Iron in Human
Iron is an essential elements for human.
Ferritin, an iron-storage protein found in animals and plants,
contains the largest cluster currently known, an ordered aggregate
containing up to 4,500 Fe(III) atoms. The cluster occurs within a protein
cavity roughly 80 angstroms in diameter.
Proteins in which heavy metal ions are bound directly to some of the
side chains of histidine, cysteine, or some other amino acid are
called metalloproteins. Two metalloproteins, transferrin and
ceruloplasmin, occur in the globulin fractions of blood serum; they
act as carriers of iron and copper, respectively.
Transferrin has a molecular weight of 84,000 and consists of two identical
subunits, each of which contains one ferric ion (Fe3+) that seems
to be bound to tyrosine. Several genetic variants of transferrin are known
to occur in man.
Another iron protein, ferritin, which contains 20 to 22 percent iron,
is the form in which iron is stored in animals; it has been obtained in
crystalline form from liver and spleen. A molecule consisting of 20
subunits, its molecular weight is approximately 480,000. The iron can be
removed by reduction from the ferric (Fe3+) to the ferrous (Fe2+) state.
The iron-free protein, apoferritin, is synthesized in the body before the
iron is incorporated.