double-stranded RNA viruses
Twinkle, Twinkle Little Cryo-EM Star
Posted on by Dr. Francis Collins
The stars are out and shining this holiday season. But there are some star-shaped structures now under study in the lab that also give us plenty of reason for hope. One of them is a tiny virus called bacteriophage phi-6, which researchers are studying in an effort to combat a similar, but more-complex, group of viruses that can cause life-threatening dehydration in young children.
Thanks to a breakthrough technology called cryo-electron microscopy (cryo-EM), NIH researchers recently captured, at near atomic-level of detail, the 3D structure of this immature bacteriophage phi-6 particle in the process of replication. At the points of its “star,” key proteins (red) are positioned to transport clipped, single-stranded segments of the virus’ own genetic information into its newly made shell, or procapsid (blue). Once inside the procapsid, an enzyme (purple) will copy the segments to make the genetic information double-stranded, while another protein (yellow) will help package them. As the procapsid matures, it undergoes dramatic structural changes.