Seeing the herpesvirus capsid at 8.5 angstrom

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