Transferrin, also known as serotransferrin and siderophilin, is an 80kD secreted glycoprotein that binds two Fe (3+) ions, transporting them from sites of absorption and heme degradation to those of storage and utilization. It is a member of the Transferrin family of proteins. Human Transferrin is synthesized as a 698 amino acid (aa) precursor that contains a 19aa signal sequence and a 679aa mature chain. The mature chain consists of two Transferrin-like domains, two high-affinity iron binding sites, one potential site for O-linked glycosylation, and two potential sites for N-linked glycosylation. Human Transferrin has sequence homology of 73% to mouse and rat Transferrin.