Collagen-binding properties of soluble GPV.

Aggregation of washed human platelets (A) was initiated in the presence of fibrinogen by adding 1.25 μg/mL collagen 30 seconds after the addition of buffer or 4 μg/mL soluble GPV (sGPV) (left tracings) or by adding 1.25 μg/mL collagen that had been incubated for 3 minutes with buffer or with 4 μg/mL sGPV (right tracings). Soluble GPV inhibited aggregation in both cases but more efficiently when preincubated with collagen. Surface plasmon resonance sensorgrams were recorded on a Biacore 2000 apparatus (B, C). Kinetic studies of the interaction of sGPV or control IgG (IgG) with surfaces bearing covalently coupled bovine insoluble type I collagen, HSA, or human von Willebrand factor (vWF) were performed as described in “Materials and methods” (B). The interaction of soluble GPVf1 fragment (sGPV) with human (dotted line) or rat (solid line) soluble type I collagen or human soluble type III collagen (broken line) was studied in the same manner (C). Binding is indicated by an increase in resonance units, and the responses were corrected by subtraction of those obtained for control HSA. After 300 seconds, the surface was rinsed by the injection of buffer.