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-mu-g (mg of total cell protein)-1 day-1 and were biologically active in clotting assays. Recombinant fibrinogen containing the gamma' chain incorporated (SO4)-S-35 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 S-35 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.