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1.
Rhodobacter capsulatus modulates its in vivo nitrogenase activity in the light in response to the addition of NH4+ in a variety of ways: with ADP-ribosylation of the Fe-protein of nitrogenase, with a switch-off response that is independent of ADP-ribosylation, and with a "magnitude response." In the light, these responses are differentially shown by cultures that differ in the degree of their nitrogen limitation. Here we examined the response of these culture types to the addition of NH4+ under dark, microoxic conditions and found that all three responses can be observed under these conditions. However, the magnitude response was much more sensitive to the ammonium concentration, and the ADP-ribosylation response correlated only poorly with activity changes, similar to results obtained in the light. In contrast to previous reports, Fe-protein was not ADP-ribosylated in response to the presence of oxygen. 相似文献
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In order to distinguish between the regulatory effects of oxygen tension and light intensity on cytochrome c oxidase protein and enzymatic activity cells of Rhodobacter capsulatus were shifted from phototrophic (anaerobic, light) growth to aerobic-light, aerobic-dark and to anaerobic-dark conditions, respectively. During shift-experiments the formation of oxidase protein and regulation of oxidase activity was followed by immunological and enzymatic means. The results support the idea, that the formation of oxidase protein is regulated by oxygen tension and light intensity changes, whereas the regulation of oxidase activity seems only to be correlated to the oxygen tension. A DNA sequence involved in the oxygen-dependent regulation of cytochrome oxidase could be identified in the regulation-deficient oxidase mutant H41 of R. capsulatus. Immunological investigations of cytochrome c
2 from mutant H41 demonstrated at the same time the participation of the c
2-polypeptide in the regulation of cytochrome c oxidase.Abbreviations Bchl
bacteriochlorophyll
- CIE
crossed immuno-electrophoresis
- DMSO
dimethyl sulfoxide 相似文献
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Nitrogen fixation as well as structural and functional properties of the photosynthetic apparatus were studied with phototrophically grown chemostat cultures of Rhodobacter capsulatus strain 37b4. Illumination was varied between 3,000 and 30,000 lx at a constant dilution rate of D=0.075 h-1. Steady state parameters of growth revealed two forms of limitation, i.e. energy limitation in the range of 3,000 to about 10,000 lx and nitrogen limitation at higher illuminations. Over the entire range of illumination, the specific bacteriochlorophyll content and the amount of total bacteriochlorophyll per photochemical reaction center remained essentially constant. Photophosphorylation activity remained constant up to 20,000 lx but was slightly increased at 30,000 lx. Hydrogen evolution and acetylene reduction activities of cellular nitrogenase were assayed under saturating light conditions with samples taken from cultures growing under steady state conditions. In spite of the apparent constancy of the composition and activity of the photosynthetic apparatus under energy limitation, maximal specific acetylene reduction and hydrogen evolution activities increased by factors of 3 and 8, respectively, when illumination of the culture was raised from 3,000 to about 15,000 lx. Above 15,000 lx, both activities of nitrogenase approached constancy.We, therefore, conclude that neither under energy limitation nor under nitrogen limitation the function of nitrogenase depended on the photosynthetic activities. Moreover, it is suggested that light did not influence nitrogenase activity under conditions of nitrogen limitation, while under conditions of energy limitation light seemed to influence nitrogenase activities indirectly via glutamate consumption of the cells. 相似文献
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Non-reciprocal regulation of Rhodobacter capsulatus and Rhodobacter sphaeroides recA genes expression 总被引:1,自引:0,他引:1
Antonio R.Fernandez de Henestrosa Eusebi Rivera Jordi Barbé 《FEMS microbiology letters》1995,129(2-3):175-181
Abstract The Rhodobacter capsulatus recA gene has been isolated and sequenced. Its deduced amino acid sequence showed the closest identity with the Rhodobacter sphaeroides RecA protein (91% identity). However, the promoter regions of both R. capsulatus and R. sphaeroides recA genes are only 64% similar. An Escherichia coli -like LexA binding site was not present in the upstream region of the R. capsulatus recA gene. Nevertheless, the R. capsulatus recA gene is inducible by DNA damage in both hetero- and phototrophically growing conditions. The R. capsulatus recA gene is poorly induced when inserted into the chromosome of R. sphaeroides , indicating that the recA gene of both bacteria possess different control sequences despite their phylogenetically close relationship. 相似文献
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David J. Richardson Louise C. Bell James W.B. Moir Stuart J. Ferguson 《FEMS microbiology letters》1994,120(3):323-328
Abstract Repeated subculturing of Rhodobacter capsulatus strain BK5 under phototrophic conditions on a medium containing butyrate and nitrate led to the appearance of cultures that, unlike the original, produced gas. Isolation of a pure culture of the gas-forming organism revealed that it was a derivative of R. capsulatus BK5 that by virtue of expressing a nitrite reductase can catalyse the complete sequence of the denitrification reactions. The nitrite reductase is of the type that contains copper rather than haem. 相似文献
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Yosepha Shahak Christof Klughammer Ulrich Schreiber Etana Padan Inge Herrman Günter Hauska 《Photosynthesis research》1994,39(2):175-181
The reduction by sulfide of exogenous ubiquinone is compared to the reduction of cytochromes in chromatophores of Rhodobacter capsulatus. From titrations with sulfide values for Vmax of 300 and 10 moles reduced/mg bacteriochlorophyll a·h, and for Km of 5 and 3 M were estimated, for decyl-ubiquinone-and cytochrome c-reduction, respectively. Both reactions are sensitive to KCN, as has been found for sulfide-quinone reductase (SQR) in Oscillatoria limnetica, which is a flavoprotein. Effects of inhibitors interfering with quinone binding sites suggest that at least part of the electron transport from sulfide in R. capsulatus employs the cytochrome bc
1-complex via the ubiquinone pool.Abbreviations BChl a
bacteriochlorophyll a
- DAD
diaminodurene
- decyl-UQ
decyl-ubiquinone
- LED
light emitting diode
- NQNO
2-n-nonyl-4-hydroxyquinoline-N-oxide
- PQ-1
plastoquinone 1
- SQR
sulfide-quinone reductase (E.C. 1.8.5.'.)
- UQ
ubiquinone 10
- Qc
the quinone reduction site on the cytochrome b
6
f/bc
1, complex (also termed Qi or Qr or Qn)
- Qs
the quinone reduction site on SQR
- Qz
quinol oxidation site on the b
6
f/bc
1, complex (also termed Qo or Qp) 相似文献
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Enhanced nitrogenase activity in strains of Rhodobacter capsulatus that overexpress the rnf genes 下载免费PDF全文
In the photosynthetic bacterium Rhodobacter capsulatus, a putative membrane-bound complex encoded by the rnfABCDGEH operon is thought to be dedicated to electron transport to nitrogenase. In this study, the whole rnf operon was cloned under the control of the nifH promoter in plasmid pNR117 and expressed in several rnf mutants. Complementation analysis demonstrated that transconjugants which integrated plasmid pNR117 directed effective biosynthesis of a functionally competent complex in R. capsulatus. Moreover, it was found that strains carrying pNR117 displayed nitrogenase activities 50 to 100% higher than the wild-type level. The results of radioactive labeling experiments indicated that the intracellular content of nitrogenase polypeptides was marginally altered in strains containing pNR117, whereas the levels of the RnfB and RnfC proteins present in the membrane were four- and twofold, respectively, higher than the wild-type level. Hence, the enhancement of in vivo nitrogenase activity was correlated with a commensurate overproduction of the Rnf polypeptides. In vitro nitrogenase assays performed in the presence of an artificial electron donor indicated that the catalytic activity of the enzyme was not increased in strains overproducing the Rnf polypeptides. It is proposed that the supply of reductants through the Rnf complex might be rate limiting for nitrogenase activity in vivo. Immunoprecipitation experiments performed on solubilized membrane proteins revealed that RnfB and RnfC are associated with each other and with additional polypeptides which may be components of the membrane-bound complex. 相似文献
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《Gene》1996,170(1):149-150
The last step in heme synthesis is the insertion of iron into the ring of protoporphyrin IX. The enzyme which catalyzes this reaction, ferrochelatase (FC), is encoded by the hemH gene. A clone containing this gene from Rhodobacter capsulatus, a purple non-sulfur photosynthetic bacterium, has been sequenced. A single open reading frame was found which could encode a protein of 351 amino acids. This putative protein is very similar to other FC and contains the FC signature sequence 相似文献
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Abstract In Chlamydomonas reinhardtii there are three glutamate dehydrogenase isozymes which can use both NADH and NADPH as cofactors and respond differently to different nitrogen sources and several stress conditions. From data of induction of isozymes in different metabolic situations, we propose a possible physiological role for each of them in algal carbon and nitrogen metabolism. 相似文献
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Portions of the Rhodobacter capsulatus hemA gene have been cloned from a hemA::Tn5 insertion strain into the lambda bacteriophage derivative EMBL3. A cosmid containing the wild-type R. capsulatus hemA gene was isolated by complementation of the hemA::Tn5 mutant. The cosmid contains a 1.4-kilobase EcoRI fragment that spans the hemA::Tn5 insertion site. The entire hemA gene is contained in this fragment and the adjacent 0.6-kilobase EcoRI fragment. 相似文献
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By using an oligonucleotide mixture corresponding to a region highly conserved among alternative sigma factors we identified a new σ factor gene (rpoH) from Rhodobacter capsulatus. This gene encodes a protein of 34?kDa with strong similarity to the RpoH (σ 32) factors from other bacterial species. It was not possible to inactivate the R.?capsulatusrpoH gene by introducing a resistance cassette, implying that it is essential for growth. The 5′ ends of the mRNAs were mapped to two sequences with similarity to an rpoH- and an rpoD-dependent promoter, respectively. The amounts of both these mRNAs increased after heat shock, but were unaffected by a decrease in oxygen tension. Western analysis using a σ factor-specific antibody revealed the accumulation of a protein of about 34?kDa after heat shock, and an increase in the amounts of a protein with the same size after reduction of oxygen tension in R.?capsulatus cultures. 相似文献
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Physiological Control and Regulation of the Rhodobacter capsulatus cbb Operons 总被引:1,自引:0,他引:1 下载免费PDF全文
George C. Paoli Padungsri Vichivanives F. Robert Tabita 《Journal of bacteriology》1998,180(16):4258-4269
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Regulation of Photosystem Synthesis in Rhodobacter capsulatus 总被引:1,自引:0,他引:1
Bauer C 《Photosynthesis research》2004,80(1-3):353-360