title: Degradation of proteins microinjected into cultured mammalian cells.
abstract: Iodinated proteins were degraded after injection into HeLa cells at first-order rates with half-lives varying from three hours for the trout monhistone chromosomal protein, HMG-T, -to 60 hours for whale myoglobin. Fluoresceinated-bovine serum albumin (fl-BSA) was degraded almost twice as fast as unmodified BSA. The rate of degradation of 125I-BSA was very similar in eight cell lines of mouse, human, monkey and rat origin. Microinjected proteins were analyzed on SDS-acrylamide gels after injection, and for BSA and immunoglobin G, all remaining intracellular 125I migrated at the molecular weight of the injected proteins. By contrasting, more than 80% of the extracellular 125I chromatographed as iodotyrosine. With the exception of fl-BSA, which exhibited perinuclear accumulation in approximately one-half of the injected cells, autoradiography showed that throughout the period of study the injected proteins remained dispersed in the cytoplasm.
mesh_terms: D000818:Animals; D001345:Autoradiography; D002460:Cell Line / Q000378:metabolism; D002478:Cells, Cultured / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D000882:Haplorhini; D006367:HeLa Cells / Q000378:metabolism; D007456:Iodine Isotopes; D007467:Iodoproteins / Q000378:metabolism; D051379:Mice; D008854:Microscopy, Electron; D011506:Proteins / Q000378:metabolism; D051381:Rats; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013997:Time Factors
chemical_list: D005452:Fluoresceins; D007456:Iodine Isotopes; D007467:Iodoproteins; D011506:Proteins; D012710:Serum Albumin, Bovine