PEPTIDE SECONDARY STRUCTURE INDUCED BY A MICELLAR PHOSPHOLIPIDIC INTERFACE - PROTON NMR CONFORMATIONAL STUDY OF A LIPOPEPTIDE

The conformational change of the model peptide Ac-K-G-R-G-D-G-amide induced by a phospholipidic interface was investigated by proton nuclear magnetic resonance (H-1 NMR). In aqueous solution, the free peptide is highly flexible and disordered, even in the presence of deuterated dodecylphosphocholine (DPC-d38) micelles which mimic a membrane interface. The lipopeptide, obtained by grafting a lipid anchor [2,3-dipalmitoyl-D-(+)-glyceric acid] to the lysine side chain of the peptide, was studied by standard 2D H-1 NMR spectroscopy combined with distance geometry and simulated annealing calculations. When anchored to a micelle interface, the peptide acquires a definite turn (II/I') conformation. We were also able to describe precisely the conformation of the diacylglyceric fragment of the lipopeptide in a lipid environment and to establish the average orientation of the peptide segment with respect to the micelle surface.