Effects of histone and diolein on the structure of phosphatidylcholine/phosphatidylserine or phosphatidylcholine/phosphatidylglycerol bilayers

The effects of the PKC substrate histone 1 and the PKC activator diolein (O le(2)Gro) on the structure of phosphatidylcholine (PtdCho)/phosphatidylseri ne (PtdSer), or PrdCho/phosphatidylglycerol (PtdGro) bilayers were studied using H-2-NMR. The results showed that in PtdCho/PtdSer bilayers, histone p referentially increased order parameters of the acyl chains of the PtdSer, but not the PtdCho lipid component, This effect was additive with the effec t of Ole(2)Gro, which equally increased the ordering of the acyl chains of both PtdCho and PtdSer. The histone-induced change in the conformation of t he PtdCho handgroups in PtdCho/PtdSer bilayers indicated that positively ch arged residues of the bound histone are located above the lipid-water inter face and their location was altered by the presence of Ole(2)Gro. A differe nt picture was observed in the case of PtdCho/PtdGro bilayers, although the effect of Ole(2)Glo on both the PtdCho or the PtdGro components was simila r to the case of the PtdCho/PtdSer bilayers, histone did not significantly affect the order parameters of PtdCho or PtdGro in either the absence or pr esence of Ole(2)Gro. The results indicate that histone 1 induces clustering of PtdSer in PtdCho bilayers which may contribute to PKC activation. Moreo ver, the observed differences in the interactions of histone with PtdCho/Pt dSer compared with PtdCho/PtdGro bilayers may explain the higher efficiency of PtdSer in activating PKC.