Tyr106 mutations do not disrupt secretion and folding of GPIbβ_E but disrupt its interaction with GPIX_E. (A) SDS gels showing the lack of disruptive effects of Tyr106 mutations on expression, secretion, and folding of GPIbβ_E expressed from transfected CHO cells. The identity of each Tyr106 mutation is marked on top of the gels. The other annotations follow those of Figure 2C. (B) Relative surface expression levels of HA-GPIbβ (gray column) and GPIX (white column) in transfected CHO cells measured by flow cytometry. The annotations follow those of Figure 2E. Note that none of the Tyr106 mutations retain the ability of wild-type HA-GPIbβ to enhance surface expression of GPIX. The data are presented as mean ± SD (n = 3). *P < .001.