Ovotransferrin

At the moment, we do not know if ovotransferrin can serve as an antibiotic protecting the egg and embryo development. In fact, if bacteria are present in the oviduet and appear in the egg-white, the baeteriostatic effect of ovotransferrin, whieh is only in the 

The role of melanotransferrin has been recently elucidated by Kennard et al. [207] who demonstrated that this membrane bound iron binding protein is involved in the transferrin-independent uptake of iron in mammals but from iron-citrate and not from iron-transferrin complexes. This alternative iron uptake pathway may not function in the normal recirculation of iron within the body but might play a role during iron overload. On the other hand, rapidly proliferative tumor cells like melanocytes could use the alternative pathway to increase iron uptake. This independent system could also participate in the absorption of iron by intestinal cells that have no transferrin receptor on their lumenal surfaces [208], but express a transferrin-like GPI-linked iron-binding protein at the apical surface of fetal intestinal epithelial cells [209]. 

Comparative study of transferrin glycan primary structures 

---

Ovoflavoprotein Ovoglycoprotein Ovoinhibitor Ovomacroglobulin Ovomucin Ovomucoid Ovotransferrin 150-Water Oxacephems Oxacillin [66-79-5]... 

Figure 5.1 Schematic diagram of the lactoferrin molecule. The positions of carbohydrate attachment are marked with a star. O, ovotransferrin T, human serotransferrin L, human lactoferrin R, rabbit serotransferrin M, melanotransferrin A, the connecting helix B, the C-terminal helix. The disulfide bridges are indicated by heavy bars, and the iron and carbonate binding sites by filled or open circles, respectively. Reprinted from Baker et al., 1987. Copyright (1987), with permission from Elsevier Science.

Isoelectric focusing of a mixture of proteins (1) soybean trypsin inhibitor (2) p-lactoglobulin A (3) p-iactoglobulin B (4) ovotransferrin (5) horse myoglobin (6) whale myoglobin and (7) cytochrome c. [Courtesy BioRaa Laboratories, Richmond, CA]... 

Milk transferrin (lactoferrin51a b c also found in leukocytes), hen egg transferrin (ovotransferrin),52 52a and rabbit and human serum transferrin54 543 all have similar structures. Each Fe3+ is bonded to oxygen anions from two tyrosine side chains, an aspartate carboxy-late, an imidazole group, and the bound carbonate ion (Fig. 16-2B). 

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. 

It appears that both halves of the transferrin molecule contain a recognition site for the receptor, and that both are necessary for binding. Thus, the two halves of ovotransferrin are much less effective than the whole molecule in binding to the receptor and donating iron into the chick embryo red blood cell.1143 One fragment of serum transferrin is ineffective.1124... 

Occasionally, the branchings are incomplete and the formation of the N-acetyl-lactosamine residues is only started in outline, as in the glycans of ovotransferrin (see Fig. 15), ovalbumin (see Fig. 16), and ovomucoid (see Fig. 18). In other instances, glycan structures such as have just been described are enriched with supplementary monosaccharide residues for example, the occurrence of disialyl groups [a-NeuAc-(2—>8)-a-NeuAc], and of /3-Gal-(l- 3) residues linked to the terminal galactosyl residues, has been demonstrated in different tissues and cell membranes,114,115 and in calf-thymocyte membranes,118 respectively. 

Ovotransferrin is also obtained from the white portion of a chicken egg and has been used as a chiral selector in liquid chromatography. This protein is also called conalbumin. It is a metal ion (iron, copper, manganese, and zinc) binding protein of molecular mass 70,000-78,000 and with an isoelectric point of 6.1-6.6. This protein is sensitive to acids and heat. 

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

Ibrahim, H.R. 1997. Insights into the structure-function relationships of ovalbumin, ovotransferrin, and lysozyme. In Hen Eggs Their Basic and Applied Science (T. Yamamoto, L.R. Juneja, H. Hatta, and M. Kim, eds), pp. 37-56. CRC Press, Boca Raton. 

---