alr0117, a two-component histidine kinase gene, is involved in heterocyst development in Anabaena sp. PCC 7120

Microbiology ◽  
2004 ◽  
Vol 150 (2) ◽  
pp. 447-453 ◽  
Author(s):  
Degang Ning ◽  
Xudong Xu
Keyword(s):  
Histidine Kinase ◽  
Regulatory System ◽  
Gene Encoding ◽  
Kinase Gene ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Anabaena Sp ◽  
Pcc 7120 ◽  
Polysaccharide Layer ◽  
Heterocyst Development

Anabaena sp. PCC 7120 was mutagenized by transposon Tn5-1087b, generating a mutant whose heterocysts lack the envelope polysaccharide layer. The transposon was located between nucleotides 342 and 343 of alr0117, a 918 bp gene encoding a histidine kinase for a two-component regulatory system. Complementation of the mutant with a DNA fragment containing alr0117 and targeted inactivation of the gene confirmed that alr0117 is involved in heterocyst development. RT-PCR showed that alr0117 was constitutively expressed in the presence or absence of a combined-nitrogen source. hepA and patB, the two genes turned on during wild-type heterocyst development, were no longer activated in an alr0117-null mutant. The two-component signal transduction system involving alr0117 may control the formation of the envelope polysaccharide layer and certain late events essential to the function of heterocysts.

An increase in the level of 2-oxoglutarate promotes heterocyst development in the cyanobacterium Anabaena sp. strain PCC 7120

Microbiology ◽  
2003 ◽  
Vol 149 (11) ◽  
pp. 3257-3263 ◽  
Author(s):  
Jian-Hong Li ◽  
Sophie Laurent ◽  
Viren Konde ◽  
Sylvie Bédu ◽  
Cheng-Cai Zhang
Keyword(s):  
Inorganic Nitrogen ◽  
Cell Types ◽  
Filamentous Cyanobacterium ◽  
Nitrogen Status ◽  
Gene Encoding ◽  
Combined Nitrogen ◽  
Cyanobacterium Anabaena ◽  
Anabaena Sp ◽  
Pcc 7120 ◽  
Heterocyst Development

In the filamentous cyanobacterium Anabaena sp. strain PCC 7120, a starvation of combined nitrogen induces differentiation of heterocysts, cells specialized in nitrogen fixation. How do filaments perceive the limitation of the source of combined nitrogen, and what determines the proportion of heterocysts? In cyanobacteria, 2-oxoglutarate provides a carbon skeleton for the incorporation of inorganic nitrogen. Recently, it has been proposed that the concentration of 2-oxoglutarate reflects the nitrogen status in cyanobacteria. To investigate the effect of 2-oxoglutarate on heterocyst development, a heterologous gene encoding a 2-oxoglutarate permease under the control of a regulated promoter was expressed in Anabaena sp. PCC 7120. The increase of 2-oxoglutarate within cells can trigger heterocyst differentiation in a subpopulation of filaments even in the presence of nitrate. In the absence of a source of combined nitrogen, it can increase heterocyst frequency, advance the timing of commitment to heterocyst development and further increase the proportion of heterocysts in a patS mutant. Here, it is proposed that the intracellular concentration of 2-oxoglutarate is involved in the determination of the proportion of the two cell types according to the carbon/nitrogen status of the filament.

scholarly journals Deletion of the Two-Component Histidine Kinase Gene (CHK1) of Candida albicans Contributes to Enhanced Growth Inhibition and Killing by Human Neutrophils In Vitro

2002 ◽  
Vol 70 (2) ◽  
pp. 985-987 ◽  
Author(s):  
Antonella Torosantucci ◽  
Paola Chiani ◽  
Flavia De Bernardis ◽  
Antonio Cassone ◽  
Jose Antonio Calera ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Histidine Kinase ◽  
Polymorphonuclear Leukocytes ◽  
Human Neutrophils ◽  
Gene Encoding ◽  
Kinase Gene ◽  
Killing Effect ◽  
Growth Inhibitory ◽  
Two Component

ABSTRACT We have observed that human neutrophils (polymorphonuclear leukocytes [PMNs]) have an increased growth-inhibitory and killing effect on a strain of Candida albicans with a deletion of CHK1, a gene encoding a putative histidine kinase. The PMN effect was not due to increased phagocytosis of the null strain. This observation may partially explain the reduced virulence in a hematogenously disseminated murine model of candidiasis.

scholarly journals The Erwinia chrysanthemi 3937 PhoQ Sensor Kinase Regulates Several Virulence Determinants

2006 ◽  
Vol 188 (8) ◽  
pp. 3088-3098 ◽  
Author(s):  
Balakrishnan Venkatesh ◽  
Lavanya Babujee ◽  
Hui Liu ◽  
Pete Hedley ◽  
Takashi Fujikawa ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Regulatory System ◽  
Soft Rot ◽  
Erwinia Chrysanthemi ◽  
Pcr Analysis ◽  
Sensor Kinase ◽  
Virulence Determinants ◽  
Gene Encoding ◽  
Reverse Transcription Pcr ◽  
Two Component

ABSTRACT The PhoPQ two-component system regulates virulence factors in Erwinia chrysanthemi, a pectinolytic enterobacterium that causes soft rot in several plant species. We characterized the effect of a mutation in phoQ, the gene encoding the sensor kinase PhoQ of the PhoPQ two-component regulatory system, on the global transcriptional profile of E. chrysanthemi using cDNA microarrays and further confirmed our results by quantitative reverse transcription-PCR analysis. Our results indicate that a mutation in phoQ affects transcription of at least 40 genes, even in the absence of inducing conditions. Enhanced expression of several genes involved in iron metabolism was observed in the mutant, including that of the acs operon that is involved in achromobactin biosynthesis and transport. This siderophore is required for full virulence of E. chrysanthemi, and its expression is governed by the global repressor protein Fur. Changes in gene expression were also observed for membrane transporters, stress-related genes, toxins, and transcriptional regulators. Our results indicate that the PhoPQ system governs the expression of several additional virulence factors and may also be involved in interactions with other regulatory systems.

Kinetic and mechanistic analyses of new classes of inhibitors of two-component signal transduction systems using a coupled assay containing HpkA–DrrA from Thermotoga maritima

Microbiology ◽  
2004 ◽  
Vol 150 (4) ◽  
pp. 885-896 ◽  
Author(s):  
J. Estelle Foster ◽  
Qin Sheng ◽  
Jonathan R. McClain ◽  
Mark Bures ◽  
Thalia I. Nicas ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Histidine Kinase ◽  
Competitive Inhibition ◽  
Thermotoga Maritima ◽  
Phosphorylation Site ◽  
Phosphoryl Group ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Coupled Assay ◽  
Signal Transduction Systems

Two-component signal transduction systems (TCSs) play fundamental roles in bacterial survival and pathogenesis and have been proposed as targets for the development of novel classes of antibiotics. A new coupled assay was developed and applied to analyse the kinetic mechanisms of three new kinds of inhibitors of TCS function. The assay exploits the biochemical properties of the cognate HpkA–DrrA histidine kinase–response regulator pair from Thermotoga maritima and allows multiple turnovers of HpkA, linear formation of phosphorylated DrrA, and Michaelis–Menten analysis of inhibitors. The assay was validated in several ways, including confirmation of competitive inhibition by adenosine 5′-β,γ-imidotriphosphate (AMP-PNP). The coupled assay, autophosphorylation and chemical cross-linking were used to determine the mechanisms by which several compounds inhibit TCS function. A cyanoacetoacetamide showed non-competitive inhibition with respect to ATP concentration in the coupled assay. The cyanoacetoacetamide also inhibited autophosphorylation of histidine kinases from other bacteria, indicating that the coupled assay could detect general inhibitors of histidine kinase function. Inhibition of HpkA autophosphorylation by this compound was probably caused by aggregation of HpkA, consistent with a previous model for other hydrophobic compounds. In contrast, ethodin was a potent inhibitor of the combined assay, did not inhibit HpkA autophosphorylation, but still led to aggregation of HpkA. These data suggest that ethodin bound to the HpkA kinase and inhibited transfer of the phosphoryl group to DrrA. A peptide corresponding to the phosphorylation site of DrrA appeared to inhibit TCS function by a mechanism similar to that of ethodin, except that autophosphorylation was inhibited at high peptide concentrations. The latter mechanism of inhibition of TCS function is unusual and its analysis demonstrates the utility of these approaches to the kinetic analyses of additional new classes of inhibitors of TCS function.

scholarly journals Anabaena sp. Strain PCC 7120 hetY Gene Influences Heterocyst Development

2003 ◽  
Vol 185 (23) ◽  
pp. 6995-7000 ◽  
Author(s):  
Ho-Sung Yoon ◽  
Martin H. Lee ◽  
Jin Xiong ◽  
James W. Golden
Keyword(s):  
Atp Binding ◽  
Binding Motif ◽  
Filamentous Cyanobacterium ◽  
Hypothetical Proteins ◽  
Nitrogen Fixing ◽  
Fixed Nitrogen ◽  
Anabaena Sp ◽  
Time Required ◽  
Pcc 7120 ◽  
Heterocyst Development

ABSTRACT The filamentous cyanobacterium Anabaena (Nostoc) sp. strain PCC 7120 responds to starvation for fixed nitrogen by producing a semiregular pattern of nitrogen-fixing cells called heterocysts. Overexpression of the hetY gene partially suppressed heterocyst formation, resulting in an abnormal heterocyst pattern. Inactivation of hetY increased the time required for heterocyst maturation and caused defects in heterocyst morphology. The 489-bp hetY gene (alr2300), which is adjacent to patS (asl2301), encodes a protein that belongs to a conserved family of bacterial hypothetical proteins that contain an ATP-binding motif.

scholarly journals Functional reconstitution of the Salmonella typhimurium PhoQ histidine kinase sensor in proteoliposomes

2005 ◽  
Vol 390 (3) ◽  
pp. 769-776 ◽  
Author(s):  
Sarah Sanowar ◽  
Hervé Le Moual
Keyword(s):  
Salmonella Typhimurium ◽  
Histidine Kinase ◽  
Catalytic Domain ◽  
Response Regulator ◽  
Phosphoryl Group ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
High Concentrations

Two-component signal-transduction systems are widespread in bacteria. They are usually composed of a transmembrane histidine kinase sensor and a cytoplasmic response regulator. The PhoP/PhoQ two-component system of Salmonella typhimurium contributes to virulence by co-ordinating the adaptation to low concentrations of environmental Mg2+. Limiting concentrations of extracellular Mg2+ activate the PhoP/PhoQ phosphorylation cascade modulating the transcription of PhoP-regulated genes. In contrast, high concentrations of extracellular Mg2+ stimulate the dephosphorylation of the response regulator PhoP by the PhoQ kinase sensor. In the present study, we report the purification and functional reconstitution of PhoQHis, a PhoQ variant with a C-terminal His tag, into Escherichia coli liposomes. The functionality of PhoQHis was essentially similar to that of PhoQ as shown in vivo and in vitro. Purified PhoQHis was inserted into liposomes in a unidirectional orientation, with the sensory domain facing the lumen and the catalytic domain facing the extraluminal environment. Reconstituted PhoQHis exhibited all the catalytic activities that have been described for histidine kinase sensors. Reconstituted PhoQHis was capable of autokinase activity when incubated in the presence of Mg2+-ATP. The phosphoryl group could be transferred from reconstituted PhoQHis to PhoP. Reconstituted PhoQHis catalysed the dephosphorylation of phospho-PhoP and this activity was stimulated by the addition of extraluminal ADP.

scholarly journals Identification of a Streptococcus pneumoniae Gene Locus Encoding Proteins of an ABC Phosphate Transporter and a Two-Component Regulatory System

1999 ◽  
Vol 181 (4) ◽  
pp. 1126-1133 ◽  
Author(s):  
Rodger Novak ◽  
Anje Cauwels ◽  
Emmanuelle Charpentier ◽  
Elaine Tuomanen
Keyword(s):  
Response Regulator ◽  
Regulatory System ◽  
Phosphate Limitation ◽  
Pho Regulon ◽  
Loss Of Function ◽  
Gene Encoding ◽  
E Coli ◽  
Two Component ◽  
Pst System

ABSTRACT The Escherichia coli Pst system belongs to the family of ABC transporters. It is part of a phosphate (PHO) regulon which is regulated by extracellular phosphate. Under conditions of phosphate limitation, the response regulator PhoB is phosphorylated by the histidine kinase PhoR and binds to promoters that share a consensus PHO box. Under conditions of phosphate excess, PhoR, Pst, and PhoU downregulate the PHO regulon. Screening of a library of pneumococcal mutants with defects in exported proteins revealed a putative two-component regulatory system, PnpR-PnpS, and a downstream ABC transporter, similar to the Pst system in E. coli including a gene encoding a PhoU protein. Similar to E. coli, mutagenesis of the ATP-binding cassette gene, pstB, resulted in decreased uptake of phosphate. The effects of the loss of the pneumococcal Pst system extended to decreased transformation and lysis. Withdrawal of phosphate led to transformation deficiency in the parent strain R6x but not to penicillin tolerance, suggesting that reduced bacterial death was independent of phosphate. None of these phenotypes was observed in the pneumococcal loss-of-function mutantphoU. By using a lacZ reporter construct, it was demonstrated that expression of the two-component regulatory system PnpR-PnpS was not influenced by different concentrations of phosphate. These results suggest a more complex role of the Pst system in pneumococcal physiology than in that of E. coli.

Molecular characterization of the two-component histidine kinase gene fromMonilinia fructicola

2006 ◽  
Vol 62 (10) ◽  
pp. 991-998 ◽  
Author(s):  
Zhonghua Ma ◽  
Yong Luo ◽  
Themis Michailides
Keyword(s):  
Molecular Characterization ◽  
Histidine Kinase ◽  
Kinase Gene ◽  
Two Component

scholarly journals PmrAB, a Two-Component Regulatory System of Pseudomonas aeruginosa That Modulates Resistance to Cationic Antimicrobial Peptides and Addition of Aminoarabinose to Lipid A

2004 ◽  
Vol 186 (2) ◽  
pp. 575-579 ◽  
Author(s):  
Samuel M. Moskowitz ◽  
Robert K. Ernst ◽  
Samuel I. Miller
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Peptides ◽  
Lipid A ◽  
Regulatory System ◽  
Signal Transduction System ◽  
Cationic Antimicrobial Peptides ◽  
Two Component ◽  
Serovar Typhimurium ◽  
Two Component Signal Transduction ◽  
Resistant Mutants

ABSTRACT Spontaneous polymyxin-resistant mutants of Pseudomonas aeruginosa were isolated. The mutations responsible for this phenotype were mapped to a two-component signal transduction system similar to PmrAB of Salmonella enterica serovar Typhimurium. Lipid A of these mutants contained aminoarabinose, an inducible modification that is associated with polymyxin resistance. Thus, P. aeruginosa possesses a mechanism that induces resistance to cationic antimicrobial peptides in response to environmental conditions.

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