scholarly journals Cytoplasmic Histidine Kinase (HP0244)-Regulated Assembly of Urease with UreI, a Channel for Urea and Its Metabolites, CO2, NH3, and NH4+, Is Necessary for Acid Survival of Helicobacter pylori

2009 ◽  
Vol 192 (1) ◽  
pp. 94-103 ◽  
Author(s):  
David R. Scott ◽  
Elizabeth A. Marcus ◽  
Yi Wen ◽  
Siddarth Singh ◽  
Jing Feng ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Histidine Kinase ◽  
Ph Sensor ◽  
Cytoplasmic Ph ◽  
Ph Homeostasis ◽  
Regulatory Complex ◽  
Cytoplasmic Acidification ◽  
Normal Human ◽  
Urea Channel ◽  
Urease Activation

ABSTRACT Helicobacter pylori colonizes the normal human stomach by maintaining both periplasmic and cytoplasmic pH close to neutral in the presence of gastric acidity. Urease activity, urea flux through the pH-gated urea channel, UreI, and periplasmic α-carbonic anhydrase are essential for colonization. Exposure to pH 4.5 for up to 180 min activates total bacterial urease threefold. Within 30 min at pH 4.5, the urease structural subunits, UreA and UreB, and the Ni2+ insertion protein, UreE, are recruited to UreI at the inner membrane. Formation of this complex and urease activation depend on expression of the cytoplasmic sensor histidine kinase, HP0244. Its deletion abolishes urease activation and assembly, impairs cytoplasmic and periplasmic pH homeostasis, and depolarizes the cells, with an ∼7-log loss of survival at pH 2.5, even in 10 mM urea. Associated with this assembly, UreI is able to transport NH3, NH4 +, and CO2, as shown by changes in cytoplasmic pH following exposure to NH4Cl or CO2. To be able to colonize cells in the presence of the highly variable pH of the stomach, the organism expresses two pH-sensor histidine kinases, one, HP0165, responding to a moderate fall in periplasmic pH and the other, HP0244, responding to cytoplasmic acidification at a more acidic medium pH. Assembly of a pH-regulatory complex of active urease with UreI provides an advantage for periplasmic buffering.

scholarly journals Energetics of Helicobacter pylori and Its Implications for the Mechanism of Urease-Dependent Acid Tolerance at pH 1

2002 ◽  
Vol 184 (11) ◽  
pp. 3053-3060 ◽  
Author(s):  
Kerstin Stingl ◽  
Eva-Maria Uhlemann ◽  
Roland Schmid ◽  
Karlheinz Altendorf ◽  
Evert P. Bakker
Keyword(s):  
Helicobacter Pylori ◽  
Membrane Potential ◽  
Urease Activity ◽  
Cytoplasmic Ph ◽  
Ph Homeostasis ◽  
Intact Cells ◽  
Ph Values ◽  
Cell Extracts ◽  
H Pylori ◽  
External Ph

ABSTRACT In the presence of urea the neutrophilic human pathogen Helicobacter pylori survives for several hours at pH 1 with concomitant cytoplasmic pH homeostasis. To study this effect in detail, the transmembrane proton motive force and cytoplasmic urease activity of H. pylori were determined at various pH values. In the absence of urea, the organism maintained a close-to-neutral cytoplasm and an internally negative membrane potential at external pH values greater than 4 to 5. In the presence of urea, H. pylori accomplished cytoplasmic pH homeostasis down to an external pH of 1.2. At this external pH, the cytoplasmic pH was 4.9 and the membrane potential was slightly negative inside. The latter finding is in contrast to the situation in acidophiles, which develop inside-positive membrane potentials under similar conditions. Measurements of the time course of the membrane potential confirmed that addition of urea to the cells led to hyperpolarization. Most likely, this effect was due to electrogenic export of ammonium cations from the cytoplasm. The urease activity of intact cells increased nearly exponentially with decreasing external pH. This activation was not due to enhanced gene expression at low external pH values. In cell extracts the pH optimum of urease activity was dependent on the buffer system and was about pH 5 in sodium citrate buffer. Since this is the cytoplasmic pH of the cells at pH 1 to 2, we propose that cytoplasmic pH is a factor in the in vivo activation of the urease at low external pH values. The mechanism by which urease activity leads to cytoplasmic pH homeostasis in H. pylori is discussed.

609 Hp0244 (FLGS) Is An Essential Cytoplasmic pH Sensor for Helicobacter pylori Acid Adaptation

2008 ◽  
Vol 134 (4) ◽  
pp. A-85
Author(s):  
Yi Wen ◽  
Jing Feng ◽  
David R. Scott ◽  
Elizabeth A. Marcus ◽  
George Sachs
Keyword(s):  
Helicobacter Pylori ◽  
Ph Sensor ◽  
Cytoplasmic Ph ◽  
Acid Adaptation

scholarly journals Prolonged Survival and Cytoplasmic pH Homeostasis of Helicobacter pylori at pH 1

2001 ◽  
Vol 69 (2) ◽  
pp. 1178-1180 ◽  
Author(s):  
Kerstin Stingl ◽  
Eva-Maria Uhlemann ◽  
Gabriele Deckers-Hebestreit ◽  
Roland Schmid ◽  
Evert P. Bakker ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Protein Synthesis ◽  
De Novo ◽  
Prolonged Survival ◽  
Cytoplasmic Ph ◽  
Ph Homeostasis ◽  
Acid Shock ◽  
H Pylori ◽  
De Novo Protein Synthesis

ABSTRACT In the presence of urea, Helicobacter pylori survived for at least 3 h at pH 1. Under these conditions, the cells maintained their cytoplasmic pH at 5.8. De novo protein synthesis during acid shock was not essential for survival of H. pylori at pH 1.

Cytoplasmic pH regulation in phorbol ester-activated human neutrophils

1986 ◽  
Vol 251 (1) ◽  
pp. C55-C65 ◽  
Author(s):  
S. Grinstein ◽  
W. Furuya
Keyword(s):  
Metabolic Pathways ◽  
Phorbol Esters ◽  
Ph Regulation ◽  
Human Neutrophils ◽  
Hexose Monophosphate ◽  
Cytoplasmic Ph ◽  
Extracellular Acidification ◽  
Hexose Monophosphate Shunt ◽  
Activated Neutrophils ◽  
Cytoplasmic Acidification

Activation of neutrophils by 12-O-tetradecanoylphorbol-13-acetate (TPA) is accompanied by an initial cytoplasmic acidification, followed by an alkalinizing phase due to Na+-H+ countertransport. The source of the acidification, which is fully expressed by activation with TPA in Na+-free or amiloride-containing media, was investigated. The acidification phase was detected also in degranulated and enucleated cytoplasts, ruling out a major contribution by the nucleus or secretory vesicles. Cytoplasmic acidification was found to be associated with an extracellular acidification, suggesting metabolic generation of H+. Two principal metabolic pathways are stimulated in activated neutrophils: the reduction of O2 by NADPH-oxidase and the hexose monophosphate shunt. A good correlation was found between the activity of these pathways and the changes in cytoplasmic pH. Inhibition of superoxide synthesis prevented the TPA-induced cytoplasmic acidification. Moreover, activation of the hexose monophosphate shunt with permeable NADPH-oxidizing agents (in the absence of TPA) also produced a cytoplasmic acidification. Cytoplasmic acidification was also elicited by exogenous diacylglycerol and by other beta-phorbol diesters, which are activators of the kinase, but not by unesterified phorbol or by alpha-phorbol diesters, which are biologically inactive. The results suggest that the cytoplasmic acidification induced by phorbol esters in neutrophils reflects accumulation of H+ liberated during the metabolic burst that follows activation.

668 Regulation of Urease Membrane Recruitment and Activation By the Cytoplasmic Histidine Kinase, HP0244 of Helicobacter pylori: A Rapid Response to Acidity

2009 ◽  
Vol 136 (5) ◽  
pp. A-103
Author(s):  
George Sachs ◽  
Yi Wen ◽  
Jing Feng ◽  
Siddharth Singh ◽  
Elizabeth A. Marcus ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Histidine Kinase ◽  
Rapid Response ◽  
Membrane Recruitment

scholarly journals Carbonic Anhydrases: New Perspectives on Protein Functional Role and Inhibition in Helicobacter pylori

2021 ◽  
Vol 12 ◽  
Author(s):  
Cristina Campestre ◽  
Viviana De Luca ◽  
Simone Carradori ◽  
Rossella Grande ◽  
Vincenzo Carginale ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Pathogenic Bacteria ◽  
Acid Tolerance ◽  
Membrane Vesicles ◽  
Research Field ◽  
Outer Membrane Vesicles ◽  
Bacterial Toxin ◽  
Carbonic Anhydrases ◽  
Ph Homeostasis ◽  
H Pylori

Our understanding of the function of bacterial carbonic anhydrases (CAs, EC 4.2.1.1) has increased significantly in the last years. CAs are metalloenzymes able to modulate CO2, HCO3– and H+ concentration through their crucial role in catalysis of reversible CO2 hydration (CO2 + H2O ⇄ HCO3– + H+). In all living organisms, CA activity is linked to physiological processes, such as those related to the transport and supply of CO2 or HCO3–, pH homeostasis, secretion of electrolytes, biosynthetic processes and photosynthesis. These important processes cannot be ensured by the very low rate of the non-catalyzed reaction of CO2 hydration. It has been recently shown that CAs are important biomolecules for many bacteria involved in human infections, such as Vibrio cholerae, Brucella suis, Salmonella enterica, Pseudomonas aeruginosa, and Helicobacter pylori. In these species, CA activity promotes microorganism growth and adaptation in the host, or modulates bacterial toxin production and virulence. In this review, recent literature in this research field and some of the above-mentioned issues are discussed, namely: (i) the implication of CAs from bacterial pathogens in determining the microorganism growth and virulence; (ii) the druggability of these enzymes using classical CA inhibitors (CAIs) of the sulfonamide-type as examples; (iii) the role played by Helicobacter pylori CAs in the acid tolerance/adaptation of the microbe within the human abdomen; (iv) the role of CAs played in the outer membrane vesicles spawned by H. pylori in its planktonic and biofilm phenotypes; (v) the possibility of using H. pylori CAIs in combination with probiotic strains as a novel anti-ulcer treatment approach. The latter approach may represent an innovative and successful strategy to fight gastric infections in the era of increasing resistance of pathogenic bacteria to classical antibiotics.

Acid Acclimation byHelicobacter pylori

Physiology ◽  
2005 ◽  
Vol 20 (6) ◽  
pp. 429-438 ◽  
Author(s):  
George Sachs ◽  
David L. Weeks ◽  
Yi Wen ◽  
Elizabeth A. Marcus ◽  
David R. Scott ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Helicobacter Pylori ◽  
Carbonic Anhydrase ◽  
Human Stomach ◽  
Peptic Ulcers ◽  
Acidic Media ◽  
Gram Negative ◽  
Urea Channel ◽  
Acid Acclimation ◽  
Unique Ability

Helicobacter pylori is a Gram-negative neutralophile associated with peptic ulcers and gastric cancer. It has a unique ability to colonize the human stomach by acid acclimation. It uses the pH-gated urea channel, UreI, to enhance urea access to intrabacterial urease and a membrane-anchored periplasmic carbonic anhydrase to regulate periplasmic pH to ~6.1 in acidic media, whereas other neutralophiles cannot regulate periplasmic pH and thus only transit the stomach.

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