tetano
Editor, Senior Moderator
Effect of envelope proteins on the mechanical properties of influenza virus
Iwan A. T. Schaap1,
Fr?d?ric Eghiaian1,
Am?d?e des Georges2 and
Claudia Veigel3,*
First Published on October 9, 2012, doi: 10.1074/jbc.M112.412726 jbc.M112.412726.
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 ~10 times softer (~0.05 nN.nm-1) than a viral protein-capsid coat, and sustains deformations of one third of the virion diameter. Compared with phosphatidylcholine liposomes it is twice as stiff, due to membrane-attached protein components. We found that virus indentation resulted in a bi-phasic force-indentation response. We propose that the first phase, including a stepwise reduction in stiffness at ~10 nm indentation and ~100 pN force, is due to mobilisation of membrane proteins by the indenting AFM-tip, consistent with the glycoprotein ectodomains protruding ~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 lifecycle and support the persistence of the virus inside and outside the host.
http://www.jbc.org/content/early/2012/10/09/jbc.M112.412726.abstract
Iwan A. T. Schaap1,
Fr?d?ric Eghiaian1,
Am?d?e des Georges2 and
Claudia Veigel3,*
First Published on October 9, 2012, doi: 10.1074/jbc.M112.412726 jbc.M112.412726.
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 ~10 times softer (~0.05 nN.nm-1) than a viral protein-capsid coat, and sustains deformations of one third of the virion diameter. Compared with phosphatidylcholine liposomes it is twice as stiff, due to membrane-attached protein components. We found that virus indentation resulted in a bi-phasic force-indentation response. We propose that the first phase, including a stepwise reduction in stiffness at ~10 nm indentation and ~100 pN force, is due to mobilisation of membrane proteins by the indenting AFM-tip, consistent with the glycoprotein ectodomains protruding ~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 lifecycle and support the persistence of the virus inside and outside the host.
http://www.jbc.org/content/early/2012/10/09/jbc.M112.412726.abstract