Seeing the herpesvirus capsid at 8.5 A.

Human herpesviruses are large and structurally complex viruses that cause a variety of diseases. The three-dimensional structure of the herpesvirus capsid has been determined at 8.5 angstrom resolution by electron cryomicroscopy. More than 30 putative alpha helices were identified in the four proteins that make up the 0.2 billion-dalton shell. Some of these helices are located at domains that undergo conformational changes during capsid assembly and DNA packaging. The unique spatial arrangement of the heterotrimer at the local threefold positions accounts for the asymmetric interactions with adjacent capsid components and the unusual co-dependent folding of its subunits.