Lipid interactions with transmembrane proteins.

Magnetic resonance results, principally from 2H-nuclear magnetic resonance, indicate that the mean lipid-chain ordering at the surface of transmembrane proteins is comparable to that in fluid lipid bilayers. Principally, it is the requirement for matching the hydrophobic lengths of lipid and protein that modulates the degree of chain ordering at the lipid-protein interface. The distribution of chain order parameters is, nonetheless, broader in the presence of integral proteins than in fluid lipid bi-layers. The chain configurations of the phospholipids that are resolved in crystals of integral membrane proteins display considerable conformational heterogeneity. Chain C-C dihedral angles are, however, not restricted to the energetically allowable trans and gauche rotamers.This indicates that the chains of a given lipid do not have a unique configuration in protein crystals.