Evaluation of the metal binding sites in a recombinant coagulation factor VIII identifies two sites with unique metal binding properties.

Coagulation factor VIII is a glycosylated, non-covalent heterodimer consisting of a heavy chain (A1-A2-B domains) and a light chain (A3-C1-C2 domains). The association of the chains, and the stability and function of the dimer depend on the presence of metal ions. We applied X-ray fluorescence, X-ray crystallographic structure determination with anomalous signals at different wavelengths, and colorimetric measurements to evaluate the metal binding sites in a recombinant factor VIII molecule, turoctocog alfa. We identified a metal binding site in domain A3 dominated by Cu(+) binding and a site in domain A1 dominated by Zn(2+) binding.