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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Rhizobium meliloti two-component system FixL/FixJ regulates nitrogen fixation in response to oxygen during symbiosis. FixJ is a transcriptional activator of critical nif and fix promoters; its in vivo activity is enhanced by FixL in diminished oxygen (David, M., Daveran, M.-L., Batut, J., Dedieu, A., Domergue, O., Ghai, J., Hertig, C., Boistard, P., and Kahn, D. (1988) Cell 54, 671-683; Virts, E. L., Stanfield, S. W., Helinski, D. R., and Ditta, G. S. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 3062-3065). FixL* is a soluble truncated version of FixL that contains heme; it catalyzes its autophosphorylation and the phosphorylation of FixJ (Gilles-Gonzalez, M.A., Ditta, G. S., and Helinski, D. R. (1991) Nature 350, 170-172). We examine the kinetics of phosphoryl transfer in this system. First, there is a slow autophosphorylation of FixL* in ATP that is accelerated in the absence of oxygen and in the presence of Mn2+. This reaction is reversible, i.e. phospho-FixL* reacts with ADP to generate ATP. Since the reverse reaction is faster, most FixL* is not phosphorylated at equilibrium. Next, there is a rapid phosphoryl transfer directly from phospho-FixL* to FixJ that is unaffected by oxygen. Finally, phospho-FixJ is hydrolyzed; this reaction is very fast and not controlled by oxygen. We propose that in addition to the oxygen signal previously noted in vivo, energy charge and manganese concentration are also indicators of symbiosis that impact on the induction of nitrogen fixation genes.
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PMID:Regulation of the kinase activity of heme protein FixL from the two-component system FixL/FixJ of Rhizobium meliloti. 839 56

Mutations truncating as many as 143 C-terminal residues from the transcriptional activator encoded by the areA gene, mediating nitrogen metabolite repression in Aspergillus nidulans, do not significantly reduce the ability of the areA product to activate expression of most genes under areA control. Such mutations can even have a gain-of-function, derepressed phenotype, consistent with a critical role for this region in modulating the activity of the areA protein. However, expression of a few genes under areA control is substantially impaired by such C-terminal truncations, indicating that regions of an activator protein can play differing roles in the control of different structural genes. This underlines the advantages of being able to monitor effects of areA mutations on expression of large numbers of structural genes. Additionally, it is shown that truncation of as many as 153 C-terminal residues, virtually all amino acids C-terminal to the DNA-binding region, is compatible with retention of some areA function.
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PMID:C-terminal truncation of the transcriptional activator encoded by areA in Aspergillus nidulans results in both loss-of-function and gain-of-function phenotypes. 843 21

The Klebsiella aerogenes nac gene, whose product is necessary for nitrogen regulation of a number of operons, was identified and its DNA sequence determined. The nac sequence predicted a protein a 305 amino acids with a strong similarity to members of the LysR family of regulatory proteins, especially OxyR from Escherichia coli. Analysis of proteins expressed in minicells showed that nac is a single-gene operon whose product has an apparent molecular weight of about 32 kDa as measured in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immediately downstream from nac is a two-gene operon, the first gene of which encodes another member of the LysR family. Upstream from nac is a tRNAAsn gene transcribed divergently from nac. About 60 bp upstream from the nac open reading frame lies a sequence nearly identical to the consensus for sigma 54-dependent promoters, with the conserved GG and GC nucleotides at -26 and -14 relative to the start of transcription. About 130 bp farther upstream (at -153 relative to the start of transcription) is a sequence nearly identical to the transcriptional activator NTRC-responsive enhancer consensus. Another weaker NTRC-binding site is located adjacent to this site (at -133 relative to the start of transcription). Thus, we propose that nac is transcribed by RNA polymerase carrying sigma 54 in response to the nitrogen regulatory (NTR) system. A transposon located between the promoter and the nac ORF prevented NTR-mediated expression of nac, supporting this identification of the promoter sequence. The insertion of over 5 kb of transposon DNA between the enhancer and its target promoter had only a weak effect on enhancer-mediated regulation, suggesting that enhancers may be able to act at a considerable distance on the bacterial chromosome.
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PMID:The nac (nitrogen assimilation control) gene from Klebsiella aerogenes. 845 53

The NIFA protein activates transcription of nitrogen fixation (nif) operons by the sigma 54-holoenzyme form of RNA polymerase. We purified active NIFA from Klebsiella pneumoniae in the form of a maltose-binding protein (MBP)-NIFA fusion; proteolytic release of MBP yielded inactive and insoluble NIFA. MBP-NIFA activated transcription from the nifHDK promoter in a purified transcription system. Like the related transcriptional activator NTRC, MBP-NIFA catalyzed the ATP-dependent isomerization of closed complexes between sigma 54-holoenzyme and a promoter to open complexes. MBP-NIFA had a broader nucleotide specificity than NTRC, being able to utilize pyrimidine in addition to purine nucleoside triphosphates. Both MBP-NIFA and a purified C-terminal fragment of NIFA bound to the upstream activation sequence for the nifHDK promoter, as assessed by DNAse I footprinting. When assays were performed at 37 degrees C instead of the usual 30 degrees C, transcriptional activation, open complex formation, and DNA binding by MBP-NIFA were all abolished, consistent with the known heat lability of NIFA. However, the purified C-terminal fragment of NIFA still bound the upstream activation sequence at 37 degrees C, indicating that the function of the helix-turn-helix DNA-binding motif is not inherently heat-labile.
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PMID:Activity of purified NIFA, a transcriptional activator of nitrogen fixation genes. 846 Jan 32

In Rhizobium meliloti, transcription of the key nitrogen-fixation regulatory genes nifA and fixK is induced in response to microaerobiosis through the action of the FixL and FixJ proteins. These two proteins are sensor and regulator homologues, respectively, of a large family of bacterial two-component systems involved in sensing and responding to environmental changes. A soluble, truncated form of the membrane protein FixL, FixL*, has been shown to be a hemoprotein that phosphorylates and dephosphorylates FixJ in response to oxygen tension. Here we use an in vitro transcription system to prove that FixJ is a transcriptional activator of both nifA and fixK and that phosphorylation of FixJ markedly increases its activity. Phosphorylation was achieved either by preincubating FixJ with FixL* and ATP or by exposing FixJ to the inorganic phospho donor ammonium hydrogen phosphoramidate. Both FixJ and FixJ-phosphate formed heparin-resistant complexes under the assay conditions used. Lastly, we were able to show that anaerobiosis, in the presence of FixL* and ATP, greatly stimulates FixJ activity at the nifA promoter with either Escherichia coli or R. meliloti RNA polymerase. This use of atmospheric oxygen to control nifA transcription in vitro represents a reconstitution of a bacterial two-component signal transduction system in its entirety, from effector to ultimate target, by the use of purified components.
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PMID:Oxygen regulation of nifA transcription in vitro. 847 99

The Sym plasmid pRL1JI encodes functions for the formation of nitrogen-fixing pea root nodules by Rhizobium leguminosarum. Some of the nodulation genes are involved in recognition of chemical signals produced by the plant root, and others are required for production of chemical signals recognized by the plant. pRL1JI also contains a regulatory gene, rhiR, that is homologous to luxR, the transcriptional activator of luminescence genes in Vibrio fischeri. LuxR requires a signal compound, an autoinducer, for its activity. We have identified an R. leguminosarum autoinducer that, together with RhiR, is required to activate both the rhizosphere-expressed rhiABC operon and a growth-inhibiting function encoded by pRL1JI. This intercellular signal is an N-acylated homoserine lactone structurally related to the V. fischeri and other autoinducers. These findings indicate a new level of intercellular communication in root nodule formation.
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PMID:Cell-to-cell signaling in the symbiotic nitrogen-fixing bacterium Rhizobium leguminosarum: autoinduction of a stationary phase and rhizosphere-expressed genes. 855 Apr 55

The alternative nitrogenase of Rhodobacter capsulatus is expressed only under conditions of nitrogen and molybdenum depletion. The analysis of anfA-lacZ fusions demonstrated that this dual control occurred at the level of transcription of anfA, which encodes a transcriptional activator specific for the alternative nitrogenase. The anfA promoter was found to be activated under nitrogen-limiting conditions by NtrC in a sigma54-independent manner. In addition, anfA transcription was repressed by traces of molybdenum. This molybdenum-dependent repression of anfA was released in R. capsulatus mutants carrying either lesions in the high-affinity molybdenum uptake system (modABCD) or a double deletion of mopA and mopB, two genes encoding molybdenum-pterin-binding proteins. The expression of the molybdenum transport system itself was shown to be negatively regulated by molybdenum and, unexpectedly, to be also regulated by NtrC. This finding is in line with the presence of two tandemly arranged DNA motifs located in front of the R. capsulatus mopA-modABCD operon, which are homologous to R. capsulatus NtrC binding sites. Mapping of the transcriptional initiation sites of mopA and anfA revealed promoter sequences exhibiting significant homology to each other but no homology to known prokaryotic promoters. In addition, a conserved DNA sequence of dyad symmetry overlapping the transcriptional initiation sites of mopA and anfA was found. Deletions within this element resulted in molybdenum-independent expression of anfA, indicating that this DNA sequence may be the target of MopA/MopB-mediated repression.
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PMID:Promoters controlling expression of the alternative nitrogenase and the molybdenum uptake system in Rhodobacter capsulatus are activated by NtrC, independent of sigma54, and repressed by molybdenum. 860 77

Transcription of the three unlinked, homologous STA1-3 glucoamylase-encoding genes, involved in starch degradation by Saccharomyces cerevisiae, was previously shown to be down-regulated by the presence of STA10, acting via three upstream repression sequence regions that were identified in the STA2 promoter. Here we report the cloning and characterization of a putative transcriptional activator gene, MSS10 (multicopy suppressor of STA10), which, when present in multiple copies, overcomes STA10 repression. Deletion of MSS10, located on chromosome XV, resulted in media-specific extinction of glucoamylase synthesis. The nucleotide sequence of MSS10 is identical to three other genes from S. cerevisiae identified as: FUP1, a gene that enhances iron-limited growth; PHD2, a gene identified for its ability to induce pseudohyphal growth in diploid cells grown on nitrogen-limited media; and MSN1, a gene encoding a transcriptional activator involved in invertase regulation.
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PMID:A multicopy suppressor gene, MSS10, restores STA2 expression in Saccharomyces cerevisiae strains containing the STA10 repressor gene. 866 91

Pseudohyphal differentiation in Saccharomyces cerevisiae was first described as a response of diploid cells to nitrogen limitation. Here we report that haploid and diploid starch-degrading S. cerevisiae strains were able to switch from a yeast form to a filamentous pseudohyphal form in response to carbon limitation in the presence of an ample supply of nitrogen. Two genes, MSS10 and MUC1, were cloned and shown to be involved in pseudohyphal differentiation and invasive growth. The deletion of MSS10 resulted in extremely reduced amounts of pseudohyphal differentiation and invasive growth, whereas the deletion of MUC1 abolished pseudohyphal differentiation and invasive growth completely. Mss10 appears to be a transcriptional activator that responds to nutrient limitation and coregulates the expression of MUC1 and the STA1-3 glucoamylase genes, which are involved in starch degradation. MUC1 encodes a 1367-amino acid protein, containing several serine/threonine-rich repeats. Muc1 is a putative integral membrane-bound protein, similar to mammalian mucin-like membrane proteins that have been implicated to play a role in the ability of cancer cells to invade other tissues.
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PMID:Muc1, a mucin-like protein that is regulated by Mss10, is critical for pseudohyphal differentiation in yeast. 871 Aug 86

During denitrification, freely diffusible nitric oxide (NO) is generated for use as a terminal electron acceptor. NO is produced by nitrite reductase (Nir) and reduced to nitrous oxide by nitric oxide reductase (Nor). Using Nir and Nor-deficient mutants of Rhodobacter sphaeroides 2.4.3, we have shown that the endogenous production of NO or the addition of exogenous NO induces transcription of certain genes encoding Nir and Nor. A Nor-deficient strain was found to be capable of expressing wild type levels of nirK-lacZ and norB-lacZ fusions in medium unamended with nitrogen oxides. When this experiment is performed in the presence of hemoglobin, fusion expression is eliminated. NO and the NO-generator, sodium nitroprusside, can induce expression of both fusions in a strain lacking Nir and the consequent ability to produce NO. Sodium nitroprusside cannot induce expression of nirK-lacZ in a strain lacking the transcriptional activator NnrR (nitrite and nitric oxide reductase regulator). Addition of the cyclic nucleotides cAMP and 8-bromoguanosine-cGMP does not result in expression of either fusion. These results demonstrate that denitrifying bacteria produce NO as a signal molecule to activate expression of the genes encoding proteins required for NO metabolism.
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PMID:Requirement of nitric oxide for induction of genes whose products are involved in nitric oxide metabolism in Rhodobacter sphaeroides 2.4.3. 879 93


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