Structures and lipid interactions of curvature-inducing membrane peptides by NMR

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Abstract Many membrane peptides and proteins generate membrane curvature to carry out their function. Examples include cationic peptides that disrupt or cross lipid membranes by forming permanent or transient pores and viral fusion proteins that merge the virus envelope and the target cell membrane to cause virus entry. Thus, elucidating the fundamental mechanism of membrane- curvature induction has broad significance for designing resistance-free antibiotics and for developing new vaccines and antiviral drugs. The long-term objective of this project is to understand and quantify lipid-specific interactions of curvature-inducing membrane peptides. We will use solid-state NMR as our main tool, because it is uniquely capable of simultaneously probing the high-resolution structures of membrane proteins and revealing the physical properties of the lipid membrane in which these proteins are embedded. We propose four specific aims. 1) We will investigate cationic-peptide-induced lipid clustering in bacteria- mimetic membranes. Potential segregation of anionic and zwitterionic lipids of bacterial membranes may be a significant factor in promoting membrane curvature. Isotope-edited NMR experiments will be conducted to measure lipid dynamics and peptide-lipid interactions. Representative antimicrobial and cell-penetrating peptides such as PG-1 and HIV TAT will be examined. 2) We will develop 31P exchange NMR techniques to measure the curvature of mixed lipid membranes and the localization of cationic peptides in curvature-distinct domains. 3) We will determine the membrane-bound conformation, dynamics, and depth of insertion of the fusion peptide and transmembrane domain of the fusion protein of the paramyxovirus, PIV5. Structure information of the PIV5 fusion protein will provide insight into the mechanism of action of class I viral fusion proteins. 4) We will investigate the lipid interactions of the PIV5 fusion peptide using 2H, 31P, and 1H NMR experiments. Membrane curvature, peptide localization and membrane hydration will be measured to understand how the peptide modifies the membrane structure to cause fusion.