title: Kinetics of degradation of "short-" and "long-lived" proteins in cultured mammalian cells.
abstract: Two distinct classes of protein referred to as short- and long-lived (Poole and Wibo, 1973) were found in pulse-chased HeLa S-3 and BHK 21/C13 cells. From experiments with pulse times ranging from 1 min to 20 h, a clear inverse correlation emerged between the pulse length and the percentage of protein which was hydrolysed intracellularly in the first h of chase. Using a 5 min pulse labelling with 3H-leucine, cells were either harvested immediately or after a 2 h chase. Approximately 35% of the label incorporated by cells was lost in a 2h chase; however, electrophoretic separation of cytosol and residual cytoplasmic fractions revealed no significant alteration in their protein profiles. The technique of selectively labelling "short" and "long-lived" proteins, which implies qualitative differences between then, is more readily interpreted as an artificial polarisation of a declining statistical probability curve of proteolysis with time which is similar for all nascent proteins.
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007668:Kidney; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D013223:Statistics as Topic
chemical_list: D011506:Proteins; D007930:Leucine