Construction of phosphorylatable chimeric monoclonal antibody CC49 with a casein kinase I recognition site.

Phosphorylation sites for casein kinase I were introduced into chimeric monoclonal antibody CC49 (MAb-chCC49) by inserting a synthetic fragment (CK1) encoding two casein kinase I phosphorylation sites into an expression vector. The phosphorylation sites were created by incorporating the predicted consensus sequences for phosphorylation by the casein kinase I at the carboxyl terminus of the heavy-chain constant region of the MAb-chCC49. The resultant modified MAb-chCC49 (MAb-chCC49CK1) was expressed and purified. The MAb-chCC49CK1 protein can be phosphorylated by the casein kinase I with [gamma-32P]ATP to high radiospecific activity. The 32P-labeled MAb-chCC49CK1 protein binds to cells expressing TAG-72 antigens. The introduction of phosphorylation sites into MAb provides new reagents for the diagnosis and treatment of cancer. This demonstrates that, as was described for the cAMP-dependent protein kinase site, the casein kinase I recognition site can also be used to introduce phosphorylation sites into proteins.