The structure of the membrane-binding 38 C-terminal residues from bovine PP3 determined by liquid- and solid-state NMR spectroscopy

The secondary structure and membrane-associated conformation of a synthetic peptide corresponding to the putative membrane-binding C-terminal 38 residues of the bovine milk component PP3 was determined using H-1 NMR in methanol, CD in methanol and SDS micelles, and N-15 solid-state NMR in planar phospholipid bilayers. The solution NMR and CD spectra reveal that the PP3 peptide in methanol and SDS predominantly adopts an alpha-helical conformation extending over its entire length with a potential bend around residue 19. N-15 solid-state NMR of two PP3 peptides N-15-labelled at the Gly(7) and Ala(32) positions, respectively, and dissolved in dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol phospholipid bilayers shows that the peptide is associated to the membrane surface with the amphipathic helix axis oriented parallel to the bilayer surface.