title: Protein-induced bilayer perturbations: Lipid ordering and hydrophobic coupling.
abstract: The host lipid bilayer is increasingly being recognized as an important non-specific regulator of membrane protein function. Despite considerable progress the interplay between hydrophobic coupling and lipid ordering is still elusive. We use electron spin resonance (ESR) to study the interaction between the model protein gramicidin and lipid bilayers of varying thickness. The free energy of the interaction is up to -6kJ/mol; thus not strongly favored over lipid-lipid interactions. Incorporation of gramicidin results in increased order parameters with increased protein concentration and hydrophobic mismatch. Our findings also show that at high protein:lipid ratios the lipids are motionally restricted but not completely immobilized. Both exchange on and off rate values for the lipid<-->gramicidin interaction are lowest at optimal hydrophobic matching. Hydrophobic mismatch of few A results in up to 10-fold increased exchange rates as compared to the 'optimal' match situation pointing to the regulatory role of hydrophobic coupling in lipid-protein interactions.
authors.affiliation: Quantum Protein Center, Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark.
authors.forename: Frederic N R
authors.initials: FN
authors.lastname: Petersen
authors.forename: Ib
authors.initials: I
authors.lastname: Laursen
authors.forename: Henrik
authors.initials: H
authors.lastname: Bohr
authors.forename: Claus Hélix
authors.initials: CH
authors.lastname: Nielsen
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D006096:Gramicidin / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D008051:Lipid Bilayers; D008055:Lipids; D006096:Gramicidin