How many atoms of iron can a protein molecule of ferritin hold?

By William Aird

About 4,500

Ferritin Structure: Apoferritin forms a roughly spherical container within which ferric iron is stored as a ferrihydrite mineral. Apoferritin refers to the iron-free form of the protein; the iron-containing form is termed holoferritin or simply ferritin. The apoferritin shell is composed of 24 subunits of two types, termed H and L, the ratio of which varies widely depending on tissue type and inflammation. Iron is toxic in cellular systems because of its capacity to generate reactive species (shown as yellow spheres) which can directly damage DNA and proteins. From Knovich et al.
ferritin structure
Ferritin is a hollow protein shell composed of 24 subunits. Two subunits have been removed to allow visualization within the core where up to 4500 iron atoms can be stored. Source