FIG. 6.

NA protein incorporation in virions. Virus-infected MDCK cells were labeled at 4 h p.i. for 12 h with 200 μCi of ³⁵S-protein labeling mix in 2:8 VGM. At 16 h p.i., medium was harvested and clarified by low-speed centrifugation and virions were pelleted by ultracentrifugation through a 25% sucrose cushion. Labeled virion lysates were immunoprecipitated with the respective antibodies; proteins were eluted, treated with PNGase F for 3 h, analyzed by SDS-PAGE, and autoradiographed.