FIG. 1.

Virus-binding activity is shed from HeLa cells upon incubation with PBS. HeLa cells grown in T flasks were incubated with PBS at 37°C. At the times indicated, cell supernatants from individual flasks were saved and an S80 was prepared and the supernatant was concentrated to 50 μl. Samples were adjusted to 1× Laemmli sample buffer without β-mercaptoethanol and run on an 8% polyacrylamide–SDS gel, and the separated proteins were electrophoretically transferred onto a PVDF membrane. The membrane was blocked, incubated with 2 × 10⁵ cpm of [³⁵S]methionine-labeled HRV2 (19, 23), and exposed to X-ray film. As a control, a HeLa cell membrane (memb.) preparation corresponding to 5 × 10⁶ cells was also used. For the position of LDLR (120 kDa), compare also with Fig. 2. Positions of marker proteins run on the same gel are indicated.