Possible artifacts in the radioiodination of surface proteins of trypanosomatids

Three different methods for the radioiodination of surface proteins in trypanosomatids have been comparatively analyzed. Data interpretation in the lactoperoxidase-mediated method was impaired by autoiodination of the enzyme and its tight retention by the cells. In the enzymobeads method, iodinated enzymes were released from the beads upon solubilization of the preparation with SDS, thus mixing with iodinated proteins of the trypanosomatids. Therefore, upon separation by polyacrylamide gel electrophoresis of the cell lysates, both methods yielded autoradiographic patterns in which prominent bands did not represent labeled cell surface components. In contrast, the autoradiographic patterns obtained by use of the Iodo-Gen method were apparently free of artifacts.