Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

A bacteriochlorophyll a biosynthesis mutant of the purple photosynthetic bacterium Rhodobacter capsulatus was functionally complemented with a cosmid genomic library from Synechocystis sp. PCC 6803. The complemented R. capsulatus strain contains a defined mutation in the bchM gene that codes for Mg-protoporphyrin IX methyltransferase, the enzyme which converts Mg-protoporphyrin IX to Mg-protoporphyrin IX methylester using S-adenosyl-L-methionine as a cofactor. Since chlorophyll biosynthesis also requires the same methylation reaction, the Synechocystis genome should similarly code for a Mg-protoporphyrin IX methyltransferase. Sequence analysis of the complementing Synechocystis cosmid indicates that it contains an open reading frame exhibiting 29% sequence identity to BchM. In addition, expression of the Synechocystis gene in the R. capsulatus bchM mutant via the strong R. capsulatus puc promoter was shown to support nearly wild-type levels of bacteriochlorophyll a synthesis. To our knowledge, the Synechocystis sequence thus represents the first chlorophyll biosynthesis gene homolog of bchM. The complementing Synechocystis cosmid was also shown to code for a gene product that is a member of a highly conserved family of RNA binding proteins, the function of which in cyanobacteria remains undetermined.
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PMID:Cloning and characterization of the chlorophyll biosynthesis gene chlM from Synechocystis PCC 6803 by complementation of a bacteriochlorophyll biosynthesis mutant of Rhodobacter capsulatus. 870 38

By use of restriction endonucleases, the DNA of the cyanobacterium Synechocystis sp. strain PCC 6803 was analyzed for DNA-specific methylation. Three different recognition sites of methyltransferases, a dam-like site including N6-methyladenosine and two other sites with methylcytosine, were identified, whereas no activities of restriction endonucleases could be detected in this strain. slr0214, a Synechocystis gene encoding a putative methyltransferase that shows significant similarities to C5-methylcytosine-synthesizing enzymes, was amplified by PCR and cloned for further characterization. Mutations in slr0214 were generated by the insertion of an aphII gene cassette. Analyses of chromosomal DNAs of such mutants demonstrated that the methylation pattern was changed. The recognition sequence of the methyltransferase was identified as 5'-CGATCG-3', corresponding to the recognition sequence of PvuI. The specific methyltransferase activity was significantly reduced in protein extracts obtained from mutant cells. Mutation of slr0214 also led to changed growth characteristics of the cells compared to wild-type cells. These alterations led to the conclusion that the methyltransferase Slr0214 might play a regulatory role in Synechocystis. The Slr0214 protein was also overexpressed in Escherichia coli, and the purified protein demonstrated methyltransferase activity and specificity for PvuI recognition sequences in vitro. We propose the designation M.Ssp6803I [corrected] (Synechocystis methyltransferase I) for the slr0214-encoded enzyme.
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PMID:The cyanobacterium Synechocystis sp. strain PCC 6803 expresses a DNA methyltransferase specific for the recognition sequence of the restriction endonuclease PvuI. 969 58

A gene encoding a methyltransferase (menG) was identified in Synechocystis sp. PCC 6803 as responsible for transferring the methyl group to 2-phytyl-1,4-naphthoquinone in the biosynthetic pathway of phylloquinone, the secondary electron acceptor in photosystem I (PS I). Mass spectrometric measurements showed that targeted inactivation of the menG gene prevented the methylation step in the synthesis of phylloquinone and led to the accumulation of 2-phytyl-1,4-naphthoquinone in PS I. Growth rates of the wild-type and the menG mutant strains under photoautotrophic and photomixotrophic conditions were virtually identical. The chlorophyll a content of the menG mutant strain was similar to that of wild type when the cells were grown at a light intensity of 50 microE m(-2) s(-1) but was slightly lower when grown at 300 microE m(-2) s(-1). Chlorophyll fluorescence emission measurements at 77 K showed a larger increase in the ratio of PS II to PS I in the menG mutant strain relative to the wild type as the light intensity was elevated from 50 to 300 microE m(-2) s(-1). CW EPR studies at 34 GHz and transient EPR studies at multiple frequencies showed that the quinone radical in the menG mutant has a similar overall line width as that for the wild type, but consistent with the presence of an aromatic proton at ring position 2, the pattern of hyperfine splittings showed two lines in the low-field region. The spin polarization pattern indicated that 2-phytyl-1,4-naphthoquinone is in the same orientation as phylloquinone, and out-of-phase, spin-echo modulation spectroscopy shows the same P700(+) to Q(-) center-to-center distance as in wild-type PS I. Transient EPR studies indicated that the lifetime for forward electron transfer from Q(-) to F(X) is slowed from 290 ns in the wild type to 600 ns in the menG mutant. The redox potential of 2-phytyl-1,4-naphthoquinone is estimated to be 50 to 60 mV more oxidizing than phylloquinone in the A(1) site, which translates to a lowering of the equilibrium constant between Q(-)/Q and F(X)(-)/F(X) by a factor of ca. 10. The lifetime of the P700(+) [F(A)/F(B)](-) backreaction decreased from 80 ms in the wild type to 20 ms in the menG mutant strain and is evidence for a thermally activated, uphill electron transfer through the quinone rather than a direct charge recombination between [F(A)/F(B)](-) and P700(+).
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PMID:Insertional inactivation of the menG gene, encoding 2-phytyl-1,4-naphthoquinone methyltransferase of Synechocystis sp. PCC 6803, results in the incorporation of 2-phytyl-1,4-naphthoquinone into the A(1) site and alteration of the equilibrium constant between A(1) and F(X) in photosystem I. 1177 39

Betaine is an important osmoprotectant, synthesized by many plants in response to abiotic stresses. Almost all known biosynthetic pathways of betaine are two-step oxidations of choline. Recently, a biosynthetic pathway of betaine from glycine, catalyzed by two N-methyltransferase enzymes, was found. Here, the potential role of N-methyltransferase genes for betaine synthesis was examined in a freshwater cyanobacterium, Synechococcus sp. PCC 7942, and in Arabidopsis plants. It was found that the coexpression of N-methyltransferase genes in Synechococcus caused accumulation of a significant amount of betaine and conferred salt tolerance to a freshwater cyanobacterium sufficient for it to become capable of growth in seawater. Arabidopsis plants expressing N-methyltransferase genes also accumulated betaine to a high level in roots, stems, leaves, and flowers and improved seed yield under stress conditions. Betaine levels were higher than those produced by choline-oxidizing enzymes. These results demonstrate the usefulness of glycine N-methyltransferase genes for the improvement of abiotic stress tolerance in crop plants.
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PMID:Genes for direct methylation of glycine provide high levels of glycinebetaine and abiotic-stress tolerance in Synechococcus and Arabidopsis. 1566 84

To elucidate influences on the tocopherol biosynthesis in cyanobacteria, wild type and mutant cells of a putative methyltransferase in tocopherol and plastoquinone biosynthesis of Synechocystis sp. PCC 6803 were grown under different conditions. The vitamin E content of cells grown under different light regimes, photomixotrophic or photoautotrophic conditions and varying carbon dioxide supplies were compared by HPLC measurements. The tocopherol levels in wild type cells increased under higher light conditions and low carbon dioxide supply. Photomixotrophic growth led to lower vitamin E amounts in the cells compared to those grown photoautotrophically. We were able to segregate a homozygous deltasll0418 mutant under photoautotrophic conditions. In contrast to former suggestions in the literature the deletion of this gene is not lethal under photomixotrophic conditions and the influence on tocopherol and plastoquinone amounts is diminutive. The methyltransferase encoded by the gene sll0418 is not essential either for tocopherol or plastoquinone synthesis.
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PMID:Influences on tocopherol biosynthesis in the cyanobacterium Synechocystis sp. PCC 6803. 1600

Cyanobacteria produce phycobilisomes, which are macromolecular light-harvesting complexes mostly assembled from phycobiliproteins. Phycobiliprotein beta subunits contain a highly conserved gamma-N-methylasparagine residue, which results from the posttranslational modification of Asn71/72. Through comparative genomic analyses, we identified a gene, denoted cpcM, that (i) encodes a protein with sequence similarity to other S-adenosylmethionine-dependent methyltransferases, (ii) is found in all sequenced cyanobacterial genomes, and (iii) often occurs near genes encoding phycobiliproteins in cyanobacterial genomes. The cpcM genes of Synechococcus sp. strain PCC 7002 and Synechocystis sp. strain PCC 6803 were insertionally inactivated. Mass spectrometric analyses of phycobiliproteins isolated from the mutants confirmed that the CpcB, ApcB, and ApcF were 14 Da lighter than their wild-type counterparts. Trypsin digestion and mass analyses of phycobiliproteins isolated from the mutants showed that tryptic peptides from phycocyanin that included Asn72 were also 14 Da lighter than the equivalent peptides from wild-type strains. Thus, CpcM is the methyltransferase that modifies the amide nitrogen of Asn71/72 of CpcB, ApcB, and ApcF. When cells were grown at low light intensity, the cpcM mutants were phenotypically similar to the wild-type strains. However, the mutants were sensitive to high-light stress, and the cpcM mutant of Synechocystis sp. strain PCC 6803 was unable to grow at moderately high light intensities. Fluorescence emission measurements showed that the ability to perform state transitions was impaired in the cpcM mutants and suggested that energy transfer from phycobiliproteins to the photosystems was also less efficient. The possible functions of asparagine N methylation of phycobiliproteins are discussed.
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PMID:CpcM posttranslationally methylates asparagine-71/72 of phycobiliprotein beta subunits in Synechococcus sp. strain PCC 7002 and Synechocystis sp. strain PCC 6803. 1846 97

The coding sequence of the cyanobacterium Synechocystis sp. strain PCC 6803 slr0095 gene was cloned and functionally expressed in Escherichia coli. The corresponding enzyme was classified as a cation- and S-adenosyl-l-methionine-dependent O-methyltransferase (SynOMT), consistent with considerable amino acid sequence identities to eukaryotic O-methyltransferases (OMTs). The substrate specificity of SynOMT was similar with those of plant and mammalian CCoAOMT-like proteins accepting a variety of hydroxycinnamic acids and flavonoids as substrates. In contrast to the known mammalian and plant enzymes, which exclusively methylate the meta-hydroxyl position of aromatic di- and trihydroxy systems, Syn-OMT also methylates the para-position of hydroxycinnamic acids like 5-hydroxyferulic and 3,4,5-trihydroxycinnamic acid, resulting in the formation of novel compounds. The x-ray structure of SynOMT indicates that the active site allows for two alternative orientations of the hydroxylated substrates in comparison to the active sites of animal and plant enzymes, consistent with the observed preferred para-methylation and position promiscuity. Lys(3) close to the N terminus of the recombinant protein appears to play a key role in the activity of the enzyme. The possible implications of these results with respect to modifications of precursors of polymers like lignin are discussed.
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PMID:Functional and structural characterization of a cation-dependent O-methyltransferase from the cyanobacterium Synechocystis sp. strain PCC 6803. 1850 65

The euryhaline, unicellular cyanobacterium Synechococcus sp. strain PCC 7002 produces the dicyclic aromatic carotenoid synechoxanthin (chi,chi-caroten-18,18'-dioic acid) as a major pigment (>15% of total carotenoid) and when grown to stationary phase also accumulates small amounts of renierapurpurin (chi,chi-carotene) (J. E. Graham, J. T. J. Lecomte, and D. A. Bryant, J. Nat. Prod. 71:1647-1650, 2008). Two genes that were predicted to encode enzymes involved in the biosynthesis of synechoxanthin were identified by comparative genomics, and these genes were insertionally inactivated in Synechococcus sp. strain PCC 7002 to verify their function. The cruE gene (SYNPCC7002_A1248) encodes beta-carotene desaturase/methyltransferase, which converts beta-carotene to renierapurpurin. The cruH gene (SYNPCC7002_A2246) encodes an enzyme that is minimally responsible for the hydroxylation/oxidation of the C-18 and C-18' methyl groups of renierapurpurin. Based on observed and biochemically characterized intermediates, a complete pathway for synechoxanthin biosynthesis is proposed.
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PMID:The Biosynthetic pathway for synechoxanthin, an aromatic carotenoid synthesized by the euryhaline, unicellular cyanobacterium Synechococcus sp. strain PCC 7002. 1884 28

The second committed step in chlorophyll biosynthesis is the transfer of a methyl group from S-adenosyl-L-methionine (SAM) to magnesium protoporphyrin IX (MgP) forming MgP monomethylester (MgPME). This reaction is catalyzed by the enzyme MgP methyltransferase (ChlM). Previous investigation of this enzyme has involved the use of time-consuming techniques requiring separation of products from substrates. More recent methyltransferase studies use coupling enzymes to monitor changes in absorption/fluorescence for the measurement of activity. However, due to the spectral properties of porphyrins, many of these assays are unsuitable for analysis of the catalytic properties of ChlM. Here we report the successful development of a coupled, continuous spectrophotometric assay to measure the activity of ChlM. The product of the methyltransferase reaction, S-adenosyl-l-homocysteine (SAH), is converted into adenine and then hypoxanthine by the recombinant coupling enzymes SAH nucleosidase and adenine deaminase, respectively. The appearance of hypoxanthine results in a decrease in absorbance at 265nm. The utility of this assay was shown by the characterization of ChlM from the cyanobacterium Synechocystis sp. PCC 6803. Kinetic parameters obtained support data acquired using the discontinuous HPLC-based assay and provide further evidence for the stimulation of ChlM by the H subunit of magnesium chelatase (ChlH).
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PMID:An enzyme-coupled continuous spectrophotometric assay for magnesium protoporphyrin IX methyltransferases. 1964 14

Mycosporine-like amino acids (MAAs) are a family of more than 20 compounds having absorption maxima between 310 and 362 nm. These compounds are well known for their UV-absorbing/screening role in various organisms and seem to have evolutionary significance. In the present investigation we tested four cyanobacteria, e.g., Anabaena variabilis PCC 7937, Anabaena sp. PCC 7120, Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 6301, for their ability to synthesize MAA and conducted genomic and phylogenetic analysis to identify the possible set of genes that might be involved in the biosynthesis of these compounds. Out of the four investigated species, only A. variabilis PCC 7937 was able to synthesize MAA. Genome mining identified a combination of genes, YP_324358 (predicted DHQ synthase) and YP_324357 (O-methyltransferase), which were present only in A. variabilis PCC 7937 and missing in the other studied cyanobacteria. Phylogenetic analysis revealed that these two genes are transferred from a cyanobacterial donor to dinoflagellates and finally to metazoa by a lateral gene transfer event. All other cyanobacteria, which have these two genes, also had another copy of the DHQ synthase gene. The predicted protein structure for YP_324358 also suggested that this product is different from the chemically characterized DHQ synthase of Aspergillus nidulans contrary to the YP_324879, which was predicted to be similar to the DHQ synthase. The present study provides a first insight into the genes of cyanobacteria involved in MAA biosynthesis and thus widens the field of research for molecular, bioinformatics and phylogenetic analysis of these evolutionary and industrially important compounds. Based on the results we propose that YP_324358 and YP_324357 gene products are involved in the biosynthesis of the common core (deoxygadusol) of all MAAs.
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PMID:Genome mining of mycosporine-like amino acid (MAA) synthesizing and non-synthesizing cyanobacteria: A bioinformatics study. 1987 48


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