Hydrophobic mismatch between helices and lipid bilayers.
alpha-Helical transmembrane peptides, named WALP, with a hydrophobic sequence of leucine and alanine of varying length bordered at both ends by two tryptophans as membrane anchors, were synthesized to study the effect of hydrophobic matching in lipid bilayers. WALPs of 13-, 16-, and 19-residues were incorporated into 1,2-dilauroyl-sn-glycero-3-phosphocholine (12C), 1,2-tridecanoyl-sn-glycero-3-phosphocholine (13C), and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (14C) bilayers in the form of oriented multilayers. Oriented circular dichroism spectra and x-ray diffraction patterns showed that the peptides were homogenously distributed in the lipid bilayers with the helical axes oriented approximately normal to the plane of bilayers. But in all cases, x-ray diffraction showed that the peptides did not alter the thickness of the bilayer. This is contrary to the case of gramicidin where 1,2-dimyristoyl-sn-glycero-3-phosphocholine and 1,2-dilauroyl-sn-glycero-3-phosphocholine clearly thinned and thickened, respectively, to approach the hydrophobic thickness of the gramicidin channels. The result seems to indicate that the packing of lipid chains around a single helix is fundamentally different from the way the chains pack against a large protein surface.
Weiss
Thomas M
TM
Department of Physics and Astronomy, Rice University, Houston, Texas 77251, USA.
van der Wel
Patrick C A
PC
Killian
J Antoinette
JA
Koeppe
Roger E
RE
Huang
Huey W
HW
D002942:Circular Dichroism / Q000379:methods; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D046911:Macromolecular Substances; D008560:Membrane Fluidity; D008565:Membrane Proteins / Q000138:chemical synthesis / Q000737:chemistry*; D008567:Membranes, Artificial; D008968:Molecular Conformation; D010713:Phosphatidylcholines / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction / Q000379:methods
D008051:Lipid Bilayers; D008081:Liposomes; D046911:Macromolecular Substances; D008565:Membrane Proteins; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D014867:Water