Cryo-electron microscopy reveals the functional organization of an enveloped virus, Semliki Forest virus.
Semliki Forest virus serves as a paradigm for membrane fusion and assembly. Our icosahedral reconstruction combined 5276 particle images from 48 cryo-electron micrographs and determined the virion structure to 9 A resolution. The improved resolution of this map reveals an N-terminal arm linking capsid subunits and defines the spike-capsid interaction sites. It illustrates the paired helical nature of the transmembrane segments and the elongated structures connecting them to the spike projecting domains. A 10 A diameter density in the fusion protein lines the cavity at the center of the spike. These clearly visible features combine with the variation in order between the layers to provide a framework for understanding the structural changes during the life cycle of an enveloped virus.
Mancini
E J
EJ
The Structural Biology Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
Clarke
M
M
Gowen
B E
BE
Rutten
T
T
Fuller
S D
SD
D020285:Cryoelectron Microscopy; D007091:Image Processing, Computer-Assisted; D008958:Models, Molecular; D008961:Models, Structural; D019251:Nucleocapsid / Q000648:ultrastructure*; D012672:Semliki forest virus / Q000648:ultrastructure*