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 spectros copy, and the effects of binding a peripheral protein, cytochrome c, w ere evaluated. The fast headgroup segmental motions (tau(c), 10(-10)-1 0(-13) s) of DOPG in fully hydrated bilayers were not affected upon bi nding of cytochrome c, as evaluated by the spin-lattice (T-1) relaxati on of deuterons in the DOPG glycerol headgroup. In contrast, the spin- spin (T-2e) relaxation is strongly affected, indicating that slow coop erative bilayer motions (tau(c), 10(-3)-10(-6) s) are enhanced upon th e interaction with cytochrome c. H-2 and P-31 NMR Spectral lineshape a nalysis reveal details of the nature of these motions. The importance of these effects are discussed in terms of a possible mechanism for mo dulating membrane-associated processes. (C) 1997 Elsevier Science B.V.