Introduction of intersubunit disulfide bonds in the membrane-distal region of the influenza hemagglutinin abolishes membrane fusion activity

Cell. 1992 Feb 21;68(4):635-45. doi: 10.1016/0092-8674(92)90140-8.


Influenza virus hemagglutinin (HA) mediates viral entry into cells by a low pH-induced membrane fusion event in endosomes. A number of structural changes occur throughout the length of HA at the pH of fusion. To probe their significance and their necessity for fusion activity, we have prepared a site-directed mutant HA containing novel intersubunit disulfide bonds designed to cross-link covalently the membrane-distal domains of the trimer. These mutations inhibited the low pH-induced conformational changes and prevented HA-mediated membrane fusion; conditions that reduced the novel disulfide bonds restored membrane fusion activity. We conclude that structural rearrangements in the membrane distal region of the HA are required for membrane fusion activity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites, Antibody
  • Bromelains
  • Cell Line
  • Cricetinae
  • Cysteine*
  • Hemagglutinin Glycoproteins, Influenza Virus
  • Hemagglutinins, Viral / chemistry*
  • Hemagglutinins, Viral / genetics
  • Hydrogen-Ion Concentration
  • Membrane Fusion*
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Protein Conformation
  • Trypsin
  • Viral Envelope Proteins / chemistry*


  • Hemagglutinin Glycoproteins, Influenza Virus
  • Hemagglutinins, Viral
  • Viral Envelope Proteins
  • Bromelains
  • Trypsin
  • Cysteine