Architecture of small RNA viruses

Symmetric organization of biological macromolecules is necessary fi)r certain structural and func- tional requirements of living cells. The mechanisms by which biomoleeules assemble unambiguously into unique structures has been a central theme of investigation in molecular biology. Simple viruses consist of a nucleic acid core which codes for the genetic information surrounded and protected by a protein coat or capsid. In a large majority of the eases, the protein coats possess exact icosa- hedral symmetry. Developments in experimental X-ray crystallography and computer technology has led recently m the elucidation of the architecture of several viruses. Systematic studies on the structure of the protein subunits, their location and orientation on the ieosahedral eapsid, and the details of interaction between subunits has provided some insights into the mechanisms of error free virus assembly. However, the structures of even the simplest viruses are sufficiently complex and do not lead to eomplete understanding of the pathway of assembly by an examination of the final structure. The current state of research in this fast advancing area is briefly reviewed