These carbohydrate groups are linked to the protein, and apparently strongly affect the recognition and conformation of the native protein.Īlthough transferrins have a high molecular weight and bind only two iron atoms, transferrin is relatively efficient, because it is used in many cycles of iron transport in its interaction with the tissues to which it delivers iron. The transferrins are all glycoproteins, and human serum transferrin contains about 6 percent carbohydrate.

This was first discovered by various spectroscopies, and most recently was confirmed by crystal-structure analysis, which shows that the environment involves two phenolate oxygens from tyrosine, two oxygens from the synergistic, bidentate bicarbonate anion, nitrogen from histidine, and (a surprise at the time of crystal-structure analysis) an oxygen from a carboxylate group of an aspartate. Although the two iron-binding sites of transferrin are sufficiently different to be distinguishable by kinetic and a few other studies, their coordination environments have been known for some time to be quite similar. 41 In contrast, transferrin has been in existence only relatively recently, since it is only found ia the phylum Chordata. The crystal structure of the related protein, lactoferrin, 39 has been reported, and recently the structure of a mammalian transferrin 40 has been deduced.įerritin is apparently a very ancient protein and is found in higher animals, plants, and even microbes in plants and animals a common ferritin progenitor is indicated by sequence conservation. Serum transferrin is a monomeric glycoprotein of molecular weight 80 kDa. 37-39 This complexation of the metal cation occurs via prior complexation of a synergistic anion that in vivo is bicarbonate (or carbonate). The transferrins are a class of proteins that are bilobal, with each lobe reversibly (and essentially independently) binding ferric ion.

The transport of iron from storage sites in cellular ferritin or hemosiderin occurs via the serum-transport protein transferrin. Only a small fraction of the body's inventory of iron is in transit at any moment. The storage of iron in humans and other mammals has been dealt with in the previous section.

Hemoglobin iron charge