HSA fusion protein design, expression, and characterization. (A) Schematic diagram of proteins. Relevant polypeptides are shown in linear form, oriented from N-terminus to C-terminus, with different regions labelled on the bar diagram. HSA residues are shown in black, while candidate FXIIIa substrate motifs are shown in grey. White bars correspond either to hexahistidine tags (H6) or to tetraglycine-tyrosyl spacer segments (G4Y). Polypeptide names and predicted length in amino acids (a.a.) is shown at right. (B) Amino acid sequence of candidate FXIIIa substrate motifs. The amino-terminal portion of α2AP previously fused to HSA  is shown, including putative sites of proteolysis deduced by amino acid sequencing, on the top line (α2AP(13-42)). The three candidate FXIIIa motifs fused to albumin with or without adjacent His tags, are shown below (XL1,2, or 3).