TFPIα variant proteins used in these studies. (A) Shown are the domain structures of TFPIα, K1K2 (amino acids 1-160), TFPIΔK2 (R107A mutation), TFPI-AAKA (L252A, I253A, T255A mutations), and K3C (amino acids 185-271). The 3 Kunitz domains are shown in gray. The C-terminal basic region is blue. (B) Western blot of the TFPI variant proteins, probed with antibodies against the K2 domain (red) and the last 12 amino acids of the C-terminus (green), with overlay indicated in yellow. The K1K2 sample contains some dimerized protein.