title: Electron microscopy of the low pH structure of influenza virus haemagglutinin.
abstract: Influenza virus haemagglutinin mediates infection of cells by fusion of viral and endosomal membranes, triggered by low pH which induces a conformational change in the protein. We report studies of this change by electron microscopy, neutron scattering, sedimentation and photon correlation on X-31 (H3N2) haemagglutinin, both intact and bromelain cleaved, in various assemblies. HAs in all preparations showed a thinning at low pH, and a marked elongation which was removed on tryptic digestion, revealing altered features in the remaining stem portion of the molecule. A tentative model of the change is proposed, with reference to the known X-ray structure at neutral pH, in which major changes occur in the stem tertiary structure, while the top portion is only affected in its quaternary structure.
mesh_terms: D000818:Animals; D002642:Chick Embryo; D006389:Hemagglutinins, Viral / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008854:Microscopy, Electron; D008970:Molecular Weight; D009502:Neutrons; D009975:Orthomyxoviridae / Q000502:physiology*; D010446:Peptide Fragments / Q000032:analysis; D012542:Scattering, Radiation; D014357:Trypsin
chemical_list: D006389:Hemagglutinins, Viral; D010446:Peptide Fragments; D014357:Trypsin