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)

Glutamine synthetase (GS) inactivation was observed in crude cell extracts and in the high-speed supernatant fraction from the cyanobacterium Synechocystis sp. strain PCC 6803 following the addition of ammonium ions, glutamine, or glutamate. Dialysis of the high-speed supernatant resulted in loss of inactivation activity, but this could be restored by the addition of NADH, NADPH, or NADP+ and, to a lesser extent, NAD+, suggesting that inactivation of GS involved ADP-ribosylation. This form of modification was confirmed both by labelling experiments using [32P]NAD+ and by chemical analysis of the hydrolyzed enzyme. Three different forms of GS, exhibiting no activity, biosynthetic activity only, or transferase activity only, could be resolved by chromatography, and the differences in activity were correlated with the extent of the modification. Both biosynthetic and transferase activities were restored to the completely inactive form of GS by treatment with phosphodiesterase.
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PMID:ADP-ribosylation of glutamine synthetase in the cyanobacterium Synechocystis sp. strain PCC 6803. 776 63

The ndhF gene of the unicellular marine cyanobacterium Synechococcus sp. strain PCC 7002 was cloned and characterized. NdhF is a subunit of the type 1, multisubunit NADH:plastoquinone oxidoreductase (NADH dehydrogenase). The nucleotide sequence of the gene predicts an extremely hydrophobic protein of 664 amino acids with a calculated mass of 72.9 kDa. The ndhF gene was shown to be single copy and transcribed into a monocistronic mRNA of 2,300 nucleotides. An ndhF null mutation was successfully constructed by interposon mutagenesis, demonstrating that NdhF is not required for cell viability under photoautotrophic growth conditions. The mutant strain exhibited a negligible rate of oxygen uptake in the dark, but its photosynthetic properties (oxygen evolution, chlorophyll/P700 ratio, and chlorophyll/P680 ratio) were generally similar to those of the wild type. Although the ndhF mutant strain grew as rapidly as the wild-type strain at high light intensity, the mutant grew more slowly than the wild type at lower light intensities and did not grow at all under photoheterotrophic conditions. The roles of the NADH:plastoquinone oxidoreductase in photosynthetic and respiratory electron transport are discussed.
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PMID:Isolation and characterization of the ndhF gene of Synechococcus sp. strain PCC 7002 and initial characterization of an interposon mutant. 850 Oct 38

NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been purified to electrophoretic homogeneity from Synechococcus PCC 7942 cells. The native enzyme had a molecular mass of 160 kDa and consisted of four subunits with a molecular mass of 41 kDa. The activity was 6-fold higher with NADPH than with NADH; the apparent Km values for NADPH and NADH were 62 +/- 4.5 and 420 +/- 10.5 microM respectively. The gene encoding NADP-dependent GAPDH was cloned from the chromosomal DNA of Synechococcus 7942. A 1140 bp open reading frame, encoding an enzyme of 380 amino acid residues (approx.molecular mass of 41.3 kDa) was observed. The deduced amino acid sequence of the gene had a greater sequence similarity to the NADP-dependent and chloroplastic form than to the NAD-dependent and cytosolic form. The Synechococcus 7942 enzyme lacked one of the cysteines involved in the light-dependent regulation of the chloroplast enzymes of higher plants. The recombinant enzyme expressed in Escherichia coli as well as the native enzyme purified from Synechococcus 7942 cells were resistant to 1 mM H2O2.
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PMID:Enzymic and molecular characterization of NADP-dependent glyceraldehyde-3-phosphate dehydrogenase from Synechococcus PCC 7942: resistance of the enzyme to hydrogen peroxide. 868 18

The sequence of a NAD(P)-reducing hydrogenase operon of Synechocystis sp. PCC 6803 containing genes for a small and a large hydrogenase subunit and six additional ORFs was determined. Until now only 11 of the 14 polypeptides of the NADH-dehydrogenase of E. coli were found in Synechocystis. By sequence homologies we suggest that the missing subunits of the peripheral part of the dehydrogenase, containing most of the FeS-clusters, are encoded by three ORFs of this operon. This hypothesis is discussed in relation to the NAD(P)-reducing hydrogenase of Synechocystis.
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PMID:Sequence analysis of an operon of a NAD(P)-reducing nickel hydrogenase from the cyanobacterium Synechocystis sp. PCC 6803 gives additional evidence for direct coupling of the enzyme to NAD(P)H-dehydrogenase (complex I). 898 Jun 40

The Synechocystis sp. PCC 6803 gene (bvdR) encoding biliverdin reductase was amplified by the polymerase chain reaction, cloned, and overexpressed in Escherichia coli as the native form and as a 6-histidine-tagged amino-terminal fusion. The latter form of the enzyme was purified by affinity chromatography and shown to have the appropriate molecular weight by electrospray mass spectrometry. Both forms of the enzyme reduced biliverdin IXalpha using NADPH or NADH, with NADPH as the preferred reductant. The His-tagged enzyme has a Km for biliverdin of 1.3 microM. The pH optimum for the NADPH-dependent activity is 5.8, whereas that for rat biliverdin reductase is at pH 8.7. Absorbance spectra and high performance liquid chromatography retention times of the reaction product reaction match those of authentic bilirubin, the product of the reduction of biliverdin by the mammalian enzymes. These results provide the first evidence for the formation of bilirubin in bacteria. Fully segregated Synechocystis sp. PCC 6803 bvdR interposon mutants produce approximately 85% of the normal amount of phycobilisome cores containing allophycocyanin and other phycocyanobilin-bearing core polypeptides, but no detectable phycocyanin. Thus, surprisingly, the blockage of the conversion of biliverdin to bilirubin interferes with normal phycobiliprotein biosynthesis in cyanobacteria. Possible interpretations of this finding are presented.
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PMID:Characterization of cyanobacterial biliverdin reductase. Conversion of biliverdin to bilirubin is important for normal phycobiliprotein biosynthesis. 915 3

A cytosolic catalase-peroxidase from the cyanobacterium Synechocystis PCC 6803 was purified to homogeneity by a six-step purification procedure. It is a homodimeric enzyme with a subunit molecular mass of 85 kDa. The isoelectric point of the protein is at pH 5.5; Michaelis constant, turnover number, and catalytic efficiency of the catalase activity for H2O2 were measured to be 4.8 mM, 3450 s-1, and 7.2 x 10(5) M-1 s-1, respectively. Preparation and spectroscopy of the pyridine ferrohemochrome identified an iron protoporphyrin IX as the prosthetic group. The enzyme was shown to exhibit both catalase and peroxidase activities, both of which were inhibited by cyanide, leading to a high-spin to low-spin transition of the heme iron center as detected by a shift of the Soret peak from 405 to 421 nm. The catalase-specific inhibitor 3-amino-1,2,4-triazole proved ineffective. o-Dianisidine, pyrogallol and guaiacol functioned as a peroxidatic substrate, but no reaction was detected with NADH, NADPH, glutathione, and ascorbate. Peptide mass mapping using matrix assisted laser desorption ionization time-of-flight mass spectrometry showed the identity between the purified protein and a putative katG gene derived from the genome of Synechocystis PCC 6803. A comparison of amino acid sequences of the catalase-peroxidase from Synechocystis PCC 6803 and those from other bacteria showed a high homology around the assumed distal and proximal histidine residues, suggesting a highly conserved histidine as the fifth ligand of the heme iron.
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PMID:Purification and characterization of a hydroperoxidase from the cyanobacterium Synechocystis PCC 6803: identification of its gene by peptide mass mapping using matrix assisted laser desorption ionization time-of-flight mass spectrometry. 991 46

Glutathione reductase (GR) from the cyanobacterium Anabaena PCC 7120 was heterologously expressed in Escherichia coli SG5. Silent random mutations were introduced in the 5' region of DNA encoding the enzyme in order to generate a high-level expression clone. To maximize protein expression, the culture conditions were also optimized. In the high-level expression clones selected, E. coli-preferred codons were selectively used at certain positions. Under the optimal expression conditions, a yield of 17 mg recombinant protein per liter was obtained, which is about 10-fold higher than that of the wild-type enzyme. A hexahistidine tag was added at the C-terminal of the protein in order to allow IMAC affinity purification. This strategy simplified the purification process and provided a homogeneous enzyme for functional characterization. Anabaena GR uses NADPH as a coenzyme, like most of the GRs from other sources, but the KM values for NADPH and GSSG are higher than those of enzymes previously studied. The Anabaena enzyme also shows significant activity when NADH is used as a reductant.
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PMID:Optimized heterologous expression of glutathione reductase from Cyanobacterium anabaena PCC 7120 and characterization of the recombinant protein. 1002 75

Analysis of the genome of Synechocystis sp. strain PCC 6803 reveals three open reading frames (slr0851, slr1743, and sll1484) that may code for type 2 NAD(P)H dehydrogenases (NDH-2). The sequence similarity between the translated open reading frames and NDH-2s from other organisms is low, generally not exceeding 30% identity. However, NAD(P)H and flavin adenine dinucleotide binding motifs are conserved in all three putative NDH-2s in Synechocystis sp. strain PCC 6803. The three open reading frames were cloned, and deletion constructs were made for each. An expression construct containing one of the three open reading frames, slr1743, was able to functionally complement an Escherichia coli mutant lacking both NDH-1s and NDH-2s. Therefore, slr0851, slr1743, and sll1484 have been designated ndbA, ndbB, and ndbC, respectively. Strains that lacked one or more of the ndb genes were created in wild-type and photosystem (PS) I-less backgrounds. Deletion of ndb genes led to small changes in photoautotrophic growth rates and respiratory activities. Electron transfer rates into the plastoquinone pool in thylakoids in darkness were consistent with the presence of a small amount of NDH-2 activity in thylakoids. No difference was observed between wild-type and the Ndb-less strains in the banding patterns seen on native gels when stained for either NADH or NADPH dehydrogenase activity, indicating that the Ndb proteins do not accumulate to high levels. A striking phenotype of the PS I-less background strains lacking one or more of the NDH-2s is that they were able to grow at high light intensities that were lethal to the control strain but they retained normal PS II activity. We suggest that the Ndb proteins in Synechocystis sp. strain PCC 6803 are redox sensors and that they play a regulatory role responding to the redox state of the plastoquinone pool.
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PMID:Type 2 NADH dehydrogenases in the cyanobacterium Synechocystis sp. strain PCC 6803 are involved in regulation rather than respiration. 1038 67

Glutathione reductase from the cyanobacterium Anabaena PCC 7120 contains a pyridine-nucleotide-binding motif differing from that of the enzyme from other sources and an insertion of 10 amino acid residues. Homology modeling was used to obtain a model of the enzyme structure. It revealed that in the Anabaena enzyme Lys(203) replaces Arg, found to interact with the 2'-phosphate of NADP(H) in the enzyme from other sources, and that it has an extra loop near the entrance of the pyridine-nucleotide-binding site. The steady-state and preequilibrium kinetic properties were characterized for the wild-type enzyme, a K203R, and a loop deletion mutant. All enzyme forms had higher catalytic efficiency with NADPH than with NADH, although the difference was less than for glutathione reductase from other sources. The specificity was most pronounced in the formation of the charge-transfer complex between the pyridine nucleotide and oxidized enzyme-bound FAD, as compared to later steps in the reaction. Unexpectedly, by replacing Lys(203) with Arg, the specificity for NADPH was diminished in the complete redox reaction. Ser(174) appears to interact with the 2'-phosphate of NADPH and introduction of arginine instead of lysine, therefore, has little effect on the interaction with this coenzyme. However, the efficiency in forming the charge-transfer complex between the pyridine nucleotide and oxidized enzyme-bound FAD was increased in the K203R mutant using NADPH but not with NADH. The lack of affinity toward 2',5'-ADP-Sepharose by the wild-type enzyme was not changed by replacing Lys(203) with Arg but deletion of the loop resulted in an enzyme that bound to the immobilized ligand. Removal of the loop increased the efficiency of the enzyme in the reductive half-reaction with both pyridine-nucleotides as well as in the overall catalytic mechanism.
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PMID:Probing the kinetic mechanism and coenzyme specificity of glutathione reductase from the cyanobacterium Anabaena PCC 7120 by redesign of the pyridine-nucleotide-binding site. 1041 99

The gene encoding the ferredoxin-dependent glutamate synthase (Fd-GOGAT), glsF, from the heterocyst-forming cyanobacterium Anabaena sp. PCC 7120, has been cloned and sequenced. Unlike other cyanobacteria, Anabaena 7120 contains only Fd-GOGAT, lacking NADH-GOGAT. The amount of glsF transcript and Fd-GOGAT activity were similar under all the nitrogen growth conditions tested. Enzyme activity, Western and Northern blot analyses indicated that Fd-GOGAT is absent in the heterocysts, while glutamine synthetase (GS) and NADP-isocitrate dehydrogenase (IDH) were present in these specialised cells. Our results clearly indicate that the GS-GOGAT pathway is not operative in the heterocysts, and hence glutamate must be imported from the adjacent vegetative cells, to sustain GS activity. Heterocysts probably export glutamine or another nitrogen rich compound like arginine to the vegetative cells.
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PMID:The GS-GOGAT pathway is not operative in the heterocysts. Cloning and expression of glsF gene from the cyanobacterium Anabaena sp. PCC 7120. 1091 29


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