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Query: UMLS:C1832526 (PCC)
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A sulfur-regulated gene (cysA) that encodes the membrane-associated ATP-binding protein of the sulfate transport system of the cyanobacterium Synechococcus sp. strain PCC 7942 was recently isolated and sequenced. Adjacent to cysA and transcribed in the opposite direction is a gene encoding the sulfate-binding protein (sbpA). Two other genes, cysT and cysW, encode proteins that may form a channel for the transport of sulfate across the cytoplasmic membrane. A fourth gene, cysR, located between cysT, and cysW, encodes a polypeptide that has some homology to a family of prokaryotic regulatory proteins. Mutant strains in which cysA, cysT, or cysW was interrupted by a drug resistance marker were not viable when grown with sulfate as the sole sulfur source and exhibited essentially no sulfate uptake. In contrast, sbpA and cysR mutants grew on sulfate, although they did not exhibit the 20-fold increase in the Vmax (concentration of sulfate at half-maximal transport rate) for sulfate transport characteristic of wild-type cells grown under sulfur-limiting conditions. Three of the sulfur-regulated genes in Synechococcus sp. strain PCC 7942 are similar to genes encoded by the chloroplast genome of the primitive plant Marchantia polymorpha. These data suggest that a sulfate transport system similar to that of Synechococcus sp. strain PCC 7942 may exist in the chloroplast envelope of photosynthetic eukaryotes.
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PMID:Characterization and mutagenesis of sulfur-regulated genes in a cyanobacterium: evidence for function in sulfate transport. 170 75

The two operons atp1 and atp2, encoding the subunits of the F0F1 ATP-synthase, have been cloned and sequenced from the cyanobacterium Synechocystis sp. PCC 6803. The organization of the different genes in the operons have been found to resemble that of the cyanobacteria Synechococcus sp. PCC 6301 and Anabaena sp. PCC 7120. The Synechocystis F0F1 ATP-synthase has nine subunits. A tenth open reading frame with unknown function was detected at the 5' end of atp1, coding for a putative gene product similar to uncI in Escherichia coli. A promoter structure was inferred for the Synechocystis atp operons and compared to other known promoters of cyanobacteria. Even though the operon structure of atp1 and atp2 in Synechocystis resembles the corresponding operons of Synechococcus, the amino acid sequences of individual gene products show marked differences. Genetic distances between cyanobacterial genes and genes for ATP-synthase subunits from other species have been calculated and compiled into evolutionary trees.
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PMID:The atp1 and atp2 operons of the cyanobacterium Synechocystis sp. PCC 6803. 183 89

delta-Aminolevulinic acid is the universal precursor for all tetrapyrroles including hemes, chlorophylls, and bilins. In plants, algae, cyanobacteria, and many other bacteria, delta-aminolevulinic acid is synthesized from glutamate in a reaction sequence that requires three enzymes, ATP, NADPH, and tRNA(Glu). The three enzymes have been characterized as glutamyl-tRNA synthetase, glutamyl-tRNA reductase, and glutamate-1-semialdehyde aminotransferase. All three enzymes have been separated and partially characterized from plants and algae. In prokaryotic phototrophs, only the glutamyl-tRNA synthetase and glutamate-1-semialdehyde aminotransferase have been decribed. We report here the purification and some properties of the glutamyl-tRNA reductase from extracts of the unicellular cyanobacterium, Synechocystis sp. PCC 6803. The glutamyl-tRNA reductase has been purified over 370-fold to apparent homogeneity. Its native molecular mass was determined to be 350 kDa by glycerol density gradient centrifugation, and its subunit size was estimated to be 39 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The N-terminal amino acid sequence was determined for 42 residues. Much higher activity occurred with NADPH than with NADH as the reduced pyridine nucleotide substrate. Half-maximal rates occurred at 5 microM NADPH, whereas saturation was not reached even at 10 mM NADH. Purified Synechocystis glutamyl-tRNA reductase was inhibited 50% by 5 microM heme. Activity was unaffected by 10 microM 3-amino-2,3-dihydrobenzoic acid. No flavin, pyridine nucleotide, or other light-absorbing prosthetic group was detected on the purified enzyme. The catalytic turnover number of purified Synechocystis glutamyl-tRNA reductase is comparable to those of prokaryotic and plastidic glutamyl-tRNA synthetases.
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PMID:Purification of glutamyl-tRNA reductase from Synechocystis sp. PCC 6803. 190 97

Bioenergetic parameters and redox properties of energy transducing membranes in rat liver mitochondria and cyanobacteria were investigated in the presence of the antipsoriatic compound anthralin (1,8-dihydroxy-9-anthrone). Transmembrane pH and electrical gradients were determined using electron paramagnetic resonance spectroscopy. In mitochondria, ubiquinones 9,10 and other redox components of the electron transport chain are reduced by anthralin; the proton motive force is increased. In the absence of ADP, anthralin slightly stimulates mitochondrial cyanide-insensitive oxygen consumption. It is suggested that increased cyanide-insensitive respiration is due to enhanced autoxidation of mitochondrial components and/or catalyzed oxidation of anthralin. In the presence of ADP mitochondrial respiration is decreased, and ATP synthesis is inhibited. Uncoupler-induced mitochondrial respiration is also decreased by anthralin, indicating inhibition of the electron transport chain. In the cyanobacterium Synechococcus PCC 6311 anthralin increases the pH gradient and decreases ATP levels. Thus, anthralin acts as an electron donor to membrane associated redox components and inhibits ATP synthesis in two different biologic systems. In human keratinocytes oxygen metabolism is influenced by anthralin in a similar pattern as in isolated mitochondria, and ATP content is decreased. Because anthralin reacts with redox components in different biologic membranes, alterations of subcellular/cellular redox status and energy metabolism might contribute significantly to its antiproliferative activity.
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PMID:The antipsoriatic compound anthralin influences bioenergetic parameters and redox properties of energy transducing membranes. 210 16

Platelet monoamine oxidase (MAO) activity, serotonin uptake rate and serotonin efflux rate have all been suggested to be markers for central serotonergic mechanisms. Platelet MAO activity is associated with certain personality traits, with low activity linked to traits such as impulsiveness, sensation-seeking and avoidance of monotony, all possible expressions of low central serotonergic activity. Low platelet serotonin uptake rate has been connected to unipolar depression and the rate of efflux, in the presence of the ATP uncoupler CCP, higher in bipolar depressives than in controls. Platelet MAO was found to be lower in 16 consecutive female inpatients fulfilling the DSM-III criteria for bulimia nervosa than in 12 female controls. Rates of serotonin uptake and efflux in the presence of CCP were, on the other hand, similar to the controls. In the controls there were no correlations between platelet MAO activity and any of the other parameters estimated. Vmax for the platelet uptake of serotonin correlated positively with the Km for the uptake, but not with any other parameter. The uninfluenced rate of efflux of serotonin correlated positively with the efflux in the presence of the ATP uncoupler CCP.
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PMID:Blood platelet monoamine oxidase activity, serotonin uptake and release rates in anorexia and bulimia patients and in healthy controls. 233 Aug 33

Glutamate was converted to the chlorophyll and heme precursor delta-aminolevulinic acid in soluble extracts of Euglena gracilis. delta-Aminolevulinic acid-forming activity depended on the presence of native enzyme, glutamate, ATP, Mg2+, NADPH or NADH, and RNA. The requirement for reduced pyridine nucleotide was observed only if, prior to incubation, the enzyme extract was filtered through activated carbon to remove firmly bound reductant. Dithiothreitol was also required for activity after carbon treatment. delta-Aminolevulinic acid formation was stimulated by RNA from various plant tissues and algal cells, including greening barley leaves and members of the algal groups Chlorophyta (Chlorella vulgaris, Chlamydomonas reinhardtii), Rhodophyta (Cyanidium caldarium), Cyanophyta (Anacystis nidulans, Synechocystis sp. PCC 6803), and Prochlorophyta (Prochlorothrix hollandica), but not by RNA derived from Escherichia coli, yeast, wheat germ, bovine liver, and Methanobacterium thermoautotrophicum. E. coli glutamate-specific tRNA was inhibitory. Several of the RNAs that did not stimulate delta-aminolevulinic acid formation nevertheless became acylated when incubated with glutamate in the presence of Euglena enzyme extract. RNA extracted from nongreen dark-grown wild-type Euglena cells was about half as stimulatory as that from chlorophyllous light-grown cells, and RNA from aplastidic mutant cells stimulated only slightly. delta-Aminolevulinic acid-forming enzyme activity was present in extracts of light-grown wild-type cells, but undetectable in extracts of aplastidic mutant and dark-grown wild-type cells. Gabaculine inhibited delta-aminolevulinic acid formation at submicromolar concentration. Heme inhibited 50% at 25 microM, but protoporphyrin IX, Mg-protoporphyrin IX, and protochlorophyllide inhibited only slightly at this concentration.
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PMID:Enzymatic conversion of glutamate to delta-aminolevulinic acid in soluble extracts of Euglena gracilis. 244 64

delta-Aminolevulinic acid is the first committed precursor in the biosynthesis of hemes, phycobilins, and chlorophylls. Plants and algae synthesize delta-aminolevulinic acid from glutamate via an RNA-dependent 5-carbon pathway. Previous reports demonstrated that cyanobacteria form delta-aminolevulinic acid from glutamate in vivo. We now report the direct measurement of this activity in vitro. Three oxygenic prokaryotes were examined, the unicellular cyanobacteria Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002 (Agmenellum quadruplicatum PR-6) and the chlorophyll a- and b-containing filamentous prochlorophyte Prochlorothrix hollandica. delta-Aminolevulinic acid-forming activity was detected in soluble extracts of all three species. delta-Aminolevulinic acid formation by Synechocystis extracts was further characterized. Activity depended upon addition of reduced pyridine nucleotide, ATP, and Mg2+ to the incubation mixture. NADPH was a more effective pyridine nucleotide than NADH at low concentrations, but NADPH inhibited delta-amino-levulinic acid formation above 1 mM, whereas NADH did not. The pH optimum was about 7.6, and the ATP concentration optimum was 0.1 mM. Activity was stimulated by addition of RNA derived from Synechocystis or Chlorella, and abolished by preincubation with RNase A. After RNase inactivation, activity was restored by addition of RNasin to block further RNase action, followed by supplementation with Synechocystis RNA. Activity was inhibited by micromolar concentrations of hemin, as was previously found with plant and algal extracts. Complete dependence on added glutamate could not be achieved. Radioactivity was incorporated into delta-aminolevulinic acid when the incubation mixture contained 1-[14C]glutamate. Activity in the Synechocystis enzyme extract was stimulated by the addition of a partially purified enzyme fraction from Chlorella. It thus appears that prokaryotic oxygenic organisms share with chloroplasts the capacity for biosynthesis of photosynthetic pigments from glutamate via the RNA-dependent 5-carbon pathway.
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PMID:Transformation of glutamate to delta-aminolevulinic acid by soluble extracts of Synechocystis sp. PCC 6803 and other oxygenic prokaryotes. 245 30

Formation of the tetrapyrrole pigment precursor delta-aminolevulinic acid (ALA) from glutamate was detected and partially characterized in extracts of the strictly anaerobic green photosynthetic bacterial species Chlorobium vibrioforme by using assay methods derived from those developed for algae and cyanobacteria. ALA formation in Chlorobium extracts was saturated at 10 mM glutamate and required NADPH and ATP at optimal concentrations of 0.3 and 3 mM, respectively. Preincubation of the enzyme extract with RNase A destroyed the ALA-forming activity completely. Activity in the RNase-treated extract was restored by supplementation with Chlorobium RNA after addition of RNasin to block further RNase action. RNA from the cyanobacterium Synechocystis sp. strain PCC 6803 and Escherichia coli tRNAGlu also restored activity. Activity was inhibited 50% by 0.2 microM hemin. ALA formation was completely abolished by the addition of 5 microM 3-amino-2,3-dihydrobenzoic acid (gabaculine). These results indicate that Chlorobium extracts share with those of plants, eucaryotic algae, cyanobacteria, prochlorophytes, and methanogens the capacity for RNA-dependent ALA formation from glutamate.
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PMID:Transformation of glutamate to delta-aminolevulinic acid by soluble extracts of Chlorobium vibrioforme. 247 78

The PII protein in the cyanobacterium Synechococcus sp. strain PCC 7942 signals the cellular state of nitrogen assimilation relative to CO2 fixation by being phosphorylated at a seryl residue. In this study, we first determined the location of the phosphorylated seryl residue within the PII amino acid sequence. The phosphorylation site exhibits an RXS motif, a recognition sequence characteristic for cyclic AMP-dependent protein serine kinases from eukaryotes. We established an in vitro PII phosphorylation assay to further analyze the PII kinase activity in Synechococcus sp. strain PCC 7942. ATP was used specifically as a phosphoryl donor, and the PII kinase activity was shown to be stimulated by alpha-ketoglutarate. Unlike the PII-modifying uridylyltransferase- and uridylyl-removing enzyme characterized in proteobacteria, the activity of the PII kinase from the cyanobacterium did not respond to glutamine.
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PMID:Phosphorylation of the PII protein (glnB gene product) in the cyanobacterium Synechococcus sp. strain PCC 7942: analysis of in vitro kinase activity. 759 28

Subunits alpha, beta, and gamma of the F1-part of cyanobacterial F0F1-ATPase have been cloned into expression vectors. Over-expressed subunit beta was found soluble in the cytoplasmic fraction of Escherichia coli cells under appropriate culture and induction conditions and was purified from cell extracts. Recombinant alpha and gamma subunits precipitated into inclusion bodies and had to be solubilized, purified and refolded. The correct folding and functional integrity of the alpha and beta subunits was monitored by their ability to bind nucleotides. Active cyanobacterial F1-ATPase was assembled from its purified subunits alpha, beta, gamma, delta and epsilon. The reassembled enzyme reconstituted ATP synthesis in F1-depleted thylakoid membranes of Synechocystis sp. PCC 6803 and hydrolyzed ATP.
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PMID:Reassembly of Synechocystis sp. PCC 6803 F1-ATPase from its over-expressed subunits. 772 Aug 66


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