FLAVOCETIN-A AND FLAVOCETIN-B, 2 HIGH-MOLECULAR-MASS GLYCOPROTEIN IB BINDING-PROTEINS WITH HIGH-AFFINITY PURIFIED FROM TRIMERESURUS-FLAVOVIRIDIS VENOM, INHIBIT PLATELET-AGGREGATION AT HIGH-SHEAR STRESS
Y. Taniuchi et al., FLAVOCETIN-A AND FLAVOCETIN-B, 2 HIGH-MOLECULAR-MASS GLYCOPROTEIN IB BINDING-PROTEINS WITH HIGH-AFFINITY PURIFIED FROM TRIMERESURUS-FLAVOVIRIDIS VENOM, INHIBIT PLATELET-AGGREGATION AT HIGH-SHEAR STRESS, Biochimica et biophysica acta (G). General subjects, 1244(2-3), 1995, pp. 331-338
Two high molecular mass proteins, flavocetin-A and flavocetin-B, were
purified from Trimeresurus flavoviridis venom. On polyacrylamide gel e
lectrophoresis in the presence of sodium dodecyl sulfate, the apparent
molecular mass of flavocetin-A and -B were 149 and 139 kDa, respectiv
ely, under nonreducing conditions. On reduction, flavocetin-A showed t
wo distinct subunits (17 and 14 kDa), and flavocetin-B three distinct
subunits (17, 15 and 14 kDa). At 1 mu g/ml, flavocetin-A and -B (flavo
cetins) inhibited the van Willebrand factor (vWF)-dependent aggregatio
n of fixed human platelets. However, flavocetins (10 mu g/ml) had no e
ffect on ADP- and collagen-induced platelet aggregation in PRP. Flavoc
etins (3 mu g/ml) also inhibited shear-induced platelet aggregation at
high shear stress, Furthermore, flavocetin-A completely inhibited the
aggregation of and ATP release from washed platelets stimulated with
a low concentration of thrombin. Flavocetin-A specifically bound to pl
atelet with high affinity (K-d = 0.35 +/- 0.13 nM) at 21 500 +/- 1760
binding sites per platelet. The N-terminal amino acid sequences of the
subunits of flavocetin-A shaw a high degree of homology with those of
echicetin, botrocetin, alboaggregin-B and factor IX/factor X-binding
protein. These results suggest that flavocetins may be a useful tool f
or further investigation of the GPIb-VWF interaction.