scholarly journals A pH-Sensitive Function and Phenotype: Evidence that EutH Facilitates Diffusion of Uncharged Ethanolamine in Salmonella enterica

2004 ◽  
Vol 186 (20) ◽  
pp. 6885-6890 ◽  
Author(s):  
Joseph T. Penrod ◽  
Christopher C. Mace ◽  
John R. Roth
Keyword(s):  
Membrane Protein ◽  
Salmonella Enterica ◽  
Sole Source ◽  
Low Ph ◽  
Ph Sensitive ◽  
External Concentration ◽  
Influx Rate ◽  
Sensitive Function ◽  
Degradative Enzyme

ABSTRACT The eutH gene is part of an operon that allows Salmonella enterica to use ethanolamine as a sole source of nitrogen, carbon, and energy. Although the sequence of EutH suggests a role in transport, eutH mutants use ethanolamine normally under standard conditions (pH 7.0). These mutants fail to use ethanolamine at a low pH. Evidence is presented that protonated ethanolamine (Eth0) does not enter cells, while uncharged ethanolamine (Eth0) diffuses freely across the membrane. The external concentration of Eth0 varies with the pH (pK = 9.5). At pH 7.0, the standard ethanolamine concentration (41 mM) provides enough Eth0 for an influx rate that can support growth with or without EutH. When a lowered pH and/or ethanolamine concentration reduced the Eth0 concentration below 25 μM, EutH was needed to facilitate diffusion. EutH+ cells grew normally at Eth0 concentrations above 3 μM, close to the Km (9 μM) of the first degradative enzyme, ethanolamine ammonia lyase. It is suggested that EutH facilitates diffusion of Eth0. As predicted for a transporter, EutH contributed to the toxicity of ethanolamine seen under some conditions; furthermore, fusion of EutH to fluorescent Yfp protein provided evidence that EutH is a membrane protein.

scholarly journals Conserving a Volatile Metabolite: a Role for Carboxysome-Like Organelles in Salmonella enterica

2006 ◽  
Vol 188 (8) ◽  
pp. 2865-2874 ◽  
Author(s):  
Joseph T. Penrod ◽  
John R. Roth
Keyword(s):  
Salmonella Enterica ◽  
Sole Source ◽  
Low Ph ◽  
Carbon And Nitrogen ◽  
Volatile Metabolite ◽  
Volatile Metabolites ◽  
Shell Proteins ◽  
Carbon Retention

ABSTRACT Salmonellae can use ethanolamine (EA) as a sole source of carbon and nitrogen. This ability is encoded by an operon (eut) containing 17 genes, only 6 of which are required under standard conditions (37°C; pH 7.0). Five of the extra genes (eutM, -N, -L, -K, and -G) become necessary under conditions that favor loss of the volatile intermediate, acetaldehyde, which escapes as a gas during growth on EA and is lost at a higher rate from these mutants. The eutM, -N, -L, and -K genes encode homologues of shell proteins of the carboxysome, an organelle shown (in other organisms) to concentrate CO2. We propose that carboxysome-like organelles help bacteria conserve certain volatile metabolites—CO2 or acetaldehyde—perhaps by providing a low-pH compartment. The EutG enzyme converts acetaldehyde to ethanol, which may improve carbon retention by forming acetals; alternatively, EutG may recycle NADH within the carboxysome.

Activation of hilA expression at low pH requires the signal sensor CpxA, but not the cognate response regulator CpxR, in Salmonella enterica serovar Typhimurium

Microbiology ◽  
2003 ◽  
Vol 149 (10) ◽  
pp. 2809-2817 ◽  
Author(s):  
Shu-ichi Nakayama ◽  
Akira Kushiro ◽  
Takashi Asahara ◽  
Ryu-ichiro Tanaka ◽  
Lan Hu ◽  
...  
Keyword(s):  
Mutant Strain ◽  
Cell Invasion ◽  
Salmonella Enterica ◽  
Response Regulator ◽  
Low Ph ◽  
Apparent Difference ◽  
Virulence Determinants ◽  
Serovar Typhimurium ◽  
Cognate Response Regulator ◽  
Invasion Capacity

A two-component regulatory system, cpxR–cpxA, plays an important role in the pH-dependent regulation of virF, a global activator for virulence determinants including invasion genes, in Shigella sonnei. The authors examined whether the cpxR–cpxA homologues have some function in the expression of Salmonella enterica serovar Typhimurium invasion genes via the regulation of hilA, an activator for these genes. In a Salmonella cpxA mutant, the hilA expression level was reduced to less than 10 % of that in the parent strain at pH 6·0. This mutant strain also showed undetectable synthesis of an invasion gene product, SipC, at pH 6·0 and reduced cell invasion capacity – as low as 20 % of that of the parent. In this mutant, the reduction in hilA expression was much less marked at pH 8·0 than at pH 6·0 – no less than 50 % of that in the parent, and no significant reduction was observed in either SipC synthesis or cell invasion rate, compared to the parent. Unexpectedly, a Salmonella cpxR mutant strain and the parent showed no apparent difference in all three characteristics described above at either pH. These results indicate that in Salmonella, the sensor kinase CpxA activates hilA, and consequently, invasion genes and cell invasion capacity at pH 6·0. At pH 8·0, however, CpxA does not seem to have a large role in activation of these factors. Further, the results show that this CpxA-mediated activation does not require its putative cognate response regulator, CpxR. This suggests that CpxA may interact with regulator(s) other than CpxR to achieve activation at low pH.

Textile materials with a pH‐sensitive function

2011 ◽  
Vol 23 (4) ◽  
pp. 269-274 ◽  
Author(s):  
Lien Van der Schueren ◽  
Karen De Clerck
Keyword(s):  
Ph Sensitive ◽  
Textile Materials ◽  
Sensitive Function

scholarly journals Regulation of igaA and the Rcs System by the MviA Response Regulator in Salmonella enterica

2009 ◽  
Vol 191 (8) ◽  
pp. 2743-2752 ◽  
Author(s):  
Clara B. García-Calderón ◽  
Josep Casadesús ◽  
Francisco Ramos-Morales
Keyword(s):  
Membrane Protein ◽  
Salmonella Enterica ◽  
Response Regulator ◽  
Regulatory System ◽  
Enteric Bacteria ◽  
Lon Protease ◽  
Dependent Manner ◽  
Independent Manner ◽  
Serovar Typhimurium

ABSTRACT IgaA is a membrane protein that prevents overactivation of the Rcs regulatory system in enteric bacteria. Here we provide evidence that igaA is the first gene in a σ70-dependent operon of Salmonella enterica serovar Typhimurium that also includes yrfG, yrfH, and yrfI. We also show that the Lon protease and the MviA response regulator participate in regulation of the igaA operon. Our results indicate that MviA regulates igaA transcription in an RpoS-dependent manner, but the results also suggest that MviA may regulate RcsB activation in an RpoS- and IgaA-independent manner.

scholarly journals Coordinating bioorthogonal reactions with two tumor-microenvironment-responsive nanovehicles for spatiotemporally controlled prodrug activation

2020 ◽  
Vol 11 (8) ◽  
pp. 2155-2160 ◽  
Author(s):  
Liping Zuo ◽  
Jingjing Ding ◽  
Changkun Li ◽  
Feng Lin ◽  
Peng R. Chen ◽  
...  
Keyword(s):  
Tumor Microenvironment ◽  
Low Ph ◽  
Ph Sensitive ◽  
Prodrug Activation ◽  
Bioorthogonal Reactions

Spatiotemporally controlled activation: Dox-TCO loaded low pH-sensitive nanovehicles and Tz-containing MMP-2-sensitive nanocarriers simultaneously dissociated in tumor microenvironment, with Dox locally liberated through IEDDA biorthogonal reaction.

The development of polyamide 6.6 nanofibres with a pH-sensitive function by electrospinning

2010 ◽  
Vol 46 (12) ◽  
pp. 2229-2239 ◽  
Author(s):  
Lien Van der Schueren ◽  
Tybo Mollet ◽  
Özgür Ceylan ◽  
Karen De Clerck
Keyword(s):  
Ph Sensitive ◽  
Sensitive Function ◽  
Polyamide 6.6

scholarly journals Involvement of the HP0165-HP0166 Two-Component System in Expression of Some Acidic-pH-Upregulated Genes of Helicobacter pylori

2006 ◽  
Vol 188 (5) ◽  
pp. 1750-1761 ◽  
Author(s):  
Yi Wen ◽  
Jing Feng ◽  
David R. Scott ◽  
Elizabeth A. Marcus ◽  
George Sachs
Keyword(s):  
Helicobacter Pylori ◽  
Sequence Similarity ◽  
Low Ph ◽  
Ph Sensitive ◽  
Cytoplasmic Ph ◽  
Two Component System ◽  
Mobility Shift ◽  
Component System ◽  
Two Component

ABSTRACT About 200 genes of the gastric pathogen Helicobacter pylori increase expression at medium pHs of 6.2, 5.5, and 4.5, an increase that is abolished or much reduced by the buffering action of urease. Genes up-regulated by a low pH include the two-component system HP0165-HP0166, suggesting a role in the regulation of some of the pH-sensitive genes. To identify targets of HP0165-HP0166, the promoter regions of genes up-regulated by a low pH were grouped based on sequence similarity. Probes for promoter sequences representing each group were subjected to electrophoretic mobility shift assays (EMSA) with recombinant HP0166-His6 or a mutated response regulator, HP0166-D52N-His6, that can specifically determine the role of phosphorylation of HP0166 in binding (including a control EMSA with in-vitro-phosphorylated HP0166-His6). Nineteen of 45 promoter-regulatory regions were found to interact with HP0166-His6. Seven promoters for genes encoding α-carbonic anhydrase, omp11, fecD, lpp20, hypA, and two with unknown function (pHP1397-1396 and pHP0654-0675) were clustered in gene group A, which may respond to changes in the periplasmic pH at a constant cytoplasmic pH and showed phosphorylation-dependent binding in EMSA with HP0166-D52N-His6. Twelve promoters were clustered in groups B and C whose up-regulation likely also depends on a reduction of the cytoplasmic pH at a medium pH of 5.5 or 4.5. Most of the target promoters in groups B and C showed phosphorylation-dependent binding with HP0166-D52N-His6, but promoters for ompR (pHP0166-0162), pHP0682-0681, and pHP1288-1289 showed phosphorylation-independent binding. These findings, combined with DNase I footprinting, suggest that HP0165-0166 is an acid-responsive signaling system affecting the expression of pH-sensitive genes. Regulation of these genes responds either to a decrease in the periplasmic pH alone (HP0165 dependent) or also to a decrease in the cytoplasmic pH (HP0165 independent).

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