I1309V mutation rescues the defect in platelet adhesion associated with the R1326H mutation. (A-B) Proposed models for the WT (A) and double-mutant (I1306V and R1326H) (B) murine VWF-A1 domains (gray) in complex with murine GPIbα (cyan). The β-switch hairpin loop of GPIbα is shown in green and key side chains involved in forming the interface are shown in stick. Zoomed images reveal details of the electrostatic interactions that may be altered by the mutations R1326H and I1309V, respectively. (C-D) Accumulation (C) and translocation velocity (WSR of 1,600 s−1) (D) of mouse platelets on surface-immobilized rVWF-A1 proteins. Platelet attachment and their subsequent motion were digitally recorded on an inverted Nikon microscope (Eclipse TE2000) with a plan ×10 or ×20 objective, respectively. The number of platelets attached per unit area and translocation velocities was determined by off-line analysis (Image-Pro Plus, Media Cybernetics, Rockville, MD). Results are representative of 3 separate experiments performed in triplicate (mean ± SD).
