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Hydrophobic mismatch between helices and lipid bilayers
Thomas M Weiss1, Patrick C A van der Wel, J Antoinette Killian
1Department of Physics and Astronomy, Rice University, Houston, Texas 77251, USA.
Biophysical Journal
|January 14, 2003
Summary
Transmembrane peptides called WALPs were studied in lipid bilayers. Unlike gramicidin, WALPs did not change bilayer thickness, suggesting different lipid chain packing around single helices versus large proteins.
Area of Science:
- Membrane biophysics
- Protein-lipid interactions
- Biomolecular structure
Background:
- Alpha-helical transmembrane peptides (WALPs) with tryptophan anchors are used to study hydrophobic matching.
- Hydrophobic matching is crucial for understanding peptide and protein behavior within lipid bilayers.
Purpose of the Study:
- To investigate the effect of hydrophobic matching on WALP peptides within different lipid bilayers.
- To compare the behavior of WALPs to other transmembrane proteins like gramicidin.
Main Methods:
- Synthesis of WALP peptides of varying lengths (13, 16, 19 residues).
- Incorporation of WALPs into synthetic lipid bilayers (12C, 13C, 14C).
- Analysis using oriented circular dichroism and x-ray diffraction.
Main Results:
- WALPs integrated homogeneously into lipid bilayers with helical axes nearly perpendicular to the bilayer plane.
- X-ray diffraction revealed that WALPs did not alter the overall bilayer thickness.
- This contrasts with gramicidin, which induced significant changes in bilayer thickness.
Conclusions:
- The packing of lipid chains around a single transmembrane helix differs fundamentally from packing around larger protein surfaces.
- WALPs provide a model system to study specific aspects of peptide-membrane interactions without altering bilayer dimensions.