A haem cofactor is required for redox and light signalling by the AppA protein of <i>Rhodobacter sphaeroides</i>

Han, Yuchen; Meyer, M Cobas; Keusgen, Michael; Klug, Gabriele

doi:10.1111/j.1365-2958.2007.05724.x

Cited by 53 publications

(93 citation statements)

References 65 publications

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“…2B). A similar oxygen-dependent increase was previously observed for the polycistronic puf and puc transcripts in Rhodobacter species (8,23). The primary puf transcript encodes proteins for the formation of the reaction center and light-harvesting I (LHI) complex, and the puc operon encodes proteins for the formation of the LHII complex.…”

Section: Resultssupporting

confidence: 50%

“…When oxygen tension decreases, the AppA antirepressor protein binds to PpsR and releases it from the DNA, allowing transcription (3,5,6). AppA can sense blue light through its N-terminal BLUF domain (5,7) and redox signals through a heme that is bound to the SCHIC domain (2,8). As long as oxygen is available, Rhodobacter performs aerobic respiration.…”

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confidence: 99%

“…As long as oxygen is available, Rhodobacter performs aerobic respiration. However, at intermediate oxygen tension blue light, even at low intensities, prevents AppA from binding to PpsR and photosynthesis genes are repressed (8,9), reducing the accumulation of the harmful singlet oxygen. The PrrB/PrrA two-component system senses the electron transport through the cbb3 oxidase and induces transcription of photosynthesis genes at very low oxygen tension or in the absence of oxygen (5,(10)(11)(12)(13).…”

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confidence: 99%

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Regulation of bacterial photosynthesis genes by the small noncoding RNA PcrZ

Mank

Berghoff

Hermanns

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The small RNA PcrZ (photosynthesis control RNA Z) of the facultative phototrophic bacterium Rhodobacter sphaeroides is induced upon a drop of oxygen tension with similar kinetics to those of genes for components of photosynthetic complexes. High expression of PcrZ depends on PrrA, the response regulator of the PrrB/ PrrA two-component system with a central role in redox regulation in R. sphaeroides. In addition the FnrL protein, an activator of some photosynthesis genes at low oxygen tension, is involved in redox-dependent expression of this small (s)RNA. Overexpression of full-length PcrZ in R. sphaeroides affects expression of a small subset of genes, most of them with a function in photosynthesis. Some mRNAs from the photosynthetic gene cluster were predicted to be putative PcrZ targets and results from an in vivo reporter system support these predictions. Our data reveal a negative effect of PcrZ on expression of its target mRNAs. Thus, PcrZ counteracts the redox-dependent induction of photosynthesis genes, which is mediated by protein regulators. Because PrrA directly activates photosynthesis genes and at the same time PcrZ, which negatively affects photosynthesis gene expression, this is one of the rare cases of an incoherent feed-forward loop including an sRNA. Our data identified PcrZ as a trans acting sRNA with a direct regulatory function in formation of photosynthetic complexes and provide a model for the control of photosynthesis gene expression by a regulatory network consisting of proteins and a small noncoding RNA.α-proteobacteria | protochlorophyllide reductase

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Section: Resultssupporting

confidence: 50%

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confidence: 99%

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Regulation of bacterial photosynthesis genes by the small noncoding RNA PcrZ

Mank

Berghoff

Hermanns

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…Also, no effect was seen with hemin ( Fig. S2C), which has been reported to bind to some proteins involved in redox-light sensing that have a B 12 -binding motif (28)(29)(30). By contrast, AdoB 12 enhanced DNA binding by CTt1 and, even more dramatically, by CTt2: a single, well defined, low-mobility retarded complex was now formed, with little or no free probe detected (Fig.…”

Section: Resultsmentioning

confidence: 94%

Light-dependent gene regulation by a coenzyme B ₁₂ -based photoreceptor

Ortiz-Guerrero

Polanco

Murillo

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

154

247

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Cobalamin (B 12 ) typically functions as an enzyme cofactor but can also regulate gene expression via RNA-based riboswitches. B 12 -directed gene regulatory mechanisms via protein factors have, however, remained elusive. Recently, we reported down-regulation of a light-inducible promoter in the bacterium Myxococcus xanthus by two paralogous transcriptional repressors, of which one, CarH, but not the other, CarA, absolutely requires B 12 for activity even though both have a canonical B 12 -binding motif. Unanswered were what underlies this striking difference, what is the specific cobalamin used, and how it acts. Here, we show that coenzyme B 12 (5′-deoxyadenosylcobalamin, AdoB 12 ), specifically dictates CarH function in the dark and on exposure to light. In the dark, AdoB 12 -binding to the autonomous domain containing the B 12 -binding motif foments repressor oligomerization, enhances operator binding, and blocks transcription. Light, at various wavelengths at which AdoB 12 absorbs, dismantles active repressor oligomers by photolysing the bound AdoB 12 and weakens repressor-operator binding to allow transcription. By contrast, AdoB 12 alters neither CarA oligomerization nor operator binding, thus accounting for its B 12 -independent activity. Our findings unveil a functional facet of AdoB 12 whereby it serves as the chromophore of a unique photoreceptor protein class acting in light-dependent gene regulation. The prevalence of similar proteins of unknown function in microbial genomes suggests that this distinct B 12 -based molecular mechanism for photoregulation may be widespread in bacteria.carotenogenesis | Thermus thermophilus | antirepressor | MerR | TtCarH

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“…Interestingly, AppA was found to contain noncovalently bound heme (70,71), and the recognition of redox signal by heme at low O 2 was proposed to strengthen its interaction with PpsR. Upon lowering O 2 tension, heme coordination by AppA (71) would be a prerequisite for COR induction.…”

Section: Discussionmentioning

confidence: 99%

Superoxide Generation by Chlorophyllide a Reductase of Rhodobacter sphaeroides

Kim

Lee

et al. 2008

Journal of Biological Chemistry

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Chlorophyllide a reductase of Rhodobacter sphaeroides, which were reconstituted with the purified subunits of BchX, BchY, and BchZ, reduced ring B of chlorophyllide a using NADH under anaerobic conditions. Interestingly, suppressor mutations rescuing the inability of R. sphaeroides Fe-SOD mutant to grow in succinate-based minimal medium were predominantly mapped to BchZ subunit of chlorophyllide a reductase. The enzyme is labile in the presence of O 2 . However, it generates superoxide at low O 2 . The enzymes reconstituted with BchX, BchY, and the mutein subunit of BchZ from suppressor mutants showed less activity not only for chlorophyllide a reduction but also for superoxide generation compared with the enzyme reconstituted with the wild-type subunits. BchX, which contains FMN, and BchY are iron-sulfur proteins, whereas BchZ is a hemoprotein containing b-type heme. Neither chlorophyllide a reduction nor superoxide generation was observed with the enzyme reconstituted with the wild-type subunits of BchX and BchY, and the apo-subunit of BchZ that had been refolded without heme, in which FMN of BchX was fully reduced. Thus, superoxide is generated not from FMN of BchX but from heme of BchZ. Consistently, the heme of BchZ muteins was half-reduced in its redox state compared with that of wild-type BchZ.Rhodobacter sphaeroides, a facultative photosynthetic bacterium, contains two SODs 3 ; CuZn-SOD is detected only under the conditions where photosynthetic complexes are formed (1), whereas Fe-SOD is constitutively expressed, although its activity of the aerobically grown cell nearly doubled as compared with that of the anaerobically grown cell. The role of CuZn-SOD in protecting the photoheterotrophic cells from periplasmic superoxide upon exposure to O 2 was proposed (1). A cambialistic SOD using manganese or iron is the only SOD found in Rhodobacter capsulatus and is essential for cell viability (2, 3). Oxidative stress defense in R. sphaeroides and R. capsulatus is also mediated by catalases as well as by glutathione-glutaredoxin and thioredoxin systems that act as thiol-disulfide redox buffer to reduce the protein thiols that were oxidized (4, 5). Mutations in glutathione-glutaredoxin and thioredoxin systems lowered the formation of the photosynthetic complex (4, 5).The formation of photosynthetic complexes of R. sphaeroides is redox-dependent. Lowering oxygen tension induces the formation of intracytoplasmic membrane housing the photosynthetic complexes of R. sphaeroides. Light captured by B800 -850 and B875 LH complexes is transferred to reaction center complex, where the redox reactions are initiated to convert light energy into ATP and reducing power. The oxygenregulated expression of apoproteins of LH and reaction center complexes, which are encoded by puc, puf, and puh operons, was elucidated (for reviews see Refs. 6 and 7).The expression of several enzymes for Bchl a synthesis is also subject to anaerobic induction (8 -10). Protoporphyrin IX, which is synthesized from 5-aminolevulinic acid, is a common in...

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A haem cofactor is required for redox and light signalling by the AppA protein of Rhodobacter sphaeroides

Cited by 53 publications

References 65 publications

Regulation of bacterial photosynthesis genes by the small noncoding RNA PcrZ

Regulation of bacterial photosynthesis genes by the small noncoding RNA PcrZ

Light-dependent gene regulation by a coenzyme B ₁₂ -based photoreceptor

Superoxide Generation by Chlorophyllide a Reductase of Rhodobacter sphaeroides

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A haem cofactor is required for redox and light signalling by the AppA protein of Rhodobacter sphaeroides

Cited by 53 publications

References 65 publications

Regulation of bacterial photosynthesis genes by the small noncoding RNA PcrZ

Regulation of bacterial photosynthesis genes by the small noncoding RNA PcrZ

Light-dependent gene regulation by a coenzyme B 12 -based photoreceptor

Superoxide Generation by Chlorophyllide a Reductase of Rhodobacter sphaeroides

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Light-dependent gene regulation by a coenzyme B ₁₂ -based photoreceptor