Ionophoric Properties Research Articles

4',4?- and 4',5?-di-sec-butyl-2,3:11,12-dibenzo-18-crown-6 ? An ionophore for magnesium in natural and model systems

The ionophoric properties of the di-sec-butyl derivatives of dibenzo-18-crown-6 have been studied in natural and model membranes. It has been shown that the di-sec-butyl substituents in the benzene rings of dibenzo-18-crown-6 impart to the cyclopolyether the properties of an ionophore for magnesium. The Mg2+/Ca2+ selectivity of the cyclopolyether investigated was 4.8 according to results obtained on artifical membranes and mitochondria.

Ionophoric properties of angiotensin II peptides. Nuclear magnetic resonance kinetic studies of the hormone-mediated transport of manganese ions across phosphatidylcholine bilayers.

The linear peptide hormones angiotensin II and [Asn1, Val5]angiotensin II are found to mediate the transport of Mn(II) ions across phosphatidylcholine bilayers. Nuclear magnetic resonance spectroscopy (NMR) is applied to monitor the rate of transport of Mn(II) ions by measuring the rate of disappearance of the 1H NMR signal of the choline methyl groups of the inner phospholipid layer. This rate of disappearance is analyzed in terms of a pseudo-first-order rate equation for the transport process. The rate of transport of Mn(II) varies linearly with both the concentrations of Mn(II) and agiotensin II (A-II) present, suggesting that the ions are transported in a complex with 1:1 stoichiometry. An analysis of the temperature dependence of the rate of transport yielded an energy of activation of 29 +/- 5 kcal/mol and an entrophy of activation of 10 eu for the transport process. The activation parameters are discussed in terms of defining the rate-limiting step in the transport process. The pH dependence of the hormone-mediated rate of Mn(II) transport is similar to the pH dependence of the metal complexation process measured in a separate study. The presence of La(III) or Tris decelerates the rate of Mn(II) transport by presumably competing with either Mn(II) or A-II, respectively, in the binding process. On the basis of the results presented here as well as literature data, we suggest that the ionophoric properties of these two hormones may be relevant to understanding the role of metal ions in their physiological activities.

Release of the α subunit of coupling factor F 1 ATPase from membranes of an uncoupled mutant of Escherichia coli

FEBS LettersVolume 109, Issue 1 p. 104-106 Full-length articleFree Access Release of the α subunit of coupling factor F1 ATPase from membranes of an uncoupled mutant of Escherichia coli Hiroshi Kanazawa, Hiroshi Kanazawa Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700, JapanSearch for more papers by this authorMasamitsu Futai, Masamitsu Futai Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700, JapanSearch for more papers by this author Hiroshi Kanazawa, Hiroshi Kanazawa Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700, JapanSearch for more papers by this authorMasamitsu Futai, Masamitsu Futai Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700, JapanSearch for more papers by this author First published: January 01, 1980 https://doi.org/10.1016/0014-5793(80)81320-2Citations: 6AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References 1 B.A. Baird, G. Hammes, Biochim. Biophys. Acta, 549, (1979), 31– 53. 2 Y. Kagawa, Biochim. Biophys. Acta, 505, (1978), 45– 93. 3 J.A. Downie, F. Gibson, G.B. Cox, Ann. Rev. Biochem., 48, (1979), 103– 131. 4 S.M. Hasan, B.P. Rosen, Biochim. Biophys. Acta, 459, (1977), 225– 240. 5 J. Boonstra, D.L. Gutnick, H.R. Kaback, J. Bacteriol, 124, (1975), 1248– 1255. 6 R.H. Fillingame, A.F. Wopat, J. Bacteriol., 134, (1978), 687– 689. 7 H. Kanazawa, M. Futai, FEBS Lett., 105, (1979), 275– 277. 8 R.D. Simoni, M.K. Shallenberger, Proc. Natl. Acad. Sci. USA, 69, (1972), 2663– 2667. 9 T. Tsuchiya, B.P. Rosen, J. Biol. Chem., 256, (1975), 8409– 8415. 10 H. Kanazawa, T. Miki, F. Tamura, T. Yura, M. Futai, Proc. Natl. Acad. Sci. USA, 76, (1979), 1126– 1130. 11 M. Futai, Biochem. Biophys. Res. Commun., 79, (1977), 1231– 1237. 12 M. Futai, P.C. Sternweis, L.A. Heppel, Proc. Natl. Acad. Sci. USA, 71, (1974), 2725– 2729. 13 M. Maeda, M. Futai, Y. Anraku, Biochem. Biophys. Res. Commun., 76, (1977), 331– 338. 14 M. Futai, H. Kanazawa, Y. Mukohata L. Packer Cation Flux Across Biomembranes (1979), Academic Press New York 291– 298. 15 S.D. Dunn, M. Futai, J. Biol. Chem., (1980), in press. 16 O. Ouchterlony, Handbook of Immunodiffusion and Immunology (1968), Arbor-Humphrey Science Ann Arbor MI 25– Citing Literature Volume109, Issue1January 01, 1980Pages 104-106 ReferencesRelatedInformation

Ionomycin stimulates mast cell histamine secretion by forming a lipid-soluble calcium complex.

The activation of cellular function following the direct introduction of Ca2+ into the cytosol by the use of a Ca2+-transporting ionophore has served to confirm the widely held idea that Ca2+ has the status of a second messenger in many cell types. However, this evidence has been obtained largely from the use of a single ionophore, the antibiotic A23187; experiments with X537A, which is another ionophorous antibiotic capable of transporting Ca2+ (ref. 3), have failed to show the expected characteristics. For example, histamine release from rat mast cells mediated by X537A is neither dependent on extracellular Ca2+ nor prevented by metabolic inhibitors. Ionomycin is a recently described polyether antibiotic produced by Streptomyces conglobatus ATCC 31005, and is active against Gram-positive bacteria. The antibiotic action is presumably due to its ionophorous properties, as it extracts Ca2+ from an aqueous phase into an organic phase with a stoichiometry of 1:1 (ref. 6). The ionophore is also capable of transporting 45Ca2+ across biological membranes (our unpublished results). Here we report the application of ionomycin to rat mast cells. We show that ionomycin stimulates mast cell secretion solely through its ability to form a lipid-soluble calcium complex, and thus to convey Ca2+ across the hydrocarbon region of the cell membrane.

Microbial transformation of A23187, a divalent cation ionophore antibiotic.

A23187 is an ionophore antibiotic that forms dimeric complexes with divalent cations such an Mn2+ and Ca2+. Over 200 randomly selected soil microorganisms were incubated with A23187. None of these cultures was capable of transforming this compound. In contrast, many microorganisms were able to modify the methyl ester of A23187. The transformation products produced by one culture, Streptomyces chartreusis, were isolated and identified as 16-hydroxy-N-demethyl A23187 methyl ester, 16-hydroxy-A23187 methyl ester, and N-demethyl A23187 methyl ester. These ester derivatives lack most of the ionophore properties of the acids and cannot readily form dimeric complexes with divalent cations. However, they could be hydrolyzed by a mild treatment with ethanolic KOH to free acids that possess good ionophore activity. The use of the ester substrate in conjunction with the hydrolysis procedure is, at the present time, the only known method for microbiologically producing A23187 derivatives.

The importance of the terminal hemi-acetal group for the ionophoric properties of nigericin.

Opening of the terminal hemi-acetal in dihydronigericin drastically reduces the ionophoric properties of nigericin and dehydroxymethylnigericin with 6 intact heterocycles. This is shown by 2 complementary methods, first with a liquid membrane electrode system, secondly by testing their ionophoric activities in rat liver mitochondria.

Physiological change in the ionophore-portion of proton-translocating ATPase in an uncoupled mutant of Escherichia coli

The proton-tr~slocating ATPase complex (Fr-Fe) has essentially the same structure and function in chloroplasts, mitochondria and bacterial membranes (reviewed [l-3]). This complex is composed of two portions: a catalytic portion, Fr, and a proton pathway, Fe. Use of Escherichia coli as a source of Fl-Fe has the advantages that this organism is well characterized genetically, and that it is possible to study the physiological regulation of the complex in the bacteria. Differences have been found in the ionophoric properties of Fe from cells of the Fi mutant (NR 70, DW4) ofE: cuEi [4,5] grown aerobically and anaerobically. The sensitivity of strain RF7 to DCCD (dicyclohexylcarbodiimide) was shown ]6] to vary with growth conditions: when this strain is grown on a respiratory substrate its ATPase is resistant to DCCD, because of a mutational alteration in the DCCD binding protein in F,,, whereas when the cells are grown on glucose or glycerol the ATPase is significantly less resistant. Their results suggest that a functional change of the ATPase complex may occur when the growth conditions are varied. The purpose of the present communication is to provide further evidence that the Fe portion of the complex changes when the growth conditions are varied in aerobic culture. As shown below the proton permeability of membranes of the Fi mutant DL54 [7] varies with the physiological conditions under which the cells are grown. 2. Materials and methods

Electrochemical reduction of monovalent cation complexes of macrocyclic ionophores. II. Valinomycin and macrotetrolide complexes

The stability and selectivity of complex formation of natural macrocyclic ionophores with alkali metal ions and monovalent thallium ion was studied by polarography. With valinomycin both stability constants and homogeneous dissociation rate constants were determined from polarographic kinetic currents. The macrotetrolides gave diffusion controlled currents. The stability of their complexes increases with the degree of substitution from nonactin to trinactin. The properties of natural ionophores were compared wiht those of crown polyethers. The selectivity of complex formation of valinomycin almost coincides with its effect on the increase of the conductivity of bilayer lipid membranes.

Ionophoric activity of acyl and alkyl derivatives of 2,3-benzo-15-crown-5

Benzo-15-crown-5 (according to the nomenclature suggested by Pedersen [i]) possesses the properties of potassium ionophores, which permits its use in the preparation of ion-selectlve electrodes and for modifying the permeability of biological membranes [2, 3]. The "hole" in this macrocyclic polyether has a diameter of 1.7-2.2 ~, which ensures complex-formation with Na + ions in a l:l stoichiometry and with larger cations in a 2:1 stolchiometry [2, 4]. The introduction of an alkyl group into the benzene ring of benzo-15-crown-5 increases its membrane activity, possibly by enhancing its lipophilicity [3]. A similar influence of substituents has been demonstrated in the case of dibenzo-18-crown-6 [5].

Change of Lecithin Aggregation Due to Valinomycin‐Lipid Interaction

AbstractValinomycin added to a suspension of lecithin vesicles with chlorophyll a or b incorporated into their membranes induces slight changes in the absorption spectrum of chlorophyll. The analysis of these changes revealed that this effect is not associated with the ionophoric properties of valinomycin but indicates a valinomycinlecithin interaction. As a consequence, the aggregational state of the lecithin molecules is altered in a domain which comprises about 40 lipids around one valinomycin molecule. The ability of the chlorophylls to detect different lipid aggregations arises from their solvatochromic behaviour. Using spectroscopic data for chlorophyll in different solvents, it could be inferred that a change in electrostatic interaction is the main reason for the difference of the spectrum of chlorophyll embedded in lecithin of different aggregational states. This interaction originates from a strong electric field associated with the polar moieties of the lipids which is much larger than the field imposed by transmembrane potentials. Hence the absorbance changes of chlorophyll due to such potentials are rather small compared to those induced by valinomycin.

Characterization of ionomycin as a calcium ionophore.

The ionophorous properties of a new antibiotic, ionomycin, have been studied. It was found that the antibiotic is capable of extracting calcium ion from the bulk of an aqueous phase into an organic phase. The antibiotic also acts as a mobile ion carrier to transport the cation across a solvent barrier. The divalent cation selectivity order for ionomycin as determined by ion competition experiments was found to be: Ca greater than Mg greater than Sr = Ba, where the binding of strontium and barium by the antibiotic is insignificant. The antibiotic also binds La3+ to some extent, but its complexation with monovalent alkali metal ions is negligible. Measurement of the binding of ionomycin with Ca2+ indicates that ionomycin complexes and transports calcium ion in a one to one stoichiometry.

Pigment containing lipid vesicles. II. Interaction of valinomycin with lecithin as sensed by chlorophyll a.

Valinomycin added to a suspension of chlorophyll a containing lecithin vesicles induces slight changes in the spectrum of chlorophyll a. These changes are measured as a difference spectrum between samples with and without valinomycin but of otherwise identical composition. The analysis of the experiments reveals that the effect is neither associated with the ionophoric properties of valinomycin nor due to a direct interaction of this agent with chlorophyll a. The molar ratio of valinomycin dissolved in the membrane to lecithin is found to be the relevant parameter, thus indicating an interaction between these two components. As a consequence, the aggregational state of the lecithin molecules is altered. Chlorophyll a incorporated into the membrane acts as a sensor, i.e. it reflects the alteration by a change in its spectroscopic parameters.

Branched bimolecular lipid membranes

Branched bimolecular lipid membranes separating three and four aqueous phases have been formed. The procedure is based on the technique of Montal and Mueller generalized to three and four lipid surface films spanning an appropriate aperture. The technique to produce Teflon structures for the mechanical support of branched bilayers is presented. The existence of the branched bilayer was established by measuring the specific capacity, specific resistance, and the gramicidin-induced single channel conductance of each branch. These structures should facilitate the study of transport properties of ionophores and other molecules and may also serve as model systems for the study of cell fusion.

Coronary vasodilation by fatty acids.

Fatty acids increase the coronary flow rate of rat hearts, perfused according to the Langendorff technique. Long-chain and medium-chain fatty acids are more effective vasodilators than short-chain fatty acids. The vasodilatation by fatty acids does not proceed through the intermediate formation of the vasodilator adenosine, nor by stimulation of adenylcyclase activity. Since at low Ca2+ concentrations fatty acids not only stimulate the coronary flow rate but also cardiac contractility, it is suggested that especially the lipophilic fatty acids have calcium ionophoric properties leading to increased Ca2+ removal from smooth muscle cytosol and hence to vasodilatation. Preliminary experiments, moreover, indicate that both medium- and long-chain fatty acids, like prostaglandin E1 and Ca2+, inhibit membrane ATPase(s) of aorta smooth muscle cells, suggesting increased Ca2+ binding to vascular smooth muscle cell membranes.

Studies on a new polyether antibiotic, Ro 21-6150.

A new polyether antibiotic, Ro 21-6150, has been isolated from culture broths of Streptomyces hygroscopicus, strain X-14563. Ro 21-6150 has ionophore properties and is active in vitro against gram-positive bacteria.

Grisorixin, an ionophorous antibiotic of the nigericin group. II. Chemical and structural study of grisorixin and some derivatives.

Grisorixin, a polycyclic polyether antibiotic of the nigericin group, showed ionophorous properties. The conformations of crystallized grisorixin and its metallic salts are very similar and are compared in this paper. The physico-chemical properties of the salts are described. The chemical oxidation of grisorixin methyl ester allowed us to isolate several oxidation products whose structures are described.

Mitochondrial Cation-Hydrogen Ion Exchange: SODIUM SELECTIVE TRANSPORT BY MITOCHONDRIA AND SUBMITOCHONDRIAL PARTICLES

Abstract The neutral exchange between Na+ or K+ ions and protons across the mitochondrial membrane was studied by means of passive swelling in isotonic acetate salts. The selectivity for Na+ over K+ was approximately 50:1. The rate of Na+-dependent swelling mediated by the natural exchange system was sensitive to pH and inhibited 70 % or more by 20 mm Mg2+. Physiological Mg2+ levels, however, inhibited only about 15 %. According to direct flux measurements with submitochondrial particles, the endogenous cation-H+ exchange possessed an apparent Na+:K+ selectivity ranging from 6 to 10:1 depending upon the experimental conditions. These ratios were found to be underestimates of the actual selectivity due to translocation of endogenous Na+ ions. Values corrected accordingly were comparable to those obtained for intact mitochondria. Natural mitochondrial cation-H+ exchange was compared to exchange mediated by the ionophore, nigericin. Kinetic studies with mitochondria and submitochondrial particles yielded a Na+:K+ selectivity ratio of 1.0 for nigericin. Cation discrimination was the major difference between endogenous and nigericin-dependent exchange. Differences between properties of ionophores in model systems and their kinetic behavior in biological membranes are discussed in the context of isolation-reconstitution studies.

Effects of antibiotic lonophore, A23187, on oxidative phosphorylation and calcium transport of liver mitochondria

A23187, a new antibiotic with ionophore properties, uncoupled oxidative phosphorylation in mitochondria which oxidized either malate plus glutamate or succinate. Ca 2+, but not Mg 2+, enhanced the uncoupling effect. Fluorescence of ANS 1 1 Abbreviations: ANS, 8-anilino-naphthalene sulfonic acid; TCA, trichloroacetic acid; EGTA, ethylene glycol bis(β-aminoethylether)- N,N′-tetraacetic acid. was increased by A23187 suggesting the mitochondrial membranes were de-energized. This de-energization was presumably by activation of the energy-dependent uptake of Ca 2+. The steady-state measurements of murexide-divalent cation complexes showed that A23187 caused mitochondria to release the accumulated Ca 2+ to the medium. This reduced the transmembrane Ca 2+ gradient even though normal active Ca 2+ uptake could take place. A23187 inhibited activity of ATPase induced by 2,4-dinitrophenol, valinomycin, and Ca 2+. The addition of Mg 2+ could prevent this inhibition presumably by maintaining the endogenous Mg 2+ concentration. The above metabolic events could be explained by the fact that molecules of A23187 function in the mitochondrial inner membrane as mobile carriers for divalent cations.