Intermolecular interactions of gramicidin A′ transmembrane channels incorporated into lysophosphatidylcholine lipid systems

Cavatorta, P.; Spisni, Alberto; Casali, Emanuela; Lindner, Luisa; Masotti, Lanfranco; Urry, Dan W.

doi:10.1016/0005-2736(82)90195-x

Cited by 36 publications

(29 citation statements)

References 19 publications

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“…It has been demonstrated that the heat incorporation of gramicidin A into lysophosphatidylcholine results in two states: one state has been considered to be metastable resulting from an initial association of aggregates of gramicidin molecules with lipid micelles [15]. The other state, more dense and stable, has been established to be a membraneous state association of peptide and lipid with a lipid peptide molar ratio of 9 f 1 .O which occurs regardless of the initial incubation mixture of lipid and peptide [16].…”

Section: Discussionmentioning

confidence: 99%

“…The incorporation process of gramicidin A studied by a fluorescence method [15] indicated an association of gramicidin A molecules utilizing tryptophan-tryptophan contacts, i.e. close interactions between tryptophan side chains.…”

Section: Discussionmentioning

confidence: 99%

“…The incorporated polypeptide molecules are located with tryptophan in contact with the lipid matrix [15]. An association of gramicidin A molecules using Trp-Trp contacts has been indicated by fluorescence studies [15] and a model of the supramolecular organisation of lysophosphatidylcholine-packed gramicidin A has been advanced [16].…”

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confidence: 99%

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A Raman spectroscopic study on the interaction of an ion‐channel protein with a phospholipid in a model membrane system (gramicidin A/l‐α‐lysophosphatidylcholine)

Aslanian

Négrerie

Chambert

1986

European Journal of Biochemistry

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The interaction of the ion channel polypeptide gramicidin A with the L-a-lysophosphatidylcholine micelles in a membrane state association (approximative molar ratio 1 : 9) was investigated by Raman spectroscopy. Studies were carried out over the spectral ranges of 700-1700 cm-' and 2800-3100 cm-' at 10°C.The Raman spectrum of L-a-lysophosphatidylcholine micelles indicated a disordered structure of the lipid acyl chains by the high intensities of the gauche conformation vibrations. Changing from the micellar phase to the membrane state of association with gramicidin A, the intensities of all-trans stretching modes increased whereas the intensities of gauche conformation vibrations decreased, reflecting the emergence of ordered lipid chains.Hydrophobic interactions between the acyl chains and the polypeptide side chain residues were demonstrated. The absence of modifications in intensities of the very strong tryptophan vibrations in the complex spectrum indicated that, if the tryptophan-stacking interactions suggested by some authors exsist, they are very weak ones.Gramicidin antibiotics are excellent models of simple ion channels [I]. It has been shown that gramicidin A, a linear hydrophobic polypentadecapeptide, is able to form helical structures in the lipid bilayers with an internal channel of about 4 nm in diameter and an approximate length of 26 nm [2-71. The helical structure of gramicidin A has been described by Urry as a new type of helix, called initially the xL,D helix [2], a name which was later changed to j-helix because of the hydrogen-bonding relationshps to fl-pleated sheets [6]. Two single-stranded helical molecules associated amino end to amino end (head to head) by means of six intermolecular hydrogen bonds to form the complete channel.A variety of physical techniques (X-ray diffraction, differential scanning calorimetry, optical and electron microscopy, electron spin resonance spectroscopy) have been used in the study of the interaction of gramicidin A with phospholipid bilayers [S]. Recently, it has been demonstrated by NMR that gramicidin A promotes the formation of the hexagonal HI, phase in aqueous dispersion of phosphatidylethanolamine and phosphatidylcholine [9 -121. Further, conformational studies of gramicidin A incorporated into lysophosphatidylcholine micelles [13] showed that the channel assumes a stable conformation with a circular dichroisc pattern that is characteristic of left-handed helices. 23Na-and I3C-NMR studies have provided arguments that the stable heat-incorporated state is that of the functional transmembrane channel [14]. The incorporated polypeptide molecules are Abbreviation. ~-a-lyso PC, L-a-lysophosphatidylcholine.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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A Raman spectroscopic study on the interaction of an ion‐channel protein with a phospholipid in a model membrane system (gramicidin A/l‐α‐lysophosphatidylcholine)

Aslanian

Négrerie

Chambert

1986

European Journal of Biochemistry

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“…' has less hydrophobic surface available for 1 -anilinonapthalene-8-sulphonate binding as the emission maximum in this case is blue shifted to a lesser degree (spectrum 4, 534 nm to 506 nm) in comparison to free fluorescent probe (spectrum 1). In a given protein, two tryptophan residues in close proximity can show aromatic-aromatic interaction which would result in the decrease of quantum yield at the emission wavelength of the tryptophan residue (Cavatorta et al, 1982). Therefore, [Gly434]0"', which has a single tryptophan in the 2.3/2.4 subdoWavelength (nm) Fig.…”

Section: Conformation Of A7' and Its Variantsmentioning

confidence: 99%

Mutations in the 1.1 Subdomain of Escherichia coli Sigma Factor σ⁷⁰ and Disruption of its Overall Structure

Gopal

Chatterji

1997

European Journal of Biochemistry

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Among various group I sigma factors, two amino acids, Val55 and Ala59 are the conserved amino acids in the 1.1 hydrophobic subdomain. These two sites have been mutated to generate variants designated as [Gly55]o7 ' and [Gly59]070, where glycine replaces valine and alanine, respectively. The function of these sigma mutants is reported here. The molecular mass of these proteins determined on denaturing gels was 70 kDa, which is the expected calculated molecular mass; wild-type 0 7 0 has an apparent molecular mass of 87 kDa. However, [Gly434]07", which contains a mutation at the DNA-binding rpoD box region, also migrates as a 70-kDa protein on SDS/PAGE. Circular dichroism spectral analysis indicated that both [Gly55]07" and [Gly59]o7O have reduced helicity (20%) compared to wild-type 07" (50%). Binding of sigma factors with the hydrophobic, surface active probe 1 -anilinonapthalene-8-sulphonate, has shown that more hydrophobic surfaces are available/exposed in [Gly55]07', [Gly59]a7" as well as in [Gly434]a7" in comparison to wild-type 07". Time-resolved emission spectroscopic studies have suggested transient binding between these mutants and DNA. The different holoenzyme RNA polymerases generated upon reconstituting these mutants independently with core RNA polymerase (a2PF) have shown reduced transcriptional activity in comparison to the enzyme containing wild-type sigma factor. However, another mutation (Val+Gly) in the hydrophobic subdomain 1.2 at position 83, which is designated as [Gly83]a7", has similar properties as the wild-type with respect to its mobility on denaturing gels, circular dichroism profile, and transcriptional activity when reconstituted with core RNA polymerase. It appears that the 1.1 subdomain in 0 ' " may interact hydrophobically with the 2.3/2.4 DNA-binding region.

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“…To the best of our knowledge, there are only two additional reports on tryptophan fluorescence measurements on lipid-aggregateincorporated gramicidin. 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).…”

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

confidence: 99%

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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Intermolecular interactions of gramicidin A′ transmembrane channels incorporated into lysophosphatidylcholine lipid systems

Cited by 36 publications

References 19 publications

A Raman spectroscopic study on the interaction of an ion‐channel protein with a phospholipid in a model membrane system (gramicidin A/l‐α‐lysophosphatidylcholine)

A Raman spectroscopic study on the interaction of an ion‐channel protein with a phospholipid in a model membrane system (gramicidin A/l‐α‐lysophosphatidylcholine)

Mutations in the 1.1 Subdomain of Escherichia coli Sigma Factor σ⁷⁰ and Disruption of its Overall Structure

Intrinsic gramicidin fluorescence lifetimes in bilayer lipid membranes and in vesicles

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Intermolecular interactions of gramicidin A′ transmembrane channels incorporated into lysophosphatidylcholine lipid systems

Cited by 36 publications

References 19 publications

A Raman spectroscopic study on the interaction of an ion‐channel protein with a phospholipid in a model membrane system (gramicidin A/l‐α‐lysophosphatidylcholine)

A Raman spectroscopic study on the interaction of an ion‐channel protein with a phospholipid in a model membrane system (gramicidin A/l‐α‐lysophosphatidylcholine)

Mutations in the 1.1 Subdomain of Escherichia coli Sigma Factor σ70 and Disruption of its Overall Structure

Intrinsic gramicidin fluorescence lifetimes in bilayer lipid membranes and in vesicles

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Mutations in the 1.1 Subdomain of Escherichia coli Sigma Factor σ⁷⁰ and Disruption of its Overall Structure