The effect of changes in gramicidin conformation on bilayer lipid properties

Morrow, Michael R.; Simatos, G.; Srinivasan, Rajani; Grandal, Nestor; Taylor, Lauren J.; Keough, K. M. W.

doi:10.1016/0005-2736(91)90166-6

Cited by 13 publications

(9 citation statements)

References 24 publications

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“…shapes, neither did incubation of the samples at 60°C for several days change the 2H-NMR spectrum. This is not surprising, because similar investigations on perdeuterated dimyristoylphosphatidylcholine bilayers indicate that the deuterium lineshape is essentially unchanged by the conversion from the nonchannel to the channel form (Morrow et al, 1991). Measurements of circular dichroism (CD) have been used to investigate the conformation of gramicidin (Killian (1992) and references cited therein), and the CD spectra obtained from the two conformations are distinctly different.…”

Section: Effect Of Solvent On Gramicidin Conformationmentioning

confidence: 75%

Phase equilibria and molecular packing in the N,N-dimethyldodecylamine oxide/gramicidin D/water system studied by 2H nuclear magnetic resonance spectroscopy

Orädd¹,

Lindblom²,

Arvidson³

et al. 1995

Biophysical Journal

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A partial phase diagram of the system N,N-dimethyldodecylamine oxide (DDAO)/water/gramicidin D was determined by 2H-NMR. Both 2H2O and perdeuterated DDAO (DDAO-d31) were studied by solid state NMR techniques. Addition of gramicidin D to the micellar (L1), normal hexagonal (HI) and cubic (I) phases of DDAO induces phase separations, giving two-phase regions, which all contain a lamellar (L alpha) phase. The L alpha phase containing gramicidin is characterized by larger order parameters for DDAO-d31 compared with the corresponding order parameters in the L alpha and HI phases of DDAO-d31/H2O. The L alpha phase may stay in equilibrium with any other phase in the phase diagram. The DDAO exchange between the coexisting phases is slow on the NMR timescale, which is why the recorded NMR spectrum consists of superimposed spectra from the different phases occurring in the sample. Gramicidin D can be solubilized in appreciable quantities only in the lamellar phase of DDAO-d31. Increasing amounts of gramicidin in the liquid crystalline phases result in a continuous increase in the molecular ordering up to about 5 mol% gramicidin, where a plateau is reached. This is consistent with a recent theoretical model describing the influence on the ordering of lipids by a membrane protein with larger hydrophobic thickness than the lipid bilayer. The solvent used for dissolving gramicidin at the incorporation of the peptide in the lipid aggregates has no effect on the 2H-NMR lineshapes of DDAO-d31. It is concluded that gramicidin is solubilized in the L alpha phase and that it always adopts the channel conformation independent of a particular solvent. The channel conformation is also supported by CD studies. In some of the samples, macroscopic orientation of the lipid aggregates is observed. It is concluded that DDAO-d31 in the binary system favors an orientation with the long axis of the hydrocarbon chain perpendicular to the magnetic field, whereas when gramicidin D is present the hydrocarbon chain orients parallel to the magnetic field. This is explained by the fact that gramicidin aligns with its helical axis parallel to the magnetic field, thereby forcing also the DDAO-d31 molecules to obtain such an orientation.

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Section: Effect Of Solvent On Gramicidin Conformationmentioning

confidence: 75%

Phase equilibria and molecular packing in the N,N-dimethyldodecylamine oxide/gramicidin D/water system studied by 2H nuclear magnetic resonance spectroscopy

Orädd¹,

Lindblom²,

Arvidson³

et al. 1995

Biophysical Journal

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“…We have investigated the effect of the small peptide gA on the molecular orientational order and dynamics of TMA- Bouchard and Auger (1993)]. The transition temperature for pure DMPC is Ttr = 23 °C (Chapman et al, 1977); however, it has been reported that the presence of gA considerably broadens the phase transition region of DMPC (Morrow et al, 1991). We therefore performed our experiments on DMPC vesicles at 35 °C.…”

Section: Resultsmentioning

confidence: 99%

Effect of Gramicidin A on Structure and Dynamics of Lipid Vesicle Bilayers. A Time-Resolved Fluorescence Depolarization Study

Muller¹,

Ginkel²,

Faassen³

1995

Biochemistry

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We investigated the effects of the hydrophobic small peptide antibiotic gramicidin A (gA) on the properties of vesicle bilayers in the liquid crystalline state. Time-resolved fluorescence anisotropy experiments were performed with unilamellar vesicles of the lipids DMPC, POPC, DOPC, EGGPC, DLPC, DOPG, and SQDG containing various concentrations of gA in two different conformations using TMA-DPH and DPHPC as fluorescent probes. These analogues of DPH were taken to study the gA induced change in the structural and dynamical properties of the lipid bilayer in different portions of the hydrophobic region. The time-resolved anisotropy data were analyzed using the recently introduced compound motion model [van der Sijs, D. A., et al. (1993) Chem. Phys. Lett. 216, 559; Muller, J. M., et al. (1994) Chem. Phys. 185, 393]. In general, gA raises the order and reduces the rotational diffusion coefficient for the probes in the bilayer. In DOPC vesicles this ordering effect of gA on the bilayer is found to depend on both the conformation of the peptide and the depth in the bilayer at which the order is probed. This significant effect of gA conformation on the lipid order parameter profile suggests that the shape of the gA dimer in the bilayer, which is determined by its conformation, affects the order of the adjacent DOPC lipid acyl chains.

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“…Gramicidin is known to adopt both channel and nonchannel conformations in the membrane. Fortunately, the circular dichroism (CD) signatures of each conformation are completely different and well documented (Lograsso et al, 1988;Morrow et al, 1991;Bano et al, 1991;Killian et al, 1988). We therefore employed this spectroscopic technique to confirm that the peptide had adopted the channel conformation in DLPC, using the sample preparation method described above.…”

Section: Verification Of the Channel Conformation By Circular Dichroismmentioning

confidence: 99%

“…Consequently, this peptide has served as a useful model in the study of lipid/protein interactions and ion conductance (for a recent review see Killian (1992)). The molecule is also known to adopt very distinct conformations depending on its environment (Bystrov and Arseniev, 1988;Wallace, 1992;Lograsso et al, 1988; Morrow et al, 1991;Cox et al, 1992;Greathouse and Koeppe, 1992). We will concentrate on the structural properties of gramicidin A in its channel conformation (Venkatachalam and Urry, 1983) based on the application of solid state deuterium (2H) NMR spectroscopy to the exchange-labeled peptide.…”

Section: Introductionmentioning

confidence: 99%

The structure of an integral membrane peptide: a deuterium NMR study of gramicidin

Prosser¹,

Daleman²,

Davis³

1994

Biophysical Journal

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Solid state deuterium NMR was employed on oriented multilamellar dispersions consisting of 1,2-dilauryl-sn-glycero-3-phosphatidylcholine and deuterium (2H) exchange-labeled gramicidin D, at a lipid to protein molar ratio (L/P) of 15:1, in order to study the dynamic structure of the channel conformation of gramicidin in a liquid crystalline phase. The corresponding spectra were used to discriminate between several structural models for the channel structure of gramicidin (based on the left- and right-handed beta 6.3 LD helix) and other models based on a structure obtained from high resolution NMR. The oriented spectrum is complicated by the fact that many of the doublets, corresponding to the 20 exchangeable sites, partially overlap. Furthermore, the asymmetry parameter, eta, of the electric field gradient tensor of the amide deuterons is large (approximately 0.2) and many of the amide groups are involved in hydrogen bonding, which is known to affect the quadrupole coupling constant. In order to account for these complications in simulating the spectra in the fast motional regime, an ab initio program called Gaussian 90 was employed, which permitted us to calculate, by quantum mechanical means, the complete electric field gradient tensor for each residue in gramicidin (using two structural models). Our results indicated that the left-handed helical models were inconsistent with our observed spectra, whereas a model based on the high-resolution structure derived by Arseniev and coworkers, but relaxed by a simple energy minimization procedure, was consistent with our observed spectra. The molecular order parameter was then estimated from the motional narrowing assuming the relaxed (right-handed) Arseniev structure. Our resultant order parameter of SZZ = 0.91 translates into an rms angle of 14 degrees, formed by the helix axis and the local bilayer normal. The strong resemblance between our spectra (and also those reported for gramicidin in 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) multilayers) and the spectra of the same peptide incorporated in a lyotropic nematic phase, suggests that the lyotropic nematic phase simulates the local environment of the lipid bilayer.

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The effect of changes in gramicidin conformation on bilayer lipid properties

Cited by 13 publications

References 24 publications

Phase equilibria and molecular packing in the N,N-dimethyldodecylamine oxide/gramicidin D/water system studied by 2H nuclear magnetic resonance spectroscopy

Phase equilibria and molecular packing in the N,N-dimethyldodecylamine oxide/gramicidin D/water system studied by 2H nuclear magnetic resonance spectroscopy

Effect of Gramicidin A on Structure and Dynamics of Lipid Vesicle Bilayers. A Time-Resolved Fluorescence Depolarization Study

The structure of an integral membrane peptide: a deuterium NMR study of gramicidin

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