Preparation and characterisation of a subviral particle of vaccinia virus containing the DNA-dependent RNA polymerase activity

A subviral particle has been obtained from purified vaccinia virus by controlled protease digestion followed by an NaCl-EDTA treatment. Digestion was carried out in the presence of a neutral detergent with papain, immobilized on nylon powder, to ensure a sequential digestion from the outside of the particle. Digestion removed 40% of the virus protein to produce a brick-shaped particle with a covering of spikes. After a defined amount of virus digestion (90 min under all conditions tested), subsequent treatment with 0.5 M NaCl in the presence of 50 m M EDTA removed a further 25–30% of the virus protein including one of the two predominant structural polypeptides 4a. The product of this treatment was a subviral particle with a smooth featureless surface. The final subviral particle obtained contained only 19 of the 48 recognised polypeptides of the virion representing 30–35% of the virion protein. This particle retained all the DNA-dependent RNA polymerase activity of the virion.