Fig. 5

Inhibition of the zinc-dependent binding of HK to platelets by anti-GPIb antibody. (A) Zinc-dependent binding of HK to platelets and (B) its inhibition by anti-GPIb antibody. Washed platelets in binding buffer (10 mM Hepes, 137 mM NaCl, 4 mM KCl, 11 mM glucose, and 0.5 mg/ml BSA) were incubated (unstirred, at room temperature) with 125I-HK (20 nM) in the presence or absence of 50 µM zinc. Aliquots were removed at the indicated times and centrifuged through a silicone oil barrier to separate the platelets from the unbound proteins. For the inhibition experiments, platelets were preincubated with anti-GPIb antibody or nonimmune IgG for 20 min before the addition of 125I-HK. Results are the mean ± standard error from three different experiments.