Solid-State NMR Approaches to Transmembrane Peptide Tilt

by Vostrikov, Vitaly V.; Koeppe II, R. Erdman

Single-span transmembrane peptides of the "WALP" family maintain bilayer-spanning orientations because of the presence of arom. or cationic groups that "anchor" to the membrane/water interface. These peptides exhibit a small tilt in model hydrated lipid bilayer membranes and precess about the bilayer normal. Example peptides include WALP19 [acetyl-GWW(LA)6LWWA-ethanolamide], WALP23 [acetyl-GWW(LA)8LWWA-ethanolamide], and KWALP23 [acetyl-GKALW(LA)6LWLAKA-amide]. Example lipids include dioleoylphosphatidylcholine [DOPC], dimyristoylphosphatidylcholine [DMPC], and dilauroylphosphatidylcholine [DLPC]. The transmembrane peptide tilt (with respect to the lipid bilayer normal) can be monitored using solid-state NMR spectroscopy, by observing either a series of 2H quadrupolar splittings (from labeled alanine side chains) or a series of 15N-1H dipolar couplings (from labeled backbone NH groups). In this report we present and compare measurements of the tilt of KWALP23 and selected other WALP family peptides using both of the NMR methods.