The influence of pH on the conductance of lipid bimolecular membranes in relation to the alkaline ion transport induced by carboxylic carriers grisorixin, alborixin and monensin

Sandeaux, Roger; Seta, P.; Jeminet, Georges; Alléaume, M.; Gavach, Claude

doi:10.1016/0005-2736(78)90284-5

Cited by 27 publications

(11 citation statements)

References 31 publications

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“…Monensin is known to promote electroneutral (one-forone) exchange of Na + and H + across lipid bilayers, whereas FCCP acts as an electrogenic carrier of H + (Sandeaux et al, 1978;McLaughlin & Dilger, 1979). The simultaneous addition of monensin and FCCP may be expected to lead to an elimination of Na + and H + concentration gradients (as well as of potential gradients).…”

Section: Current Transients In the Presence Of Monensinmentioning

confidence: 97%

Fast charge translocations associated with partial reactions of the Na,K-pump: I. Current and voltage transients after photochemical release of ATP

1987

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Nonstationary electric currents are described which are generated by the Na,K-pump. Flat membrane sheets 0.2-1 micron in diameter containing a high density of oriented Na,K-ATPase molecules are bound to a planar lipid bilayer acting as a capacitive electrode. In the aqueous phase adjacent to the bound membrane sheets, ATP is released within milliseconds from an inactive, photolabile precursor ("caged" ATP) by an intense flash of light. After the ATP-concentration jump, transient current and voltage signals can be recorded in the external circuit corresponding to a translocation of positive charge across the pump protein from the cytoplasmic to the extracellular side. These electrical signals which can be suppressed by inhibitors of the Na,K-ATPase require the presence of Na+ but not of K+ in the aqueous medium. The intrinsic pump current Ip(t) can be evaluated from the recorded current signal, using estimated values of the circuit parameters of the compound membrane system. Ip(t) exhibits a biphasic behavior with a fast rising period, followed by a slower decline towards a small quasi-stationary current. The time constant of the rising phase of Ip(t) is found to depend on the rate of photochemical ATP release. Further information on the microscopic origin of the current transient can be obtained by double-flash experiments and by chymotrypsin modification of the protein. These and other experiments indicate that the observed charge-translocation is associated with early events in the normal transport cycle. After activation by ATP, the pump goes through the first steps of the cycle and then enters a long-lived state from which return to the initial state is slow.

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Section: Current Transients In the Presence Of Monensinmentioning

confidence: 97%

Fast charge translocations associated with partial reactions of the Na,K-pump: I. Current and voltage transients after photochemical release of ATP

1987

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“…Two concentrations of nigericin were employed (10 -3 and 10 -4 M) according to its solubility in media of different dielectric constant. b Pressman, 1973. case of compound X-14547A (Bolte et al, 1982), grisorixin (Sandeaux et al, 1978), X-537A (Cells et al, 1974) and nigericin (Toro et al, 1976). However, others which otherwise are almost identical to the former group, except for their different cationic selectivity, do not aggregate in oligomeric forms, nor do they have the ability to transfer net charge across black lipid membranes.…”

Section: Discussionmentioning

confidence: 92%

“…It is likely that the amphipatic properties of nigericin contribute to the establishment of a micellial-like process which determines the formation of mobile dimeric and trimeric conducting oligomers. This process is shared with nigericin by compounds X-537A (Celis et al, 1974) and grisorixin (Sandeaux et al, 1978) but not by the monensins, dianemycin and HLR-X-206 (Toro et al, data to be published elsewhere).…”

Section: Dependence Of the Aggregation On The Concentration Of Ionophmentioning

confidence: 91%

“…Moreover, similar to nigericin, X-ray diffraction studies of X-537A (Chiang & Paul, 1977) have shown that the latter carboxylic ionophore forms dimers in nonpolar media, reverting to a monomeric structure in a polar environment. Furthermore, some intents to obtain the X-ray diffraction pattern for the grisorixin dimers, assumed to exist from the bilayer conductance measurements (Sandeaux et al, 1978). Thus, it appears that the polarity of the solvent has an influence on the structure of the metal ion-carboxylic ionophore complex.…”

Section: Dependence Of the Aggregation On The Polarity Of The Solventmentioning

confidence: 99%

“…The property to aggregate into dimers is also shared by etheromycin (Donis et al, 1981) and the calcium ionophore ionomycin (Anteunis & Verhegge, 1981). Other carboxylic antibiotics subjected to monomer-dimer transitions are X-14547A (Bolte et al, 1982) and grisorixin (Sandeaux et al, 1978), while neither the monensins (Estrada-O. et al, 1967b) nor dianemycin, HLR-X-206 or Lilly A217 (Lardy et al, 1967) show the ability to aggregate in oligomers or to conduct net charge across membranes at acidic or alkaline pH (Toro et al, data to be published elsewhere).…”

Section: Introductionmentioning

confidence: 97%

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Formation of ion-translocating oligomers by nigericin

et al. 1987

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At pH 4.0, greater than 10(-7) M nigericin was found capable of conducting net charge transfer across bimolecular lecithin membranes, with a stoichiometry of three uncharged ionophore moieties per cation. At neutral or alkaline pH, nigericin catalyzed the transfer of net charge through dimer forms. In agreement with these results, quantitative analysis of nigericin-potassium complexes formed at pH 4.0 showed a 3:1 ratio, and a 2:1 ratio at neutral or alkaline pH. A 1:1 stoichiometry was observed when the ionophore complex was not transferred from methanol-water to chloroform. Moreover, 1H-NMR spectra of nigericin-cation complexes formed at pH 4.0, displayed clear-cut chemical shift variations different to those observed at neutral or alkaline pH. Thus, it is apparent that acid pH causes a transition from dimeric to trimeric forms of nigericin-cation complexes. The membrane conductance increased up to ten times when negatively charged phosphatidyl glycerol was used, while the conductance decreased in positively charged cetylpyridinium containing membranes at pH 4.0. These results suggest that the nigericin-K+ oligomeric complex is positively charged. In this respect, pKa values around 8.0 were obtained for the nigericin carboxylate group in media of different dielectric constant, indicating that this chemical group is undissociated under these conditions. Moreover, the values for the complex formation constants as well as the delta G values calculated for the dimers and trimers indicated that such ionophore cation oligomeric complexes are thermodynamically stable.

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Phospholipids and bile acids as diffusional carriers of Na+ across nonpolar media

Accatino¹,

P²

1988

Hepatology

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Phospholipids and bile acids, by virtue of their amphiphilic properties, can interact in nonpolar media forming "inverted" structures (micelles) which presumably have an hydrophilic core and might act as diffusional carriers (ionophores) of electrolytes across low dielectric constant media or lipid membranes. The Na+ ionophoretic capability of various purified phospholipids and the modulating effects of bile acids and phosphatidylcholine was examined by: (a) measurement of 22Na+ partition into the organic phase (chloroform) of a two-phase system and (b) direct measurement of the translocation of 22Na+ across a bulk chloroform phase separating two aqueous phases in a Pressman cell. All phospholipids tested, except for phosphatidylcholine, showed ionophoretic capability for Na+ at micromolar concentrations. Cardiolipin and phosphatidylserine were the most efficient Na+ carriers, comparable with monensin, an established Na+ ionophore. In contrast, cholic acid as well as other bile acids demonstrated only marginal or no Na+ ionophoretic capability. However, hydroxylated bile acids (particularly cholic acid), sodium dodecyl sulfate and Triton X-100, which can induce and stabilize inverted structures in lipid membranes, were able to increase 5- to 8-fold the phospholipid-mediated Na+ transport. Interaction of cardiolipin with Na+ in the chloroform phase followed a rectangular hyperbolic function with an apparent Kd within the physiological Na+ concentration range (16.9 +/- 5.1 mM). Addition of cholic acid to the cardiolipin-containing organic phase resulted in a 10-fold increase of maximal Na+ uptake and no change in apparent Kd. The effect of cholic acid on both cardiolipin-mediated Na+ partition and Na+ translocation across the chloroform phase showed a marked dependence on pH, being greater at pH 7.4.(ABSTRACT TRUNCATED AT 250 WORDS)

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The influence of pH on the conductance of lipid bimolecular membranes in relation to the alkaline ion transport induced by carboxylic carriers grisorixin, alborixin and monensin

Cited by 27 publications

References 31 publications

Fast charge translocations associated with partial reactions of the Na,K-pump: I. Current and voltage transients after photochemical release of ATP

Fast charge translocations associated with partial reactions of the Na,K-pump: I. Current and voltage transients after photochemical release of ATP

Formation of ion-translocating oligomers by nigericin

Phospholipids and bile acids as diffusional carriers of Na+ across nonpolar media

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