Iodination of zeta protein by lactoperoxidase. Chloroperoxidase and chloramine T.

Normal and Rous sarcoma virus transformed chicken embryo fibroblasts cultured on petri dishes were labeled with ¹²⁵I by two enzymic methods and one chemical method. The enzymic labeling systems employed chloroperoxidase and lactoperoxidase. Hydrogen peroxide was generated by glucose oxidase and glucose. The chemical method used chloramine T as the oxidant for iodide ion. After solubilization of cells, SDS disc gel electrophoresis and gamma counting, it was found that only one cell protein was predominantly labeled in all three reactions. This protein, a major cell surface protein, has been previously identified and termed Zeta protein. Zeta protein disappears from transformed cells and is susceptible to trypsin digestion.