The molecular structure and some transport properties of valinomycin

Pinkerton, Mary; Steinrauf, L. K.; Dawkins, Phillip R.

doi:10.1016/0006-291x(69)90376-3

Cited by 283 publications

(118 citation statements)

References 3 publications

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“…In the case of fungal infection, the cost of inhibiting growth of the garden fungus L. gongylophorus may be outweighed by the benefit of preventing the spread of infection in the nest. Valinomycin (3) (28) and structural variants (29) are ionophores that selectively bind potassium ions, leading to the disintegration of the cellular membrane potential and thus, destroying cells (38). However, in the agar diffusion assays, valinomycins did not inhibit the fungi tested, including the symbiotic garden fungus (Table 1).…”

Section: Discussionmentioning

confidence: 99%

Chemical basis of the synergism and antagonism in microbial communities in the nests of leaf-cutting ants

Schoenian

Spiteller

Ghaste

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

169

187

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Leaf-cutting ants cultivate the fungus Leucoagaricus gongylophorus, which serves as a major food source. This symbiosis is threatened by microbial pathogens that can severely infect L. gongylophorus. Microbial symbionts of leaf-cutting ants, mainly Pseudonocardia and Streptomyces, support the ants in defending their fungus gardens against infections by supplying antimicrobial and antifungal compounds. The ecological role of microorganisms in the nests of leaf-cutting ants can only be addressed in detail if their secondary metabolites are known. Here, we use an approach for the rapid identification of established bioactive compounds from microorganisms in ecological contexts by combining phylogenetic data, database searches, and liquid chromatography electrospray ionisation high resolution mass spectrometry (LC-ESI-HR-MS) screening. Antimycins A 1 -A 4 , valinomycins, and actinomycins were identified in this manner from Streptomyces symbionts of leaf-cutting ants. Matrix-assisted laser desorption ionization (MALDI) imaging revealed the distribution of valinomycin directly on the integument of Acromyrmex echinatior workers. Valinomycins and actinomycins were also directly identified in samples from the waste of A. echinatior and A. niger leaf-cutting ants, suggesting that the compounds exert their antimicrobial and antifungal potential in the nests of leaf-cutting ants. Strong synergistic effects of the secondary metabolites produced by ant-associated Streptomyces were observed in the agar diffusion assay against Escovopsis weberi. Actinomycins strongly inhibit soil bacteria as well as other Streptomyces and Pseudonocardia symbionts. The antifungal antimycins are not only active against pathogenic fungi but also the garden fungus L. gongylophorus itself. In conclusion, secondary metabolites of microbial symbionts of leaf-cutting ants contribute to shaping the microbial communities within the nests of leaf-cutting ants.

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Section: Discussionmentioning

confidence: 99%

Chemical basis of the synergism and antagonism in microbial communities in the nests of leaf-cutting ants

Schoenian

Spiteller

Ghaste

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

169

187

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“…If indeed ternary complexes are formed it is plausible that first K + is bound by the ionophore followed by the binding of a thiocyanate ion. Although the formation of ternary complexes has been suggested by several authors [3,5,6] it might be that the electrical coupling of the anion transport to the valinomycin-mediated K + transport kinetically behaves as if ternary complexes are formed. Since the turnover rate at infinite K + concentration and 150 mM CNS-does not differ significantly from that at infinite thiocyanate concentration and 150 mM K + (Table I) this result suggests that the thiocyanate ion has a very high affinity for a valinomycin-K + complex, leaving open the question whether a chemical ternary complex is formed or the electrical coupling behaves as if a ternary complex is formed.…”

Section: Discussionmentioning

confidence: 99%

“…K +, in apolar media [1]. Evidence that valinomycin acts as a mobile carrier comes from experiments which demonstrate that valinomycin is capable of extracting [2][3][4] and transporting [3,5,6] alkali ions from an aqueous phase into or through an organic phase in the presence of lipophilic anions.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the valinomycin-induced potassium ion leak from liposomes with potassium thiocyanate enclosed

Blok

Gier

Deenen

1974

Biochimica et Biophysica Acta (BBA) - Biomembranes

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SUMMARYThe kinetics of the valinomycin-induced K + leak from egg lecithin liposomes with KCNS enclosed were studied by measuring the initial increase of the leak following the addition of the ionophore. Variation of liposome and valinomycin concentrations enabled a discrimination between the affinity of the ionophore for the lipid bilayer and the turnover rate of the transport process. The results indicate that valinomycin is distributed immediately between the outer liposomal bilayer and the aqueous phase. A partition constant of 0.0222 cm at 30 C was obtained for egg lecithin liposomes. By varying the temperature it was shown that the partition constant has a negative temperature coefficient. The Arrhenius activation energy of the transport process itself is 15.7"-~ I. I kcals/mole. Concerning the mechanism of the valinomycinmediated transport it was found that the complex formation can be described kinetically by the formation of a ternary complex in which K + and a thiocyanate ion are bound by the ionophore.By varying the fatty acid composition of the membrane constituents it was found that the turnover rate of the transport increased with increasing unsaturation of the phospholipids present in the membrane. This result suggests that the translocation of the complex is the rate-limiting step of the transport cycle. At 30 c'C a turnover constant of 328±44 potassium ions/molecule valinomycin per second was obtained for egg lecithin lipsomes.

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“…spectra of CLP in the presence of several salts produced shifts in the carbonyl C resonances of CLP by no more than a maximum of 0.1 ppm, far lower than those seen with ionophores such as antamanide [8]. Ion transport experiments wherein the transport of alkali picrate between two limbs of a U-tube via a central organic layer containing the peptide [9] was monitored, showed negative results with CLP while antamanide does indeed transport Na ÷ ions. Thus CLP has little affinity for any of the group IA of IIA metal ions.…”

Section: Introductionmentioning

confidence: 95%