PROTON PUMPS AND CHANNELS: STUDIES WITH BACTERIORHODOPSIN AND A PROTEOLIPID OF THE MITOCHONDRIAL ADENOSINETRIPHOSPHATASE

1978 ◽  
pp. 187-199
Author(s):  
Lester Packer ◽  
Tetsuya Konishi ◽  
Richard Criddle
Keyword(s):  
Proton Pumps

In vitro antibacterial and antibiotic-potentiation activities of five edible plant extracts and mode of action against several MDR Gram-negative phenotypes

2020 ◽  
Vol 4 (1) ◽  
pp. 1-14
Author(s):  
Carine M.N. Ngaffo ◽  
Simplice B. Tankeo ◽  
Michel-Gael F. Guefack ◽  
Brice E. N. Wamba ◽  
Paul Nayim ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Bioactive Compounds ◽  
Plant Extracts ◽  
Theobroma Cacao ◽  
Efflux Pumps ◽  
Phoenix Dactylifera ◽  
Food Plants ◽  
Proton Pumps ◽  
Gram Negative ◽  
E Coli

Abstract Background: Bacterial infections involving the multidrug resistant (MDR) strains are among the top leading causes of death throughout the world. Healthcare system across the globe has been suffering from an extra-ordinary burden in terms of looking for the new and more potent antimicrobial compounds. The aim of the present study was to determine the antibacterial activity of some Cameroonian edible plants (Garcinia lucida bark, Phoenix dactylifera pericarps, Theobroma cacao pod, Solanum macrocarpon leaves and Termitomyces titanicus whole plant) and their antibiotics-potentiation effects against some MDR Gram-negative bacteria phenotypes expressing efflux pumps (Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Pseudomonas aeruginosa and Providencia stuartii strains). Methods: The antibacterial activities of plant extract alone and in combination with usual antibiotics were carried out using the micro-dilution method. The effects of the most active plant extract (Garcinia lucida bark) on H+-ATPase-mediated proton pumps and on bacterial growth kinetic were performed using experimental protocols, while qualitative reference methods were used to highligh the major groups of secondary metabolites present in the extracts. Results: Qualitative phytochemical screening of plant extracts indicated that all analysed secondary metabolites were present in Theobroma cacao and Termitomyces titanicus while one (saponins) of them was absent in Garcinia lucida and Solanum macrocarpon. Only three of them (polyphenols, flavonoids and saponins) were detected in Phoenix dactylifera. Antibacterial essays showed that G. lucida was the most active plant as it inhibited the growth of all studied bacteria with strong activity (MIC<100 µg/mL) against E. coli ATCC8739, significant activity (100≤MIC≤512 µg/mL) against 80% of bacteria and moderate activity (512<MIC≤2048 µg/mL) against E. coli AG100A and E. aerogenes (EA289 and CM64). It was followed by T. cacao and S. macrocarpon extracts which exhibited an antibacterial potential against 95% and 80% of bacterial strains, respectively. These three extracts exhibited a bactericidal effect on a few bacteria. Extracts from T. titanicus and P. dactylifera were less active as they moderately (512<MIC≤2048 µg/mL) inhibited the growth of 35% and 10% of bacteria. All extracts selectively potentiated the activities of all antibiotics with improvement activity factors (IAF) ranging from 2 to 256. G. lucida, T. cacao and S. macrocarpon potentiated the activities of 100%, 89% and 67% of antibiotics respectively against more than 70%, suggesting that they contain bioactive compounds which could be considered as efflux pumps inhibitors. Whereas T. titanicus and P. dactylifera improved the activities of almost 40% and 20% of antibiotics, respectively. This increase of activities also characterizes synergistic effects between antibiotics and these bioactive compounds. G. lucida extract at all tested concentrations, strongly inhibited the growth of bacterial strain E. coli ATCC8739 and exhibited an inhibitory effect on this bacterial H+-ATPase-mediated proton pumps increasing the pH of the medium. Conclusion: The overall results indicated that food plants among which G. lucida, T. cacao and S. macrocarpon could have a benefit interest in combatting resistant types of bacteria. Keywords: Food plants; infectious diseases; MDR bacteria; efflux pumps; antibiotics; secondary metabolites.

Is the Acidic pH of the External Auditory Canal Playing a Significant Role in the Treatment of Acute Otitis Externa?

2018 ◽  
Vol 69 (8) ◽  
pp. 2304-2305
Author(s):  
Oana Ruxandra Iana ◽  
Dragos Cristian Stefanescu ◽  
Viorel Zainea ◽  
Razvan Hainarosie
Keyword(s):  
External Auditory Canal ◽  
Otitis Externa ◽  
Proton Pumps ◽  
Acidic Ph ◽  
External Ear ◽  
Ph Values ◽  
The World ◽  
Subcutaneous Tissues ◽  
Low Levels ◽  
Value Changes

Variable pH values for skin have been reported in the literature, all within the acidic range, varying from 4.0 up to 7. 0. The origin of the acidic pH remains conjectural, and several factors have been incriminated with this role, such as eccrine and sebaceous secretions as well as proton pumps. Keeping low levels of pH prevents microbial dispersal as well as multiplication. The skin in the external auditory canal is also covered with this acidic mantle with antimicrobial value. Changes of pH in the external ear can lead to acute otitis externa. This condition is defined by the inflammation and infection of the cutaneous and subcutaneous tissues of the external auditory canal. 10% of the world�s population may suffer from acute otitis externa at least once in their lifetime. This paper aims to consolidate the relevance of an acidic pH in the healthy external ear and its relation to the pathogenesis and treatment of otitis externa through a prospective and interventional clinical study on 80 patients who presented to the outpatient department at Prof. Dr D. Hociota ENT Institute in Buch

Acidification of rat liver lysosomes: quantitation and comparison with endosomes

1993 ◽  
Vol 265 (4) ◽  
pp. C901-C917 ◽  
Author(s):  
R. W. Van Dyke
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Rat Liver ◽  
Proton Pumps ◽  
Intact Cells ◽  
Early Endosomes ◽  
Medium Permeability ◽  
Electrogenic Proton Pump ◽  
Secondary Lysosomes ◽  
Permeability Studies

Both lysosomes and endosomes are acidified by an electrogenic proton pump, although studies in intact cells indicate that the steady-state internal pH (pHi) of lysosomes is more acid than that of endosomes. We undertook the present study to examine in detail the acidification mechanism of purified rat liver secondary lysosomes and to compare it with that of a population of early endosomes. Both endosomes and lysosomes exhibited ATP-dependent acidification, but proton influx rates were 2.4- to 2.7-fold greater for endosomes than for lysosomes because of differences in both buffering capacity and acidification rates, suggesting that endosomes exhibited greater numbers or rates of proton pumps. Lysosomes, however, exhibited a more acidic steady-state pHi due in part to a slower proton leak rate. Changes in medium Cl- increased acidification rates of endosomes more than lysosomes, and the lysosome ATP-dependent interior-positive membrane potential was only partially eliminated by high-Cl- medium. Permeability studies suggested that lysosomes were less permeable to Na+, Li+, and Cl- and more permeable to K+ and PO4(2-) than endosomes. Na-K-adenosine-triphosphatase did not appear to regulate acidification of either vesicle type. Endosome and lysosome acidification displayed similar inhibition profiles to N-ethylmaleimide, dicyclohexyl-carbodiimide, and vanadate, although lysosomes were somewhat more sensitive [concentration producing 50% maximal inhibition (IC50) 1 nM] to bafilomycin A1 than endosomes (IC50 7.6 nM). Oligomycin (1.5-3 microM) stimulated lysosome acidification due to shunting of membrane potential. Overall, acidification of endosomes and lysosomes was qualitatively similar but quantitatively somewhat different, possibly related to differences in the density or rate of proton pumps as well as vesicle permeability to protons, anions, and other cations.

scholarly journals Comparative genomics reveals new functional insights in uncultured MAST species

2021 ◽  
Author(s):  
Aurelie Labarre ◽  
David López-Escardó ◽  
Francisco Latorre ◽  
Guy Leonard ◽  
François Bucchini ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Genomic Data ◽  
Proton Pumps ◽  
Functional Annotations ◽  
The Core ◽  
Unicellular Eukaryotes ◽  
Microbial Eukaryotes ◽  
Core Energy ◽  
Marine Surface ◽  
Environmental Sequences

AbstractHeterotrophic lineages of stramenopiles exhibit enormous diversity in morphology, lifestyle, and habitat. Among them, the marine stramenopiles (MASTs) represent numerous independent lineages that are only known from environmental sequences retrieved from marine samples. The core energy metabolism characterizing these unicellular eukaryotes is poorly understood. Here, we used single-cell genomics to retrieve, annotate, and compare the genomes of 15 MAST species, obtained by coassembling sequences from 140 individual cells sampled from the marine surface plankton. Functional annotations from their gene repertoires are compatible with all of them being phagocytotic. The unique presence of rhodopsin genes in MAST species, together with their widespread expression in oceanic waters, supports the idea that MASTs may be capable of using sunlight to thrive in the photic ocean. Additional subsets of genes used in phagocytosis, such as proton pumps for vacuole acidification and peptidases for prey digestion, did not reveal particular trends in MAST genomes as compared with nonphagocytotic stramenopiles, except a larger presence and diversity of V-PPase genes. Our analysis reflects the complexity of phagocytosis machinery in microbial eukaryotes, which contrasts with the well-defined set of genes for photosynthesis. These new genomic data provide the essential framework to study ecophysiology of uncultured species and to gain better understanding of the function of rhodopsins and related carotenoids in stramenopiles.

scholarly journals Bafilomycin inhibits proton flow through the H+ channel of vacuolar proton pumps

1994 ◽  
Vol 269 (26) ◽  
pp. 17379-17381
Author(s):  
B.P. Crider ◽  
X.S. Xie ◽  
D.K. Stone
Keyword(s):  
Proton Pumps ◽  
Flow Through

scholarly journals Activation of vacuolar-type proton pumps by protein kinase C. Role in neutrophil pH regulation

1992 ◽  
Vol 267 (32) ◽  
pp. 22740-22746
Author(s):  
A Nanda ◽  
A Gukovskaya ◽  
J Tseng ◽  
S Grinstein
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ph Regulation ◽  
Proton Pumps ◽  
Kinase C

scholarly journals Potassium depletion increases proton pump (H+-ATPase) activity in intercalated cells of cortical collecting duct

2000 ◽  
Vol 279 (1) ◽  
pp. F195-F202 ◽  
Author(s):  
Randi B. Silver ◽  
Sylvie Breton ◽  
Dennis Brown
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Collecting Duct ◽  
Proton Pumps ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Collecting Ducts ◽  
Acid Load ◽  
Collecting Tubules ◽  
Atpase Staining

Intercalated cells (ICs) from kidney collecting ducts contain proton-transporting ATPases (H+-ATPases) whose plasma membrane expression is regulated under a variety of conditions. It has been shown that net proton secretion occurs in the distal nephron from chronically K+-depleted rats and that upregulation of tubular H+- ATPase is involved in this process. However, regulation of this protein at the level of individual cells has not so far been examined. In the present study, H+-ATPase activity was determined in individually identified ICs from control and chronically K+-depleted rats (9–14 days on a low-K+ diet) by monitoring K+- and Na+-independent H+ extrusion rates after an acute acid load. Split-open rat cortical collecting tubules were loaded with the intracellular pH (pHi) indicator 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, and pHiwas determined by using ratiometric fluorescence imaging. The rate of pHi recovery in ICs in response to an acute acid load, a measure of plasma membrane H+-ATPase activity, was increased after K+ depletion to almost three times that of controls. Furthermore, the lag time before the start of pHirecovery after the cells were maximally acidified fell from 93.5 ± 13.7 s in controls to 24.5 ± 2.1 s in K+-depleted rats. In all ICs tested, Na+- and K+-independent pHi recovery was abolished in the presence of bafilomycin (100 nM), an inhibitor of the H+-ATPase. Analysis of the cell-to-cell variability in the rate of pHi recovery reveals a change in the distribution of membrane-bound proton pumps in the IC population of cortical collecting duct from K+-depleted rats. Immunocytochemical analysis of collecting ducts from control and K+-depleted rats showed that K+-depletion increased the number of ICs with tight apical H+ATPase staining and decreased the number of cells with diffuse or basolateral H+-ATPase staining. Taken together, these data indicate that chronic K+ depletion induces a marked increase in plasma membrane H+ATPase activity in individual ICs.

scholarly journals Cryo-EM structure and dynamics of the green-light absorbing proteorhodopsin

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Stephan Hirschi ◽  
David Kalbermatter ◽  
Zöhre Ucurum ◽  
Thomas Lemmin ◽  
Dimitrios Fotiadis
Keyword(s):  
Proton Translocation ◽  
Functional Characterization ◽  
Green Light ◽  
Proton Donor ◽  
Molecular Organization ◽  
Primary Proton ◽  
Proton Pumps ◽  
Model Protein ◽  
Dynamics Simulations ◽  
And Function

AbstractThe green-light absorbing proteorhodopsin (GPR) is the archetype of bacterial light-driven proton pumps. Here, we present the 2.9 Å cryo-EM structure of pentameric GPR, resolving important residues of the proton translocation pathway and the oligomerization interface. Superposition with the structure of a close GPR homolog and molecular dynamics simulations reveal conformational variations, which regulate the solvent access to the intra- and extracellular half channels harbouring the primary proton donor E109 and the proposed proton release group E143. We provide a mechanism for the structural rearrangements allowing hydration of the intracellular half channel, which are triggered by changing the protonation state of E109. Functional characterization of selected mutants demonstrates the importance of the molecular organization around E109 and E143 for GPR activity. Furthermore, we present evidence that helices involved in the stabilization of the protomer interfaces serve as scaffolds for facilitating the motion of the other helices. Combined with the more constrained dynamics of the pentamer compared to the monomer, these observations illustrate the previously demonstrated functional significance of GPR oligomerization. Overall, this work provides molecular insights into the structure, dynamics and function of the proteorhodopsin family that will benefit the large scientific community employing GPR as a model protein.

scholarly journals Fusicoccin (FC)-Induced Rapid Growth, Proton Extrusion and Membrane Potential Changes in Maize (Zea mays L.) Coleoptile Cells: Comparison to Auxin Responses

2021 ◽  
Vol 22 (9) ◽  
pp. 5017
Author(s):  
Małgorzata Polak ◽  
Waldemar Karcz
Keyword(s):  
Membrane Potential ◽  
Rapid Growth ◽  
Proton Pumps ◽  
Proton Extrusion ◽  
Membrane Hyperpolarization ◽  
Fungal Toxin ◽  
Maize Coleoptile ◽  
Lag Times ◽  
Kinetics Of ◽  
Indole 3 Acetic Acid

The fungal toxin fusicoccin (FC) induces rapid cell elongation, proton extrusion and plasma membrane hyperpolarization in maize coleoptile cells. Here, these three parameters were simultaneously measured using non-abraded and non-peeled segments with the incubation medium having access to their lumen. The dose–response curve for the FC-induced growth was sigmoidal shaped with the maximum at 10−6 M over 10 h. The amplitudes of the rapid growth and proton extrusion were significantly higher for FC than those for indole-3-acetic acid (IAA). The differences between the membrane potential changes that were observed in the presence of FC and IAA relate to the permanent membrane hyperpolarization for FC and transient hyperpolarization for IAA. It was also found that the lag times of the rapid growth, proton extrusion and membrane hyperpolarization were shorter for FC compared to IAA. At 30 °C, the biphasic kinetics of the IAA-induced growth rate could be changed into a monophasic (parabolic) one, which is characteristic for FC-induced rapid growth. It has been suggested that the rates of the initial phase of the FC- and IAA-induced growth involve two common mechanisms that consist of the proton pumps and potassium channels whose contribution to the action of both effectors on the rapid growth is different.

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