Phospholipid headgroup dynamics in DOPG-d(5) cytochrome c complexes as revealed by H-2 and P-31 NMR: The effects of a peripheral protein on collective lipid fluctuations

The dynamics of the glycerol headgroup of dioleoylphosphatidylglycerol (DOPG) in hydrated bilayers were studied by H-2 and P-31 NMR spectroscopy, and the effects of binding a peripheral protein, cytochrome c, were evaluated. The fast headgroup segmental motions (tau(c), 10(-10)-10(-13) s) of DOPG in fully hydrated bilayers were not affected upon binding of cytochrome c, as evaluated by the spin-lattice (T-1) relaxation of deuterons in the DOPG glycerol headgroup. In contrast, the spin-spin (T-2e) relaxation is strongly affected, indicating that slow cooperative bilayer motions (tau(c), 10(-3)-10(-6) s) are enhanced upon the interaction with cytochrome c. H-2 and P-31 NMR Spectral lineshape analysis reveal details of the nature of these motions. The importance of these effects are discussed in terms of a possible mechanism for modulating membrane-associated processes. (C) 1997 Elsevier Science B.V.