Reassembly of Apoferritin Molecules from Subunits

Abstract

APOFERRITIN, the protein component of the iron-storage protein ferritin, consists of twenty polypeptide chains, each of molecular weight about 23,000, arranged symmetrically to form a hollow shell¹. In the ultracentrifuge apoferritin molecules sediment with a coefficient S°_20,w, equal to 17.6S (ref. 2). Negatively stained preparations of apoferritin show molecules with circular profiles about 105 Å in diameter, many molecules being penetrated by stain to give an annular appearance³. Ferritin consists of a mixture of molecules, some of which are empty shells, while the majority have shells which are filled, or partially filled, with a core of a hydrated ferric oxide–phosphate complex⁴. The experiments reported here were designed to investigate the possible dissociation and reassembly of apoferritin and ferritin.