CIRCULAR ASSEMBLIES

During 1994 and 1995, the structures of the serum amyloid P component, the bacterial chaperonin GroEL, the 20S proteasome, the bacterial lig ht-harvesting complexes and the tryptophan operon RNA-binding attenuat ion protein have been determined. These structures all form circular a ssemblies in which the individual subunits are related by rotational s ymmetry. In most cases the circular organization generates a new bioph ysical property and a specific biological function which have presumab ly been selected by evolution.