Transferrins are iron binding transport proteins which can bind two Fe(3+) ions in association with the binding of an anion, usually bicarbonate. It is responsible for the transport of iron from sites of absorption and heme degradation to those of storage and utilization. Serum transferrin may also have a further role in stimulating cell proliferation. (Microbial infection) Serves as an iron source for Neisseria species, which capture the protein and extract its iron for their own use. Monomer. (Microbial infection) Binds to Neisseria transferrin-binding protein A (tbpA or tbp1). Forms a large complex with TbpA and TbpB. (Microbial infection) Binds to Neisseria transferrin-binding protein B (tbpb or tbp2). Expressed by the liver and secreted in plasma. Has a bilobed structure, each lobe binds a single Fe(3+) ion. Does not always bind 2 Fe(3+) ions. (Microbial infection) Binds to Neisseria transferrin-binding proteins A and B via its C-terminal lobe only. The L3 helix finger of TbpA inserts into the C-terminal lobe of TF, altering its conformation and probably disturbing the coordination of iron 2. Electron microscopy suggests that in the TbpA-TbpB-TF complex, TF is captured directly above the loop domain of TbpA in a chamber of about 1000 Angstroms(3) formed by the 3 proteins, where interactions between the proteins serve to abstract iron 2 from TF (PubMed:22343719, PubMed:22327295). Binding to TbpB does not alter the conformation of the C-terminal lobe (PubMed:22343719). Different polymorphic variants of transferrin are known. The sequence shown is the predominant electrophoretic variant (C1 or TF*C1). The disease is caused by variants affecting the gene represented in this entry. Belongs to the transferrin family. Truncated N-terminus. Transferrin entry