Organization of the vaccinia envelope and relationship to the structure of intracellular mature virions.

Protrusions covering the surface of intracellular mature virions (IMV), termed by us surface tubular elements (STE), are released in a quasi-intact form during stripping of the envelope. The concentrated, reproducibly isolable STE were shown to contain the 58-kDa 4c polypeptide and prominent protein antigens residing at the surface of IMV. The major core protein 4b, identified as a minor contaminant of STE, presumably became detached along with STE during the shearing off process. Antibodies against protein 4b became specifically bound to the surface of isolated cores, where a palisade layer of rodlets occurs. The same antibodies absorbed onto isolated STE where similar rodlets were evident. Based on the new observations we constructed a model of the organization of the IMV envelope and its relationship to the core.