Nonlamellar Phases Induced by the Interaction of Gramicidin S with Lipid Bilayers. A Possible Relationship to Membrane-Disrupting Activity
The interactions of the cyclic peptide gramicidin S (GS) with a variety of single-component lipid bilayers, and with membrane polar lipid extracts of Acholeplasma laidlawii B and Escherichia coli, were examined by differential scanning calorimetry (DSC), 31P-nuclear magnetic resonance (NMR) spectros...
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Published in | Biochemistry (Easton) Vol. 36; no. 25; pp. 7906 - 7916 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
24.06.1997
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Subjects | |
Online Access | Get full text |
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Summary: | The interactions of the cyclic peptide gramicidin S (GS) with a variety of single-component lipid bilayers, and with membrane polar lipid extracts of Acholeplasma laidlawii B and Escherichia coli, were examined by differential scanning calorimetry (DSC), 31P-nuclear magnetic resonance (NMR) spectroscopy, and X-ray diffraction. The DSC data indicate that the effects of GS on the thermotropic phase behavior of phosphatidylcholine and phosphatidylethanolamine dispersions are compatible with those expected of peptides interacting primarily with the polar headgroup and/or the polar/apolar interfaces of lipid bilayers. These DSC studies also suggest that GS exhibits stronger interactions with the more fluid bilayers. For mixtures of GS with lipids such as phosphatidylcholine, phosphatidylserine, cardiolipin, and sphingomyelin, axially symmetric 31P-NMR powder patterns are observed throughout the entire temperature range examined (0−90 °C), and there is little evidence for significant destabilization of the lipid bilayer with respect to nonlamellar phases. With mixtures of GS with either phosphatidylethanolamine, phosphatidylglycerol, or a nonlamellar phase-forming phosphatidylcholine, axially symmetric 31P-NMR powder patterns are also observed at low temperatures. However, at high temperatures, an isotropic component is observed in their 31P-NMR spectra, and the relative intensity of this component increases significantly with temperature and with GS concentration. Once formed at high temperatures, this isotropic component exhibits a marked cooling hysteresis and in most cases disappears only when the sample is recooled to temperatures well below the lipid hydrocarbon chain-melting phase transition temperature. We also show that GS induces the formation of isotropic components in the 31P-NMR spectra of heterogeneous lipid mixtures such as occur in A. laidlawii B and E. coli membranes. These observations suggest that GS induces the formation of cubic or other three dimensionally ordered inverted nonlamellar phases when it interacts with some types of lipid bilayers, a suggestion strongly supported by our X-ray diffraction studies. Our results also suggest that the capacity of GS to induce the formation of such phases increases with the intrinsic nonlamellar phase-preferring tendencies of the lipids with which it interacts probably by producing localized increases in membrane monolayer curvature stress. The latter effect could be part of the mechanism through which this peptide exhibits its antimicrobial and hemolytic activities. |
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Bibliography: | Abstract published in Advance ACS Abstracts, May 15, 1997. ark:/67375/TPS-WFTX6T02-5 istex:1FF143F0271BC8926C19099C1A47D6B4F9A90731 This work was supported by operating and major equipment grants from the Medical Research Council of Canada (R.N.M. and R.S.H.), by major equipment grants from the Alberta Heritage Foundation for Medical Research (R.N.M. and R.S.H.), by the Protein Engineering Network of Centers of Excellence, by grants from the U.S. DOE (S.M.G.), by a Liposome fellowship to K.C.N., and by postdoctoral fellowships to E.J.P. and L.H.K. from the Alberta Heritage Foundation for Medical Research and the Protein Engineering Network of Centers of Excellence, respectively. ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 0006-2960 1520-4995 |
DOI: | 10.1021/bi962785k |