This is the Wikipedia entry entitled "Transferrin". More...
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Transferrin Edit Wikipedia article
PDB rendering based on 1a8e.
|Symbols||; PRO1557; PRO2086; TFQTL1|
|External IDs||ChEMBL: GeneCards:|
|RNA expression pattern|
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). Transferrin has a molecular weight of around 80 KDa and contains two specific high-affinity Fe(III) binding sites. The affinity of transferrin for Fe(III) is extremely high (1023 Mâˆ’1 at pH 7.4) but decreases progressively with decreasing pH below neutrality.
When not bound to iron, transferrin is known as "apotransferrin" (see also apoprotein).
When a transferrin protein loaded with iron encounters a transferrin receptor on the surface of a cell (e.g., to erythroid precursors in the bone marrow), it binds to it and, as a consequence, is transported into the cell in a vesicle by receptor-mediated endocytosis. The pH of the vesicle is reduced by hydrogen ion pumps (H+
ATPases) to about 5.5, causing transferrin to release its iron ions. The receptor (with its ligand, transferrin, bound) is then transported through the endocytic cycle back to the cell surface, ready for another round of iron uptake. Each transferrin molecule has the ability to carry two iron ions in the ferric form (Fe3+
In humans, transferrin consists of a polypeptide chain containing 679 amino acids. The protein is composed of alpha helices and beta sheets that form two domains. The N- and C- terminal sequences are represented by globular lobes and between the two lobes is an iron-binding site.
The amino acids which bind the iron ion to the transferrin are identical for both lobes; two tyrosines, one histidine, and one aspartic acid. For the iron ion to bind, an anion is required, preferably carbonate (CO2âˆ’
Transferrin also has a transferrin iron-bound receptor; it is a disulfide-linked homodimer. In humans, each monomer consists of 760 amino acids. It enables ligand bonding to the transferrin, as each monomer can bind to one or two molecules of iron. Each monomer consists of three domains: the protease, the helical, and the apical domains. The shape of a transferrin receptor resembles a butterfly based on the intersection of three clearly-shaped domains.
The liver is the main site of transferrin synthesis but other tissues and organs, including the brain, also produce transferrin. The main role of transferrin is to deliver iron from absorption centers in the duodenum and white blood cell macrophages to all tissues. Transferrin plays a key role in areas where erythropoiesis and active cell division occur. The receptor helps maintain iron homeostasis in the cells by controlling iron concentrations.
Transferrin also associated with the innate immune system. It is found in the mucosa and binds iron, thus creating an environment low in free iron that impedes bacterial survival in a process called iron withholding. The level of transferrin decreases in inflammation.
Role in disease
An increased plasma transferrin level is often seen in patients suffering from iron deficiency anemia. A decreased plasma transferrin can occur in iron overload diseases and protein malnutrition. An absence of transferrin results from a rare genetic disorder known as atransferrinemia, a condition characterized by anemia and hemosiderosis in the heart and liver that leads to heart failure and many other complications.
The metal-binding properties of transferrin have a great influence on the biochemistry of plutonium in humans.
Atransferrinemia is associated with a deficiency in transferrin.
A high transferrin level may indicate an iron deficiency anemia. Levels of serum iron and total iron binding capacity (TIBC) are used in conjunction with transferrin to specify any abnormality. See interpretation of TIBC.
Members of the family include blood serotransferrin (or siderophilin, usually simply called transferrin); lactotransferrin (lactoferrin); milk transferrin; egg white ovotransferrin (conalbumin); and membrane-associated melanotransferrin.
- Crichton RR, Charloteaux-Wauters M (1987). "Iron transport and storage". Eur. J. Biochem. 164 (3): 485â€“506. doi:10.1111/j.1432-1033.1987.tb11155.x. PMID 3032619.
- Yang F, Lum JB, McGill JR, Moore CM, Naylor SL, van Bragt PH, Baldwin WD, Bowman BH (May 1984). "Human transferrin: cDNA characterization and chromosomal localization". Proceedings of the National Academy of Sciences of the United States of America 81 (9): 2752â€“6. doi:10.1073/pnas.81.9.2752. PMC 345148. PMID 6585826.
- Aisen P, Leibman A, Zweier J (March 1978). "Stoichiometric and site characteristics of the binding of iron to human transferrin" (PDF). J. Biol. Chem. 253 (6): 1930â€“7. PMID 204636.
- "Transferrin Structure". St. Edward's University. 2005-07-18. Retrieved 2009-04-24.
- Macedo MF, de Sousa M (March 2008). "Transferrin and the transferrin receptor: of magic bullets and other concerns". Inflammation & Allergy Drug Targets 7 (1): 41â€“52. doi:10.2174/187152808784165162. PMID 18473900.
- PDB 1suv; Cheng Y, Zak O, Aisen P, Harrison SC, Walz T (February 2004). "Structure of the human transferrin receptor-transferrin complex". Cell 116 (4): 565â€“76. doi:10.1016/S0092-8674(04)00130-8. PMID 14980223.
- PDB 2nsu; Hafenstein S, Palermo LM, Kostyuchenko VA, Xiao C, Morais MC, Nelson CD, Bowman VD, Battisti AJ, Chipman PR, Parrish CR, Rossmann MG (April 2007). "Asymmetric binding of transferrin receptor to parvovirus capsids". Proceedings of the National Academy of Sciences of the United States of America 104 (16): 6585â€“9. doi:10.1073/pnas.0701574104. PMC 1871829. PMID 17420467.
- Ritchie RF, Palomaki GE, Neveux LM, Navolotskaia O, Ledue TB, Craig WY (1999). "Reference distributions for the negative acute-phase serum proteins, albumin, transferrin and transthyretin: a practical, simple and clinically relevant approach in a large cohort". J. Clin. Lab. Anal. 13 (6): 273â€“9. doi:10.1002/(SICI)1098-2825(1999)13:6<273::AID-JCLA4>3.0.CO;2-X. PMID 10633294.
- Sharpe PC (November 2001). "Biochemical detection and monitoring of alcohol abuse and abstinence". Ann. Clin. Biochem. 38 (Pt 6): 652â€“64. doi:10.1258/0004563011901064. PMID 11732647.
- "Normal Reference Range Table". Interactive Case Study Companion to Pathlogical Basis of Disease. The University of Texas Southwestern Medical Center at Dallas. Retrieved 2008-10-25.
Kumar V, Hagler HK (1999). Interactive Case Study Companion to Robbins Pathologic Basis of Disease (6th Edition (CD-ROM for Windows & Macintosh, Individual) ed.). W B Saunders Co. ISBN 0-7216-8462-9.
- Storch S, KÃ¼bler B, HÃ¶ning S, Ackmann M, Zapf J, Blum W, Braulke T (December 2001). "Transferrin binds insulin-like growth factors and affects binding properties of insulin-like growth factor binding protein-3". FEBS Lett. 509 (3): 395â€“8. doi:10.1016/S0014-5793(01)03204-5. PMID 11749962.
- Weinzimer SA, Gibson TB, Collett-Solberg PF, Khare A, Liu B, Cohen P (April 2001). "Transferrin is an insulin-like growth factor-binding protein-3 binding protein". J. Clin. Endocrinol. Metab. 86 (4): 1806â€“13. doi:10.1210/jcem.86.4.7380. PMID 11297622.
- Hsu SL, Lin YF, Chou CK (April 1992). "Transcriptional regulation of transferrin and albumin genes by retinoic acid in human hepatoma cell line Hep3B". Biochem. J. 283 (2): 611â€“5. PMC 1131079. PMID 1315521.
- M Ching-Ming Chung (October 1984). "Structure and function of transferrin". Biochemical Education 12 (4): 146â€“154. doi:10.1016/0307-4412(84)90118-3.
- Hershberger CL, Larson JL, Arnold B et al. (1992). "A cloned gene for human transferrin". Annals of the New York Academy of Sciences 646: 140â€“54. doi:10.1111/j.1749-6632.1991.tb18573.x. PMID 1809186.
- Bowman BH, Yang FM, Adrian GS (1989). "Transferrin: evolution and genetic regulation of expression". Adv. Genet. Advances in Genetics 25: 1â€“38. doi:10.1016/S0065-2660(08)60457-5. ISBN 9780120176250. PMID 3057819.
- Parkkinen J, von Bonsdorff L, Ebeling F, Sahlstedt L (2003). "Function and therapeutic development of apotransferrin". Vox Sang. 83 (Suppl 1): 321â€“6. doi:10.1111/j.1423-0410.2002.tb05327.x. PMID 12617162.
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No Pfam abstract.
Internal database links
|Similarity to PfamA using HHSearch:||Phosphonate-bd|
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR001156
Transferrins are eukaryotic iron-binding glycoproteins that control the level of free iron in biological fluids [PUBMED:3032619]. The proteins have arisen by duplication of a domain, each duplicated domain binding one iron atom. Members of the family include blood serotransferrin (siderophilin); milk lactotransferrin (lactoferrin); egg white ovotransferrin (conalbumin); and membrane-associated melanotransferrin.
Additional members of this family include inhibitor of carbonic anhydrase (ICA; mammals), major yolk protein (sea urchins), saxiphilin (frog), pacifastin (crayfish), and TTF-1 (algae). Most family members contain two transferrin-like domains of around 340 amino acids, the result of an ancient duplication event [PUBMED:15621505]. Each of the duplicated domains can be further divided into two subdomains that form a cleft inside of which the iron atom is bound in iron-transporting transferrin [PUBMED:2585506]. The iron-coordinating residues consist of an aspartic acid, two tyrosines and a histidine, as well as an arginine that coordinates a requisite anion. In addition to iron and anion liganding residues, the transferrin-like domain contains conserved cysteine residues involved in disulphide bond formation.
Human lactoferrin is a serine peptidase belonging to MEROPS peptidase family S60, clan SR. It is found at high concentrations in all human secretions, where it plays a major role in mucosal defence. Lactoferrin cleaves IgA1 protease at an arginine-rich region defined by amino acids RRSRRSVR and digests Hap at a similar arginine-rich sequence (VRSRRAAR). Ser259 and Lys73 form a catalytic dyad, reminiscent of a number of bacterial serine proteases.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Cellular component||extracellular region (GO:0005576)|
|Molecular function||ferric iron binding (GO:0008199)|
|Biological process||cellular iron ion homeostasis (GO:0006879)|
|iron ion transport (GO:0006826)|
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Periplasmic binding proteins (PBPs) consist of two large lobes that close around the bound ligand. This architecture is reiterated in transcriptional regulators, such as the lac repressors. In the process of evolution, genes encoding the PBPs have fused with genes for integral membrane proteins. Thus, diverse mammalian receptors contain extracellular ligand binding domains that are homologous to the PBPs; these include glutamate/glycine-gated ion channels such as the NMDA receptor, G protein-coupled receptors, including metabotropic glutamate, GABA-B, calcium sensing, and pheromone receptors, and atrial natriuretic peptide-guanylate cyclase receptors .
The clan contains the following 25 members:DctP DUF3834 HisG Lig_chan-Glu_bd Lipoprotein_8 Lipoprotein_9 LysR_substrate Mycoplasma_p37 NMT1 NMT1_2 NMT1_3 OpuAC PBP_like PBP_like_2 Phosphonate-bd SBP_bac_1 SBP_bac_11 SBP_bac_3 SBP_bac_5 SBP_bac_6 SBP_bac_8 TctC Transferrin VitK2_biosynth YhfZ_C
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Curation and family details
|Number in seed:||8|
|Number in full:||1802|
|Average length of the domain:||253.60 aa|
|Average identity of full alignment:||32 %|
|Average coverage of the sequence by the domain:||85.73 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 80369284 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||13|
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There are 12 interactions for this family. More...
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Transferrin domain has been found. There are 270 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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