Filamin A binds to a discrete domain in the cytoplasmic tail of GpIbα. (A) Expression of human filamin A in CHO cells transduced with the cDNAs of GpIbβ, GpIX, and filamin A. (B) Constructs used to identify GpIbα's primary structural requirements for filamin A binding. (C) Several truncations and deletions N-terminal to residue 594 in GpIbα's cytoplasmic domain eliminate filamin A binding.