The interaction of [Met5]enkephalin-Arg-Phe with phosphatidylserine (PtdSer) was studied by circular dichroism (CD), two-dimensional nuclear magnetic resonance spectroscopy, hybrid distance geometry simulated annealing (DG-SA) and molecular dynamics (MD) calculations. The very low solubility of [Met5]enkephalin-Arg-Phe and the instability of the solution containing PtdSer vesicles at low pH values did not allow us to observe the amide proton resonances in the usual two-dimensional NMR work. NOESY cross-peaks of protons of side chains from two-dimensional NMR were converted into distances which were used as restraints for modelling with DG-SA and MD. Our results indicate that, in aqueous solutions at pH 7.68 [Met5]enkephalin-Arg-Phe exists in the absence of PtdSer as a random distribution of conformers, whereas in the presence of PtdSer it adopts conformations containing a common orientation of the bonds of C alpha 2, C alpha 3, C alpha 4 and C alpha 5, although different orientations of the peptide planes are consistent with the results. Two of the reported conformers from MD simulations are characterized by the presence of a 2<--4 gamma and inverse gamma turns centered on Gly3. A gradual decline of order was observed when moving from the central moiety of the peptide to both the N-terminus and C-terminus. Finally, the DG-SA and MD calculations resulted in a structure such that the orientation of the Phe4 and MetS side chains favours hydrophobic interactions with the apolar portion of the PtdSer vesicle to form a hydrophobic cluster These data support the hypothesis of a role of lipids to modify the conformation of [Met5]enkephalin-Arg-Phe to permit the interactions with the receptor site.
D'Alagni, M., Delfini, M., Di Nola, A., Eisenberg, M., Paci, M., Roda, L., et al. (1996). Conformational study of [Met5]enkephalin-Arg-Phe in the presence of phosphatidylserine vesicles. EUROPEAN JOURNAL OF BIOCHEMISTRY, 240(3), 540-549 [10.1111/j.1432-1033.1996.0540h.x].
Conformational study of [Met5]enkephalin-Arg-Phe in the presence of phosphatidylserine vesicles
PACI, MAURIZIO;
1996-01-01
Abstract
The interaction of [Met5]enkephalin-Arg-Phe with phosphatidylserine (PtdSer) was studied by circular dichroism (CD), two-dimensional nuclear magnetic resonance spectroscopy, hybrid distance geometry simulated annealing (DG-SA) and molecular dynamics (MD) calculations. The very low solubility of [Met5]enkephalin-Arg-Phe and the instability of the solution containing PtdSer vesicles at low pH values did not allow us to observe the amide proton resonances in the usual two-dimensional NMR work. NOESY cross-peaks of protons of side chains from two-dimensional NMR were converted into distances which were used as restraints for modelling with DG-SA and MD. Our results indicate that, in aqueous solutions at pH 7.68 [Met5]enkephalin-Arg-Phe exists in the absence of PtdSer as a random distribution of conformers, whereas in the presence of PtdSer it adopts conformations containing a common orientation of the bonds of C alpha 2, C alpha 3, C alpha 4 and C alpha 5, although different orientations of the peptide planes are consistent with the results. Two of the reported conformers from MD simulations are characterized by the presence of a 2<--4 gamma and inverse gamma turns centered on Gly3. A gradual decline of order was observed when moving from the central moiety of the peptide to both the N-terminus and C-terminus. Finally, the DG-SA and MD calculations resulted in a structure such that the orientation of the Phe4 and MetS side chains favours hydrophobic interactions with the apolar portion of the PtdSer vesicle to form a hydrophobic cluster These data support the hypothesis of a role of lipids to modify the conformation of [Met5]enkephalin-Arg-Phe to permit the interactions with the receptor site.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.