Biosynthesis of ferritin in rat hepatoma cells and rat livers. II. Binding of iron by ferritin protein.
Ferritin and its protein subunits in rat hepatoma cell clone M-5123-C1 were biosynthetically labeled with [14C]leucine and 59Fe. Radioimmunoassays of ferritin/apoferritin and of protein subunits in the free polyribosome, membrane-bound polyribosome, smooth membrane, and cytosol fractions were done with ferritin-specific and subunit-specific rabbit IgG antibodies at various time intervals after pulsing. Much more 59Fe was bound by ferritin/apoferritin than by subunits in all of the cell fractions. Binding of iron to subunits may have been a random process. When hepatoma cells were simultaneously pulse-labeled with 59Fe and [14C]leucine, uptake of much of the 59Fe by ferritin occurred relatively early, in comparison to incorporation of [14C]leucine, in all of the cell fractions examined. Thus, 59Fe was readily incorporated into pre-existing ferritin. We conclude that most, if not nearly all, of the iron is incorporated after assembly of protein subunits.
D000818:Animals; D001052:Apoferritins / Q000378:metabolism; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005293:Ferritins / Q000096:biosynthesis*; D007501:Iron / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008113:Liver Neoplasms / Q000378:metabolism*; D046911:Macromolecular Substances; D008297:Male; D009374:Neoplasms, Experimental / Q000378:metabolism; D011132:Polyribosomes / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D011912:Rats, Inbred ACI
D046911:Macromolecular Substances; D005293:Ferritins; D001052:Apoferritins; D007501:Iron