Lactoferrin is a member of the subgroup of transferrins. This group of proteins is responsible for iron transport and protects indirectly against infections. This is due to their high affinity for iron, which causes the vital element to be taken from infectious microbes. Lactoferrin is usually found in breast milk.
The metal is bound in two independent domains by two phenol oxygen atoms from tyrosine residues, one nitrogen atom from a histidine residue, one oxygen atom from the carboxyl group of an asparagine residue and two oxygen atoms of a carbonate ligand. The binding of carbonate is essential and is stabilised by additional hydrogen bonds to arginine and threonine side chains.