title: De novo design of a peptide which partitions between water and phospholipid bilayers as a monomeric alpha-helix.
abstract: To dissect the determinants of protein insertion into membranes, we designed a model peptide which partitions between water and phospholipid bilayers as an alpha-helical monomer. We used a simplex method to optimize the 'a, d hydrophobicity' and 'e, g charge' of a series of five peptides, where 'abcdefg' correspond to the positions in two turns of an alpha-helix. Circular dichroism and analytical ultra-centrifugation experiments showed that the final peptide (helix5) is monomeric and has an alpha-helix content of approximately 89% at 0 degrees C in aqueous solution. In the presence of large unilamellar vesicles (LUVs), helix5 partitions between the aqueous and membranous phases with a partition constant well suited for measurements by electron paramagnetic resonance (EPR) spectroscopy. EPR power saturation experiments with a cysteine-scanning strategy showed that the alpha-helicity of helix5 is conserved upon binding to LUVs and that the alpha-helix binds parallel to the membrane surface with the central axis approximately 5 A below the lipid phosphate groups. Helix5 should be a useful model peptide for studies aimed at dissecting the determinants of the membrane binding of alpha-helices. The simplex-based strategy may be useful in the rational design of proteins when desired structural or partitioning properties cannot be selected or screened from libraries.
authors.affiliation: Department of Chemistry, University of California, Berkeley 94720, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Russell
authors.forename: D S
authors.initials: DS
authors.lastname: King
authors.forename: T E
authors.initials: TE
authors.lastname: Thorgeirsson
authors.forename: Y K
authors.initials: YK
authors.lastname: Shin
mesh_terms: D015195:Drug Design; D008051:Lipid Bilayers; D010455:Peptides / Q000737:chemistry*; D010743:Phospholipids; D015202:Protein Engineering; D017510:Protein Folding; D014867:Water
chemical_list: D008051:Lipid Bilayers; D010455:Peptides; D010743:Phospholipids; D014867:Water