scholarly journals Evidence for an electrogenic 3-deoxy-2-oxo-d-gluconate–proton co-transport driven by the protonmotive force in Escherichia coli K12

1977 ◽  
Vol 168 (2) ◽  
pp. 211-221 ◽  
Author(s):  
A Lagarde
Keyword(s):  
Escherichia Coli ◽  
Membrane Potential ◽  
Membrane Vesicles ◽  
Ph Gradient ◽  
Protonmotive Force ◽  
Chemical Gradient ◽  
Escherichia Coli K12 ◽  
Relative Contribution ◽  
Isolated Membrane Vesicles ◽  
External Ph

Evidence is presented indicating that the carrier-mediated uptake of 3-deoxy-2-oxo-D-gluconate and D-glucuronate in Escherichia coli K12 is driven by the deltapH and deltapsi components of the protonmotive force. 1. Approximately two protons enter the cells with each sugar molecule, independent of the sugar and the strain used. 2. In respiring cells, the magnitude of the pH gradient alone, as measured by distribution of [3H]acetate, appears to be insufficient to account for the chemical gradient of 3-deoxy-2-oxo-D-gluconate that is developed between pH 6.0 and 8.0. 3. If the external pH is varied between 5.5 and 8.0, 3-deoxy-2-oxo-D-gluconate uptake is gradually inhibited by valinomycin plus K+ ions, whereas the inhibition caused by nigericin is concomitantly relieved, thus reflecting the relative contribution of deltapH and deltapsi to the total protonmotive force at each external pH. 4. 3-Deoxy-2-oxo-D-gluconate can be transiently accumulated into isolated membrane vesicles in response to an artificially induced pH gradient. The process is stimulated when the membrane potential is collapsed by valinomycin in the presence of K+ ions.

scholarly journals The use of valinomycin, nigericin and trichlorocarbanilide in control of the protonmotive force in Escherichia coli cells

1983 ◽  
Vol 212 (1) ◽  
pp. 105-112 ◽  
Author(s):  
S Ahmed ◽  
I R Booth
Keyword(s):  
Escherichia Coli ◽  
Membrane Potential ◽  
Mode Of Action ◽  
Ph Gradient ◽  
Protonmotive Force ◽  
Modes Of Action ◽  
Escherichia Coli Cells ◽  
Low Concentrations ◽  
High K ◽  
Specific Control

Valinomycin, nigericin and trichlorocarbanilide were assessed for their ability to control the protonmotive force in Escherichia coli cells. Valinomycin, at high K+ concentrations, was found to decrease the membrane potential delta phi and indirectly to decrease the pH gradient delta pH. Nigericin was found to have two modes of action. At low concentrations (0.05-2 microM) it carried out K+/H+ exchange and decreased delta pH. At higher concentrations (50 microM) it carried out a K+-dependent transfer of H+, decreasing both delta phi and delta pH. In EDTA-treated cells only the latter mode of action was evident, whereas in a mutant sensitive to deoxycholate both types of effect were observed. Trichlorocarbanilide is proposed as an alternative to nigericin for the specific control of delta pH, and it can be used in cells not treated with EDTA.

scholarly journals Quantitative analysis of proton-linked transport systems. The lactose permease of Escherichia coli

1979 ◽  
Vol 182 (3) ◽  
pp. 687-696 ◽  
Author(s):  
I R Booth ◽  
W J Mitchell ◽  
W A Hamilton
Keyword(s):  
Escherichia Coli ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Protonmotive Force ◽  
Lactose Permease ◽  
Whole Cells ◽  
E Coli ◽  
Ph Dependent ◽  
Ph Range ◽  
External Ph

Evidence is presented that lactose uptake into whole cells of Escherichia coli occurs by symport with a single proton over the range of external pH 6.5–7.7. The proton/lactose stoicheiometry has been measured directly over this pH range by comparison of the initial rates of proton and lactose uptake into anaerobic resting cell suspensions of E. coli ML308. Further, the relationship between the protonmotive force and lactose accumulation has been studied in E. coli ML308-225 over the range of external pH 5.9–8.7. At no point was the accumulation of the beta-galactoside in thermodynamic equilibrium with the protonmotive force. It is concluded that the concentration of lactose within the cell is governed by kinetic factors rather than pH-dependent changes in the proton/substrate stoicheiometry. The relevance of these findings to the model of pH-dependent proton/substrate stoicheiometries derived from studies with E. coli membrane vesicles is discussed.

scholarly journals The protonmotive force in phosphorylating membrane vesicles from Paracoccus denitrificans. Magnitude, sites of generation and comparison with the phosphorylation potential

1978 ◽  
Vol 174 (1) ◽  
pp. 257-266 ◽  
Author(s):  
Douglas B. Kell ◽  
Philip John ◽  
Stuart J. Ferguson
Keyword(s):  
Membrane Potential ◽  
Paracoccus Denitrificans ◽  
Atp Synthesis ◽  
Membrane Vesicles ◽  
Energy Coupling ◽  
Ph Gradient ◽  
Protonmotive Force ◽  
Electron Mediator ◽  
Succinate Oxidation ◽  
Phosphorylation Potential

1. The magnitude of the protonmotive force in phosphorylating membrane vesicles from Paracoccus denitrificans was estimated. The membrane potential component was determined from the uptake of S14CN−, and the transmembrane pH gradient component from the uptake of [14C]methylamine. In each case a flow-dialysis technique was used to monitor uptake. 2. With NADH as substrate, the membrane potential was about 145mV and the pH gradient was below 0.5 pH unit. The membrane potential was decreased by approx. 15mV during ATP synthesis, and was abolished on addition of carbonyl cyanide p-trifluoromethoxyphenylhydrazone. In the presence of KCl plus valinomycin the membrane potential was replaced by a pH gradient of 1.5 units. 3. Succinate oxidation generated a membrane potential of approx. 125mV and the pH gradient was below 0.5 pH unit. Oxidation of ascorbate (in the presence of antimycin) with either 2,3,5,6-tetramethyl-p-phenylenediamine or NNN′N′-tetramethyl-p-phenylenediamine as electron mediator usually generated a membrane potential of approx. 90mV. On occasion, ascorbate oxidation did not generate a membrane potential, suggesting that the presence of a third energy-coupling site in P. denitrificans vesicles is variable. 4. With NADH or succinate as substrate, the phosphorylation potential (ΔGp=ΔG0′+RTln[ATP]/ [ADP][Pi]) was approx. 53.6kJ/mol (12.8kcal/mol). Comparison of this value with the protonmotive force indicates that more than 3 protons need to be translocated via the adenosine triphosphatase of P. denitrificans for each molecule of ATP synthesized by a chemiosmotic mechanism. In the presence of 10mm-KNO3 the protonmotive force was not detectable (<60mV) but ΔGp was not altered. This result may indicate either that there is no relationship between the protonmotive force and ΔGp, or that for an unidentified reason the equilibration of SCN− or methylamine with the membrane potential and the pH gradient is prevented by NO3− in this system.

scholarly journals The association of proton movement with galactose transport into subcellular membrane vesicles of Escherichia coli

1983 ◽  
Vol 210 (3) ◽  
pp. 699-705 ◽  
Author(s):  
P Horne ◽  
P J F Henderson
Keyword(s):  
Escherichia Coli ◽  
Transport System ◽  
Direct Evidence ◽  
Membrane Vesicles ◽  
Protonmotive Force ◽  
Ph Values ◽  
Subcellular Membrane ◽  
System 2 ◽  
Galactose Transport ◽  
Proton Movement

1. Subcellular membrane vesicles were prepared from a strain of Escherichia coli constitutive for the GalP galactose-transport system. 2. The addition of substrates of the GalP transport system to vesicle suspensions promoted alkaline pH changes, which provided direct evidence for the coupling of sugar and proton transport. 3. Respiration-energized galactose transport was progressively inhibited at pH values above 6.0, and was abolished by agents that render the membrane permeable to protons. 4. The combined effects of valinomycin, the nigericin-like compound A217 and pH on galactose transport suggested that both delta pH and delta psi components of the protonmotive force contributed to energization of galactose transport. 5. These results substantiate the conclusion that the GalP transport system operates by a chemiosmotic mechanism.

Sign in / Sign up

Export Citation Format

Share Document