Ferriitin

Ferritin, sometimes misspelled ferriitin, is an intracellular protein complex that stores iron and releases it in a controlled manner to maintain iron homeostasis in the body. It is found in nearly all organisms and tissues, with high concentrations in the liver, spleen, and bone marrow, and it also circulates in the blood as serum ferritin.

Structurally, ferritin forms a nearly spherical shell composed of 24 subunits, arranged as a protein cage with a central cavity capable of holding up to about 4,500 iron atoms in the ferric form as ferrihydrite. In mammals, the shell consists of two types of subunits, heavy (H) and light (L). The H-subunits contain a ferroxidase site that oxidizes Fe2+ during storage, while the L-subunits support long-term mineralization of iron within the core.

Biologically, ferritin serves two main roles: iron storage and iron release as needed by cellular processes. The expression of ferritin is regulated by cellular iron levels and is influenced by inflammatory signals. Serum ferritin is commonly used as a biomarker of iron stores, with low levels suggesting iron deficiency and high levels indicating iron overload or inflammatory states. However, ferritin is also an acute-phase protein and can be elevated in infection, liver disease, or cancer regardless of iron status.

Genes encoding ferritin subunits include FTH1 (heavy chain) and FTL (light chain) in humans. Beyond its physiological role, ferritin nanostructures are explored in nanotechnology and biomedicine for drug delivery and imaging due to their uniform size and hollow interior.