Iron‐binding Proteins

Abstract

Brock, J. H. (Department of Bacteriology and Immunology, Western Infirmary, Glasgow, UK). Iron‐binding proteins. The structure and properties of the iron‐binding proteins transferrin, lactoferrin and transferrin are reviewed. Transferrin and lactoferrin are structurally similar, consisting of a single polypetide chain and reversibly binding two iron atoms per molecule. Transferrin is found mainly in serum, whereas lactoferrin is found in neutrophils and in external secretions. Transferrin functions mainly as a donor of iron to cells, but there is no established iron‐transport role for lactoferrin. Both these proteins may have antimicrobial activity as a result of their ability to sequester iron. Lactoferrin may act principally as a scavenger of iron in conditions where transferrin may not bind iron well, e.g. at low pH. Ferritin is a multisubunit protein capable of binding up to 4 000 iron atoms and serves principally as an iron‐storage protein, though it may also serve to detoxify iron. In iron‐rich tissues ferritin is largely degraded and the iron is converted to haemosiderin.

Iron-withholding strategy in innate immunity

“…Some of the ingenious ways that pathogens pirate and acquire host iron are summarized in Table 1. In the vertebrates, bacterial infection can drastically reduce plasma iron level (Lauffer, 1992) as the vertebrate host withholds iron within the cells and tissues (Konijn and Hershko, 1977;Roeser, 1980;Brock, 1989). Some features of the iron-withholding defense system include constitutive iron-binding components such as transferrin, lactoferrin and ovotransferrin, as well as processes which are induced at the time of microbial invasion.…”

Chronic Toxicity of Environmental Contaminants: Sentinels and Biomarkers

“…The known biological functions of lactoferrin are the stimulation of DNA synthesis (200), the transport of iron through the fetal intestine (201), the modulation of the immune system (202,203), and bacteriostatic/bactericidal activities by chelating iron (204). Lactoferrin is believed to play a role in the uterus by one or more of the following mechanisms: as an iron reservoir (205), by maintaining uterine proliferation (206), by tissue remodeling through its intrinsic RNase activity (207)(208)(209), or by fighting infections through its bacteriostatic (194) and bacteriocidal (204) activities. (190) Tilapia (191) Tiger prawn (192) Blue crab (193) Like vitellogenin, lactoferrin is under the positive regulatory control of estrogen.…”

Advanced Dairy Chemistry Volume 3

“…the strong affinity of lactoferrin for iron would enable this protein to sequester iron from its surroundings and thus prevent the growth of bacteria that require iron (Bullen et a/., 1972). While there is evidence that this does occur in vitro (Bullen et a/., 1972;Arnold et al, 1977), definitive evidence that it occurs in vivo is still lacking (Brock, 1989). While it is well established that the incidence of gastrointestinal infections is much lower in breast-fed than in bottle-fed infants (Cunningham, 1979;Fallott et al, 1980), whether this is influenced by lactoferrin is unknown since other constituents of breast milk, such as immunoglobulins and enzymes, are probably involved also (Hambreus, 1977).…”