Structure of the Reaggregated Protein Shells of Two Spherical Viruses

Abstract

AFTER the reconstitution of the rod shaped tobacco-mosaic virus (TMV) from its protein and RNA components¹, several spherical viruses have now been reconstituted^2–7. In the case of TMV, the protein component alone can, in suitable conditions, be repolymerized. into a form in which the arrangement of subunits is, closely similar to that in the original virus^8,9. Although the reaggregation of the protein of certain spherical viruses into shells similar in size to the original virus, particles has been reported^10,11, they have not been shown to have the same arrangement of subunits. Naturally occurring empty protein shells (“top component”) devoid: of RNA are found associated with virus particles ini many different systems, and artificial top components can be made in some cases, for example from turnip, yellow mosaic virus¹², by removal of RNA from the-virus particles. Both natural and artificial top components of turnip yellow mosaic virus are structurally very similar to the intact virus particles^13,14. In this communication we show that the structures of shells formed by the reaggregation of the protein subunits of two spherical viruses are identical or very similar to those of the original RNA-containing virus particles.