title: Conformational change of influenza virus hemagglutinin is sensitive to ionic concentration.
abstract: The homotrimeric spike glycoprotein hemagglutinin (HA) of influenza virus undergoes a low pH-mediated conformational change which mediates the fusion of the viral envelope with the target membrane. Previous approaches predict that the interplay of electrostatic interactions between and within HA subunits, HA 1 and HA2, are essential for the metastability of the HA ectodomain. Here, we show that suspension media of low ionic concentration promote fusion of fluorescent labelled influenza virus X31 with erythrocyte ghosts and with ganglioside containing liposomes. By measuring the low pH mediated inactivation of the fusion competence of HA and the Proteinase K sensitivity of low pH incubated HA we show that the conformational change is promoted by low ionic concentration. We surmise that electrostatic attraction within the HA ectodomain is weakened by lowering the ionic concentration facilitating the conformational change at low pH.
authors.affiliation: Institute of Biology, Molecular Biophysics, Humboldt University, Berlin 10115, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Korte
authors.forename: Kai
authors.initials: K
authors.lastname: Ludwig
authors.forename: Qiang
authors.initials: Q
authors.lastname: Huang
authors.forename: P Sivaramakrishna
authors.initials: PS
authors.lastname: Rachakonda
authors.forename: Andreas
authors.initials: A
authors.lastname: Herrmann
mesh_terms: D002478:Cells, Cultured; D004910:Erythrocyte Membrane / Q000821:virology*; D006389:Hemagglutinins, Viral / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009975:Orthomyxoviridae / Q000737:chemistry* / Q000502:physiology*; D011487:Protein Conformation; D014775:Virus Activation / Q000502:physiology*; D053585:Virus Attachment; D053586:Virus Internalization
chemical_list: D006389:Hemagglutinins, Viral; C452559:hemagglutinin HA-2 fusogenic peptide, Influenza virus