Iron binding proteins

Ferritin, an iron-binding protein, prevents ionized iron (Fe ) from reaching toxic levels within cells. Elemental iron stimulates ferritin synthesis by causing the release of a cytoplasmic protein that binds to a specific region in the 5 nontranslated region of ferritin mRNA. Disruption of this protein-mRNA interaction activates ferritin mRNA and results in its translation. This mechanism provides for rapid control of the synthesis of a protein that sequesters Fe +, a potentially toxic molecule. 

Lactoferrin j Iron-binding protein May inhibit growth of certain bacteria by binding iron and may be involved in regulation of proliferation of myeloid cells... 

The 4 g of iron in the human body is normally com-partmented into its functional locations in the haem- and non-haem-containing, and iron-binding proteins and enzymes (Fig. 3.5). The majority (65%) of the iron is in the divalent state in haemoglobin and myoglobin, which are involved in the transport and storage of oxygen in erythrocytes and myocytes, respectively. The remainder is distributed between storage sites, predominantly in the... 

Transferrin iron uptake via receptor-mediated endocytosis has clearly appeared fairly late in evolution, when we consider that the bilobal iron-binding protein is found only as far back as insects . As we have seen in the preceding chapters, iron-uptake mechanisms involving the synthesis of more or less specific siderophores have evolved together with strategies implying the solubilization of insoluble ferric iron by the combined effects of pH and reduction, and even the development of receptor proteins capable of taking up transferrin-, lactoferrin- or haem-bound iron from specific hosts. 

For most living bacteria (lactobacilli being the only notable exception [154]) iron is an essential nutrient. Iron is not readily available under normal conditions, although it is the fourth most abundant metal on earth. In the environment it is mainly found as a component of insoluble hydroxides in biological systems it is chelated by high-affinity iron binding proteins (e.g. transferrins,... 

This receptor-mediated endocytotic pathway has been especially well studied in the uptake of iron from blood plasma. Iron, because of its very low-solubility product (< 1(T17 at pH 7.4), is transported in plasma bound to the iron-binding protein transferrin. Two Fe3+ ions bind to each transferrin molecule. Entry into... 

So called because they are found in milk, where the iron-binding protein lactoferrin sequesters iron so tightly... 

In addition to the amino acid side chains mentioned above, a number of other low molecular weight ligands are found in metalloproteins. These include cyanide and carbon monoxide, which we will describe later in this chapter. Here we consider carbonate and phosphate anions in the context of the super family of iron-binding proteins, the transferrins. 

In the extracellular fluids of mammals, the iron-binding protein transferrin is usually only 30% saturated, so that it has 70% of its metal-binding capacity free. If Al3+ could get... 

Iron absorption occurs predominantly in the duodenum and upper jejunum. The physical state of iron entering the duodenum greatly influences its absorption. At physiological pH, ferrous iron is rapidly oxidized to the insoluble ferric form. Gastric acid lowers the pH in the proximal duodenum, enhancing the solubility and uptake of ferric iron. When gastric acid production is impaired, iron absorption is reduced substantially. Ascorbic acid enhances iron absorption. Ascorbic acid mobilizes iron from iron-binding proteins in vivo, which in turn could catalyze lipid peroxidation. Iron absorption is inhibited by antacids, phytates, phosphates and tetracyclines. 

Steinbiichel A, Muller M (1986) Anaerobic pyruvate metabolism of Tritrichomonas foetus and Trichomonas vaginalis hydrogenosomes. Mol Biochem Parasitol 20 57-65 Suchan P et al. (2003) Incorporation of iron into Tritrichomonas foetus cell compartments reveals ferredoxin as a major iron-binding protein in hydrogenosomes. Microbiology 149 1911-1921... 

Transferrin of blood plasma is encoded by a separate gene but has a similar structure. Transferrin of chickens appears to be identical to conalbumin of egg whites. The iron-binding proteins of body fluids are sometimes given the group name siderophilins. Transferrins may function not only in transport of iron throughout the body but also as iron buffers that provide a relatively constant iron concentration within tissues. 

The transferrins are proteins that bind and transport iron as peIII 16-U.8 They indude lactoferrin from milk, ovotransferrin from egg white, and serum transferrin from a range of organisms. Uteroferrin, considered in Section 62.1.5.5.2 on the purple acid phosphatases, is an iron-binding protein with phosphatase activity, that has been proposed to transport iron from maternal to foetal circulation.824 826 There are distinct differences between the iron-binding sites in uteroferrin and transferrin, and so uteroferrin will not be discussed in this section. 

Lactofenin, transferrin Iron-binding proteins with effects apparently similar to ETDA... 

Ovotransferrin Gal d3 12-13 76-78 6.0 686 2.6% Antimicrobial defense and iron-binding protein... 

Human lactoferrin (HL) is a component of innate immunity. Human lactoferrin is an iron-binding protein found in milk, granulocytes and exocrine secretions. It is released during inflammation, has bactericidal effects and reduces cytokine production by binding to the lipid A portion of endotoxin (Appelmelk et al., 1994). 

Bullen, J.J., Rogers, H.J., and Leigh, L. 1972. Iron-binding proteins in milk and resistance to Escherichia coli infections in infants. Br. Med. J. 1, 69—75. 

Crouch, S.P., Slater, K.J., and Fletcher, J. 1992. Regulation of cytokine release from mononuclear cells by the iron-binding protein lactoferrin. Blood 80, 235 - 240. 

Masson, P.L. and Heremans, J.F. 1966. Studies on lactoferrin, the iron-binding protein of secretions. Prot. Biol. Fluids 14, 115-142. 

Spik, G., Cheron, A., Montreuil, J., and Dolby, J.M. 1978. Bacteriostasis of a milk-sensitive strain of Escherichia coli by immunoglobulins and iron-binding proteins in association. Immunology 35, 663-671. 

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