Membrane-Dependent Conformation, Dynamics, and Lipid Interactions of the Fusion Peptide of the Paramyxovirus PIV5 from Solid-State NMR

The entry of enveloped viruses into cells requires protein-catalyzed fusion of the viral and cell membranes. The structure-function relation of a hydrophobic fusion peptide (FP) in viral fusion proteins is still poorly understood. We report magic-angle-spinning solid-state NMR results of the membrane-bound conformation, dynamics, and lipid interactions of the FP of the F protein of the paramyxovirus, parainfluenza virus 5 (PIV5). C-13 chemical shifts indicate that the PIV5 FP structure depends on the composition of the phospholipid membrane: the peptide is alpha-helical in palmitoyloleoylphosphatidylglycerol-containing anionic membranes but mostly beta-sheet in neutral phosphocholine membranes. Other environmental factors, including peptide concentration, cholesterol, membrane reconstitution protocol, and a Lys solubility tag, do not affect the secondary structure. The alpha-helical and beta-sheet states exhibit distinct dynamics and lipid interactions. The beta-sheet FP is immobilized, resides on the membrane surface, and causes significant membrane curvature. In contrast, the alpha-helical FP undergoes intermediate-timescale motion and maintains the lamellar order of the membrane. Two-dimensional P-31-H-1 correlation spectra show clear P-31-water cross peaks for anionic membranes containing the alpha-helical FP but weak or no P-31-water cross peak for neutral membranes containing the beta-sheet FP. These results suggest that the beta-sheet FP may be associated with high-curvature dehydrated fusion intermediates, while the alpha-helical state may be associated with the extended prehairpin state and the post-fusion state. Conformational plasticity is also a pronounced feature of the influenza and human immunodeficiency virus FPs, suggesting that these Gly-rich sequences encode structural plasticity to generate and sense different membrane morphologies. (C) 2012 Published by Elsevier Ltd.