Search results for "proton transport"
showing 10 items of 21 documents
Functional reconstitution of a proton-translocating system responsive to fusicoccin
1988
Crude fusicoccin binding proteins and a partially purified plasma membrane H+-transporting ATPase (EC 3.6.1.34), both solubilized from maize tissues, were simultaneously inserted into liposomes by the freeze-thaw method. ATP-driven intravesicular acidification in the proteoliposomes, measured by the fluorescence quenching of the dye 9-amino-6-chloro-2-methoxyacridine, markedly increased upon addition of fusicoccin to the reconstituted system. This effect could not be observed when binding sites and ATPase preparations were separately reconstituted into the proteoliposomes, thus demonstrating that fusicoccin binding to its receptor is a prerequisite for ATPase stimulation.
Characterization of a proton pump from Acer pseudoplatanus cell microsomes
1985
Abstract An Acer pseudoplatanus cell microsomal fraction was enriched in ATPase by sedimentation through a sucrose cushion and treatment with Triton X-100. This activity, which reached 0.9 μmol P i min −1 mg −1 protein, was specific for ATP, slightly stimulated by K + , inhibited by orthovanadate and diethylstilbestrol, insensitive to oligomycin and azide, and had a K m - value of 0.51 mM for MgATP. ATP-dependent proton translocation was demonstrated by the ΔpH probe acridine orange. This activity had a optimum at pH 6.5, was substrate specific for ATP, and was strongly dependent on K + . Preparations of plasma membrane ATPase from A. pseudoplatanus cell culture thus posses biochemical prop…
The Tonoplast H+ -ATPase of Acer pseudoplatanus is a vacuolar-type ATPase that operates with a phosphoenzyme intermediate
1995
The tonoplast H+-ATPase of Acer pseudoplatanus has been purified from isolated vacuoles. After solubilization, the purification procedure included size-exclusion and ion-exchange chromatography. The H+-ATPase consists of at least eight subunits, of 95, 66, 56, 54, 40, 38, 31, and 16 kD, that did not cross-react with polyclonal antibodies raised to the plasmalemma ATPase of Arabidopsis thaliana. The 66-kD polypeptide cross-reacted with monoclonal antibodies raised to the 70-kD subunit of the vacuolar H+-ATPase of oat roots. The functional molecular size of the tonoplast H+-ATPase, analyzed in situ by radiation inactivation, was found to be around 400 kD. The 66-kD subunit of the tonoplast H+…
Cercospora beticola toxins. IX. Relationship between structure of beticolins, inhibition of plasma membrane H+ -ATPase and partition in lipid membran…
1996
Beticolins are yellow toxins produced by the fungus Cercospora beticola. The effect of one of them, beticolin-1, has been investigated on corn root plasma membrane H + -ATPase (EC 3.6.1.35) at different purification levels (plasma membrane fraction. partially, or highly purified enzyme). The results obtained demonstrated that (1) the purified proton pump was inhibited directly by low amounts of the toxin (I 50 =1.62 ± 0.18 μM), (2) the biological effects of beticolin-1 were similar to those of CBT (Cercospora beticola toxin). Furthermore, it was established that the efficiency of the different beticolins was clearly related to their ability to interact with the lipid bilayers, determined by…
Active vanadate-sensitive H+ translocation in corn roots membrane vesicles and proteoliposomes
1988
Abstract A member fraction from corn roots which contains a vanadate-sensitive ATPase activity has been prepared. The specific activity at 38°C is between 3 and mol 12 μmol · min −1 · mg −1 , depending on the age of roots. Addition of ATP promotes a very rapid quenching of the fluorescence of 9-amino-6-chloro-3-methoxy-acridin (ACMA). Proton pumping exhibits a delayed sensitivity to vanadate but is strongly and instantaneously inhibited by the new inhibitor SW 26. Both proton pumping, measured by the initial quenching rate, and ATP hydrolysis show maximum activities at ATP concentrations in the millimolar range, but the apparent K m -value for hydrolysis is higher than that observed for pro…
Influence of ATPase activity on PPi dependent H+-transport in tonoplast vesicles of Acer pseudoplatanus
1994
Abstract Tonoplast H + -ATPase and H + -pyrophosphatase (H + -PPase) were previously characterized in Acer pseudoplatanus cells (A. Pugin et al., Plant Sci., 73 (1991) 23–34; A. Fraichard et al., Plant Physiol. Biochem., 31 (1993) 349–359). The present study concerns the relationships between these two enzymes in vitro. ATP and PPi hydrolysis were additive and the inhibition of one did not affect the activity of the second one. ATP and PPi H + -transports were also additive. The H + -PPase inhibition did not change ATP-dependent H + -transport but H + -ATPase inhibition inhibited the PPi dependent H + -transport. Because H + -PPase was reported to transport H + and K + into the vacuole (Dav…
Current‐voltage curves of bipolar membranes
1992
Bipolar membranes consist of a layered ion‐exchange structure composed of a cation selective membrane joined to an anion selective membrane. They are analogous to semiconductor p‐n devices as both of them present current‐voltage curves exhibiting similar rectification properties. In this article, we present some current‐voltage curves obtained for different bipolar membranes at several temperatures. The results can be interpreted in terms of a simple model for ion transport and field‐enhanced water dissociation previously developed. The mechanism responsible for water splitting is assumed to be a catalytic proton transfer reaction between the charged groups and the water at the membrane int…
Reconstitution of bacteriorhodopsin and ATP synthase from Micrococcus luteus into liposomes of the purified main tetraether lipid from Thermoplasma a…
1995
The archaebacterium Thermoplasma acidophilum is cultivated at 59 degrees C in a medium containing sulfuric acid of pH 2. The purified bipolar membrane spanning main phospholipid (MPL) of this organism can be used to produce stable liposomes of 100-500 nm in diameter either using a French pressure cell detergent dialysis or sonication. Despite a potassium diffusion potential of 186 mV very low ionic permeability of sonicated MPL liposomes was measured using the potassium binding fluorescent indicator benzofuran isophthalate PBF1, which measures net K+ uptake. The latter also remained very low, in the presence of the K(+) ionophore valinomycin and palmitic acid. Addition of valinomycin and th…
Alternative Rieske Iron-Sulfur Subunits and Small Polypeptides of Cyanobacterial Cytochrome b 6 f Complexes
2016
The cytochrome (cyt) b6f complex is a central component of both, photosynthetic and respiratory electron- and proton transport processes in cyanobacteria. Among its eight bona fide subunits, the Rieske [2Fe-2S] protein is encoded by multiple genes in most cyanobacterial genomes. However, the significance of the resulting protein heterogeneity is essentially not yet understood. The following chapter provides an overview on the Rieske [2Fe-2S] protein diversity in cyanobacteria, and related aspects. In addition, potential roles of small cyt b6f complex subunits are discussed.
Structural and conductivity study of the proton conductor BaCe(0.9−x)ZrxY0.1O(3−ı) at intermediate temperatures.
2009
International audience; The perovskite BaCe(0.9−x)ZrxY0.1O(3−ı) is prepared by solid-state reaction at 1400 ◦C and sintering at 1700 ◦C. It is characterised using X-ray diffraction, Raman spectroscopy and electrical measurements. A distortion fromthe cubic structure at roomtemperature is noticeable in the Raman spectra for 0.2 < x < 0.8, but not in the X-ray diffraction patterns. This work points out the rhombohedral nature of this distortion. Phase transitions are studied up to 600 ◦C. The direct current conductivity is measured as a function of oxygen partial pressure, and at a water vapour partial pressure of 0.015 atm. The total conductivity is resolved into an ionic and a p-type compon…