ferritinfamily

The ferritin family comprises iron-storage proteins that self-assemble into hollow, spherical nanocages. These cages sequester iron as a mineral core of ferric oxide/hydroxide and release it in a controlled manner. Ferritin and related proteins protect cells from iron-mediated oxidative damage and help maintain iron homeostasis. The family includes ferritin, bacterioferritin, and Dps (DNA-binding protein from starved cells).

Canonical ferritin cages are formed by 24 subunits and yield an inner cavity about 8 nm across. In vertebrates, two subunit types exist—heavy (H) and light (L)—which assemble together. H subunits provide a ferroxidase center that oxidizes Fe2+ to Fe3+, promoting mineral core formation; L subunits aid nucleation and long-term storage. Bacterioferritins incorporate a heme group and can have distinct iron-relay properties. Dps proteins are ferritin-like and form 12-subunit cages that can bind DNA, providing protection against stress.

Ferritin-family proteins are widespread in bacteria, archaea, and eukaryotes; in plants and animals, mitochondria and chloroplasts harbor ferritin homologs.

Function and regulation: They store iron when plentiful and release it when needed, buffering cytosolic iron and reducing oxidative damage. Expression is commonly regulated by cellular iron status through iron-responsive regulators in bacteria and by transcriptional or post-transcriptional mechanisms in eukaryotes.

Applications and medical relevance: Apoferritin nanocages serve as delivery vehicles in nanomedicine and bioimaging. Ferritin mutations, particularly in the light chain, cause neuroferritinopathy and related iron-storage disorders.