Identification of a key fibrinogen αC amino acid residue involved in binding activated rFXIII-A. (A) Multiple sequence alignment³⁶  of fibrinogen αC region 371-425 in 7 species to identify conserved residues for site-directed mutagenesis within the activated rFXIII-A binding region of α389-403. Amino acid residues highlighted in bold are highly conserved. (B) Displays the binding of each α fragment 9 variant to activated rFXIII-A by SPR. Each α fragment 9 variant (1μM) was injected for 60 seconds over immobilized activated rFXIII-A at a flow rate of 30 μL/min. The SPR response at 55 seconds was plotted for each of the variants and compared with wild-type (WT) α fragment 9 (n = 3). Error bars show ± 1 SD.