Scaffolding proteins often play a catalytic role in the assembly process, rather like molecular chaperones. Although macromolecular assembly processes are fundamental to all biological systems, they have been characterized most thoroughly in viral systems, such as the icosahedral Eschcrichia coli bacteriophage 4X174. The XI74 virion contains the proteins F, G, H and I. During assembly, two scaffolding proteins B and D are required for the formation of a 108S, 360-A diameter procapsid from pentameric precursors containing the F, G and H proteins. The procapsid contains 240 copies of protein D, forming an external scaffold, and 60 copies each of the internal scaffolding protein B, the capsid protein F, and the spike protein G. Maturadon involves packaging of DNA andJ proteins and loss of protein B, producing a 132S intermediate. Subsequent removal of the external scaffold yields the mature virion. Both the F and G proteins have the eight-stranded antiparallel -sandwich motif common to many plant and animal viruses. The structure of a procapsid-like particle at 3.5 A resolution will be described, showing how the scaffolding proteins coordinate assembly of the virus by interactions with the F and G proteins, and the F protein undergoes conformational changes during capsid maturation.
|Original language||English (US)|
|State||Published - Dec 1 1998|
ASJC Scopus subject areas
- Molecular Biology