Influenza hemagglutinin membrane anchor

Area of Science:

• Structural Biology
• Virology
• Biochemistry

Background:

• Viral membrane fusion is essential for infection, mediated by glycoproteins like influenza hemagglutinin (HA).
• Previous 3D structures of HA were derived from soluble ectodomain fragments, lacking the membrane anchor region.
• The membrane anchor's role in fusion necessitates understanding its structure and interaction with the HA ectodomain.

Purpose of the Study:

• To determine the high-resolution structure of the intact, full-length influenza hemagglutinin (HA) protein, including its membrane anchor.
• To investigate the structural basis of HA-mediated viral membrane fusion.
• To characterize a neutralizing antibody fragment (Fab) binding near the ectodomain-membrane anchor junction.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to analyze the intact, full-length HA in detergent micelles.
• Comparison of full-length HA-detergent micelles with full-length HA-Fab complex detergent micelles.
• High-resolution structural analysis and characterization of molecular components.

Main Results:

• A high-resolution cryo-EM structure of full-length HA was obtained, comparable to X-ray crystallography data of the ectodomain.
• All five N-linked carbohydrate side chains of HA were clearly resolved.
• Flexible, eight-residue linkers connect the HA ectodomain to the membrane anchor, joining a central triple-helical structure.

Conclusions:

• The structure of the full-length influenza hemagglutinin provides new insights into viral membrane fusion mechanisms.
• The flexible linkers and membrane anchor structure are critical components for HA function in viral entry.
• Structural data aids in the development of novel antiviral strategies targeting HA.