ABSTRACT
CHENGHUA LI, ZHEN LI, YE LI, JUN ZHOU, CHUNDAN ZHANG, XIURONG SU, AND TAIWU LI
14.1 INTRODUCTION
As one of a major member of iron homeostasis proteins, ferritin plays an important role in storage and detoxification of excess iron in living cells. Structure analysis indicates the protein complex usually composed of 24 subunits, which surrounds an inorganic microcrystalline hollow capable of accommodating up to 4500 Fe3+ [1], [2]. In vertebrates, two types of subunits called heavy (H) and light (L) chains are identified and demonstrated to be encoded by separate genes. The H subunit has been studied in a variety of species including vertebrate and invertebrate animals, plants and bacteria [3], [4]. The L subunit, however, has been only found in vertebrates [5], [6]. The H subunits from different species contain seven conserved residues that confer ferroxidase activity for converting Fe2+ to Fe3+ allowing rapid detoxification of iron cations. The L subunit does not have
ferroxidase activity, but serves as a salt bridge that stabilizes the ferritin structure, thus playing a role in iron nucleation and long-term storage [7].
