Figure 1.

Rotated views of the crystal structure of the engineered triple-thiol human serum albumin in complex with the FcRn receptor. The β-2-microglobulin/FcRn complex is shown in gold, and human serum albumin is shown in red. The location of the naturally occurring cysteine (Cys-34) and the two positions where cysteines with reactive thiol groups have been inserted (K93C and E294C) are shown in dark blue and teal, respectively. Interface residues within a distance of 5 Å from albumin are marked in green on the surface representation of the FcRn receptor. Modified from Protein Data Bank entry 4N0F.