Fig. 1.

The Ad19a E3/49K protein is proteolytically processed and secreted from Ad19a infected cells and cells stably expressing E3/49K. A549 cells infected with Ad19a for 16 h (A and B) and A549 cells stably expressing E3/49K (C) were metabolically labeled for 30 min with 200 µCi/mL [³⁵S]-methionine and chased with medium containing nonradioactive methionine for the indicated times. Subsequently, E3/49K was immunoprecipitated from cell lysates and supernatants with rabbit antibodies R25050 and R48 directed against the C terminus (A) and N terminus, respectively (B and C). The ∼120-kDa protein species (asterisk) coprecipitating unspecifically at late stages of infection using the C-terminal specific serum corresponds to the abundant hexon protein. It was previously shown that it is not visible in the early phase of infection or in transfected cells (24).