ABSTRACT
Chang, J., Weigele, P., King, J., Chiu, W. and Jiang, W. (2006) Structure, in press.
Asymmetric reconstruction of bacteriophage P22 by cryo-electron microscopy.
The mechanisms by which most double-stranded DNA viruses package and release their genomic DNA are not fully understood. Single particle cryo-electron microscopy and asymmetric 3-D reconstruction reveal the organization of the complete bacteriophage P22 virion, including the protein channel through which DNA is first packaged and later ejected. This channel is formed by a dodecamer of protal proteins and sealed by a tail hub consisting of two stacked barrels capped by a protein needle. Six trimeric tailspikes attached around this tail hub are kinked, suggesting a functional hinge that may be used to trigger DNA release. Inside the capsid, the portal's central channel is plugged by densities interpreted as pilot/injection proteins. A short rod-like density near the injection proteins may be the terminal segment of the dsDNA genome. The coaxially packed DNA genome is encapsidated by the icoshedral shell. This complete structure unifies various biochemical, genetic and crystallographic data of its components from the past several decades.
