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Global Regulator (global + regulator)
Selected AbstractsComplex phenotypes of a mutant inactivated for CymR, the global regulator of cysteine metabolism in Bacillus subtilisFEMS MICROBIOLOGY LETTERS, Issue 2 2010Marie-Françoise Hullo Abstract We characterized various phenotypes of a mutant inactivated for CymR, the master regulator of cysteine metabolism in Bacillus subtilis. The deletion of cymR resulted in impaired growth in the presence of cystine and increased sensitivity to hydrogen peroxide-, disulfide-, paraquat- and tellurite-induced stresses. Estimation of metabolite pools suggested that these phenotypes could be the result of profound metabolic changes in the ,cymR mutant including an increase of the intracellular cysteine pool and hydrogen sulfide formation, as well as a depletion of branched-chain amino acids. [source] Control of nitrogen metabolism by Bacillus subtilis glutamine synthetaseMOLECULAR MICROBIOLOGY, Issue 2 2008Abraham L. Sonenshein Summary Two recent papers describe the molecular mechanism by which the activity of GlnR, the repressor of the glutamine synthetase operon in Bacillus subtilis, is stimulated by glutamine-bound (i.e. feedback-inhibited) glutamine synthetase (FBI-GS). Remarkably, FBI-GS acts as a molecular chaperone to stabilize the association of GlnR dimers with their DNA binding sites. This mechanism allows the cell to shut off synthesis of GS, and hence of glutamine, when both the enzyme and its product are in excess. FBI-GS also regulates the activity of TnrA, the global regulator of nitrogen metabolism genes, but by a very different mechanism. Thus, the same enzyme,metabolite complex has two different roles in transcriptional regulation. [source] Positive regulation of Bacillus subtilis ackA by CodY and CcpA: establishing a potential hierarchy in carbon flowMOLECULAR MICROBIOLOGY, Issue 3 2006Robert P. Shivers Summary Conversion of pyruvate to acetate via the phosphotransacetylase-acetate kinase pathway generates ATP and is a major overflow pathway under conditions of carbon and nitrogen excess. In Bacillus subtilis, this pathway is positively regulated by CcpA, a global regulator of carbon metabolism genes. Transcription of the acetate kinase gene (ackA) proved to be activated as well by a second global regulatory protein, CodY. Expression of an ackA,lacZ fusion was reduced in a codY mutant strain. CodY was found to bind in vitro to two sites in the ackA promoter region and to stimulate ackA transcription in a run-off transcription assay. This is the first known case of direct positive regulation by CodY. CodY and CcpA were found to bind to neighbouring sites and their effects were additive both in vivo and in vitro. Surprisingly, positive regulation by CodY, unlike repression, responded primarily to only one type of effector molecule. That is, branched-chain amino acids (BCAAs) served as more potent co-activators of CodY-dependent ackA transcription than did GTP. Given the roles of CcpA and CodY in regulating genes whose products determine the metabolic fate of pyruvate, these two proteins may act together to mediate a hierarchical conversion of pyruvate to its many potential products. [source] Small non-coding RNAs, co-ordinators of adaptation processes in Escherichia coli: the RpoS paradigmMOLECULAR MICROBIOLOGY, Issue 4 2003F. Repoila Summary Adaptation to the changing environment requires both the integration of external signals and the co-ordination of internal responses. Around 50 non-coding small RNAs (sRNAs) have been described in Escherichia coli; the levels of many of these vary with changing environmental conditions. This suggests that they play a role in cell adaptation. In this review, we use the regulation of RpoS (,38) translation as a paradigm of sRNA-mediated response to environmental conditions; rpoS is currently the only known gene regulated post-transcriptionally by at least three sRNAs. DsrA and RprA stimulate RpoS translation in response to low temperature and cell surface stress, respectively, whereas OxyS represses RpoS translation in response to oxidative shock. However, in addition to regulating RpoS translation, DsrA represses the translation of HNS (a global regulator of gene expression), whereas OxyS represses the translation of FhlA (a transcriptional activator), allowing the cell to co-ordinate different pathways involved in cell adaptation. Environmental cues affect the synthesis and stability of specific sRNAs, resulting in specific sRNA-dependent translational control. [source] Crystal structure of Mycobacterium tuberculosis LrpA, a leucine-responsive global regulator associated with starvation responsePROTEIN SCIENCE, Issue 1 2008Manchi C.M. Reddy Abstract The bacterial leucine-responsive regulatory protein (Lrp) is a global transcriptional regulator that controls the expression of many genes during starvation and the transition to stationary phase. The Mycobacterium tuberculosis gene Rv3291c encodes a 150-amino acid protein (designated here as Mtb LrpA) with homology with Escherichia coli Lrp. The crystal structure of the native form of Mtb LrpA was solved at 2.1 Å. The Mtb LrpA structure shows an N-terminal DNA-binding domain with a helix-turn-helix (HTH) motif, and a C-terminal regulatory domain. In comparison to the complex of E. coli AsnC with asparagine, the effector-binding pocket (including loop 100,106) in LrpA appears to be largely preserved, with hydrophobic substitutions consistent with its specificity for leucine. The effector-binding pocket is formed at the interface between adjacent dimers, with an opening to the core of the octamer as in AsnC, and an additional substrate-access channel opening to the outer surface of the octamer. Using electrophoretic mobility shift assays, purified Mtb LrpA protein was shown to form a protein,DNA complex with the lat promoter, demonstrating that the lat operon is a direct target of LrpA. Using computational analysis, a putative motif is identified in this region that is also present upstream of other operons differentially regulated under starvation. This study provides insights into the potential role of LrpA as a global regulator in the transition of M. tuberculosis to a persistent state. [source] Probing bacterial nucleoid structure with optical tweezersBIOESSAYS, Issue 3 2007Charles J. Dorman The H-NS protein is a major component of the nucleoid in Gram-negative bacterial cells. It is a global regulator of transcription that affects the expression of many genes, including virulence genes in pathogenic species. At a local level, it facilitates the formation of nucleoprotein structures that repress transcriptional promoter function. H-NS can form bridges between different DNA molecules or between different sections of the same molecule, allowing it to compact and impose structure on the nucleoid. A recent paper by Dame et al.1 reports new insights into H-NS-mediated DNA bridging that were obtained using an optical tweezers device. BioEssays 29: 212,216, 2007. © 2007 Wiley Periodicals, Inc. [source] Crystallization and preliminary crystallographic analysis of the global nitrogen regulator AmtR from Corynebacterium glutamicumACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009Kristin Hasselt AmtR, a member of the TetR family of transcription regulators, is a global regulator of nitrogen control in Corynebacterium glutamicum. Unlike other TetR-family members, which are regulated by small-molecule effectors, AmtR is regulated by a protein called GlnK. It has been shown that a GlnK trimer has to become adenylylated prior to formation of a complex with AmtR. The physiological function of AmtR has been very well studied, but structural characterization of the mechanistic aspects of AmtR-regulated transcription has yet to be accomplished. AmtR has successfully been crystallized in space group P21212, with six molecules in the asymmetric unit and unit-cell parameters a = 153.34, b = 163.10, c = 51.93,Å. Preliminary phases were obtained using Se-SAD. [source] Crystallization and preliminary X-ray characterization of a PaaX-like protein from Sulfolobus solfataricus P2ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2009Yi Cao PaaX is a global regulator of the phenylacetyl-coenzyme A catabolon that adjusts the expression of different operons to that of the paa -encoded central pathway. In this study, the PaaX-like protein from the hyperthermophilic archaeon Sulfolobus solfataricus P2 was successfully crystallized by the hanging-drop vapour-diffusion method using ammonium sulfate as a precipitant. Diffraction data were obtained to a resolution of 3.0,Å using synchrotron radiation at the Photon Factory. The crystal belonged to space group P321, with unit-cell parameters a = 86.4, b = 86.4, c = 105.5,Å. [source] Crystallization and X-ray diffraction analysis of the DNA-remodelling protein DnaD from Bacillus subtilisACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2007Sabine Schneider The DnaD protein is an essential component of the chromosome-replication machinery of the Gram-positive bacterium Bacillus subtilis and is part of the primosomal cascade that ultimately loads the replicative ring helicase DnaC onto DNA. Moreover, DnaD is a global regulator of DNA architecture, as it forms higher order nucleoprotein structures in order to open supercoiled DNA. Here, the crystallization and preliminary X-ray diffraction analysis of the two domains of DnaD from B. subtilis are reported. Crystals of the N-terminal domain are trigonal, with either P3121 or P3221 space-group symmetry, and diffracted X-rays to 2.0,Å resolution; crystals of the C-terminal domain are hexagonal, with space group P61 or P65, and diffracted X-rays to 2.9,Å resolution in-house. Determination of the structure of the DnaD domains will provide insight into how remodelling of the nucleoid is associated with priming of replication in the model Gram-positive organism B. subtilis. [source] The multicopper oxidase (CueO) and cell aggregation in Escherichia coliENVIRONMENTAL MICROBIOLOGY, Issue 8 2007Jai J. Tree Summary cueO encodes a periplasmic multicopper oxidase, which is known to be involved in copper homeostasis and protection against oxidative stress in Escherichia coli K12. Transcriptional profiling showed that expression of genes associated with motility was lowered in a cueO mutant while expression of genes associated with autoaggregation was elevated. Increased aggregation was correlated with increased expression of cell surface proteins antigen 43 and curli. Changes in gene expression caused by the deletion of cueO were essentially independent of SoxR and OxyR, the global regulators of oxidative stress response. [source] Prokaryotic genome regulation: multifactor promoters, multitarget regulators and hierarchic networksFEMS MICROBIOLOGY REVIEWS, Issue 5 2010Akira Ishihama Abstract The vast majority of experimental data have been accumulated on the transcription regulation of individual genes within a single model prokaryote, Escherichia coli, which form the well-established on,off switch model of transcription by DNA-binding regulatory proteins. After the development of modern high-throughput experimental systems such as microarray analysis of whole genome transcription and the Genomic SELEX search for the whole set of regulation targets by transcription factors, a number of E. coli promoters are now recognized to be under the control of multiple transcription factors, as in the case of eukaryotes. The number of regulation targets of a single transcription factor has also been found to be more than hitherto recognized, ranging up to hundreds of promoters, genes or operons for several global regulators. The multifactor promoters and the multitarget transcription factors can be assembled into complex networks of transcription regulation, forming hierarchical networks. [source] Expression of ribosome modulation factor (RMF) in Escherichia coli requires ppGppGENES TO CELLS, Issue 8 2001Kaori Izutsu Background During the transition from the logarithmic to the stationary phase, 70S ribosomes are dimerized into the 100S form, which has no translational activity. Ribosome Modulation Factor (RMF) is induced during the stationary phase and binds to the 50S ribosomal subunit, which directs the dimerization of 70S ribosomes. Unlike many other genes induced in the stationary phase, rmf transcription is independent of the sigma S. To identify the factors that regulate the growth phase-dependent induction of rmf, mutant strains deficient in global regulators were examined for lacZ expression directed by the rmf promoter. Results Among mutants of defective global regulators, only ppGpp deficiency (relA-spoT double mutant) drastically reduced the level of rmf transcription to less than 10% of that seen in the wild-type. Neither RMF nor 100S ribosomes were detected in this mutant in the stationary phase. rmf transcription correlated well with cellular ppGpp levels during amino acid starvation, IPTG induction of Ptrc-relA455 and in other mutants with artificially increased ppGpp levels. Although the growth rate also correlated inversely with both ppGpp levels and rmf transcription, the observation that the growth rates of the ppGpp-deficient and wild-type strains varied equivalently when grown on different media indicates that the link between rmf transcription and ppGpp levels is not a function of the growth rate. Conclusions ppGpp appears to positively regulate rmf transcription, at least in vivo. Thus, RMF provides a novel negative translational control by facilitating the formation of inactive ribosome dimers (100S) under the stringent circumstances of the stationary phase. [source] Activity of Serratia plymuthica IC1270 gene chiA promoter region in Escherichia coli mutants deficient in global regulators of transcriptionJOURNAL OF BASIC MICROBIOLOGY, Issue 6 2005I. A. Khmel To study the regulation of expression of the Serratia plymuthica gene chiA encoding a 58-kDa endochitinase, its 586-bp-long upstream regulatory region was cloned, sequenced and fused to a promoterless lac operon in phage ,RS45 to obtain a single-copy transcriptional fusion (PF1chiA - lac ) in lysogens of Escherichia coli wild-type strains or their mutants deficient in various global regulators of transcription. The level of PF1chiA - lac expression increased about 20- and 90-fold, respectively, in E. coli K12 ,hns and double ,hns stpA mutants deficient in H-NS, and in both H-NS and StpA DNA-binding histone-like proteins, as compared to levels in the wild-type strain. In a ,lrp mutant deficient in the leucine-responsive transcriptional regulator Lrp, the level of PF1chiA - lac expression increased only up to threefold, whereas even smaller differences relative to the wild-type strain were observed in rpoS and ,crp mutants deficient in the ,S subunit of RNA polymerase and catabolite-repression protein (CRP), respectively. Deletion of the inverted-repeat sequences and curved DNA regions located in the upstream region of chiA essentially did not influence strain IC1270's chiA promoter activity in E. coli . (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] RivR and the small RNA RivX: the missing links between the CovR regulatory cascade and the Mga regulonMOLECULAR MICROBIOLOGY, Issue 6 2007Samantha A. Roberts Summary The CovR/S two-component system regulates the transcription of many genes that are crucial for the virulence of Streptococcus pyogenes (group A Streptococcus, GAS). Previously, we demonstrated that one gene repressed directly by CovR is rivR, which encodes a member of the RofA-like family of transcriptional regulators. In this study, we deleted rivR and its downstream gene rivX in a ,covR background. Microarray analysis revealed that the products of the rivRX locus exert positive control over the transcription of members of the Mga regulon. Using mutational analysis, we established that rivX encodes a small regulatory RNA. We found that RivR enhances transcriptional activation by Mga in vivo and in vitro. An M1 ,covR,rivRX strain is attenuated for virulence in a murine model of invasive soft tissue infection and this attenuation is complemented by rivRX expressed from a plasmid, demonstrating the importance of the rivRX locus in pathogenesis. This study provides the first link between the CovR and Mga regulatory networks. By integrating the signals received through these two global regulators, GAS is able to select from its repertoire different combinations of specific virulence factors to express in response to a broad spectrum of environmental conditions. [source] Riboregulation by DsrA RNA: trans -actions for global economyMOLECULAR MICROBIOLOGY, Issue 4 2000MicroReview DsrA is an 87 nucleotide Escherichia coli RNA with extraordinary regulatory properties. The profound impact of its actions stems from DsrA regulating translation of two global transcription regulators, H-NS and RpoS (,s), by sequence-specific RNA,RNA interactions. H-NS is a major nucleoid-structuring and global repressor protein, and RpoS is the stationary phase and stress response sigma factor of RNA polymerase. DsrA changes its conformation to bind to these two different mRNA targets and thereby inhibits H-NS translation, while stimulating that of RpoS in a mechanistically distinct fashion. DsrA apparently binds both the start and the stop codons of hns mRNA and sharply decreases the mRNA half-life. DsrA also binds sequences in the 5,-untranslated leader region of rpoS mRNA, enhancing rpoS mRNA stability and RpoS translation. A cohort of genes, governed by H-NS repression and RpoS activation, are thus regulated. Low temperatures increase the levels of DsrA, with differential effects on H-NS and RpoS. Additionally, the RNA chaperone protein Hfq is involved with DsrA regulation, as well as with other small RNAs that also act on RpoS to co-ordinate stress responses. We address the possible functions of this genetic regulatory mechanism, as well as the advantages of using small RNAs as global regulators to orchestrate gene expression. [source] | |||||||||||||||||||||||||