Tryptophan-anchored transmembrane peptides promote formation of nonlamellar phases in phosphatidylethanolamine model membranes in a mismatch-dependent manner
by Van der Wel, Patrick C. A.; Pott, Tanja; Morein, Sven; Greathouse, Denise V.; Koeppe II, R. Erdman; Killian, Josephine Antoinette
TO better understand the mutual interactions between lipids and membrane-spanning peptides, we investigated the effects of tryptophan-anchored hydrophobic peptides of various lengths on the phase behavior of 1,2-dielaidoylphosphatidylethanolamine (DEPE) dispersions, using (31)p nuclear magnetic resonance and small-angle X-ray diffraction. Designed cc-helical transmembrane peptides (WALPn peptides, with n being the total number of amino acids) with a hydrophobic sequence of leucine and alanine: of varying length, bordered at both ends by two tryptophan membrane anchors, were used as model peptides and were effective at low concentrations in DEPE. Incorporation of 2 mol % of relatively short peptides (WALP14-17) lowered the inverted hexagonal phase transition temperature (T-H) of DEPE, with an efficiency that seemed to be independent of the extent of hydrophobic mismatch. However, the tube diameter of the Hu phase induced by the peptides was clearly dependent on mismatch and decreased with shorter peptide length. Longer peptides (WALP19-27) induced a cubic phase, both below and above Ts, Incorporation of WALP27, which is significantly longer than the DEPE bilayer thickness, did not stabilize the bilayer. The longest peptide used, WALP31, hardly affected the Lipid's phase behavior, and appeared not to incorporate into the bilayer. The consequences of hydrophobic mismatch between peptides and lipids are therefore more dramatic with shorter peptides. The data allow us to suggest a detailed molecular model of the mechanism by which these transmembrane peptides can affect lipid phase behavior.
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- 1520-4995; 0006-2960