Studies on the forms of iron-transferrin released from rabbit reticulocytes.
Measurement of the distribution of the four species of transferrin, viz, apotransferrin, diferric transferrin and the two monoferric transferrin, before and after incubation of iron-rich rabbit transferrin with rabbit reticulocytes showed that not all transferrin released from the cells were in the form of apotransferrin. Instead, a mixture of all four species of the protein was released with apotransferrin and C-terminal monoferric transferrin being the major fractions. The buffer solution containing 125I-labelled transferrin showed a continuous gain in percentages in apotransferrin and C-terminal monoferric transferrin after each incubation with reticulocytes. The N-terminal monoferric transferrin, however, remained unchanged suggesting that in the process of transferrin uptake by cells, the diferric transferrin releases its iron from the acid-labile site at N-domain first before the other iron from the acid-stable site.
D000818:Animals; D001059:Apoproteins; D004591:Electrophoresis, Polyacrylamide Gel; D005290:Ferric Compounds / Q000378:metabolism; D007457:Iodine Radioisotopes; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism*; D014168:Transferrin / Q000378:metabolism*
D001059:Apoproteins; D005290:Ferric Compounds; D007457:Iodine Radioisotopes; D014168:Transferrin; C028284:apotransferrin