Analysis of the Quantity and Synthesis of the Virion Proteins of Infectious Hematopoietic Necrosis Virus.

The structural polypeptides of the Round Butte strain of infectious hematopoietic necrosis virus (IHNV) were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and stained with silver nitrate. Five virion proteins were identified. The relative contribution of each protein species to the total protein content of the virus was determined. An approximation of the number of molecules of each protein per virion was calculated.The time of the intracellular appearance for each virion protein of IHNV was investigated during the infection cycle. The first protein for IHNV to appear in the course of infection was the N protein, at 2-3 h after infection. At 6-7 h after infection, the membrane proteins, M1 and M2, could be identified in the autoradiograms. The two forms of the glycoprotein, G1 and G2, were found at 9-10 h after infection. The results from both pulse and pulse-chase labeling experiments suggest that G2 is synthesized immediately and then is further glycosylated to form G1. Since cellular protein synthesis was not inhibited during early infection, it was difficult to distinguish the viral L protein from host protein in the early samples. The temporal synthesis of the viral polypeptides suggests that those polypeptides are the translation products of independently transcribed monocistronic mRNA.