14-3-3ζ binding to GpIb and GpIbβ regulated by partial deletions within the cytoskeletal interaction domain of GpIb.

Two deletions were made within the large actin-binding protein (ABP)/cytoskeletal interaction domain(s) (see Figure 2). One encompassed the primary ABP domain as determined by peptide inhibition assays: residues 542-570. The second encompassed a second, perhaps regulatory, cytoskeletal interaction domain identified by mutagenesis assays: residues 570-590. Deletion of residues 542-570 enhanced the binding of GpIbα to a GST-14-3-3ζ fusion protein (right) and did not affect the quantity of 14-3-3ζ that coimmunoprecipitated with GpIbα (left). Deletion of the sequence 570-590 of GpIbα eliminated all binding of 14-3-3ζ to GpIbα. The absence of GpIbα (vector) or the deletion of residues 570-590 prevented GpIbβ from binding to the GST-14-3-3ζ protein (bottom panels) (n = 5).