Properties of Membrane-Incorporated WALP Peptides That Are Anchored on Only One End

by Rankenberg, J. M.; Vostrikov, V. V.; Greathouse, D. V.; Grant, C. V.; Opella, S. J.; Koeppe, R. E.

Peptides of the "WALP" family, acetyl-GWW(LA)(n)LWWA-[ethanol]amide, have proven to be opportune models for investigating lipid peptide interactions. Because the average orientations and motional behavior of the N- and C-terminal Trp (W) residues differ, it is of interest to investigate how the positions of the tryptophans influence the properties of the membrane-incorporated peptides. To address this question, we synthesized acetyl-GGWW-(LA)(n)-ethanolamide and acetyl-(AL)(n)WWG-ethanolamide, in which n = 4 or 8, which we designate as "N-anchored" and "C-anchored" peptides, respectively. Selected H-2 or N-15 labels were incorporated for solid-state nuclear magnetic resonance (NMR) spectroscopy. These peptides can be considered "half-anchored WALP peptides, having only one pair of interfacial Trp residues near either the amino or the carboxyl terminus. The hydrophobic lengths of the (n = 8) peptides are similar to that of WALP23. These longer half-anchored WALP peptides incorporate into lipid bilayers as a-helices, as reflected in their circular dichroism spectra. Solid-state NMR experiments indicate that the longer peptide helices assume defined transmembrane orientations with small non-zero average tilt angles and moderate to high dynamic averaging in bilayer membranes of 1,2-dioleoylphosphatidylcholine, 1,2-dimyristoylphosphatidylcholine, and 1,2-dilauroylphosphatidylcholine. The intrinsically small apparent tilt angles suggest that interactions of aromatic residues with lipid headgroups may play an important role in determining the magnitude of the peptide tilt in the bilayer membrane. The shorter (n = 4) peptides, in stark contrast to the longer peptides, display NMR spectra that are characteristic of greatly reduced motional averaging, probably because of peptide aggregation in the bilayer environment, and CD spectra that are characteristic of beta-structure.

Journal
Biochemistry
Volume
51
Issue
50
Year
2012
Start Page
10066-10074
URL
https://dx.doi.org/10.1021/bi301394z
ISBN/ISSN
1520-4995; 0006-2960
DOI
10.1021/bi301394z