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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We identified eight bands by staining native gels for NADPH-nitroblue tetrazolium oxidoreductase activity after electrophoresis of n-dodecyl-beta-d-maltoside-treated membranes of Synechocystis sp. strain PCC 6803. Among them, bands A, C, D and E were attributed to the activity of NADPH dehydrogenase (NDH-1). Band A is a highly active supercomplex of NDH-1 (about 1,000 kDa) that was absent in the DeltandhD1/D2 mutant and was suppressed under low CO(2). Band C was induced under low CO(2) or in the DeltandhD1/D2 mutant and was converted to bands D and E. Bands A and C appear to be an NDH-1L dimer and NDH-1M, respectively, with subunits essential for the activity.
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PMID:Active NDH-1 complexes from the cyanobacterium Synechocystis sp. strain PCC 6803. 1698 Jul 3

The gene drgA of the cyanobacterium Synechocystis sp. PCC 6803 encoding soluble NAD(P)H:quinone-oxidoreductase is involved in NADPH oxidation and controls cell sensitivity to nitroaromatic inhibitors as well as resistance to the oxidative stress inducer menadione. The expression of drgA was analyzed by means of Northern blot hybridization and RT-PCR technique. Two transcripts, which gave a positive hybridization signal with a drgA probe were observed in photoautotrophycally grown cells. One of them (0.6 kb) corresponds in size to mRNA read from the drgA gene; another transcript (1.3 kb), to mRNA transcribed from two genes: drgA and slr1718 located upstream of drgA and having homology with genes of the family comB. The expression of genes drgA and slr1718 was repressed during cell incubation in the dark, but the addition of glucose led to a drastically enhanced expression both in the dark and after illumination of cells. Menadione or nitrophenolic herbicide dinoseb did not induce drgA or slr1718 expression. The results obtained suggest that the expression of these genes in the cytoplasm of cyanobacterium cells is regulated by the NADPH content.
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PMID:[Expression of drgA gene encoding NAD(P)H:quinone-oxidoreductase in cells of the cyanobacterium Synechocystis sp. PCC 6803]. 1702 55

The effect of pH on the initial-rate kinetic behaviour of BVR-A (biliverdin-IXalpha reductase) exhibits an alkaline optimum with NADPH as cofactor, but a neutral optimum with NADH as cofactor. This has been described as dual cofactor and dual pH dependent behaviour; however, no mechanism has been described to explain this phenomenon. We present evidence that the apparent peak of activity observed at neutral pH with phosphate buffer and NADH as cofactor is an anion-dependent activation, where inorganic phosphate apparently mimics the role played by the 2'-phosphate of NADPH in stabilizing the interaction between NADH and the enzyme. The enzymes from mouse, rat and human all exhibit this behaviour. This behaviour is not seen with BVR-A from Xenopus tropicalis or the ancient cyanobacterial enzyme from Synechocystis PCC 6803, which, in addition to being refractory to activation by inorganic phosphate, are also differentiated by an acid pH optimum with both nicotinamide nucleotides.
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PMID:Activation of biliverdin-IXalpha reductase by inorganic phosphate and related anions. 1740 39

A highly active NADPH dehydrogenase supercomplex, which is essential for cyclic electron transport around photosystem I (cyclic PSI) and respiration, was newly identified in cyanobacteria. Synechocystis sp. strain PCC 6803 cells were treated with exogenous glucose (Glc) or 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU); subsequently, active staining of NADPH-nitroblue tetrazolium oxidoreductase, western blot, and the initial rate of P700+ dark reduction were assessed in the cyanobacterium at several time points. The expression and enzyme activity levels of NADPH dehydrogenase supercomplex were gradually inhibited and closely associated with the decrease in the rate of cyclic PSI accompanying the addition of exogenous Glc to the cultures. In contrast, the activity levels were significantly stimulated but did not cause an increase in the rate of cyclic PSI as expected in the presence of DCMU. Since Glc results in the partial reduction of the plastoquinone (PQ) pool while DCMU results in the overoxidation of the PQ pool, the present results demonstrate that the expression and activity of NADPH dehydrogenase supercomplex are under the influence of the redox control of the PQ pool while the operation of cyclic PSI as mediated by this supercomplex requires an appropriate redox poise of the PQ pool.
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PMID:Redox of plastoquinone pool regulates the expression and activity of NADPH dehydrogenase supercomplex in Synechocystis sp. strain PCC 6803. 1800 Jul 4

The heterocyst is a specialized cell for nitrogen fixation in some filamentous cyanobacteria. Here we report that a rubrerythrin (RbrA) from Anabaena sp. PCC 7120 functions as a peroxidase in heterocysts and plays an important role in protection of nitrogenase. The electron donor for RbrA in H(2)O(2) reduction is NADPH and the electron transfer from NADPH to RbrA depends on ferredoxin:NADP(+) oxidoreductase. A rbrA mutant (r27) grew much more slowly than the wild type under diazotrophic conditions. Its nitrogenase activity measured in air was only 8% of that measured under anoxic conditions. Staining r27 filaments with 2',7'-dichlorodihydrofluorescein diacetate indicated that heterocysts had a higher H(2)O(2) concentration than the vegetative cells. The expression of rbrA was controlled by two promoters and the promoter for the smaller transcript was regulated by HetR. Spatial expression of rbrA was studied and the results showed that the transcription is localized predominantly in heterocysts. In a mutant lacking nifH and rbrA, the H(2)O(2) concentration in heterocysts was lower than that in the vegetative cells, suggesting that NifH is involved in H(2)O(2) generation. Our results demonstrate that RbrA is a critical enzyme for H(2)O(2) decomposition and provide evidence that nitrogenase autoprotection is important in heterocysts.
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PMID:RbrA, a cyanobacterial rubrerythrin, functions as a FNR-dependent peroxidase in heterocysts in protection of nitrogenase from damage by hydrogen peroxide in Anabaena sp. PCC 7120. 1800 48

Active NADPH dehydrogenase super- and medium-complexes were newly identified in cyanobacteria and are essential to cyclic photosystem I (PSI) activity and respiration and to CO(2) uptake, respectively. Synechocystis sp. strain PCC 6803 cells were treated with exogenous glucose (Glc) for different times. Active staining of NADPH-nitroblue tetrazolium oxidoreductase and western blot were conducted, and the initial rate of P700(+) dark reduction was measured. The expression and enzyme activity of the NADPH dehydrogenase super-complex were gradually inhibited and were found to be closely associated with the decrease in cyclic PSI activity, as reflected by the initial rate of P700(+) dark reduction. By contrast, those of the NADPH dehydrogenase medium-complex and the activity of CO(2) uptake reflected by the expression levels of NdhD3 and NdhF3 were not significantly affected by the addition of exogenous Glc to the cultures; however, the expression and enzyme activity of this medium-complex were found to be significantly influenced by the changes in CO(2) concentration. These results indicated that (1) the responses of the 2 cyanobacterial NADPH dehydrogenase complexes to exogenous Glc in terms of their expression and activity differed and that (2) these responses were closely associated with their respective physiological roles.
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PMID:Effect of exogenous glucose on the expression and activity of NADPH dehydrogenase complexes in the cyanobacterium Synechocystis sp. strain PCC 6803. 1852 9

Capillary electrophoresis mass spectrometry (CE/MS) was applied for the comprehensive survey of changes in the amounts of metabolites upon the shift from photoautotrophic to photomixotrophic conditions in Synechocystis sp. PCC 6803. When glucose was added to the photoautotrophically grown culture, the increase in the metabolites for the oxidative pentose phosphate (OPP) pathway and glycolysis, together with the decrease in those for the Calvin cycle, was observed. Concomitantly, the increase in respiratory activity and the decrease in photosynthetic activity took place in the wild-type cells. In the pmgA-disrupted mutant that shows growth inhibition under photomixotrophic conditions, lower enzymatic activities of the OPP pathway and higher photosynthetic activity were observed, irrespective of trophic conditions. These defects brought about metabolic disorders such as a decrease in ATP and NADPH contents, a failure in the activation of respiratory activity, and the aberrant accumulation of isocitrate under photomixotrophic but not under photoautotrophic conditions. A delicate balancing of the carbon flow between the Calvin cycle and the OPP pathway seems indispensable for growth specifically under photomixotrophic conditions and PmgA is likely to be involved in the regulation.
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PMID:Difference in metabolite levels between photoautotrophic and photomixotrophic cultures of Synechocystis sp. PCC 6803 examined by capillary electrophoresis electrospray ionization mass spectrometry. 1861 12

A new ketoreductase useful for asymmetric synthesis of chiral alcohols was identified in the cyanobacterium Synechococcus sp. strain PCC 7942. Mass spectrometry of trypsin-digested peptides identified the protein as 3-ketoacyl-[acyl-carrier-protein] reductase (KR) (EC 1.1.1.100). The gene, referred to as fabG, was cloned, functionally expressed in Escherichia coli, and subsequently purified to homogeneity. The enzyme displayed a temperature optimum at 44 degrees C and a broad pH optimum between pH 7 and pH 9. The NADPH-dependent KR was able to asymmetrically reduce a variety of prochiral ketones with good to excellent enantioselectivities (>99.8%). The KR showed particular high specific activity for asymmetric reduction of ethyl 4-chloroacetoacetate (38.29 +/- 2.15 U mg(-1)) and 2',3',4',5',6'-pentafluoroacetophenone (8.57 +/- 0.49 U mg(-1)) to the corresponding (S)-alcohols. In comparison with an established industrial enzyme like the alcohol dehydrogenase from Lactobacillus brevis, the KR showed seven-times-higher activity toward 2',3',4',5',6'-pentafluoroacetophenone, with a remarkably higher enantiomeric excess (>99.8% [S] versus 43.3% [S]).
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PMID:Identification, cloning, and characterization of a novel ketoreductase from the cyanobacterium Synechococcus sp. strain PCC 7942. 1879 Oct 6

Anabaena sp. PCC7120 contains a gene, mrpA (all1838), which forms part of a seven gene-cluster (all1843-all1837) with significant sequence similarity to bacterial operons that putatively code for a multicomponent cation/proton antiporter involved in alkaline pH adaptation and salt resistance. We previously showed that growth and photosynthesis were inhibited in a strain mutated in mrpA, denoted as PHB11, particularly at alkaline pH. Here, we show that respiration was also impaired in the mutant independently of the external pH. In addition, at high pH, less ATP and vegetative cell ferredoxin were present in PHB11, which also showed lower levels of ferredoxin-NADP(+) oxidoreductase (FNR). Ferredoxin and FNR are involved in the generation of reductant NADPH in cyanobacteria. These results suggest an energetic role of mrpA (and perhaps of the whole mrp-gene cluster) in Anabaena sp. PCC 7120 that is further supported by the significant similarity of putative Anabaena Mrp proteins to membrane subunits of complex I.
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PMID:mrpA (all1838), a gene involved in alkali and Na(+) sensitivity, may also have a role in energy metabolism in the cyanobacterium Anabaena sp. strain PCC 7120. 1941 Mar 33

Photosynthetic organisms experience changes in light quantity and light quality in their natural habitat. In response to changes in light quality, these organisms redistribute excitation energy and adjust photosystem stoichiometry to maximize the utilization of available light energy. However, the response of other cellular processes to changes in light quality is mostly unknown. Here, we report a systematic investigation into the adaptation of cellular processes in Synechocystis species PCC 6803 to light that preferentially excites either photosystem II or photosystem I. We find that preferential excitation of photosystem II and photosystem I induces massive reprogramming of the Synechocystis transcriptome. The rewiring of cellular processes begins as soon as Synechocystis senses the imbalance in the excitation of reaction centers. We find that Synechocystis utilizes the cyclic photosynthetic electron transport chain for ATP generation and a major part of the respiratory pathway to generate reducing equivalents and carbon skeletons during preferential excitation of photosystem I. In contrast, cytochrome c oxidase and photosystem I act as terminal components of the photosynthetic electron transport chain to produce sufficient ATP and limited amounts of NADPH and reduced ferredoxin during preferential excitation of photosystem II. To overcome the shortage of NADPH and reduced ferredoxin, Synechocystis preferentially activates transporters and acquisition pathways to assimilate ammonia, urea, and arginine over nitrate as a nitrogen source. This study provides a systematic analysis of cellular processes in cyanobacteria in response to preferential excitation and shows that the cyanobacterial cell undergoes significant adjustment of cellular processes, many of which were previously unknown.
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PMID:A systems-level analysis of the effects of light quality on the metabolism of a cyanobacterium. 1975 42


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