Immunoprecipitation of Marek's disease virus-specific polypeptides with chicken antibodies purified by affinity chromatography

The sulfhydryl-containing polypeptides of vaccinia virus strain IHD-J were studied in an attempt to gain further insight into their roles in virus assembly. The virus showed 39 diagonally oriented spots in the profile of two-dimensional sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. In spite of the reducing conditions in the electrophoretic system, two dimer spots appeared in the profile. An extraordinary highly reactive sulfhydryl residue(s) of VP17K converted the polypeptide reciprocally into monomer and dimer forms (VP17K-VP25K) due to the disulfide-sulfhydryl exchange reaction. In order to detect the structural proteins linked with disulfide bond(s), vaccinia virus was solubilized and electrophoresed under nonreducing conditions in the first dimension and then under reducing conditions in the second dimension. The viral polypeptides linked originally with disulfide bond(s) were separated into subunits. The complexes were dimers or oligomers of some polypeptides (VP133K, VP61K, VP21K, VP17K) and heterocomplexes such as VP57K + VP16K, VP63K + VP32K, VP27K + VP13K. VP57K and VP22K were not soluble in the nonreducing SDS solution. The apparent molecular sizes of VP37K, VP29K, and VP17K-25K changed significantly according to the composition of the denaturing agent used, suggesting that the differences in their molecular sizes were due to conformational changes produced by reduction of their intramolecular disulfide bonds and also by breakage of their hydrogen bonds.