scholarly journals Acid-Sensing Histidine Kinase With a Redox Switch

2021 ◽  
Vol 12 ◽  
Author(s):  
Shinya Inada ◽  
Toshihide Okajima ◽  
Ryutaro Utsumi ◽  
Yoko Eguchi
Keyword(s):  
Histidine Kinase ◽  
Acid Resistance ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Acidic Ph ◽  
Pas Domain ◽  
Linker Region ◽  
Two Component Signal Transduction ◽  
Redox Switch ◽  
Ph Conditions

The EvgS/EvgA two-component signal transduction system in Escherichia coli is activated under mildly acidic pH conditions. Upon activation, this system induces the expression of a number of genes that confer acid resistance. The EvgS histidine kinase sensor has a large periplasmic domain that is required for perceiving acidic signals. In addition, we have previously proposed that the cytoplasmic linker region of EvgS is also involved in the activation of this sensor. The cytoplasmic linker region resembles a Per-ARNT-Sim (PAS) domain, which is known to act as a molecular sensor that is responsive to chemical and physical stimuli and regulates the activity of diverse effector domains. Our EvgS/EvgA reporter assays revealed that under EvgS-activating mildly acidic pH conditions, EvgS was activated only during aerobic growth conditions, and not during anaerobic growth. Studies using EvgS mutants revealed that C671A and C683A mutations in the cytoplasmic PAS domain activated EvgS even under anaerobic conditions. Furthermore, among the electron carriers of the electron transport chain, ubiquinone was required for EvgS activation. The present study proposes a model of EvgS activation by oxidation and suggests that the cytoplasmic PAS domain serves as an intermediate redox switch for this sensor.

scholarly journals Novel Two-Component Regulatory System Involved in Biofilm Formation and Acid Resistance in Streptococcus mutans

2002 ◽  
Vol 184 (22) ◽  
pp. 6333-6342 ◽  
Author(s):  
Yung-Hua Li ◽  
Peter C. Y. Lau ◽  
Nan Tang ◽  
Gunnel Svensäter ◽  
Richard P. Ellen ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Streptococcus Mutans ◽  
Biofilm Formation ◽  
Regulatory System ◽  
Acid Resistance ◽  
Low Ph ◽  
Acidic Ph ◽  
Genetic Competence ◽  
Two Component ◽  
Two Component Signal Transduction

ABSTRACT The abilities of Streptococcus mutans to form biofilms and to survive acidic pH are regarded as two important virulence determinants in the pathogenesis of dental caries. Environmental stimuli are thought to regulate the expression of several genes associated with virulence factors through the activity of two-component signal transduction systems. Yet, little is known of the involvement of these systems in the physiology and pathogenicity of S. mutans. In this study, we describe a two-component regulatory system and its involvement in biofilm formation and acid resistance in S. mutans. By searching the S. mutans genome database with tblastn with the HK03 and RR03 protein sequences from S. pneumoniae as queries, we identified two genes, designated hk11 and rr11, that encode a putative histidine kinase and its cognate response regulator. To gain insight into their function, a PCR-mediated allelic-exchange mutagenesis strategy was used to create the hk11 (Emr) and rr11 (Emr) deletion mutants from S. mutans wild-type NG8 named SMHK11 and SMRR11, respectively. The mutants were examined for their growth rates, genetic competence, ability to form biofilms, and resistance to low-pH challenge. The results showed that deletion of hk11 or rr11 resulted in defects in biofilm formation and resistance to acidic pH. Both mutants formed biofilms with reduced biomass (50 to 70% of the density of the parent strain). Scanning electron microscopy revealed that the biofilms formed by the mutants had sponge-like architecture with what appeared to be large gaps that resembled water channel-like structures. The mutant biofilms were composed of longer chains of cells than those of the parent biofilm. Deletion of hk11 also resulted in greatly diminished resistance to low pH, although we did not observe the same effect when rr11 was deleted. Genetic competence was not affected in either mutant. The results suggested that the gene product of hk11 in S. mutans might act as a pH sensor that could cross talk with one or more response regulators. We conclude that the two-component signal transduction system encoded by hk11 and rr11 represents a new regulatory system involved in biofilm formation and acid resistance in S. mutans.

scholarly journals Heterocyclic boronic acids display sialic acid selective binding in a hypoxic tumor relevant acidic environment

2017 ◽  
Vol 8 (9) ◽  
pp. 6165-6170 ◽  
Author(s):  
A. Matsumoto ◽  
A. J. Stephenson-Brown ◽  
T. Khan ◽  
T. Miyazawa ◽  
H. Cabral ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Boronic Acids ◽  
Sialic Acids ◽  
Strong Interactions ◽  
Acidic Ph ◽  
Acidic Environment ◽  
Selective Binding ◽  
High Affinity ◽  
Ph Conditions ◽  
Hypoxic Tumor

A group of heterocyclic boronic acids demonstrating unusually high affinity and selectivity for sialic acids are described, with strong interactions under the weakly acidic pH conditions associated with a hypoxic tumoral microenvironment.

scholarly journals Acute Peritonitis Caused by Propionibacterium Acnes in a Peritoneal Dialysis Patient

2017 ◽  
Vol 15 (1) ◽  
pp. 33-34
Author(s):  
Nikolina Basic-Jukic ◽  
Vesna Furic-Cunko ◽  
Ivana Juric ◽  
Lea Katalinic ◽  
Ana Rukavina ◽  
...  
Keyword(s):  
Peritoneal Dialysis ◽  
Human Skin ◽  
Dialysis Patient ◽  
Propionibacterium Acnes ◽  
Peritoneal Dialysis Patient ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Gram Positive ◽  
Acute Peritonitis ◽  
Clinical Conditions

AbstractPropionibacterium acnes is a gram-positive human skin commensal that is involved in the pathogenesis of acne and prefers anaerobic growth conditions. It has been considered as a low virulence pathogen in different clinical conditions. We present the case of acute peritonitis caused by Propionibacterium acnes in a peritoneal dialysis patient.

scholarly journals Computation of condition-dependent proteome allocation reveals variability in the macro and micro nutrient requirements for growth

2020 ◽  
Author(s):  
Colton J. Lloyd ◽  
Jonathan Monk ◽  
Laurence Yang ◽  
Ali Ebrahim ◽  
Bernhard O. Palsson
Keyword(s):  
Amino Acids ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Metabolic Phenotype ◽  
E Coli ◽  
Scale Models ◽  
Protein Components ◽  
K 12 ◽  
Genome Scale ◽  
Prosthetic Groups

AbstractSustaining a robust metabolic network requires a balanced and fully functioning proteome. In addition to amino acids, many enzymes require cofactors (coenzymes and engrafted prosthetic groups) to function properly. Extensively validated genome-scale models of metabolism and gene expression (ME-models) have the unique ability to compute an optimal proteome composition underlying a metabolic phenotype, including the provision of all required cofactors. Here we use the ME-model for Escherichia coli K-12 MG1655 to computationally examine how environmental conditions change the proteome and its accompanying cofactor usage. We found that: (1) The cofactor requirements computed by the ME model mostly agree with the standard biomass objective function used in models of metabolism alone (M models); (2) ME-model computations reveal non-intuitive variability in cofactor use under different growth conditions; (3) An analysis of ME-model predicted protein use in aerobic and anaerobic conditions suggests an enrichment in the use of prebiotic amino acids in the proteins used to sustain anaerobic growth (4) The ME-model could describe how limitation in key protein components affect the metabolic state of E. coli. Genome-scale models have thus reached a level of sophistication where they reveal intricate properties of functional proteomes and how they support different E. coli lifestyles.

scholarly journals The Anaerobic Regulatory Network Required for Pseudomonas aeruginosa Nitrate Respiration

2007 ◽  
Vol 189 (11) ◽  
pp. 4310-4314 ◽  
Author(s):  
Kerstin Schreiber ◽  
Robert Krieger ◽  
Beatrice Benkert ◽  
Martin Eschbach ◽  
Hiroyuki Arai ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Dna Bending ◽  
Regulatory Gene ◽  
Regulatory System ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Nitrate Respiration ◽  
Genetic Response ◽  
Anaerobic Conditions ◽  
Regulatory Model

ABSTRACT In Pseudomonas aeruginosa, the narK 1 K 2 GHJI operon encodes two nitrate/nitrite transporters and the dissimilatory nitrate reductase. The narK 1 promoter is anaerobically induced in the presence of nitrate by the dual activity of the oxygen regulator Anr and the N-oxide regulator Dnr in cooperation with the nitrate-responsive two-component regulatory system NarXL. The DNA bending protein IHF is essential for this process. Similarly, narXL gene transcription is enhanced under anaerobic conditions by Anr and Dnr. Furthermore, Anr and NarXL induce expression of the N-oxide regulator gene dnr. Finally, NarXL in cooperation with Dnr is required for anaerobic nitrite reductase regulatory gene nirQ transcription. A cascade regulatory model for the fine-tuned genetic response of P. aeruginosa to anaerobic growth conditions in the presence of nitrate was deduced.

scholarly journals Identification and Characterization ofMAE1, the Saccharomyces cerevisiae Structural Gene Encoding Mitochondrial Malic Enzyme

1998 ◽  
Vol 180 (11) ◽  
pp. 2875-2882 ◽  
Author(s):  
Eckhard Boles ◽  
Patricia de Jong-Gubbels ◽  
Jack T. Pronk
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Enzyme Activity ◽  
Pyruvate Kinase ◽  
Malic Enzyme ◽  
Fold Increase ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Oxidative Decarboxylation ◽  
Mrna Levels ◽  
Malic Enzyme Activity

ABSTRACT Pyruvate, a precursor for several amino acids, can be synthesized from phosphoenolpyruvate by pyruvate kinase. Nevertheless, pyk1 pyk2 mutants of Saccharomyces cerevisiae devoid of pyruvate kinase activity grew normally on ethanol in defined media, indicating the presence of an alternative route for pyruvate synthesis. A candidate for this role is malic enzyme, which catalyzes the oxidative decarboxylation of malate to pyruvate. Disruption of open reading frame YKL029c, which is homologous to malic enzyme genes from other organisms, abolished malic enzyme activity in extracts of glucose-grown cells. Conversely, overexpression ofYKL029c/MAE1 from the MET25 promoter resulted in an up to 33-fold increase of malic enzyme activity. Growth studies with mutants demonstrated that presence of either Pyk1p or Mae1p is required for growth on ethanol. Mutants lacking both enzymes could be rescued by addition of alanine or pyruvate to ethanol cultures. Disruption of MAE1 alone did not result in a clear phenotype. Regulation of MAE1 was studied by determining enzyme activities and MAE1 mRNA levels in wild-type cultures and by measuring β-galactosidase activities in a strain carrying a MAE1::lacZ fusion. Both in shake flask cultures and in carbon-limited chemostat cultures,MAE1 was constitutively expressed. A three- to fourfold induction was observed during anaerobic growth on glucose. Subcellular fractionation experiments indicated that malic enzyme in S. cerevisiae is a mitochondrial enzyme. Its regulation and localization suggest a role in the provision of intramitochondrial NADPH or pyruvate under anaerobic growth conditions. However, since null mutants could still grow anaerobically, this function is apparently not essential.

scholarly journals Glutathionylspermidine metabolism in Escherichia coli

1995 ◽  
Vol 312 (2) ◽  
pp. 465-469 ◽  
Author(s):  
K Smith ◽  
A Borges ◽  
M R Ariyanayagam ◽  
A H Fairlamb
Keyword(s):  
Escherichia Coli ◽  
Glutathione Reductase ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Growth Phases ◽  
Total Glutathione ◽  
Apparent Lack ◽  
E Coli ◽  
Catalytic Constant ◽  
Glutathione Disulphide

Intracellular levels of glutathione and glutathionylspermidine conjugates have been measured throughout the growth phases of Escherichia coli. Glutathionylspermidine was present in mid-log-phase cells, and under stationary and anaerobic growth conditions accounted for 80% of the total glutathione content. N1,N8-bis(glutathionyl)spermidine (trypanothione) was undetectable under all growth conditions. The catalytic constant kcat/Km of recombinant E. coli glutathione reductase for glutathionylspermidine disulphide was approx. 11,000-fold lower than that for glutathione disulphide. The much higher catalytic constant for the mixed disulphide of glutathione and glutathionylspermidine (11% that of GSSG), suggests a possible explanation for the low turnover of trypanothione disulphide by E. coli glutathione reductase, given the apparent lack of a specific glutathionylspermidine disulphide reductase in E. coli.

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