is required neither for cytcbb 3 oxidase activity or assembly nor for respiratory or photosynthetic energy transduction in R. capsulatus. The remaining cyt c oxidase-minus mutants mapped outside of ccoNOQP and formed four additional groups. In one of these groups, a fully assembled but inactive cytcbb 3 oxidase was found, while another group had only extremely small amounts of it. The next group was characterized by a pleiotropic effect on all membrane-bound c-type cytochromes, and the remaining mutants not complemented by the plasmids complementing the first four groups formed at least one additional group affecting the biogenesis of the cyt cbb 3oxidase of R. capsulatus.

scholarly journals Hierarchical Regulation of Photosynthesis Gene Expression by the Oxygen-Responsive PrrBA and AppA-PpsR Systems of Rhodobacter sphaeroides

2008 ◽  
Vol 190 (24) ◽  
pp. 8106-8114 ◽  
Author(s):  
Larissa Gomelsky ◽  
Oleg V. Moskvin ◽  
Rachel A. Stenzel ◽  
Denise F. Jones ◽  
Timothy J. Donohue ◽  
...  
Keyword(s):  
Gene Expression ◽  
Rhodobacter Sphaeroides ◽  
Response Regulator ◽  
Photosynthetic Apparatus ◽  
Regulatory System ◽  
Structural Proteins ◽  
Gene Encoding ◽  
Genes Encoding ◽  
Photosynthetic Complexes ◽  
Photosynthesis Gene

ABSTRACT In the facultatively phototrophic proteobacterium Rhodobacter sphaeroides, formation of the photosynthetic apparatus is oxygen dependent. When oxygen tension decreases, the response regulator PrrA of the global two-component PrrBA system is believed to directly activate transcription of the puf, puh, and puc operons, encoding structural proteins of the photosynthetic complexes, and to indirectly upregulate the photopigment biosynthesis genes bch and crt. Decreased oxygen also results in inactivation of the photosynthesis-specific repressor PpsR, bringing about derepression of the puc, bch, and crt operons. We uncovered a hierarchical relationship between these two regulatory systems, earlier thought to function independently. We also more accurately assessed the spectrum of gene targets of the PrrBA system. First, expression of the appA gene, encoding the PpsR antirepressor, is PrrA dependent, which establishes one level of hierarchical dominance of the PrrBA system over AppA-PpsR. Second, restoration of the appA transcript to the wild-type level is insufficient for rescuing phototrophic growth impairment of the prrA mutant, whereas inactivation of ppsR is sufficient. This suggests that in addition to controlling appA transcription, PrrA affects the activity of the AppA-PpsR system via an as yet unidentified mechanism(s). Third, PrrA directly activates several bch and crt genes, traditionally considered to be the PpsR targets. Therefore, in R. sphaeroides, the global PrrBA system regulates photosynthesis gene expression (i) by rigorous control over the photosynthesis-specific AppA-PpsR regulatory system and (ii) by extensive direct transcription activation of genes encoding structural proteins of photosynthetic complexes as well as genes encoding photopigment biosynthesis enzymes.

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.

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