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Subnanometer-resolution Structural Determination of Hemagglutinin from Cryo-electron Tomography of Influenza Viruses
Published on: November 7, 2025
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Influenza virus-mediated membrane fusion: Structural insights from electron microscopy
Juan Fontana1, Alasdair C Steven1
1Laboratory of Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Archives of Biochemistry and Biophysics
|May 11, 2015
Summary
Electron microscopy reveals the structural changes in influenza hemagglutinin (HA) during viral entry. This technique visualizes HA-mediated membrane fusion, crucial for understanding flu virus replication and developing antivirals.
Area of Science:
- Structural biology
- Virology
- Cell biology
Background:
- Influenza virus enters host cells via endocytosis.
- Low pH in endosomes triggers hemagglutinin (HA) conformational changes, mediating membrane fusion.
- This fusion releases the viral genome, initiating replication.
Purpose of the Study:
- To investigate the structural basis of hemagglutinin (HA)-mediated membrane fusion.
- To review the contributions of electron microscopy (EM) techniques to understanding influenza virus entry.
Main Methods:
- X-ray crystallography provided pre- and post-fusion HA structures.
- Various EM techniques (cryo-EM, cryo-ET, negative staining, thin section EM) were employed.
- Subtomogram averaging was used to analyze intermediate HA conformations.
Main Results:
- EM visualized influenza virus entry via endocytosis.
- Large-scale HA structural changes upon low pH exposure were observed.
- Acidification-induced changes in M1 matrix layer and viral envelope separation were detected.
- Intermediate HA conformations and virion-liposome fusion were visualized.
Conclusions:
- EM techniques have significantly advanced the characterization of influenza virus-mediated membrane fusion.
- Future EM developments hold potential for further insights into viral entry mechanisms.
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