Structure and dynamics of the antibiotic peptide PGLa in membranes by solution and solid-state nuclear magnetic resonance spectroscopy

PGLa, a 21-residue member of the magainin family of antibiotic peptides, is shown to be helical between residues 6 and 21 when associated with detergent micelles by multidimensional solution nuclear magnetic resonance (NMR) spectroscopy. Solid-state NMR experiments on specifically N-15-labeled peptides in oriented phospholipid bilayer samples show that the helix axis is parallel to the plane of the bilayers, N-15 solid-state NMR powder pattern line shapes obtained on unoriented samples demonstrate that the amino-terminal residues are highly mobile and that the fluctuations of backbone sites decrease from Ala6 toward the carboxy terminus. The powder pattern observed for N-15-labeled Ala20 is essentially that expected for a rigid site. These findings are similar to those for the 23-residue magainin2 peptide in membrane environments.