GPIbβ with N-terminal deletions to residue 31 and N-terminal deletions of GPIbβ distal to residue 58.

GPIbβ with N-terminal deletions to residue 31 is expressed on the cell surface and recognized by MoAb 257.4, whereas N-terminal deletions of GPIbβ distal to residue 58 are not detected on the cell surface. HEK293T cells were transfected with wildtype GPIbβ alone (panel A) and with GPIbβ truncated at residue 14 (panel B), 26 (panel C), 31 (panel D), 58 (panel E), and 65 (panel F). The cells were then reacted with MoAb 257.4. There is a significant increase in fluorescence on the cells expressing wildtype GPIbβ and GPIbβ truncated at residues 14, 26, and 31. There is no increase in surface fluorescence in cells transfected with GPIbβ truncated at residue 58 or 65 compared with mock-transfected cells. Thus, N-terminal truncations to residue 31 appear to be expressed while truncations to 58 do not.