title: Combined NMR and EPR spectroscopy to determine structures of viral fusion domains in membranes.
abstract: Methods are described to determine the structures of viral membrane fusion domains in detergent micelles by NMR and in lipid bilayers by site-directed spin labeling and EPR spectroscopy. Since in favorable cases, the lower-resolution spin label data obtained in lipid bilayers fully support the higher-resolution structures obtained by solution NMR, it is possible to graft the NMR structural coordinates into membranes using the EPR-derived distance restraints to the lipid bilayer. Electron paramagnetic dynamics and distance measurements in bilayers support conclusions drawn from NMR in detergent micelles. When these methods are applied to a structure determination of the influenza virus fusion domain and four point mutations with different functional phenotypes, it is evident that a fixed-angle boomerang structure with a glycine edge on the outside of the N-terminal arm is both necessary and sufficient to support membrane fusion. The human immunodeficiency virus fusion domain forms a straight helix with a flexible C-terminus. While EPR data for this fusion domain are not yet available, it is tentatively speculated that, because of its higher hydrophobicity, a critically tilted insertion may occur even in the absence of a kinked boomerang structure in this case.
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA. lkt2e@virginia.edu
authors.forename: Lukas K
authors.initials: LK
authors.lastname: Tamm
authors.forename: Alex L
authors.initials: AL
authors.lastname: Lai
authors.forename: Yinling
authors.initials: Y
authors.lastname: Li
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D015700:HIV Envelope Protein gp41 / Q000737:chemistry; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008823:Micelles; D017434:Protein Structure, Tertiary
chemical_list: D015700:HIV Envelope Protein gp41; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D008051:Lipid Bilayers; D008823:Micelles