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

The cyanobacterial ntcA gene encodes a DNA-binding protein that belongs to the Crp family of bacterial transcriptional regulators. In this work, we describe the isolation of an ntcA insertional mutant of the dinitrogen-fixing, heterocyst-forming cyanobacterium Anabaena sp. PCC 7120. The Anabaena ntcA mutant was able to use ammonium as a source of nitrogen for growth, but was unable to assimilate atmospheric nitrogen (dinitrogen) or nitrate. Nitrogenase and enzymes of the nitrate reduction system were not synthesized in the ntcA mutant under derepressing conditions, and glutamine synthetase levels were lower in the mutant than in the wild-type strain. In the ntcA mutant, in response to removal of ammonium, accumulation of mRNA of the genes encoding nitrogenase (nifHDK), nitrite reductase (nir, the first gene of the nitrate assimilation operon), and glutamine synthetase (glnA) was not observed. A transcription start point of the Anabaena glnA gene (corresponding to RNAl), that has been shown to be used preferentially after nitrogen step-down, was not used in the ntcA insertional mutant. Heterocyst development (which is necessary for the aerobic fixation of dinitrogen) and induction of hetR (a regulatory gene that is required for heterocyst development) were also impaired in the ntcA mutant. These results showed that the ntcA gene product, NtcA, is required in Anabaena sp. PCC 7120 for the expression of genes encoding proteins involved in the assimilation of nitrogen sources alternative to ammonium including dinitrogen and nitrate, and that the process of heterocyst development is also controlled by NtcA.
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PMID:Requirement of the regulatory protein NtcA for the expression of nitrogen assimilation and heterocyst development genes in the cyanobacterium Anabaena sp. PCC 7120. 753 71

The Anabaena sp. strain PCC 7120 ntcA (bifA) gene encodes a sequence-specific DNA-binding protein, NtcA (BifA, VF1) that interacts with the upstream region of several genes, including glnA, xisA, rbcL, and nifH. We have constructed a ntcA null mutant by interrupting the gene with an omega Spr-Smr cassette. The ntcA mutant was not able to grow with nitrate or atmospheric dinitrogen as the sole nitrogen source but could be grown on medium containing ammonium. The ntcA mutant was unable to form heterocysts and did not rearrange the nifD or fdxN elements after induction on a medium lacking combined nitrogen. Northern (RNA) analysis of ntcA in the wild-type strain during nitrogen stepdown showed a peak of ntcA message at an early stage (12 h) of heterocyst induction. Complementation of the ntcA mutant with a DNA fragment containing the ntcA gene and 251 bp of upstream sequence on a shuttle vector restored a wild-type phenotype; however, a similar construction containing 87 bp of upstream sequence only partially restored the phenotype. Northern analysis of RNA samples isolated from ammonium-grown cultures of the ntcA mutant showed reduced amounts of glnA message and the absence of a 1.7-kb transcript. In the wild type, the 1.7-kb transcript represents the majority of glnA transcripts after nitrogen stepdown. The ntcA mutant showed a normal pattern of rbcLS messages under these growth conditions.
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PMID:Anabaena sp. strain PCC 7120 ntcA gene required for growth on nitrate and heterocyst development. 791 26

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

Nitrite, either exogenously supplied or endogenously generated by nitrate reduction, activates transcription of the nitrate assimilation operon (nirA-nrtABCD-narB) in Synechococcus sp. strain PCC 7942 cells treated with L-methionine-DL-sulfoximine (an inhibitor of glutamine synthetase), in which there is no negative feedback resulting from fixation of the ammonium generated by nitrite reduction (Kikuchi et al., J. Bacteriol. 178:5822-5825, 1996). Other transcription units related to nitrogen assimilation, i.e., the nirB-ntcB operon, glnA, and ntcA, were not activated by nitrite. Nitrite did not activate nirA operon transcription in a mutant with a deletion of ntcB, an ammonium-repressible gene encoding a LysR-type DNA-binding protein. Introduction of plasmid-borne ntcB into the ntcB deletion mutant restored the response of the cells to nitrite, indicating that NtcB activates the nirA operon in response to nitrite. Supplementation of nitrite or nitrate to nitrogen-starved cultures of the wild-type strain, but not of the ntcB deletion mutant, caused activation of the nirA operon without L-methionine-DL-sulfoximine treatment of the cells. The results suggested that the positive-regulation mechanism of nirA operon transcription plays a role in rapid adaptation of nitrogen-starved cells to changing availability of nitrate and nitrite.
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PMID:Involvement of NtcB, a LysR family transcription factor, in nitrite activation of the nitrate assimilation operon in the cyanobacterium Synechococcus sp. strain PCC 7942. 924 51

In Synechococcus sp. strain PCC 6301, ribosomal RNA (rRNA) synthesis occurs at specific times during the growth cycle in the light. When light-grown cultures are placed in the dark, rRNA synthesis and cell division stop abruptly. It is shown here that a partially purified DNA-binding protein binds downstream of the rRNA operon (rrnA) P1 promoter in the light but not in the dark. When the DNA binding protein is added to in vitro transcription assays, run-off transcripts are produced in the light but not, under dark conditions. The results indicate that a light-activated regulatory molecule is involved in stimulating rRNA synthesis during the normal cell growth cycle of Synechococcus in the light.
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PMID:A light-activated DNA-binding factor stimulates transcription of the rrnA operon in the cyanobacterium Synechococcus sp. PCC 6301. 982 29

The Synechococcus sp. strain PCC 7942 dpsA gene encodes a stress-inducible DNA-binding protein whose transcription increases in the stationary phase. Such transcription is likely under the control of an alternative sigma factor. Our current work indicated that dpsA transcription is also important under metal-ion limitation, because dpsA mRNA levels increased 12-fold under low-iron conditions, and that dpsA function is essential for growth under iron-limiting conditions. Promoter activity of the dpsA-promoter-lacZ reporter gene constructs implied that a region of dyad symmetry centered 28 nucleotides from the transcription start is required for metal-dependent repression, as judged by the level of lacZ induction following treatment of cultures with the chelator 2,2'-dipyridyl. This potential operator sequence is distinct from the site recognized by the cyanobacterial Fur repressor homologue. No other nutrient stresses (nitrogen, sulfur, phosphorus) yielded the high level of induction seen following chelator treatment. These studies suggest that there may be more than one class of metal-dependent repressor in cyanobacteria.
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PMID:Growth phase and metal-dependent regulation of the dpsA gene in Synechococcus sp. strain PCC 7942, USA. 1089 14

The relevance of pilus-related genes to motility, pilus structure on the cell surface and competency of natural transformation was studied by gene disruption analysis in the unicellular motile cyanobacterium Synechocystis: sp. PCC 6803. The genes disrupted in this study were chosen as related to the pil genes for biogenesis of the type IV pili in a Gram-negative bacterium Pseudomonas aeruginosa. It was found that motility of Synechocystis cells was lost in the mutants of slr0063, slr1274, slr1275, slr1276, slr1277 and sll1694 together with a simultaneous loss of the thick pili on the cell surface. Competency of the natural transformation was lost in the mutants listed above and slr0197-disruptant. The gene slr0197 was previously predicted as a competence gene by a search with sequence-independent DNA-binding structure [Yura et al. (1999) DNA Res. 6: 75]. It was suggested that both DNA uptake for natural transformation and motility are mediated by a specific type IV-like pilus structure, while a putative DNA-binding protein encoded by slr0197 is additionally required for the DNA uptake. Based on the homology with the pil genes in P: aeruginosa, slr0063, slr1274, slr1275, slr1276, slr1277 and sll1694 were designated pilB1, pilM, pilN, pilO, pilQ and pilA1, respectively. The gene slr0197 was designated comA.
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PMID:Mutational analysis of genes involved in pilus structure, motility and transformation competency in the unicellular motile cyanobacterium Synechocystis sp. PCC 6803. 1115 45

Fur (ferric uptake regulator) protein is a DNA-binding protein which regulates iron-responsive genes. Recombinant Fur from the nitrogen-fixing cyanobacterium Anabaena PCC 7119 has been purified and characterized, and polyclonal antibodies obtained. The experimental data show that Fur from Anabaena dimerizes in solution with the involvement of disulphide bridges. Cross-linking experiments and MALDI-TOF (matrix-assisted laser desorption/ionization time of flight) MS also show several oligomerization states of Fur, and the equilibrium of these forms depends on protein concentration and ionic strength. In intact recombinant Fur, four cysteine residues out of five were inert towards DTNB [5,5'-dithiobis-(2-nitrobenzoic acid)], and their modification required sodium borohydride. Metal analysis and electrospray ionization MS revealed that neither zinc nor other metals are present in this Fur protein. Purified recombinant Fur bound to its own promoter in gel-shift assays. Fur was shown to be a constitutive protein in Anabaena cells, with no significant difference in its expression in cells grown under iron-sufficient compared with iron-deficient conditions.
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PMID:Biochemical analysis of the recombinant Fur (ferric uptake regulator) protein from Anabaena PCC 7119: factors affecting its oligomerization state. 1201 14

An iron-rich protein was isolated from the Archaeon Halobacterium salinarum sharing a sequence identity of 35% with the starvation-induced DNA-binding protein, DpsA, of Synechecoccus sp. PCC 7942. It consists of 20 kDa subunits, forming a dodecameric structure. The protein exhibits a ferric iron loading of up to 103 Fe ions/mol of holoprotein. CD spectra are consistent with an alpha-helical contribution of 58%. The UV/visible spectrum provides no evidence for the presence of haem groups. This protein exhibits features of a non-haem-type bacterial ferritin although it shares only little sequence homology with non-haem bacterial ferritin.
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PMID:Characterization of a non-haem ferritin of the Archaeon Halobacterium salinarum, homologous to Dps (starvation-induced DNA-binding protein). 1219 73

HetR plays a key role in regulation of heterocyst differentiation. When the Cys-48 residue of the HetR from Anabaena sp. PCC 7120 was replaced with an Ala residue, the mutant HetR (HetR(C48A)) could not dimerize, indicating that HetR forms a homodimer through a disulfide bond. The Anabaena strain C48, containing the hetRc48a gene, could not produce HetR homodimer and failed to form heterocyst. We show that HetR is a DNA-binding protein and that its homodimerization is required for the DNA binding. HetR binds the promoter regions of hetR, hepA, and patS, suggesting a direct control of the expression of these genes by HetR. We present evidence that shows that the up-regulation of patS and hetR depends on DNA binding by HetR dimer. The pentapeptide RGSGR, which is present at the C terminus of PatS and blocks heterocyst formation, inhibits the DNA binding of HetR and prevents hetR up-regulation.
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PMID:HetR homodimer is a DNA-binding protein required for heterocyst differentiation, and the DNA-binding activity is inhibited by PatS. 1505 91


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