CHARACTERIZATION OF SOLUBILIZED PROTEINS FROM TISSUE CULTURE-DERIVED AND HOST-DERIVED NUCLEAR POLYHEDRA OF LYMANTRIA-DISPAR AND AUTOGRAPHA-CALIFORNICA

A proteolytic activity capable of degrading solubilized proteins was detected by SDS-PAGE [sodium dodecyl sulfate-polyacrylamide gel electrophoresis] in alkaline carbonate-chloride dissolutions of polyhedra isolated from the larvae of L. dispar and A. californica. This activity could not be detected in dissolutions of the respective tissue culture-derived polyhedra. Tissue culture-derived polyhedra passaged once through their respective hosts displayed the proteolytic activity. Proteolytic degradation was prevented by heating an aqueous suspension of polyhedra at 70.degree. C for 20 min prior to dissolution or adding a proteolytic enzyme inhibitor (phenylmethylsulfonyl fluoride) to the dissolutions. SDS-PAGE of the undegraded solubilized proteins from dissolutions of larval- and tissue culture-derived polyhedra showed identical profiles for the 2 nuclear polyhedrosis virus isolates. Each profile consisted of 2 bands: a minor component (MW 59,000-63,000) and a major component (MW 30,000-32,000). None of these bands stained positive for glycoprotein using the periodic acid-Schiff method. Immunodiffusion analyses of the solubilized proteins from larval- and tissue culture-derived polyhedra were run with rabbit antisera produced against the solubilized proteins of L. dispar and A. californica larval-derived polyhedra. There was complete identity (type I) among the proteins of L. dispar and A. californica when assayed in their respective homologous systems. Complete identity between A. californica proteins and L. dispar proteins, independent of polyhedral origin, occurred when assayed against A. californica antiserum, but only partial identity (type IV) occurred between the same proteins with L. dispar antiserum.