Effect of Envelope Proteins on the Mechanical Properties of Influenza Virus

Iwan A. T. Schaap, Frederic Eghiaian, Amedee des Georges, Claudia Veigel

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

The envelope of the influenza virus undergoes extensive structural change during the viral life cycle. However, it is unknown how lipid and protein components of the viral envelope contribute to its mechanical properties. Using atomic force microscopy, here we show that the lipid envelope of spherical influenza virions is similar to 10 times softer (similar to 0.05 nanonewton nm(-1)) than a viral protein-capsid coat and sustains deformations of one-third of the virion's diameter. Compared with phosphatidylcholine liposomes, it is twice as stiff, due to membrane-attached protein components. We found that virus indentation resulted in a biphasic force-indentation response. We propose that the first phase, including a stepwise reduction in stiffness at similar to 10-nm indentation and similar to 100 piconewtons of force, is due to mobilization of membrane proteins by the indenting atomic force microscope tip, consistent with the glycoprotein ectodomains protruding similar to 13 nm from the bilayer surface. This phase was obliterated for bromelain-treated virions with the ectodomains removed. Following pH 5 treatment, virions were as soft as pure liposomes, consistent with reinforcing proteins detaching from the lipid bilayer. We propose that the soft, pH-dependent mechanical properties of the envelope are critical for the pH-regulated life cycle and support the persistence of the virus inside and outside the host.

Original languageEnglish
Pages (from-to)41078-41088
Number of pages11
JournalJournal of Biological Chemistry
Volume287
Issue number49
DOIs
Publication statusPublished - 30 Nov 2012

Keywords

  • ATOMIC-FORCE MICROSCOPY
  • A VIRUS
  • ELECTRON-MICROSCOPY
  • CELL-MEMBRANES
  • ELASTIC PROPERTIES
  • VIRAL CAPSIDS
  • LOW PH
  • HEMAGGLUTININ
  • NEURAMINIDASE
  • PARTICLES

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