Transferrin Receptor
Transferrin is a plasma protein that is able to combine with iron ions: It is the vehicle with which iron is carried around the body. Free ferric ions are toxic; but cells need iron to build many of their proteins including cytochromes and hemoglobin. Ferric ions are carried in the blood tightly bound to transferrin as ferritransferrin. Dividing cells, which need the iron, gain it by binding the ferritransferrin to transferrin receptors on their surfaces. These receptors also have a high affinity for coated pits. Like the LDL receptor, the transferrin receptor is internalised into a coated vesicle. The iron is released inside the cell and the receptor returned to the cell surface. The route this receptor takes inside the cell appears to be different from that taken by the LDL receptor, because it takes about 10 minutes before it is exocytosed.
Read more about this topic: Endocytic Cycle
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