FIG. 4.

Sucrose density gradient analysis of particles secreted from MVE wt- and mutant-infected cells. (A) BHK cells were infected with wt or PQAQA mutant MVE and metabolically labeled from 40 to 47 h p.i. Infected culture supernatants were subjected, in parallel, to centrifugation on 10 to 30% sucrose gradients (10.5 ml), and radioactivity of fractions (∼0.4 ml) collected from the bottoms of the gradients was determined. (B) Comparable numbers of HA units from preparations of mouse brain- or C6/36 cell-grown wt MVE (MVE.wt) and MVE.PQAQA were subjected, in parallel, to centrifugation on 10 to 30% sucrose density gradients (33 ml), and the HA activity of fractions (∼1.1 ml) collected from the bottoms of the gradients was determined.