Composition of artificially produced and naturally occurring empty capsids of poliovirus type 1

The polypeptide composition of the empty capsids of poliovirus type 1 represented either by the 73 S component isolated from sucrose gradients or by the top component from CsCl gradients is different from that ot the whole infectious virion. One protein (VP4) is absent from the empty capsids, another (VP2) is lower in relative amount, while an additional protein (NCVP6), not present in purified virions, is found in large amounts. Artificial production of 73 S particles by borate buffer, pH 10.5, treatment of purified virions results in removal of one protein component (VP4) and the RNA of the virus. The observed differences in composition of these virus-specific particles are discussed with regard to their possible role in the architecture and the assembly of the virion.