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Upon release into the bloodstream, Fe 3+ binds transferrin and circulates to tissues. In contrast, ferroportin is post-translationally repressed by hepcidin, a 25-amino acid peptide hormone. The body regulates iron levels by regulating each of these steps.
Ferroportin-1, also known as solute carrier family 40 member 1 (SLC40A1) or iron-regulated transporter 1 (IREG1), is a protein that in humans is encoded by the SLC40A1 gene. [5] Ferroportin is a transmembrane protein that transports iron from the inside of a cell to the outside of the cell.
Iron-binding proteins are carrier proteins and metalloproteins that are important in iron metabolism [1] and the immune response. [2] [3] Iron is required for life.Iron-dependent enzymes catalyze a variety of biochemical reactions and can be divided into three broad classes depending on the structure of their active site: non-heme mono-iron, non-heme diiron , or heme centers. [4]
Another player assisting ferroportin in effecting cellular iron export is GAPDH. [47] A specific post translationally modified isoform of GAPDH is recruited to the surface of iron loaded cells where it recruits apo-transferrin in close proximity to ferroportin so as to rapidly chelate the iron extruded. [48]
Human transferrin is encoded by the TF gene and produced as a 76 kDa glycoprotein. [7] [8] Transferrin glycoproteins bind iron tightly, but reversibly. Although iron bound to transferrin is less than 0.1% (4 mg) of total body iron, it forms the most vital iron pool with the highest rate of turnover (25 mg/24 h).
Iron is transported by transferrin whose binding site consists of two tyrosines, one aspartic acid and one histidine. [22] The human body has no controlled mechanism for excretion of iron. [ 23 ] This can lead to iron overload problems in patients treated with blood transfusions , as, for instance, with β- thalassemia .
Ferroportin is upregulated in the reticuloendothelial macrophages after phagocytosis occurs so that iron from the degraded red blood cells can be released into the bloodstream and transported to other types of cells as needed. Hepcidin, a protein synthesized in the liver in response to iron or inflammation, is a regulator of ferroportin ...
In HEK 293 cells, Q248H was as predisposed to the activities of hepcidin-25 as wild type ferroportin. [27] Ferroportin Q248H also unregulated the expression of transferrin receptor-1 in the same way as wild type. This indicates the ferroportin Q248H is associated with mild clinical phenotype or causes iron disorder in the presence of other factors.