'Clearest ever' image of Ebola virus protein
Image: 3D rendering of the cryo-EM reconstruction of the Ebola virus protein. [Yukihiko Sugita]
Using cryo-electron microscopy, Japan-based researchers have, for the first time, imaged the structure of a central component of the Ebola virus to 3.6 Å resolution.
To image the viral protein complex, leading virologist, Professor Yoshihiro Kawaoka, University of Tokyo and University of Wisconsin-Madison, joined forces with Professor Matthias Wolf and Dr Yukihiko Sugita from the Molecular Cryo-Electron Microscopy Unit at Okinawa Institute of Science and Technology Graduate University, and colleagues.
Filamentous Ebola viruses budding from the surface of a host cell captured by a scanning electron microscope. [Takeshi Noda]
Together, the researchers focused on a part of the virus called the nucleocapsid (NC), a complex of proteins that acts as a support structure for the viral genetic material and allows the virus to replicate its deadly payload, to devastating effect.
Sugita first isolated nucleoprotein-RNA complexes, which make up the core of NCs, to a high degree of purity, then analysed the structures using a Titan Krios cryo-TEM equipped with a Gatan energy filter, at 300 kV in energy filtered TEM nanoprobe mode.
As he says: “Before this study, we only knew about the smallest pieces of the NC structure. Now that we can see it as a whole, it may help find targets for antiviral drugs.”
Left: A 3D rendering of the cryo-EM reconstruction. The RNA and nuceloprotein are coloured in red and grey, respectively. A single nuceloprotein molecule is highlighted in blue. Right: An atomic model of a single nucleoprotein molecule with the RNA in the complex. The model is superposed with the cryo-EM map in a polygon mesh representation. [Yukihiko Sugita]
The complete Ebola virus is a filamentous structure that appears like a short strand of hair when magnified thousands of times.
Inside these filaments are the pieces that make up a functioning virus: NC and matrix proteins, both of which are wrapped by surface glycoproteins and a viral envelope.
A tour of a 3D rendering and atomic model of the Ebola virus nucleocapsid core based upon the cryo-EM reconstruction created by the OIST team.
Previous studies had analysed the NC structure using a technique called electron tomography, but the latest cryo-EM reconstruction has much higher definition, resolving individual RNA nucleotides and amino-acid side chains.
“[We have shown] for the first time what the NC structure looks like at near-atomic resolution,” highlights Wolf.
Once the samples were prepared, it took the researchers more than eighteen months to reconstruct the NC as a digital model.
Dr Yukihiko Sugita (left) and Professor Matthias Wolf [Sugita/OIST]
As Wolf says: “Now that we have a clear picture of what this structure really looks like... [This brings us] one step closer to figuring out how the whole virus works.”
Research is published in Nature.