Chapter 2 The nature of the lipid-protein interface and the influence of protein structure on protein-lipid interactions

Abstract

Publisher Summary The integration of transmembrane proteins in the lipid bilayer is one of the most crucial features of biological membrane architecture. Each integral protein is surrounded by a shell of lipids , which mediate the coupling between the hydrophobic intramembranous surface residues and the fluid lipid bilayer. The lipid–protein interface is characterized by the configuration of the lipid chains and by the interaction of the lipid polar headgroups with the protein residues at the polarapolar interface of the membrane. The secondary structure, overall conformation, and the state of oligomerization of the protein clearly play an essential role in determining these parameters. Two important basic parameters that can be used to characterize the lipid–protein interface are the stoichiometry and specificity of the lipid-protein interaction. These quantities are available directly from electron spin resonance (ESR) measurements and can be defined rigorously in thermodynamic/structural terms. The degree of lipid chain ordering in lipid–protein systems can be determined experimentally from magnetic resonance experiments in which the lipid chain segments are labeled either isotopically with deuterium or covalently with free radical spin labels. The dynamic configuration of the lipid chains then can be obtained directly from the segmental order parameter deduced from the 2H nuclear magnetic resonance (NMR) spectrum, or from the angular dependence of the spin label ESR spectrum from oriented specimens.