Structure of spherical viruses aren’t as perfect as we thought

Determining the structure of a virus is an important step in understanding and treating viral disease. For decades, structural biologists have been using cryo-electron microscopy to create increasingly accurate pictures of biomolecules, but one of the assumptions they’ve been relying on could be wrong. Flaviviruses, such as dengue and Zika, were assumed to be symmetrical icosahedrons (shapes with 20 identical faces) based on data from microscopes. But these icosahedral viruses might not be perfectly symmetrical after all, according to a new study in the journal Proceedings of the National Academy of Sciences. “Up until now, any such viruses that have ever been examined have been looked at with the assumption that they had icosahedral symmetry,” said Michael Rossmann, the Hanley Distinguished Professor of Biological Sciences at Purdue University. “Now we realize that’s an approximation – it’s not completely accurate. A large proportion of viruses are nearly icosahedral, and just now we’re beginning to see...