Stoichiometry of Reovirus Structural Proteins in Virus, ISVP, and Core Particles

Abstract

All eight reovirus structural proteins were resolved in a new tris, glycine, and urea (TGU) electrophoretic gel system. The specific identities of proteins were determined immunologically, biochemically, and genetically. Structural proteins of reovirus type 1 Lang had different mobilities in the TGU gel than did type 3 Dearing proteins. Intertypic reassortant viruses that contained various combinations of parental genes were used to identify each of the viral protein bands. Type 1 Lang virions were metabolically-labelled with either3H-amino acids or35S-methionine/cysteine and gradient purified. Aliquots of purified virions were treated to generate infectious subviral particles (ISVPs) and core particles. Radiolabelled virus, ISVP, and core proteins were resolved in the TGU gel and protein band intensities were used to determine copy numbers of each structural protein. These studies confirmed the copy numbers and locations of most reovirus proteins. However, important new findings include the discovery that virions contain approximately 120 copies of major core protein ς2 and 20 copies of the polymerase cofactor protein μ2, and ISVP particles contain about 24 copies of μ1C that has not been processed to the δ peptide. These data are used to generate a new model of the arrangement of structural proteins within the reovirus particle.