noun, plural: transferrins
A glycoprotein (80 kD) that carries iron in the bloodstream; a beta globulin found in mammalian serum
Transferrin is a glycoprotein that can bind with, and thus transport, iron via the bloodstream to liver, spleen, and bone marrow. It regulates the blood serum levels of free iron (Fe).
In humans, transferrin is synthesized in different tissues and organs, but the major site is the liver. It is encoded by the TF gene in chromosome band 3q21. Mutations involving TF gene could lead to atransferrinemia, an autosomal recessive metabolic disorder characterized by a deficiency in transferrin.
Transferrin is made up of a polypeptide chain (679 amino acids) and two carbohydrate chains. It has a molecular weight of about 80 kDa. It has two iron-binding sites. When not bound to iron, it is referred to as apotransferrin.
When transferrin is carrying iron ions and then docks on the transferrin receptor on the surface of the cell. Then, it is endocytosed to be transported inside the cell within a vesicle. Inside the vesicle, H+ ATPases pump hydrogen ions to reduce the pH to about 5.5. This causes transferrin to release the iron ions.