Immobilization and Aggregation of the Antimicrobial Peptide Protegrin-1 in Lipid Bilayers Investigated by Solid-State NMR

• Published in: Biochemistry (Easton) Vol. 42; no. 46; pp. 13725 - 13734
• Main Authors: Buffy, Jarrod J, Waring, Alan J, Lehrer, Robert I, Hong, Mei
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 25-11-2003
• Subjects: Anisotropy; Antimicrobial Cationic Peptides; Diffusion; Lipid Bilayers - chemistry; Nuclear Magnetic Resonance, Biomolecular - methods; Phosphorylcholine - chemistry; Protein Structure, Secondary; Proteins - chemistry
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi035187w

The dynamics and aggregation of a β-sheet antimicrobial peptide, protegrin-1 (PG-1), are investigated using solid-state NMR spectroscopy. Chemical shift anisotropies of F12 and V16 carbonyl carbons are uniaxially averaged in 1,2-dilauryl-sn-glycero-3-phosphatidylcholine (DLPC) bilayers but approach rigid-limit values in the thicker 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphatidylcholine (POPC) bilayers. The Cα−Hα dipolar coupling of L5 is scaled by a factor of 0.16 in DLPC bilayers but has a near-unity order parameter of 0.96 in POPC bilayers. The larger couplings of PG-1 in POPC bilayers indicate immobilization of the peptide, suggesting that PG-1 forms oligomeric aggregates at the biologically relevant bilayer thickness. Exchange NMR experiments on F12 13CO-labeled PG-1 show that the peptide undergoes slow reorientation with a correlation time of 0.7 ± 0.2 s in POPC bilayers. This long correlation time suggests that in addition to aggregation, geometric constraints in the membrane may also contribute to PG-1 immobilization. The PG-1 aggregates contact both the surface and the hydrophobic center of the POPC bilayer, as determined by 1H spin-diffusion measurements. Thus, solid-state NMR provides a wide range of information about the molecular details of membrane peptide immobilization and aggregation in lipid bilayers.