Recombinant human fibrinogen and sulfation of the gamma' chain

Human fibrinogen and the homodimeric gamma'-chain-containing variant have been expressed in BHK cells using cDNAs coding for the alpha, beta, and gamma (or gamma') chains. The fibrinogens were secreted at levels greater than 4 micrograms (mg of total cell protein)-1 day-1 and were biologically active in clotting assays. Recombinant fibrinogen containing the gamma' chain incorporated 35SO4 into its chains during biosynthesis, while no incorporation occurred in the protein containing the gamma chain. The identity of the sulfated gamma' chain was verified by its ability to form dimers during clotting. In addition, carboxypeptidase Y digestion of the recombinant fibrinogen containing the gamma' chain released 96% of the 35S label from the sulfated chain, and the radioactive material was identified as tyrosine O-sulfate. These results clarify previous findings of the sulfation of tyrosine in human fibrinogen.