Ferritin, found in all living organisms, is an intracellular blood protein that is the body’s primary iron storage mechanism. Most commonly, ferritin acts as a cytosolic protein, but small amounts are also secreted into the serum where it functions as an iron carrier, keeping iron to a non-toxic form. When not combined with iron, ferritin is known as ‘apoferritin.’ It must combine with a ferric hydroxide–phosphate compound to enable safe iron storage and distribution.
In its free form, iron is a toxic catalyst for free radicals and reactive oxygen species. Ferritin largely offsets these risks, though its precise function and structure vary in different cell types, typically triggered by the presence of iron alone. Ferritin tests are commonly used to gain an understanding of iron stores, but the presence of ferritin has been linked to various functions, including –
In some industrial applications, ferritin has also been used as a precursor for making iron nanoparticles.
Ferritin is a hollow globular protein that is present in every cell type. It consists of 24 subunits, the nature of which vary among organisms. Vertebrates have two subtypes – FTL (light) and FTH (heavy.) Amphibians have an additional M (medium) ferritin, while plants and bacteria have a single ferritin that most closely resembles the vertebrate H-type. These ferritins are all similar in terms of their primary sequence, and iron ions form crystallites together with phosphate and hydroxide ions inside the ferritin shell, around 4500 of which can be stored in each ferritin compound.