title: Dynamic changes during acid-induced activation of influenza hemagglutinin.
abstract: Influenza hemagglutinin (HA) mediates virus attachment to host cells and fusion of the viral and endosomal membranes during entry. While high-resolution structures are available for the pre-fusion HA ectodomain and the post-fusion HA2 subunit, the sequence of conformational changes during HA activation has eluded structural characterization. Here, we apply hydrogen-deuterium exchange with mass spectrometry to examine changes in structural dynamics of the HA ectodomain at various stages of activation, and compare the soluble ectodomain with intact HA on virions. At pH conditions approaching activation (pH 6.0-5.5) HA exhibits increased dynamics at the fusion peptide and neighboring regions, while the interface between receptor binding subunits (HA1) becomes stabilized. In contrast to many activation models, these data suggest that HA responds to endosomal acidification by releasing the fusion peptide prior to HA1 uncaging and the spring-loaded refolding of HA2. This staged process may facilitate efficient HA-mediated fusion.
authors.affiliation: Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195, USA.
authors.forename: Natalie K
authors.initials: NK
authors.lastname: Garcia
authors.affiliation: Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195, USA.
authors.forename: Miklos
authors.initials: M
authors.lastname: Guttman
authors.affiliation: Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195, USA.
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Ebner
authors.affiliation: Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195, USA. Electronic address: kklee@uw.edu.
authors.forename: Kelly K
authors.initials: KK
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry* / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D021122:Protein Subunits; D006859:Hydrogen