Lack of force-induced unfolding in GPIb-IX complexes with altered MSD. (A) Sequences illustrating various deletion mutations in MSD. (B) Expression and assembly of the mutant complexes, as shown by Western blots under nonreducing (N.R.) or reducing (R.) conditions. Lane 1, cells expressing wild-type complex GPIbα/GPIbβ/GPIX; lane 2, GPIbα∆S/GPIbβ/GPIX; lane 3, GPIbα∆S_N/GPIbβ/GPIX; lane 4, GPIbα∆S_C/GPIbβ/GPIX. (C) Lifetimes (mean ± SEM of >3 experiments) of the bonds between VWF-A1 and the 3 constructs as a function of force. Each plot is identified by the identity of GPIbα subunit in the complex and the pulling ligand. (D) Representative force-distance traces of pulling VWF-A1 on GPIbα∆S_N/GPIbβ/GPIX (thick trace) or GPIbα∆S_C/GPIbβ/GPIX (thin trace) complex that was captured by biotin at the GPIX cytoplasmic, showing the lack of force-induced unfolding.