Ala140 was mutated to Thr, Asp, Lys, or Phe, and the mutational effects on the surface (A) and overall (B) expression level of GPIbα (gray bar) and GPIX (white bar), as well as (C) the effects on GPIb formation were characterized. For some reason, GPIXA140D migrated at a pace different from the other variants. The data shown were either the average or a representative of 4 independent experiments.