Radioiodination of surface proteins and glycoproteins of lymphocytes by immobilized lactoperoxidase.

Radioiodination of lymphocyte surface proteins employing soluble lactoperoxidase was found to be unsatisfactory for the quantitative isolation and characterization of cell surface glycoproteins: either the glycoproteins were contaminated by self-iodinated lactoperoxidase or were in part removed by the washing step following the radioiodination procedure. Therefore, optimal conditions for cell surface radioiodination by lactoperoxidase covalently linked to Sepharose 4B (lacto-beads) were worked out. By the employment of immobilized lactoperoxidase, the enzyme could easily be removed following solubilization of the radiolabelled cells by a simple washing step. Radioiodinated cell surface proteins and glycoproteins were obtained without any loss as shown by SDS polyacrylamide gel electrophoresis.