Transferrin receptor protein 1 (TfR1) also known as (Cluster of Differentiation 71) (CD71) is a protein that in humans is encoded by the TFRC gene. TfR1 is required for iron delivery from transferrin to cells. TfR1 is a transmembrane glycoprotein composed of two disulfide-linked monomers joined by two disulfide bonds. Each monomer binds one holo-transferrin molecule creating an iron-Tf-TfR complex which enters the cell by endocytosis.