Location of DNA-binding proteins and disulfide-linked proteins in vaccinia virus structural elements

Abstract

Treatment with sodium dodecyl sulfate (SDS) converted the vaccinia virus strain IHD-J into particles of two types: (i) ghosts which possessed a thin-membrane vesicle derived from basement part of the virus membrane with attached lateral bodies and a membranous structure derived from the core wall and (ii) aggregates of a DNA-nucleoprotein eluted from the core. These particles lacked lipids, and all the viral phospholipids were detected in the SDS-soluble fraction. The viral membrane was composed of an SDS-soluble coat layer and the basement membrane, and the basement membrane was maintained by a mechanism other than the lipid bilayer. By comparisons of protein species in morphologically distinct subviral particles prepared by several solubilizing methods, protein compositions of viral structural elements were suggested as follows: 25,000-molecular-weight viral protein-17,000-molecular-weight viral protein ( VP25K - VP17K ), viral basement membrane; VP13 . 8K , major component of the lateral body; VP70K , VP69K , VP66K , and VP64K , minor components of the lateral body; VP61K , outer layer of core wall; VP57K - VP22K , inner layer of core wall; and VP27K - VP13K , nucleoprotein. These structural elements found in the SDS-insoluble particles dissolved in the same SDS solution under reducing conditions, indicating that the disulfide linkages seem to have a principal role in maintaining their morphological integrity. VP57K , VP27K , VP13 . 8K , and VP13K were revealed to possess affinity for DNA. Denatured calf thymus DNA and viral DNA in double- or single-stranded form associated equally well with these proteins, but RNA did not bind. Therefore, it was strongly suggested that disulfide-linked VP27K - VP13K represented the nucleoproteins of vaccinia virus. A structural model of vaccinia virus is proposed and discussed.