Ferritin: design and formation of an iron-storage molecule

TLDR

Iron is essential for life but excess iron is toxic, and ferritin is a 24‑subunit spherical protein that stores iron as a ferrihydrite core within its hollow cavity. The paper investigates how ferritin evolved to store iron safely, balancing its essentiality and toxicity. Ferritin assembles from apoferritin in the presence of oxygen using Fe²⁺, with intersubunit channels controlling the rate of Fe²⁺ oxidation and the resulting oxide form.

Abstract

Although essential for most forms of life, too much iron is harmful. To cope with these antagonistic phenomena an iron-storage molecule, ferritin, has evolved. The structure of horse spleen apoferritin, which has recently been refined, consists of 24 symmetrically related subunits forming a near-spherical hollow shell. In ferritin the central cavity is occupied by an iron core of ‘ferrihydrite’, a geologically ephem eral mineral found in hot or cold springs and in mine workings, or produced in the laboratory by heating solutions of ferric salts. Ferritin itself forms most readily from apoferritin, in the presence of dioxygen, from Fe II , not Fe III . Access to its interior is through small intersubunit channels, and the protein influences both the rate of Fe II -oxidation and the form of oxide produced.