Influence of flanking residues on tilt and rotation angles of transmembrane peptides in lipid bilayers. A solid-state2H NMR study

Özdirekcan, S., Rijkers, D.T.S., Liskamp, R.M.J. and Killian, J.A. (2005) Influence of flanking residues on tilt and rotation angles of transmembrane peptides in lipid bilayers. A solid-state2H NMR study. Biochemistry, 44(3), pp. 1004-1012. (doi: 10.1021/bi0481242)

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To gain insight into the parameters that determine the arrangement of proteins in membranes, 2H NMR experiments were performed to analyze tilt and rotation angles of membrane-spanning α-helical model peptides upon incorporation in diacylphosphatidylcholine bilayers with varying thickness. The peptides consisted of the sequence acetyl-GW2(LA)8LW2A-NH2 (WALP23) and analogues thereof, in which the interfacial Trp residues were replaced by Lys (KALP23) and/or the hydrophobic sequence was replaced by Leu (WLP23 and KLP23). The peptides were synthesized with a single deuterium-labeled alanine at four different positions along the hydrophobic segment. For all peptides a small but systematic increase in tilt angle was observed upon decreasing the bilayer thickness. However, significantly larger tilt angles were obtained for the Lys-flanked KALP23 than for the Trp-flanked WALP23, suggesting that interfacial anchoring interactions of Trp may inhibit tilting. Increasing the hydrophobicity resulted in an increase in tilt angle for the Trp-flanked analogue only. For all peptides the maximum tilt angle obtained was remarkably small (less than 12°), suggesting that further tilting is inhibited, most likely due to unfavorable packing of lipids around a tilted helix. The results furthermore showed that the direction of tilt is determined almost exclusively by the flanking residues:  Trp- and Lys-flanked peptides were found to have very different rotation angles, which were influenced significantly neither by hydrophobicity of the peptides nor by the extent of hydrophobic mismatch. Finally, very small changes in the side chain angles of the deuterated alanine probes were observed in Trp-flanked peptides, suggesting that these peptides may decrease their hydrophobic length to help them to adapt to thin membranes.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Liskamp, Professor Robert
Authors: Özdirekcan, S., Rijkers, D.T.S., Liskamp, R.M.J., and Killian, J.A.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Biochemistry
Publisher:American Chemical Society
ISSN (Online):1520-4995

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