FIG. 1.

Newly synthesized VP40 interacts with membranes. (A) HeLa cells expressing VP40 were pulse-labeled at 10 h posttransfection with 50 μCi of [³⁵S]Promix for 30 min. Cells were lysed either immediately after labeling (upper panel) or after a 2-h chase in DMEM (bottom panel). The postnuclear supernatant was supplemented with sucrose to give a final concentration of 63%, placed at the bottom of a centrifuge tube, and overlaid with 45 and 10% sucrose. The gradient was centrifuged to equilibrium at 40,000 rpm in an SW60 rotor. Fractions were collected from the top and subjected to immunoprecipitation with a mouse monoclonal antibody against VP40. (B) The intensities of VP40-specific signals in panel A were quantified as described in Materials and Methods. The extent of VP40 in all fractions was set to 100%. The data represent averages and standard deviations from three independent experiments.