| Ovotransferrin | |||||||
|---|---|---|---|---|---|---|---|
 PDB 1gvc EBI | |||||||
| Identifiers | |||||||
| Organism | Gallus gallus | ||||||
| Symbol | ? | ||||||
| UniProt | P02789 | ||||||
| |||||||
Ovotransferrin (conalbumin) is aglycoprotein ofegg white albumen.[1] Egg white albumen is composed of multipleproteins, of which ovotransferrin is the most heat reliable. It has a molecular weight of 76,000daltons and contains about 700amino acids. Ovotransferrin makes up approximately 13% of egg albumen (in contrast toovalbumin, which comprises 54%).[2] As a member of thetransferrin andmetalloproteinase family, ovotransferrin has been found to possess antibacterial and antioxidant and immunomodulatory properties, arising primarily through its iron (Fe3+) binding capacity by locking away a key biochemical component necessary for micro-organismal survival. Bacteria starved of iron are rendered incapable of moving, making ovotransferrin a potent bacteriostatic.
Ovotransferrin isfolded in a way that forms two lobes (N- and C- terminals) and each lobe consists of abinding site. Each lobe is then divided into two domains of 160amino acid residues. Its structure also consists of fifteendisulfide crosslinks and no freesulfhydryl groups. Disulfide groups stabilize the tertiary structures of proteins. Transferrins are iron binding proteins andacute phase reactants of animal serum. It has a binding log of 15 at a pH of 7 or above, meaning that the iron binding capacity of ovotransferrin rapidly decreased at a pH that is less than 6. This family is also known for their role in cell maturation by transporting essential nutrients to developingembryos. Ovotransferrin functions as anantimicrobial agent and transportsiron to the developing embryo. Because they bind to iron, this makes it difficult for harmfulbacteria to be nutritionally satisfied with them so it acts as an antimicrobial.
The primary sequence of ovotransferrin is similar to that of many serum transferrins found in other species. Recently, scientists have discovered a blood serum transferrin in humans, that binds iron like ovotransferrin and which shows 50%homology to ovotransferrin, i.e., they have similar amino acid composition andcarbohydrate content. At the C- lobe, human serum has two N-glycans while the hen ovotransferrin has a single N-glycan. Consequently, structurally this protein differs from its serum counterpart because of itsglycosylation pattern. These proteins are said to be glycosylated because they have carbohydrates attached to them. Glycosylation is the most commoncovalent modification (formation of chemical bonds) that occurs in living organisms. This process is determined by the structure of the protein backbone and the carbohydrate attachment site.
In addition, ovotransferrin is glycosylated by the N-linkage to the amino acid known asasparagine, meaning that theglycan, the carbohydrate chain, is attached to thenitrogen on the amino acid. Asparagine, found abundantly inasparagus (hence, its name), is one of twenty of the most common amino acids and was the first amino acid to be isolated. While ovotransferrin identifies with its family, there are two types of ovotransferrin proteins: apo and holo. Apo-Ovotransferrin is deprived of iron and holo-Ovotransferrin is saturated with iron. Because the apo-ovotransferrin is iron-deprived, it is easily destroyed by physical and chemical treatments.
Biologically, conalbumin isolates and sequesters metallic contaminants in the egg white.[3] Ovotransferrin is functionally and structurally analogous to mammalianlactoferrin[4] A recent study has shown superior performance of ovotransferrin when compared tolactoferrin in its capability to deliver iron without accumulation or inducing gastric irritability, rendering ovotransferrin as an excellent potential iron carrier for the treatment ofIron-deficiency anemia (IDA). Ovotransferrin showed superior physiological iron delivery over lactoferrin in a gastric barrier model. This data holds much promise for ovotransferrin's use in food supplements, with dual functionality as both antimicrobial and iron delivery mechanism.[5]
Numerous studies have identified dual anti-osteoporotic properties of ovotransferrin, both reducing bone resorption and promoting bone formation.[6] Beyond this, ovotransferrin shows promise as a drug carrier with potential applications in cancer treatment.[7] Indeed, ovotransferrin alone is toxic to cancer cells in-vitro. Its antioxidant and anti-inflammatory properties may also make ovotransferrin a viable treatment forcardiovascular disease.[8][9]