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Description

Transferrin receptor protein 2 (UniProt: Q9UP52, also known as TfR2) is encoded by the TFR2 gene (Gene ID: 70360 in human. TfR2 is a single-pass type II membrane glycoprotein that plays a critical role in iron metabolism. It has a large C-terminal ectodomain and a small N-terminal cytoplasmic domain and shares 45% amino acid sequence with extracellular region of transferrin receptor (TfR). This homodimeric membrane receptor binds 2 molecules of transferrin and is internalized into endosomes that are acidified, resulting in the release of iron from transferrin. TfR2 contains a cytoplasmic internalization motif similar to TfR, and has 2 cysteines, which form inter subunit disulfide bonds, in the ectodomain proximal to the transmembrane domain. TfR2 mediates cellular uptake of transferrin-bound iron in a non-iron dependent manner. Both TfR and TfR2 bind diferric transferrin better than apo-transferrin at neutral pH. However, TFR2 displays about 25-fold lower affinity for transferrin compared to TfR and its expression is not controlled by cellular levels of iron. TfR2 is also suggested to be involved in involved in hepatocyte function and erythrocyte differentiation. Mutations in TFR2 gene are known to cause hemochromatosis 3 that is characterized by an iron overload where excess iron is deposited in several organs leading to organ failure. (Ref.: Kawabata H., et al (1999). J. Biol. Chem. 274 (30): 20826-20832, Vogt, TM et al. (2003). Blood 101(5):2008-2014.