Nuclear magnetic resonance studies of the interactions of anions and solvent with cation complexes of valinomycin

Davis, Donald G.; Tosteson, D. C.

doi:10.1021/bi00689a006

Cited by 38 publications

(10 citation statements)

References 26 publications

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“…The expected affinities of cation and peptide in a 1:l complex with the cation in the cavity and in a peptide sandwich with the cation in a cavity formed between the two of the cations are close (2.66 w vs. 2.70 A), the ratio of the Journal of the American Chemical Society / 99: 25 / December 7, 1977 peptides should, therefore, follow the same trends. It is likely that the P2C species are true "peptide sandwich" complexes (as opposed to dimeric peptides binding one cation), similar to those found for valin o m y~i n ,~~,~~ the e n n i a t i n~,~~.…”

Section: Resultsmentioning

confidence: 86%

Cyclic peptides. 19. Cation binding of a cyclic dodecapeptide cyclo (L-Val-Gly-Gly-L-Pro)3 in an aprotic medium

Baron¹,

Lg²,

Er³

1977

J. Am. Chem. Soc.

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The synthesis of cyclo-(~-Val-Gly-Gly-~-Pro)3 is reported. This homodetic cyclic dodecapeptide contains only naturally occurring amino acids and is a model of an ion carrier related to valinomycin. Titration curves obtained from circular dichroism data in acetonitrile solutions reveal three kinds of cyclic dodecapeptide (P)-cation (C) complexes: PC (1:l complex), P2C (peptide-sandwich complex), and PC2 (ion-sandwich complex). Binding constants of several cations and molar ellipticities of the bound species were determined using a new computer program. The stabilities of the 1: 1 complexes are found to be correlated with the diameter of the divalent cation in the series Mg2+ << Ca2+ << Ba2+. The charge of the cation is also an important factor: Ca2+ is more strongly bound than K+, which has a diameter close to that of Ba2+. Nevertheless, the stability of the peptide-K+ complex is comparable to that of valinomycin-K+. Another important finding is that P2C complexes are stable; indeed, these are the major species for small cations, e.g., Li+, Mg2+, and Na+.Current interest in the functions of biological membranes, particularly ion transport, has led to several studies of ion binding and transport with antibiotics4 and other natural peptides5 and with synthetic ionophore^.^,' Extrapolation of

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Section: Resultsmentioning

confidence: 86%

Cyclic peptides. 19. Cation binding of a cyclic dodecapeptide cyclo (L-Val-Gly-Gly-L-Pro)3 in an aprotic medium

Baron¹,

Lg²,

Er³

1977

J. Am. Chem. Soc.

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“…Thallium, the ionic radius of which Tables 2, 3, 5 and 6), evidence of the complete similarity of the two complexed spatial structures [48].…”

Section: Relation Between the 4 Torsion Angles And The Dihedral Angmentioning

confidence: 83%

Refinement of the Solution Conformation of Valinomycin with the Aid of Coupling Constants from the 13C-Nuclear-Magnetic-Resonance Spectra

Bystrov¹,

Gavrilov²,

Иванов³

et al. 1977

Eur J Biochem

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The C′= O and Cα signals in the 13C nuclear magnetic resonance (NMR) spectra of valinomycin have been assigned and the vicinal 1H…13C coupling constants have been determined by double and triple heteronuclear resonance. In conjunction with the vicinal H‐NCα‐H and H‐CαCβ‐H proton‐proton constants, the results led to unequivocal determination of the torsion angles φ and of the population distribution of the Cα‐Cβ rotational states. The Φ torsion angles for the hydroxy acid residues were estimated from the vicinal 1H‐CαC′‐15N constants. The combined data permitted refinement of the conformational states of valinomycin in different solvents. For the KS+ complex of valinomycin the observed couplings are in complete accord with the conformations we had earlier proposed for solutions and that had also been established by X‐ray analysis. In the 13C spectra of the valinomycin‐Tl+ complex 13C…203,205Tl+ spin‐spin couplings were observed for the l and d‐valine carbonyls, unequivocal proof of the donor‐acceptor interaction with the cation. In media of weak polarity (cyclohexane, chloroform) the conformation of the valinomycin molecule is similar to that of the K+ complex. In such a ‘bracelet’ structure formed by six fused β‐turns of type II and II′, the amino acid carbonyls are axial with certain inclination towards the symmetry axis. On formation of a 1:1 complex with a cation the carbonyl orientation changes, now bending towards the center of the molecular cavity. In the ‘propeller’ conformation, predominant in solvents of medium polarity (for instance CCl4/(C2H3)2SO, 3/1) the three β‐turns are of type II. The 1H and 13C chemical shifts are interpreted in terms of conformational changes in the valinomycin molecule, intermolecular and intramolecular hydrogen bonds and interaction with the metal cation.

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“…This was accomplished in the present studies by the addition of K +-valinomycin to the system and forming a TNBS-K+-valinomycin complex which is a sufficiently stable complex having zero net charge which permeates the cell membrane. The idea to use K+-valinomycin for this purpose was based on the work of Davis and Tosteson (1975) who reported complex formation of trinitrocresolate ion with K § valinomycin.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore K § conductance of lipid bilayers in the presence of valinomycin was markedly enhanced by trinitrocresol. The formation of an ion pair complex of trinitrocresolate anion with K § has been sustantiated by nuclear magnetic resonance studies (Davis & Tosteson, 1975).…”

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confidence: 99%

Transport of organic anions through the erythrocyte membrane as K+-valinomycin complexes

1978

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Summary. K +, Rb +, or Cs + complexes of valinomycin form ion pair complexes with picric acid and trinitrobenzenesulfonate (TNBS). The formation of a picrate-K +-valinomycin complex is supported by spectral evidence. These complexes have zero net charge and readily permeate the intact erythrocyte membrane. The K+-valinomycin complex has been used to convert the nonpenetrating TNBS into a penetrating covalent probe, making it as useful vectorial probe to measure accessible amino groups of proteins and phospholipids on both sides of the erythrocyte membrane.The enhanced transport of TNBS into the cell by valinomycin is dependent on external K § in the medium. The entry of TNBS into the cell is manifested by an increased labeling of hemoglobin and membrane phosphatidylethanolamine (PE).Stilbeneisothiocyanatedisulfonate (SITS) and anilinonaphthalenesulfonate (ANS) inhibit both the basal and K +-valinomycin stimulated labeling of PE and hemoglobin by TNBS. The data suggest two independent effects of ANS and SITS, one mediated by an inhibition of the anion transport protein and another by the incorporation of these hydrobic anions into the cell membrane with an increase in negative charge on the membrane which leads to an inhibition of TNBS permeation into the cell by electrostatic repulsion.In order to determine the asymmetry of amino-phospholipids in cell membranes, two different chemical probes have been used. One probe readily penetrates the membrane and labels aminophospholipids on both sides of the membrane. The second probe does not penetrate the membrane to any significant extent and labels aminophospholipids on the exterior surface only. These two probes must have different chemical properties since one penetrates and one does not penetrate the cell. Indeed the penetrating probe is usually nonionic and hydrophobic whereas the nonpenetrating probe is anionic. This creates inherent difficulties in chemical reactivity and solubility of the probes which opens to question a direct comparison of the degree of labeling of membrane components by these two probes. If a method were developed

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Nuclear magnetic resonance studies of the interactions of anions and solvent with cation complexes of valinomycin

Cited by 38 publications

References 26 publications

Cyclic peptides. 19. Cation binding of a cyclic dodecapeptide cyclo (L-Val-Gly-Gly-L-Pro)3 in an aprotic medium

Cyclic peptides. 19. Cation binding of a cyclic dodecapeptide cyclo (L-Val-Gly-Gly-L-Pro)3 in an aprotic medium

Refinement of the Solution Conformation of Valinomycin with the Aid of Coupling Constants from the 13C-Nuclear-Magnetic-Resonance Spectra

Transport of organic anions through the erythrocyte membrane as K+-valinomycin complexes

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