Fig. 3: Type 2B VWD mutations alter AIM unfolding and A1 activity.

A Steady-state analysis of WT AIM-A1, H1268D, and R1341Q to immobilized GPIbα. Protein was serially diluted from 1 μM to 15.6 nM and fit a hyperbola. B Washed platelet aggregation responses to 60 nM H1268D (purple), R1341Q (aquamarine), or WT (black). Resting washed platelets are shown in green. C Representative force-extension traces of H1268D (purple), R1341Q (aquamarine), and WT AIM-A1 (black). The extension event in each trace is marked by an arrowhead. D Superimposed plots of unfolding force versus unfolding extension data and their fits to the worm-like chain model. Force data are presented as mean values ± standard deviation, and extension data are presented as the peak of the Gaussian fit ± the FWHM of Gaussian fit divided by the square root of counts. The data were obtained from n = 52, 37, and 42 biologically independent single-molecule tethers for AIM-A1, H1268D, and R1341Q, respectively. E Regression of most probable unfolding forces fits the Bell–Evans model. Unfolding force data are presented as the center of the tallest bin of the histogram ± one-half of the bin width. The data were obtained from n = 52, 37, and 42 biologically independent single-molecule tethers for AIM-A1, H1268D, and R1341Q, respectively. Source data for D, E are provided in two worksheets of the Source Data file. F Structure of AIM-A1/VHH81 with highlighted interactions between H1268 (purple) to E1305 and R1341 (aquamarine) to E1264.