Recently some of my final year virology students commented to me that it was a shame I was not still making regular MicrobiologyBytes podcasts. But as I said when I stopped posting weekly podcasts, I don’t feel that audio adds value to the content of what I like to share here. But video may be a different matter. Not that you’re going to see videos of me talking, because you won’t learn much microbiology that way, and I’ve only ever seen one good talking head video. But some papers lend themselves to a more visual treatment, and this is a very good example:
Structural dissection of Ebola virus and its assembly determinants using cryo-electron tomography. PNAS USA 27 February 2012 doi: 10.1073/pnas.1120453109
Ebola virus is a highly pathogenic filovirus causing severe hemorrhagic fever with high mortality rates. It assembles heterogenous, filamentous, enveloped virus particles containing a negative-sense, single-stranded RNA genome packaged within a helical nucleocapsid (NC). We have used cryo-electron microscopy and tomography to visualize Ebola virus particles, as well as Ebola virus-like particles, in three dimensions in a near-native state. The NC within the virion forms a left-handed helix with an inner nucleoprotein layer decorated with protruding arms composed of VP24 and VP35. A comparison with the closely related Marburg virus shows that the N-terminal region of nucleoprotein defines the inner diameter of the Ebola virus NC, whereas the RNA genome defines its length. Binding of the nucleoprotein to RNA can assemble a loosely coiled NC-like structure; the loose coil can be condensed by binding of the viral matrix protein VP40 to the C terminus of the nucleoprotein, and rigidified by binding of VP24 and VP35 to alternate copies of the nucleoprotein. Four proteins (NP, VP24, VP35, and VP40) are necessary and sufficient to mediate assembly of an NC with structure, symmetry, variability, and flexibility indistinguishable from that in Ebola virus particles released from infected cells. Together these data provide a structural and architectural description of Ebola virus and define the roles of viral proteins in its structure and assembly.