FIGURE 7.

Kistrin induces binding of AP5 to clamped αIIbβ3 to a lesser extent than to normal αIIbβ3; the defect is rescued by incubation with DTT. The fluorescently labeled ligand-induced binding site mAb AP5 was incubated with either untreated cells or cells pretreated with kistrin (200 nm) and/or DTT (5 mm) for 1 h at 37 °C. Antibody binding was assessed via flow cytometry and expressed as NNFI as indicated in the legend to Fig. 4, but using excess unlabeled AP5 to assess nonspecific binding. The values were further normalized for the ∼40% difference in the intensity of fluorescent labeling (F/P ratio) of the two AP5 preparations used in this study. The data for normal αIIbβ3 and clamped αIIbβ3 are from 10 experiments, and the data for αIIbβ3 N339S and clamped αIIbβ3 are from five experiments.