L-Malate transport and proton symport in vesicles prepared from Pseudomonas putida

1986 ◽  
Vol 64 (11) ◽  
pp. 1190-1194 ◽  
Author(s):  
F. R. Agbanyo ◽  
G. Moses ◽  
N. F. Taylor
Keyword(s):  
Membrane Potential ◽  
Pseudomonas Putida ◽  
Kinetic Analysis ◽  
Transport System ◽  
Electron Donor ◽  
Proton Transport ◽  
Proton Motive Force ◽  
Alkaline Ph ◽  
Proton Symport ◽  
Malate Transport

In vesicles from glucose-grown Pseudomonas putida, L-malate is transported by nonspecific physical diffusion. L-Malate also acts as an electron donor and generates a proton motive force (Δp) of 129 mV which is composed of a membrane potential (Δψ) of 60 mV and a ΔpH of 69 mV. In contrast, vesicles from succinate-grown cells (a) transport L-malate by a carrier-mediated system with a Km value of 14.3 mM and a Vmax of 313 nmol∙mg protein−1∙min−1, (b) generate no Δψ, ΔpH, or Δp when L-malate is the electron donor, and (c) produce an extravesicular alkaline pH during the transport of L-malate. A kinetic analysis of this L-malate-induced proton transport gives a Km value of 16 mM and a Vmax of 667 nmol H+∙mg protein−1∙min−1. This corresponds to a H+/L-malate ratio of 2.1. The failure to generate a Δp in these vesicles is considered, therefore, to be consistent with the induction in succinate-grown cells of an electrogenic proton symport L-malate transport system.

scholarly journals Na+/Ca2+ exchange in coated microvesicles

1986 ◽  
Vol 233 (3) ◽  
pp. 643-648 ◽  
Author(s):  
T Saermark ◽  
M Gratzl
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Kinetic Analysis ◽  
Transport System ◽  
Proton Transport ◽  
Ion Accumulation ◽  
Secretory Vesicles ◽  
Proton Permeability ◽  
Total Capacity

Coated microvesicles isolated from bovine neurohypophyses could be loaded with Ca2+ in two different ways, either by incubation in the presence of ATP or by imposition of an outwardly directed Na+ gradient. Na+, but not K+, was able to release Ca2+ accumulated by the coated microvesicles. These results suggest the existence of an ATP-dependent Ca2+-transport system as well as of a Na+/Ca2+ carrier in the membrane of coated microvesicles similar to that present in the membranes of secretory vesicles from the neurohypophysis. A kinetic analysis of transport indicates that the apparent Km for free Ca2+ of the ATP-dependent uptake was 0.8 microM. The average Vmax. was 2 nmol of Ca2+/5 min per mg of protein. The total capacity of microvesicles for Ca2+ uptake was 3.7 nmol/mg of protein. Both nifedipine (10 microM) and NH4Cl (50 mM) inhibited Ca2+ uptake. The ATPase activity in purified coated-microvesicles fractions from brain and neurohypophysis was characterized. Micromolar concentrations of Ca2+ in the presence of millimolar concentrations of Mg2+ did not change enzyme activity. Ionophores increasing the proton permeability across membranes activated the ATPase activity in preparations of coated microvesicles from brain as well as from the neurohypophysis. Thus the enzyme exhibits properties of a proton-transporting ATPase. This enzyme seems to be linked to the ion accumulation by coated microvesicles, although the precise coupling of the proton transport to Ca2+ and Na+ fluxes remains to be determined.

scholarly journals The active transport of 2-keto-d-gluconate in vesicles prepared from Pseudomonas purida

1985 ◽  
Vol 228 (1) ◽  
pp. 257-262 ◽  
Author(s):  
F Agbanyo ◽  
N F Taylor
Keyword(s):  
Membrane Potential ◽  
Pseudomonas Putida ◽  
Active Transport ◽  
Proton Motive Force ◽  
Electron Donors ◽  
Antimycin A ◽  
Carrier System ◽  
Carbonyl Cyanide ◽  
Km Value ◽  
Phenazine Methosulphate

The transport of 2-keto-D-gluconate (alpha-D-arabino-2-hexulopyranosonic acid; 2KGA) in vesicles prepared from glucose-grown Pseudomonas putida occurs by a saturable process with a Km of 110.0 +/- 2.9 microM and a Vmax. of 0.55 +/- 0.04 nmol X min-1 X (mg of protein)-1. The provision of phenazine methosulphate/ascorbate or L-malate leads to an accumulation of intravescular 2KGA, a decrease in the Km value to 50 +/- 2.1 microM and 35 +/- 2.9 microM respectively and no change in the Vmax. In the presence of electron donors the transport of 2KGA is inhibited by the respiratory poisons antimycin A, rotenone and the uncoupler 2,4-dinitrophenol. 2KGA transport is also competitively inhibited by 4-deoxy-4-fluoro-2-keto- or 3-deoxy-3-fluoro-2-keto-D-gluconate with Ki values of 50 microM and 160 microM respectively. The carrier system for 2KGA is repressed in vesicles from cells grown on succinate. Such vesicles transport 2KGA by non-specific physical diffusion with a Km value of infinity in the absence or presence of electron donors. Vesicles from glucose or succinate grown cells, in the presence of phenazine methosulphate/ascorbate at pH 6.6, generate a proton-motive force (delta p) of approx. 140 mV. The delta p, composed of proton gradient (delta pH) and a membrane potential (delta psi), is collapsed in the presence of dinitrophenol. Based on the results obtained with valinomycin, nigericin and carbonyl cyanide m-chlorophenylhydrazone, the active transport of 2KGA at pH 6.6 is coupled predominately to the delta pH component of delta p.

scholarly journals Myo-inositol transport system in Pseudomonas putida.

1977 ◽  
Vol 131 (3) ◽  
pp. 872-875 ◽  
Author(s):  
G Rber ◽  
M Belet ◽  
J Deshusses
Keyword(s):  
Pseudomonas Putida ◽  
Transport System

Proton motive force as a function of the pH at which Methanobacterium bryantii is grown

1985 ◽  
Vol 31 (11) ◽  
pp. 1031-1034 ◽  
Author(s):  
G. Dennis Sprott ◽  
Sharon E. Bird ◽  
Ian J. McDonald
Keyword(s):  
Membrane Potential ◽  
Proton Motive Force ◽  
Motive Force ◽  
Ph Gradient ◽  
Alkaline Media ◽  
Cytoplasmic Ph ◽  
Acidic Media ◽  
Generation Times ◽  
Optimum Ph ◽  
Ph Range

Methanobacterium bryantii was grown on CO2 and H2 over a pH range between the extremes of 5.0 and 8.1. Generation times were shortest between pH 6.6 and 7.1. Cells grown at optimum pH had a proton motive force consisting predominantly of the membrane potential but those grown at nonoptimal pH generated a transmembrane pH gradient as well. This pH gradient was, however, insufficient to maintain a constant cytoplasmic pH during growth in very acidic or basic media. The results suggest that in acidic media growth may be limited by the cytoplasmic pH and that in alkaline media it may be limited by the cytoplasmic pH and (or) by the magnitude of the proton motive force.

scholarly journals Near-infrared light control of membrane potential by an electron donor–acceptor linked molecule

2020 ◽  
Vol 56 (83) ◽  
pp. 12562-12565
Author(s):  
Yuta Takano ◽  
Kazuaki Miyake ◽  
Jeladhara Sobhanan ◽  
Vasudevanpillai Biju ◽  
Nikolai V. Tkachenko ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Excited States ◽  
Electron Donor ◽  
Near Infrared ◽  
Infrared Light ◽  
Light Control ◽  
Near Infrared Light ◽  
Donor Acceptor ◽  
Molecular Excited States

(π-Extended porphyrin)–fullerene linked molecules are synthesized to utilize the molecular excited states induced by near-infrared light. One of the molecules successfully alters the membrane potential.

scholarly journals Proton-linked l-rhamnose transport, and its comparison with l-fucose transport in Enterobacteriaceae

1993 ◽  
Vol 290 (3) ◽  
pp. 833-842 ◽  
Author(s):  
J A R Muiry ◽  
T C Gunn ◽  
T P McDonald ◽  
S A Bradley ◽  
C G Tate ◽  
...  
Keyword(s):  
Transport System ◽  
Erwinia Carotovora ◽  
Alkaline Ph ◽  
Transport Activity ◽  
Ph Change ◽  
Kinetic Measurements ◽  
E Coli ◽  
Steady State Kinetic ◽  
Competitive Inhibitors ◽  
State Kinetic

1. An alkaline pH change occurred when L-rhamnose, L-mannose or L-lyxose was added to L-rhamnose-grown energy-depleted suspensions of strains of Escherichia coli. This is diagnostic of sugar-H+ symport activity. 2. L-Rhamnose, L-mannose and L-lyxose were inducers of the sugar-H+ symport and of L-[14C]rhamnose transport activity. L-Rhamnose also induced the biochemically and genetically distinct L-fucose-H+ symport activity in strains competent for L-rhamnose metabolism. 3. Steady-state kinetic measurements showed that L-mannose and L-lyxose were competitive inhibitors (alternative substrates) for the L-rhamnose transport system, and that L-galactose and D-arabinose were competitive inhibitors (alternative substrates) for the L-fucose transport system. Additional measurements with other sugars of related structure defined the different substrate specificities of the two transport systems. 4. The relative rates of H+ symport and of sugar metabolism, and the relative values of their kinetic parameters, suggested that the physiological role of the transport activity was primarily for utilization of L-rhamnose, not for L-mannose or L-lyxose. 5. L-Rhamnose transport into subcellular vesicles of E. coli was dependent on respiration, was optimal at pH 7, and was inhibited by protonophores and ionophores. It was insensitive to N-ethylmaleimide or cytochalasin B. 6. L-Rhamnose, L-mannose and L-lyxose each elicited an alkaline pH change when added to energy-depleted suspensions of L-rhamnose-grown Salmonella typhimurium LT2, Klebsiella pneumoniae, Klebsiella aerogenes, Erwinia carotovora carotovora and Erwinia carotovora atroseptica. The relative rates of subsequent acidification varied, depending on both the organism and the sugar. L-Fucose promoted an alkaline pH change in all the L-rhamnose-induced organisms except the Erwinia species. No L-rhamnose-H+ symport occurred in any organism grown on L-fucose. 7. All these results showed that L-rhamnose transport into the micro-organisms occurred by a system different from that for L-fucose transport. Both systems are energized by the trans-membrane electrochemical gradient of protons. 8. Neither steady-state kinetic measurements nor binding-protein assays revealed the existence of a second L-rhamnose transport system in E. coli.

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