| Abstract: | Using an affinity-purified antibody prepared against the major coat protein of brain-coated vesicles, clathrin, we have localized this protein by ultrastructural immunocytochemistry in Swiss 3T3 cultured fibroblasts. Fixation, permeabilization, and labeling were performed using the EGS and ferritin bridge labeling techniques. Localization of clathrin was detected on the coated regions of both the plasma membrane and the GERL apparatus. Almost no clathrin was found in the cytosol or in association with any other organelles. A very low concentration of labeling was occasionally seen randomly distributed on the inner surface of the plasma membrane and reticular membranous structures near the plasma membrane. The significance of these results in the role of the clathrin-coated regions in receptor-mediated endocytosis and Golgi function are discussed. |
