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

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

VF1 is a DNA-binding protein from the cyanobacterium Anabaena sp. strain PCC 7120. VF1 was originally identified on the basis of its binding affinity to the upstream region of xisA, which encodes a heterocyst-specific site-specific recombinase. VF1 also binds to the glnA, rbcL, and nifH promoters in vitro, suggesting that VF1 interacts with genes expressed in both vegetative cells and heterocysts. The role of VF1 in regulating gene expression in PCC 7120 is unknown. As a step towards the goal of understanding the role of VF1 in regulating gene expression, we have cloned the bifA gene by using a genetic selection strategy. bifA encodes a protein, BifA, that has chromatographic and DNA-binding properties indistinguishable from those of VF1. The cloning strategy was based on a transcriptional interference assay in which a strong synthetic promoter, conII, interferes with the expression of an aadA gene, which provides resistance to spectinomycin and streptomycin (S. J. Elledge, P. Sugiono, L. Guarente, and R. W. Davis, Proc. Natl. Acad. Sci. USA 86:3689-3693, 1989). A selection plasmid, pAM994, which has the conII promoter negatively regulated by a VF1-binding site, was used to enrich for VF1-producing clones from an expression library containing PCC 7120 DNA fragments. Mobility shift assays were used to identify a 672-bp open reading frame that encoded VF1-like binding activity. The deduced BifA amino acid sequence shows 77% identity to NtcA, which is a global regulator involved in nitrogen control in Synechococcus sp. strain PCC 7942. Both BifA and NtcA belong to the cyclic AMP receptor protein (CRP) family of prokaryotic regulatory proteins. Genes similar to envM, hisB, and ORF60-5 were found near the bifA gene.
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PMID:Anabaena sp. strain PCC 7120 bifA gene encoding a sequence-specific DNA-binding protein cloned by in vivo transcriptional interference selection. 839 34

In Synechococcus PCC 7942 cells, two catalytic fructose-1,6-bisphosphatase isoenzymes, designated F-I and F-II, have been resolved by chromatography on a HiLoad 26/10 Q Sepharose column at 0.24 and 0.34 M of NaCl, respectively; the former represented the major part of the total extractable enzyme activity. F-I has been purified to electrophoretic homogeneity from the cells. F-I and F-II had respective molecular masses of 160 and 150 kDa and each enzyme was composed of four identical subunits. F-I hydrolyzed both fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate, whereas F-II hydrolyzed only fructose 1,6-bisphosphate. The apparent Km values of F-I and F-II for fructose 1,6-bisphosphate were 52 +/- 4.5 and 25 +/- 1.5 microM, respectively. F-I was inhibited by AMP with a Ki value of 0.26 mM, but F-II was not affected by AMP. The F-I failed to cross-react by Western blotting with the antibody raised against F-II; similarly, the F-II did not react with the F-I antibody. The genes encoding F-I and F-II were cloned from the chromosomal DNA of Synechococcus PCC 7942. A 1068-bp open reading frame, encoding F-I of 356 amino acid residues (approx molecular mass of 38.3 kDa) was observed. The nucleotide sequence of the F-II gene showed an open reading frame of 1017 bp that encodes a protein of 339 amino acid residues (approx molecular mass of 37.2 kDa). The recombinant enzymes expressed in Escherichia coli as well as the native enzymes of F-I and F-II from Synechococcus PCC 7942 cells were resistant to 1 mM hydrogen peroxide unlike the light-activated higher plant chloroplast enzymes.
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PMID:Molecular characterization and resistance to hydrogen peroxide of two fructose-1,6-bisphosphatases from Synechococcus PCC 7942. 883 35

Adenylate cyclase genes, designated cyaA, cyaB1, cyaB2, cyaC, and cyaD, were isolated from the filamentous cyanobacterium Anabaena sp. strain PCC 7120 by complementation of a strain of Escherichia coli defective for the presence of cya. These genes encoded polypeptides consisting of 735, 859, 860, 1,155, and 546 amino acid residues, respectively. Deduced amino acid sequences of the regions near the C-terminal ends of these cya genes were similar to those of catalytic domains of eukaryotic adenylate cyclases. The remaining part of each cya gene towards its N-terminal end showed a characteristic structure. CyaA had two putative membrane-spanning regions. Both CyaB1 and CyaB2 had regions that were very similar to the cyclic GMP (cGMP)-binding domain of cGMP-stimulated cGMP phosphodiesterase. CyaC consisted of four distinct domains forming sequentially from the N terminus: a response regulator-like domain, a histidine kinase-like domain, a response regulator-like domain, and the catalytic domain of adenylate cyclase. CyaD contained the forkhead-associated domain in its N-terminal region. Expression of these genes was examined by reverse transcription-PCR. The transcript of cyaC was shown to be predominant in this cyanobacterium. The cellular cyclic AMP level in the disruptant of the cyaC mutant was much lower than that in the wild type.
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PMID:Isolation and characterization of multiple adenylate cyclase genes from the cyanobacterium Anabaena sp. strain PCC 7120. 917 4

We have previously described that Synechococcus PCC 7942 cells contain two fructose-1,6-bisphosphatase isozymes, designated F-I and F-II the former belongs to a new type of fructose-1,6-bisphosphatase, while the latter is a typical enzyme similar to the cytosolic and chloroplastic forms from eukaryotic cells [Tamoi et al., Arch. Biochem. Biophys., 334, 1996, 27-36]. The genes of F-I and F-II were found in three species of cyanobacteria, Synechocystis PCC 6803, Anabaena 7120, and Plectonema boryanum according to the results of Southern hybridization with a probe from the S. 7942 F-I and F-II genes. In Western blotting, antibody raised against the S. 7942 F-I cross-reacted with a protein band corresponding to the F-I in each crude extract from cyanobacterial cells, whereas the antibody against F-II failed to cross-react with any protein band corresponding to the F-II. In cyanobacterial cells, only one form of F-I has been resolved by ion-exchange chromatography at same concentration of NaCl as shown in the F-I of S. 7942. The F-I from Synechocystis 6803 has been purified to electrophoretic homogeneity. The enzyme hydrolyzed both fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate. The apparent K(m) values of the enzyme for fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate were 57 +/- 2.4 and 180 +/- 6.3 microM, respectively. The enzyme activity was inhibited by AMP with a Ki value of 0.57 +/- 0.03 mM for fructose 1,6-bisphosphate and 0.35 +/- 0.02 mM for sedoheptulose 1,7-bisphosphate. The enzyme showed a molecular mass of 168 kDa which was composed of four identical subunits. The activities of FBPase and SBPase from the F-I were resistant to hydrogen peroxide up to 1 mM. The nucleotide sequence of the S. 6803 F-I gene showed an open reading frame of 1164 bp that encoded a protein of 388 amino acid residues (approx. molecular mass of 41.6 kDa). The deduced amino acid sequences had homologous sequences with the S. 7942 F-I.
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PMID:Acquisition of a new type of fructose-1,6-bisphosphatase with resistance to hydrogen peroxide in cyanobacteria: molecular characterization of the enzyme from Synechocystis PCC 6803. 960 37

Synechocystis strain PCC 6803 exhibits similar levels of cyclic AMP (cAMP) and cyclic GMP (cGMP). A thorough analysis of its genome showed that Cya2 (Sll0646) has all the sequence determinants required in terms of activity and purine specificity for being a guanylyl cyclase. Insertional mutagenesis of cya2 caused a marked reduction in cGMP content without altering the cAMP content. Thus, Cya2 represents the first example of a prokaryotic guanylyl cyclase.
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PMID:Synechocystis strain PCC 6803 cya2, a prokaryotic gene that encodes a guanylyl cyclase. 1085 Oct 2

The devH gene was identified in a screen for Anabaena sp. strain PCC 7120 sequences whose transcripts increase in abundance during a heterocyst development time course. The product of devH contains a helix-turn-helix motif similar to the DNA binding domain of members of the cyclic AMP receptor protein family, and the protein is most closely related to the cyanobacterial transcriptional activator NtcA. devH transcripts are barely detectable in vegetative cells and are induced approximately fivefold after nitrogen starvation. This induction is absent in the two developmental mutants hetR and ntcA. The gene is expressed as monocistronic transcripts with multiple 5' termini, and the approximately 500-bp region 5' to devH was shown to have promoter activity in vivo. The devH gene was insertionally inactivated by the integration of plasmid sequences within the open reading frame. Nitrogen starvation of the devH mutant induces heterocysts of wild-type morphology, but the mutant is inviable in the absence of fixed nitrogen and unable to reduce acetylene aerobically.
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PMID:Characterization of devH, a gene encoding a putative DNA binding protein required for heterocyst function in Anabaena sp. strain PCC 7120. 1085 91

Pyruvate kinase (PK) from the cyanobacterium Synechococcus PCC 6301 was purified 1,300-fold to electrophoretic homogeneity and a final specific activity of 222 micromol of pyruvate produced/min/mg of protein. The enzyme was shown to have a pI of 5.7 and to exist as a 280-kDa homotetramer composed of 66-kDa subunits. This PK appears to be immunologically related to Bacillus PK and a green algal chloroplast PK, but not to rabbit muscle PK, or vascular plant cytosolic and plastidic PKs. The N-terminal amino acid sequence of the Synechococcus PK exhibited maximal (67%) identity with the corresponding region of a putative PK-A sequence deduced from the genome of the cyanobacterium, Synechocystis PCC 6803. Synechococcus PK was relatively heat-labile and displayed a broad pH optimum around pH 7.0. Its activity was not influenced by K(+), but required high concentrations of Mg(2+), and was relatively nonspecific with respect to the nucleoside diphosphate substrate. Potent allosteric regulation by various effectors was observed (activators: hexose monophosphates, ribose 5-phosphate, glycerol 3-phosphate, and AMP; inhibitors: fructose 1,6-bisphosphate, inorganic phosphate, ATP, and several Krebs' cycle intermediates). The enzyme exhibited marked positive cooperativity for phosphoenolpyruvate, which was eliminated or reduced by the presence of the allosteric activators. The results are discussed in terms of the phylogeny and probable central role of PK in the control of cyanobacterial glycolysis.
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PMID:Structural and regulatory properties of pyruvate kinase from the Cyanobacterium synechococcus PCC 6301. 1129 47

The transcription factor of the cyclic AMP receptor protein/FNR family, NtcA, and the P(II) signaling protein play central roles in global nitrogen control in cyanobacteria. A dependence on P(II) for NtcA-regulated transcription, however, has not been observed. In the present investigation, we examined alterations in gene expression following nitrogen deprivation in Synechococcus elongatus strain PCC 7942 and specifically the roles of NtcA and P(II). Global changes in de novo protein synthesis following combined-nitrogen deprivation were visualized by in vivo [(35)S]methionine labeling and two-dimensional polyacrylamide gel electrophoresis analysis. Nearly all proteins whose synthesis responded specifically to combined-nitrogen deprivation in wild-type cells of S. elongatus failed to respond in P(II)- and NtcA-deficient mutants. One of the proteins whose synthesis was down-regulated in a P(II)- and NtcA-dependent manner was RbcS, the small subunit of RubisCO. Quantification of its mRNA revealed that the abundance of the rbcLS transcript following combined-nitrogen deprivation rapidly declined in wild-type cells but not in P(II) and NtcA mutant cells. To investigate further the relationship between P(II) and NtcA, fusions of the promotorless luxAB reporter genes to the NtcA-regulated glnB gene were constructed and these constructs were used to transform wild-type cells and P(II)(-) and NtcA(-) mutants. Determination of bioluminescence under different growth conditions showed that NtcA represses gene expression in the presence of ammonium in a P(II)-independent manner. By contrast, NtcA-dependent activation of glnB expression following combined-nitrogen deprivation was impaired in the absence of P(II). Together, these results suggest that under conditions of combined-nitrogen deprivation, the regulation of NtcA-dependent gene expression requires the P(II) signal transduction protein.
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PMID:Signal transduction protein P(II) is required for NtcA-regulated gene expression during nitrogen deprivation in the cyanobacterium Synechococcus elongatus strain PCC 7942. 1267 Sep 83

Activities of glucokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucose isomerase, phosphofructokinase (PFK), enolase, pyruvate kinase (PK) and phosphoenolpyruvate (PEP) carboxylase were determined in extracts of photoautotrophic, mixotrophic, and heterotrophic cultures of Synechocystis sp. PCC 6803. Annotated genomes of Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120 were analyzed for the respective predicted physical properties of each enzyme investigated here. Enzymatic activity was largely unaffected by nutritional mode, with the exception of glucokinase and PK whose activities were significantly elevated in heterotrophic cultures of Synechocystis sp. PCC 6803. PFK activity was insensitive to bacterial PFK-A (allosteric) effectors such as PEP, implying that Synechocystis PFK should be classified as a PFK-B (non-allosteric). Immunoblot and kinetic studies indicated that irrespective of nutritional mode, the Synechocystis PK corresponds to a PK-A (AMP activated) rather than PK-F (fructose-1,6-bisphosphate activated).
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PMID:From genome to enzyme: analysis of key glycolytic and oxidative pentose-phosphate pathway enzymes in the cyanobacterium Synechocystis sp. PCC 6803. 1288 4


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