FIG. 6.

Saturable binding of gB-S to CHO cell monolayers. CHO-K1 (□) and CHO-677 (⧫) cells were cultured in a 96-well plate, chilled, and blocked at 4°C. Increasing concentrations of [³⁵S]gB-S were added to the cell monolayers, which were incubated for 90 min at 4°C. Unbound and bound fractions were collected and subjected to scintillation counting. Experiments for all data points were performed in triplicate. Bars represent standard deviations. The specific activity of the [³⁵S]gB-S preparation used for this experiment was 320.5 cpm/μg of protein. On the basis of the specific activity of the [³⁵S]gB-S preparation, the amounts of total input and free and bound proteins were determined and subjected to Scatchard analysis (49). Shown in the inset are lines representing the best fits as determined by a linear regression analysis.