Dynamic properties of gramicidin A in phospholipid membranes

Macdonald, P. M. and Seelig, J.. (1988) Dynamic properties of gramicidin A in phospholipid membranes. Biochemistry, Vol. 27, H. 7. pp. 2357-2364.

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Official URL: http://edoc.unibas.ch/dok/A5257485

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The flexibility of the tryptophan side chains of gramicidin A and the rotational diffusion of the peptide in methanolic solution and in three membrane systems were studied with deuterium nuclear magnetic resonance (NMR). Gramicidin A was selectively deuterated at the aromatic ring systems of its four tryptophan side chains. In methanolic solution, the tryptophan residues remained immobile and served as a probe for the overall rotation of the peptide. The experimentally determined rotational correlation time of tau c = 0.6 X 10(-9) s was consistent with the formation of gramicidin A dimers. For gramicidin A incorporated into bilayer membranes, quite different results were obtained depending on the chemical and physical nature of the lipids employed. When mixed with 1-palmitoyl-sn-glycero-3-phosphocholine (LPPC) at a stoichiometric lipid:peptide ratio of 4:1, gramicidin A induced the formation of stable bilayer membranes in which the lipids were highly fluid. In contrast, the gramicidin A molecules of this membrane remained completely static over a large temperature interval, suggesting strong protein-protein interactions. The peptide molecules appeared to form a rigid two-dimensional lattice in which the interstitial spaces were filled with fluidlike lipids. When gramicidin A was incorporated into bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) above the lipid phase transition, the deuterium NMR spectra were motionally narrowed, indicating large-amplitude rotational fluctuations. From the measurement of the quadrupole echo relaxation time, a rotational correlation time of 2 X 10(-7) s was estimated, leading to a membrane viscosity of 1-2 P if the rotational unit was assumed to be a gramicidin A dimer. (ABSTRACT TRUNCATED AT 250 WORDS)
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Biophysical Chemistry (Seelig J)
UniBasel Contributors:Seelig, Joachim
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:19
Deposited On:22 Mar 2012 13:18

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