Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The glnA gene from Synechocystis sp. strain PCC 6803 was cloned by hybridization with the glnA gene from Anabaena sp. strain PCC 7120, and a deletion-insertion mutation of the Synechocystis gene was generated in vitro. A strain derived from Synechocystis sp. strain PCC 6803 which contained integrated into the chromosome, in addition to its own glnA gene, the Anabaena glnA gene was constructed. From that strain, a Synechocystis sp. glnA mutant could be obtained by transformation with the inactivated Synechocystis glnA gene; this mutant grew by using Anabaena glutamine synthetase and was not a glutamine auxotroph. A Synechocystis sp. glnA mutant could not be obtained, however, from the wild-type Synechocystis sp. The Anabaena glutamine synthetase enzyme was subject to ammonium-promoted inactivation when expressed in the Synechocystis strain but not in the Anabaena strain itself.
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PMID:Regulation of Anabaena sp. strain PCC 7120 glutamine synthetase activity in a Synechocystis sp. strain PCC 6803 derivative strain bearing the Anabaena glnA gene and a mutated host glnA gene. 134 14

Ferredoxin-glutamate synthase from the unicellular cyanobacterium Synechococcus sp. PCC 6301 has been purified using, as main steps, ethanol fractionation in the presence of high ionic strength, ion-exchange chromatography and ferredoxin-Sepharose affinity chromatography. The overall process yielded an homogeneous enzyme with a specific activity of 30 U/mg protein, after a purification of 2800-fold with a recovery of 43%. The molecular mass of the native protein was 156 kDa, as calculated from its Stokes radius (rS, 4.32 nm) and sedimentation coefficient (S20,w, 8.46 S). The size was also estimated by SDS/PAGE as 160 kDa, indicating that the native protein was a monomer. The enzyme exhibited absorption maxima at 279, 370 and 438 nm and a A279/A438 absorbance ratio of 11. One molecule of FMN, but not FAD, was found/molecule native protein. The addition of dithionite resulted in the loss of the absorption peak at 438 nm, which was restored by the addition of 2-oxoglutarate, thus indicating that the prosthetic group is functional in catalysis. Classical hyperbolic kinetics with substrate inhibition was seen for 2-oxoglutarate. The Km values determined for glutamine and ferredoxin were 0.7 mM and 7 microM, respectively, and the apparent Km for 2-oxoglutarate was estimated to be 1.7 mM. Azaserine and 6-diazo-5-oxo-L-norleucine were potent inhibitors of the activity, while pyridoxal 5-phosphate, known to react with Lys residues, partially inactivated the enzyme. This ferredoxin-dependent glutamate synthase is, as far as we know, the first purified from prokaryotic organisms and resembles its counterpart from chloroplasts, suggesting that cyanobacterial glutamate synthase may have been the ancestor of ferredoxin-glutamate synthase in plants.
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PMID:Purification and characterization of the ferredoxin-glutamate synthase from the unicellular cyanobacterium Synechococcus sp. PCC 6301. 158 84

Glutamine synthetase activity from Synechocystis sp. strain PCC 6803 is regulated as a function of the nitrogen source available in the medium. Addition of 0.25 mM NH4Cl to nitrate-grown cells promotes a clear short-term inactivation of glutamine synthetase, whose enzyme activity decreases to 5 to 10% of the initial value in 25 min. The intracellular levels of glutamine, determined under various conditions, taken together with the results obtained with azaserine (an inhibitor of transamidases), rule out the possibility that glutamine per se is responsible for glutamine synthetase inactivation. Nitrogen starvation attenuates the ammonium-mediated glutamine synthetase inactivation, indicating that glutamine synthetase regulation is modulated through the internal balance between carbon-nitrogen compounds and carbon compounds. The parallelism observed between the glutamine synthetase activity and the internal concentration of alpha-ketoglutarate suggests that this metabolite could play a role as a positive effector of glutamine synthetase activity in Synechocystis sp. Despite the similarities of this physiological system to that described for enterobacteria, the lack of in vivo 32P labeling of glutamine synthetase during the inactivation process excludes the existence of an adenylylation-deadenylylation system in this cyanobacterium.
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PMID:Regulation of glutamine synthetase activity in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 by the nitrogen source: effect of ammonium. 167 97

Bicarbonate (HCO3-) causes a significant and reversible stimulation of anion-inhibited electron flow in photosystem II of higher plants and cyanobacteria. To test if selected arginine (Arg) residues are involved in the binding of HCO3-, we utilized oligonucleotide-directed mutagenesis to construct Synechocystis sp. PCC 6803 mutants carrying mutations in Arg residues in the D2 protein. Measurements of oxygen evolution showed that the D2 mutants R233Q (arginine-233----glutamine) and R251S (arginine-251----serine) were 10-fold more sensitive to formate than the wild type. The formate concentration giving half-maximal inhibition of the steady-state oxygen evolution rate was 48 mM, 4.5 mM and 4 mM for the wild type, R233Q and R251S, respectively. Measurements of oxygen evolution in single-turnover flashes confirm that the mutants are more sensitive to formate than the wild type. Measurements of chlorophyll a fluorescence decay kinetics after the second saturating actinic flash indicated that, after formate treatment, the halftime of QA- oxidation was decreased by approximately a factor of 2, 4 and 6 in the wild type, R251S and R233Q, respectively. The recombination rate between QA- and S2 was approx. 2-fold slower in R251S and R233Q than in the wild type. In the presence of 100 mM sodium formate, reactivation of the Hill reaction by bicarbonate showed that the wild type had an apparent Km for bicarbonate of 0.5 mM, while the Km values for R233Q and R251S were 1.4 and 1.5 mM, respectively. We suggest that Arg-233 and Arg-251 in the D2 polypeptide contribute to stabilization of HCO3- binding in Photosystem II.
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PMID:Arginine residues in the D2 polypeptide may stabilize bicarbonate binding in photosystem II of Synechocystis sp. PCC. 190 78

Glutamine synthetases (GSs) from two cyanobacteria, one unicellular (Synechocystis sp. strain PCC 6803) and the other filamentous (Calothrix sp. strain PCC 7601 [Fremyella diplosiphon]), were purified to homogeneity. The biosynthetic activities of both enzymes were strongly inhibited by ADP, indicating that the energy charge of the cell might regulate the GS activity. Both cyanobacteria exhibited an ammonium-mediated repression of GS synthesis. In addition, the Synechocystis sp. showed an inactivation of GS promoted by ammonium that had not been demonstrated previously in cyanobacteria.
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PMID:Purification and properties of glutamine synthetases from the cyanobacteria Synechocystis sp. strain PCC 6803 and Calothrix sp. strain PCC 7601. 197 29

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

The glnA gene of the cyanobacterium Agmenellum quadruplicatum PR-6 (Synechococcus sp. strain PCC 7002) was isolated by complementing an Escherichia coli strain auxotrophic for glutamine (YMC11) with a PR-6 cosmid library. PR-6 glnA is a single-copy gene that encodes a deduced amino acid sequence that is highly homologous to the deduced glnA amino acid sequences reported for other bacteria. No homology was found between the PR-6 glnA flanking sequences and the ntrB, ntrC, or glnB genes of other bacteria. Northern (RNA) and primer extension analyses of PR-6 RNA revealed one predominant and several minor glnA transcripts of about 1.5 to 1.7 kb. The steady-state amounts of these transcripts increased three- to fivefold when the cells were starved for nitrogen. However, we found that mutant PR-6 cells lacking glnA were still able to use nitrate or ammonium as a sole nitrogen source. Although no RNA homologous to an internal fragment of the glnA gene could be detected in the mutant cells, they retained about 60% of wild-type glutamine biosynthetic activity. The mutant cells were more sensitive than the wild-type cells to methionine sulfoximine, a transition state analog of glutamate, a result that might indicate the presence of an additional glutamine synthetase; however, cell extracts of wild-type PR-6 cells and those lacking glnA were both able to use carbamyl phosphate instead of ammonium as a nitrogen donor for the synthesis of glutamine, a result that indicates the use of carbamyl phosphate synthetase to assimilate ammonium and produce glutamine.
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PMID:The glnA gene of the cyanobacterium Agmenellum quadruplicatum PR-6 is nonessential for ammonium assimilation. 767 91

We have identified the existence of two genes, trnQ and aroA, located upstream of the psbO gene in Synechocystis sp. PCC 6803. The trnQ gene encodes a glutamine-specific transfer RNA (tRNA(Gln)) and the sequence given is the first reported for any cyanobacterium. The gene seems to exist as a single copy since its deletion results in non-viable mutation. The aroA gene encodes for 5-enolpyruvylshikimate 3-phosphate synthase and its discovery in the genome of Synechocystis 6803 is the first genetic evidence for the existence of the shikimate biosynthetic pathway in cyanobacteria. Interestingly, the partial sequence shares close homologies with the sequences of aroA from Gram-positive bacteria.
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PMID:The genes aroA and trnQ are located upstream of psbO in the chromosome of Synechocystis 6803. 768 11

The PII protein (glnB gene product) in the cyanobacterium Synechococcus sp. strain PCC 7942 signals the cellular N status by being phosphorylated or dephosphorylated at a seryl residue. Here we show that the PII-modifying system responds to the activity of ammonium assimilation via the glutamine synthase-glutamate synthase pathway and to the state of CO2 fixation. To identify possible functions of PII in this microorganism, a PII-deficient mutant was created and its general phenotype was characterized. The analysis shows that the PII protein interferes with the regulation of enzymes required for nitrogen assimilation, although ammonium repression is still detectable in the PII-deficient mutant. We suggest that the phosphorylation and dephosphorylation of PII are part of a complex signal transduction network involved in global nitrogen control in cyanobacteria. In this regulatory process, PII might be involved in mediating the tight coordination between carbon and nitrogen assimilation.
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PMID:Functional analysis of the phosphoprotein PII (glnB gene product) in the cyanobacterium Synechococcus sp. strain PCC 7942. 772 95

The first two genes of ferredoxin-dependent glutamate synthase (Fd-GOGAT) from a prokaryotic organism, the cyanobacterium Synechocystis sp. PCC 6803, were cloned in Escherichia coli. Partial sequencing of the cloned genomic DNA, of the 6.3 kb Hind III and 9.3 kb Cla I fragments, confirmed the existence of two different genes coding for glutamate synthases, named gltB and gltS. The gltB gene was completely sequenced and encodes for a polypeptide of 1550 amino acid residues (M(r) 168,964). Comparative analysis of the gltB deduced amino acid sequence against other glutamate synthases shows a higher identity with the alfalfa NADH-GOGAT (55.2%) than with the corresponding Fd-GOGAT from the higher plants maize and spinach (about 43%), the red alga Antithamnion sp. (42%) or with the NADPH-GOGAT of bacterial source, such as Escherichia coli (41%) and Azospirillum brasilense (45%). The detailed analysis of Synechocystis gltB deduced amino acid sequence shows strongly conserved regions that have been assigned to the 3Fe-4S cluster (CX5CHX3C), the FMN-binding domain and the glutamine-amide transferase domain. Insertional inactivation of gltB and gltS genes revealed that both genes code for ferredoxin-dependent glutamate synthases which were nonessential for Synechocystis growth, as shown by the ferredoxin-dependent glutamate synthase activity and western-blot analysis of the mutant strains.
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PMID:Existence of two ferredoxin-glutamate synthases in the cyanobacterium Synechocystis sp. PCC 6803. Isolation and insertional inactivation of gltB and gltS genes. 772 52


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