FIG. 4.

Identification of an extracellular form of PRRSV GP₃ protein. (A) 293 cells (10⁷) infected with the nonrecombinant parental adenovirus (Ad5CMVlacZ) or infected with the recombinant adenovirus expressing GP₃ (AdCMV5/ORF3) were labelled for 1 h and then chased for 6 h. The culture medium was clarified at 3,000 × g, and 5× lysis buffer was added prior to radioimmunoprecipitation with α3 antiserum. The immunoprecipitates were then analyzed by SDS–12% PAGE. (B) 293 cells infected with AdCMV5/ORF3 were starved in DMEM lacking methionine and containing 5 μg of TUN/ml and then labelled and chased as described for panel A in the presence of the same drug. After the chase, the clarified culture medium (M) and the cell lysates (C) were processed for radioimmunoprecipitation with α3 antiserum and SDS–12% PAGE. Positions and sizes of ¹⁴C-radiolabelled marker proteins are on the left.