Forum 02/26/2009

“Cryo-electron tomography of viral fusion intermediates”

Kelly Lee – Department of Molecular Biology, The Scripps  Research Institute, La Jolla, CA

Influenza virus is an enveloped RNA virus that uses its hemagglutinin surface glycoprotein to catalyze fusion of the viral and host cell membranes following receptor-mediated endocytosis. Cryo-electron tomography (cryo-ET) is being used to determine the 3-dimensional architecture of transient membrane fusion states during fusion of influenza virus particles and liposomal model membranes. This technique is beautifully suited for characterizing native fusion intermediates at moderate resolution. The reconstructed density we have observed thus far allows individual hemagglutinin (HA) and neuraminidase (NA) glycoproteins to be resolved on the virus surface. Furthermore, in the reconstructed tomograms, the two leaflets of the viral and liposomal bilayers, as well as the matrix protein layer and transmembrane anchor domains can be resolved. This acuity is essential in order to determine how the fusion machinery orchestrates the many stages of membrane fusion: from grappling the two membranes together to destabilizing the lipid ordering and inducing two previously separate membrane bilayers to flow together.