Tryptophan interactions of gramicidin A′ channels in lipids: a time-resolved fluorescence study

Masotti, Lanfranco; Cavatorta, P.; Sartor, Giorgio; Casali, Emanuela; Szabo, Arthur G.

doi:10.1016/0005-2736(86)90227-0

Cited by 23 publications

(26 citation statements)

References 14 publications

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“…Furthermore, the lack of any significant perturbation of gramicidin on the acyl chain order of these systems [14] has been taken as indication of the presence of gramicidin aggregates. Heat incorporation of gramicidin into lysophosphatidylcholine also results in formation of bilayers [15] in which the gramicidin molecules are aggregates [16] but now they are present as N-terminal linked dimers [17] thus with the Cterminus at the bilayer/water interface.…”

Section: Introductionmentioning

confidence: 99%

Importance of the tryptophans of gramicidin for its lipid structure modulating activity in lysophosphatidylcholine and phosphatidylethanolamine model membranes. A comparative study employing gramicidin analogs and a synthetic α-helical hydrophobic polypeptide

Aranda

Killian

Kruijff

1987

Biochimica et Biophysica Acta (BBA) - Biomembranes

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The importance of the tryptophan residues of gramicidin for the lipid structure modulating activity of this pentadecapeptide was investigated by studying the interaction of gramicidin analogs A, B, C (which have a tryptophan, phenylalanine and tyrosine in position 11, respectively) and tryptophan-N-formylated gramicidin (in which the four tryptophan residues have been formylated) with several phospholipid systems. In addition an a-helical model pentadecapeptide (P15) was studied to further test the specificity of the gramicidin-lipid interaction. DSC experiments showed that all the gramicidin analogs produced a significant decrease in the gel to liquid-crystalline transition enthalpy of dipalmitoylphosphatidylcholine. The P15 peptide was much less effective in this respect. In dielaidoyiphosphatidylethanolamine the gel ~ liquid-crystalline transition enthalpy was much less affected by the incorporation of these molecules. In this lipid system tryptophan-Nformylated gramicidin was found to be the most ineffective. 31p-NMR and small angle X-ray diffraction experiments showed that the ability of the peptides to induce bilayer structures in paimitoyilysophosphatidyicholine and H n phase promotion in dielaidoylphosphatidylethanolamine systems follows the order. gramicidin A' (natural mixture) -~ gramicidin A > gramicidin B = gramicidin C > tryptophan-N-formylated gramicidin > P15. These results support the hypothesis that the shape of gramicidin and its aggregational behaviour, in which the tryptophan residues play an essential role, are major determinants in the unique lipid structure modulating activity of gramicidin.

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Section: Introductionmentioning

confidence: 99%

Importance of the tryptophans of gramicidin for its lipid structure modulating activity in lysophosphatidylcholine and phosphatidylethanolamine model membranes. A comparative study employing gramicidin analogs and a synthetic α-helical hydrophobic polypeptide

Aranda

Killian

Kruijff

1987

Biochimica et Biophysica Acta (BBA) - Biomembranes

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“…This has been observed for tryptophan decays in proteins (36,37). The three exponential fluorescence decays of gramicidin in lysolecithin dispersions have been attributed to three different sets of tryptophans in the polypeptide ionophore (21 exciton interactions between the indole groups in neighboring tryptophan moieties, 9 and 15. The long (6-8ns) lifetime component was ascribed to tryptophans that are "deeply buried" in the bilayer, 11 and 13, while the medium lifetime was attributed to tryptophans that are located close to the membrane surface, 13 and 15.…”

Section: Gramicidin A' In Bilayer Lipid Membranesmentioning

confidence: 73%

“…Steady-state (20) and time-resolved (21) intrinsic gramicidin fluorescence were measured in lysolipid dispersions. The data obtained were fitted to three exponentials with decay times in the 6-8 ns, 1.8-3.0 ns, and 0.3-0.8 ns ranges (21). The low emission efficiency of tryptophan has to date precluded intrinsic fluorescence measurements of the tiny amounts of gramicidin present in a bilayer lipid membrane (BLM).…”

Section: ' -D -~E U ' 2 -L -~~' 3 -D -~E U ' 4 -L -~~' 5 -mentioning

confidence: 99%

“…Since iodide ions cannot penetrate into bilayers, their inability to quench gramicidin fluorescence has been taken as evidence for the incorporation of this polypeptide into the vesicle matrix (1 9). The shift of the gramicidin emission maximum to a wavelength shorter than 340 nm was used as an additional criterion for gramicidin incorporation into apolar medium of vesicles (21 'Average lifetimes were calculated as (7) = CA,T~'/FA,T;. below 340 nm.…”

Section: Gramicidin a ' In Vesiclesmentioning

confidence: 99%

“…Gramicidin in lysolecithin dispersions has a similar (7) value (3.4 ns; ref. 21). There is a notable deviation: the average gramicidin fluorescence lifetime in DPhPC vesicles is much shorter ((7) = 2.2 ns) than those determined in other vesicles in the present work (Table 4).…”

Section: Gramicidin a ' In Vesiclesmentioning

confidence: 99%

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Intrinsic gramicidin fluorescence lifetimes in bilayer lipid membranes and in vesicles

Camaleńo-Delgado¹,

Zhao²,

Fendler³

1990

Can. J. Chem.

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Intrinsic Gramicidin A' tryptophan steady-state fluorescence anisotropies and fluorescence lifetimes have been determined in bilayer lipid membranes (BLMs) prepared from glyceryl monooleate (GMO). In GMO BLMs, fluorescence anisotropy, the r value, was found to be 0.05 5 0.02. Decays of Gramicidin A' fluorescence intensities were fitted to the sum of three exponentials ( T~, 72, and T~) and appropriate pre-exponentials (Al, A2, and A3). These values allowed for the assessment of average fluorescence lifetimes, (7). These values related to those determined in vesicles prepared from dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylcholine (DOPC), distearoylphosphatidylcholine (DSPC), and diphytanoylphosphatidylcholine (DPhPC). In BLMs, (7) = 1.9 ns, 3.6 ns, and 2.3 ns were determined for vertically, horizontally, and unpolarized average fluorescence lifetimes, respectively. Increasing the applied potential across the BLM from 0 to 80 mV increased (7) from 2.2 ns to 4.9 ns and T~ from 0.43 5 0.05 to 0.73 5 0.06 ns, as well as the contributions and lifetimes of the longer lived fluorescence (A2 and A3, 7 2 and T~) .The emission maximum of Gramicidin A' (334 nm in DPPC) and the absence of quenching by iodide ions indicated complete incorporation of the polypeptide into vesicles. The r values were of the order of 0.10 in vesicles prepared from DPPC and DSPC, both in the absence and in the presence of added 1.2 X M CsC1. In vesicles prepared from DOPC and DPhPC, r values increased to 0.13 and 0.14 in water and to 0.15 and 0.20 in 1.2 X M CsCl, respectively. At 25.0°C, the temperature of the measurements, DPPC and DSPC are in their "solid states, but DOPC and DPhPC are in their "liquid states. (7) values for Gramicidin A' in vesicles prepared from DPPC, DOPC, and DSPC were all in the 3.0 + 0.3 ns range. In DPhPC vesicles, (7) = 2.2 ns was determined. Time-dependent anisotropies became observable in DOPC and DPhPC vesicles, particularly in the presence of 1.2 X lop4 M CsCl.

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The Gramicidin a Channel: Left Versus Right-Handed Helix

Etchebest

Pullman

1988

The Jerusalem Symposia on Quantum Chemistry and Biochemistry

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Tryptophan interactions of gramicidin A′ channels in lipids: a time-resolved fluorescence study

Cited by 23 publications

References 14 publications

Importance of the tryptophans of gramicidin for its lipid structure modulating activity in lysophosphatidylcholine and phosphatidylethanolamine model membranes. A comparative study employing gramicidin analogs and a synthetic α-helical hydrophobic polypeptide

Importance of the tryptophans of gramicidin for its lipid structure modulating activity in lysophosphatidylcholine and phosphatidylethanolamine model membranes. A comparative study employing gramicidin analogs and a synthetic α-helical hydrophobic polypeptide

Intrinsic gramicidin fluorescence lifetimes in bilayer lipid membranes and in vesicles

The Gramicidin a Channel: Left Versus Right-Handed Helix

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