title: Self-association of model transmembrane alpha-helices is modulated by lipid structure.
abstract: We have developed a fluorescence quenching method using peptides containing 3,5-dibromotryrosine to measure oligomerization of model transmembrane alpha-helices in lipid bilayers. Peptides of the type Ac-LysLysGlyLeu(m)XLeu(n)LysLysAla-amide where X is tryptophan or 3,5-dibromotyrosine were found to form heterodimers in bilayers of phosphatidylcholine in the liquid-crystalline phase. The free energy of dimer formation changed little with increasing number of Leu residues from 16 to 22 but increased with increasing phospholipid fatty acyl chain length, with a slope of about 0.5 kJ mol(-1) per fatty acyl chain carbon. Peptides were excluded from lipid in the gel phase, resulting in increased levels of oligomerization. Addition of cholesterol to form the liquid-ordered state led to increased dimerization but without phase separation. The presence of phosphatidylethanolamine had little effect on dimerization.
authors.affiliation: Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK.
authors.forename: S
authors.initials: S
authors.lastname: Mall
authors.forename: R
authors.initials: R
authors.lastname: Broadbridge
authors.forename: R P
authors.initials: RP
authors.lastname: Sharma
authors.forename: J M
authors.initials: JM
authors.lastname: East
authors.forename: A G
authors.initials: AG
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D019281:Dimerization; D005453:Fluorescence; D005782:Gels; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D008567:Membranes, Artificial; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D005782:Gels; D008051:Lipid Bilayers; D008565:Membrane Proteins; D008567:Membranes, Artificial; D010455:Peptides; D014443:Tyrosine; C082610:3,5-dibromotyrosine