Redox property and regulation of PpsR, a transcriptional repressor of photosystem gene expression in Rhodobacter sphaeroides

Cho, Seung-Hyun; Youn, Sang-Hee; Lee, Seung-Rock; Yim, Hyung-Soon; Kang, Sa-Ouk

doi:10.1099/mic.0.26777-0

Cited by 17 publications

(15 citation statements)

References 31 publications

(43 reference statements)

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“…Both in vitro (4,15,32) and bioinformatic approaches (29) enabled detailed studies of PpsR repressor activity under different growth conditions to be performed. Also, gel mobility shift analyses allowed studies of in vitro binding of PpsR to the puc promoter of R. sphaeroides to be performed under oxidizing and reducing conditions in the absence of the antirepressor AppA and other cellular molecules (4,30). In addition, the use of transcriptional fusions and a heterologous expression system demonstrated that PpsR directly represses the transcription of puc and bchF in R. sphaeroides (15).…”

Section: Discussionmentioning

confidence: 99%

“…It has been proposed that two palindromes (TGTcN 10 gACA) corresponding to the refined PpsR consensus binding sequence must be present for functional repression (33). Two mechanisms have been described as mechanisms that are responsible for the control of binding by PpsR: (i) oxidation-reduction of two conserved cysteine residues (Cys251 and Cys424) (13,31), which requires further investigation (4), and (ii) the interaction between PpsR and the AppA antirepressor protein, which has the unique property of being able to integrate oxygen and light signals (3). Since AppA is apparently present under all growth conditions at various levels, its effect on PpsR and the ultimate role of PpsR in PS gene expression is very complex.…”

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confidence: 99%

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The Use of Chromatin Immunoprecipitation to Define PpsR Binding Activity in Rhodobacter sphaeroides 2.4.1

et al. 2008

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The expression of genes involved in photosystem development in Rhodobacter sphaeroides is dependent upon three major regulatory networks: FnrL, the PrrBA (RegBA) two-component system, and the transcriptional repressor/antirepressor PpsR/AppA. Of the three regulators, PpsR appears to have the narrowest range of physiological effects, which are limited to effects on the structural and pigment biosynthetic activities involved in photosynthetic membrane function. Although a PrrA ؊ mutant is unable to grow under photosynthetic conditions, when a ppsR mutation was present, photosynthetic growth occurred. An examination of the double mutant under anaerobic-dark-dimethyl sulfoxide conditions using microarray analysis revealed the existence of an "extended" PpsR regulon and new physiological roles. To characterize the PpsR regulon and to better ascertain the significance of degeneracy within the PpsR binding sequence in vivo, we adapted the chromatin immunoprecipitation technique to R. sphaeroides. We demonstrated that in vivo there was direct and significant binding by PpsR to newly identified genes involved in microaerobic respiration and periplasmic stress resistance, as well as to photosynthesis genes. The new members of the PpsR regulon are located outside the photosynthesis gene cluster and have degenerate PpsR binding sequences. The possible interaction under physiologic conditions with degenerate binding sequences in the presence of other biologically relevant molecules is discussed with respect to its importance in physiological processes and to the existence of complex phenotypes associated with regulatory mutants. This study further defines the DNA structure necessary for PpsR binding in situ.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

The Use of Chromatin Immunoprecipitation to Define PpsR Binding Activity in Rhodobacter sphaeroides 2.4.1

et al. 2008

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“…Masuda et al (23) determined the midpoint potential (E m ) for the disulfide bond formation of CrtJ to be Ϫ180 mV (at pH 7.0) by redox titration with GSH/ GSSG and also demonstrated that the intramolecular disulfide bond occurs only in aerobic and not in anaerobic cells. In contrast, however, Cho et al (4) reported that in R. sphaeroides cells, both critical cysteines of PpsR constantly exist in the reduced thiol form irrespective of the oxygen and light conditions. Strikingly, the E m value of PpsR, determined by Kim et al (18) is much more negative than CrtJ with a value of Ϫ320 mV.…”

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confidence: 92%

A Glutathione Redox Effect on Photosynthetic Membrane Expression in Rhodospirillum rubrum

Carius¹,

Henkel²,

Grammel³

2011

J Bacteriol

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The formation of intracytoplasmic photosynthetic membranes by facultative anoxygenic photosynthetic bacteria has become a prime example for exploring redox control of gene expression in response to oxygen and light. Although a number of redox-responsive sensor proteins and transcription factors have been characterized in several species during the last several years in some detail, the overall understanding of the metabolic events that determine the cellular redox environment and initiate redox signaling is still poor. In the present study we demonstrate that in Rhodospirillum rubrum, the amount of photosynthetic membranes can be drastically elevated by external supplementation of the growth medium with the low-molecular-weight thiol glutathione. Neither the widely used reductant dithiothreitol nor oxidized glutathione caused the same response, suggesting that the effect was specific for reduced glutathione. By determination of the extracellular and intracellular glutathione levels, we correlate the GSH/GSSG redox potential to the expression level of photosynthetic membranes. Possible regulatory interactions with periplasmic, membrane, and cytosolic proteins are discussed. Furthermore, we found that R. rubrum cultures excrete substantial amounts of glutathione to the environment.It is well established that the thiol-containing tripeptide glutathione (␥-Glu-Cys-Gly [GSH]) is the most abundant redox buffer in all eukaryotic and in many prokaryotic cells and that GSH is critically important for the defense of oxidative stress which inevitably is associated with respiratory life. Various functions and mechanisms where GSH is involved in bacteria are summarized in a recent review (22). During many of these reactions, two molecules of GSH are oxidized to glutathione disulfide (GSSG), and the reduced form has to be recycled by the enzyme glutathione reductase at the expense of NADPH. A signaling role for GSH, however, is thus far not readily established. In bacteria, the reversible formation of intramolecular or intermolecular disulfide bonds of cysteines of regulatory proteins appears to be a common motif in molecular redox switches. For example, the ArcB sensor of Escherichia coli or the PpsR-and RegB-type regulators in facultative anoxygenic photosynthetic bacteria undergo reversible thiol/disulfide switches when exposed to different redox conditions in vitro (21, 32). The latter group of bacteria (Rhodospirillaceae) has contributed significantly to the recent paradigms of redox signaling and control of gene expression due to its facultative phototrophic lifestyle, which allows these bacteria to adapt their energy metabolism to the redox conditions of the environment. Under conditions of limiting oxygen, the Rhodospirillaceae induce the biosynthesis of an extensive system of pigmented intracytoplasmic membranes (ICM) which harbor photosynthetic reaction centers and light-harvesting complexes. The major environmental factor that determines the amount of ICM is the availability of oxygen, since aerobic growth conditio...

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“…Oxidized CrtJ has lower affinity for DNA, and repression is released (37,44). Redox-dependent binding of PpsR has been demonstrated in vitro (7,37). However, the redox state of PpsR appears not to change in the cell with varying redox and light conditions (7; unpublished data).…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2007

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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-lightdependent 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.

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Redox property and regulation of PpsR, a transcriptional repressor of photosystem gene expression in Rhodobacter sphaeroides

Cited by 17 publications

References 31 publications

The Use of Chromatin Immunoprecipitation to Define PpsR Binding Activity in Rhodobacter sphaeroides 2.4.1

The Use of Chromatin Immunoprecipitation to Define PpsR Binding Activity in Rhodobacter sphaeroides 2.4.1

A Glutathione Redox Effect on Photosynthetic Membrane Expression in Rhodospirillum rubrum

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

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