title: Synthesis of apoferritin in mouse peritoneal macrophages. Characterization of 20 S particles.
abstract: Apoferritin particles were found in mouse peritoneal macrophages cultured in vitro. They were found as 20S particles in the "ribosomal fraction" of macrophages labeled with L-[14C]glutamic acid. Possibilities that they were breakdown products of ribosomes or of other well-known contaminants of the ribosomal fraction were excluded because they did not incorporate [5-3H]uridine. They were resistant to RNase and were relatively resistant to detergent. The antibody against horse spleen apoferritin precipitated about 70% of the particles in the 20S region, judging by measurement of radioactivity. On in vitro incubation with Fe2+ and suitable oxidizing agents the sedimentation coefficient of 80% of the 20S particles changed to about 60S, which corresponds to that of ferritin. SDS-polyacrylamide gel electrophoresis revealed the presence of subunit structures with the same molecular size as that of mouse liver apoferritin. Under the electron microscope, the particles appeared spherical with a relatively uniform diameter of about 130 A.
mesh_terms: D000818:Animals; D001052:Apoferritins / Q000096:biosynthesis*; D001202:Ascitic Fluid / Q000378:metabolism*; D002458:Cell Fractionation; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D005293:Ferritins / Q000031:analogs & derivatives*; D005971:Glutamates / Q000378:metabolism; D005779:Immunodiffusion; D007501:Iron / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D013347:Subcellular Fractions / Q000378:metabolism; D014508:Urea / Q000494:pharmacology; D014529:Uridine / Q000378:metabolism
chemical_list: D005971:Glutamates; D014508:Urea; D005293:Ferritins; D001052:Apoferritins; D007501:Iron; D014529:Uridine