Chapter 2
Maxi- and Mini-Ferritins: Minerals
and Protein Nanocages
Loes E. Bevers and Elizabeth C. Theil
Contents
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.2 Ferritin Distribution in Organisms of Land and Sea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.2.1 Ferritin in Prokaryotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.2.2 Ferritin in Eukaryotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.2.3 Conservation of Active Sites in Ferritins of Prokaryotes and Eukaryotes . . . . . . . 35
2.3 Ferritin Iron Biomineral Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.3.1 Step i. Fe(II) Entry and Binding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.3.2 Step ii. O 2 or H 2 O 2 Binding and Formation of Transition Intermediates . . . . . . . . 38
2.3.3 Step iii. Release of Differric Oxo Mineral Precursors from Active Sites . . . . . . . . 39
2.3.4 Step iv. Nucleation and Mineralization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39
2.4 Ferritin Iron Biominerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.5 Ferritin Iron Biomineral Dissolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . 42
2.5.1 Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Abstract Ferritins synthesize ferric oxide biominerals and are central to all life for
concentrating iron and protection against oxidative stress from the ferrous and
oxidant chemistry. The ferritin protein nanocages and biomineral synthesis are
discussed in terms of wide biological distribution of the maxi-ferritins (24 subunit
Æ heme) and mini-ferritins (Dps) (12 subunit), conservations of the iron/oxygen
catalytic sites in the protein cages, mineral formation (step i. Fe(II) entry and
binding, step ii. O 2 or H 2 O 2 binding and formation of transition intermediates,
step iii. release of differric oxo mineral precursors from active sites, step iv.
E.C. Theil (*)
Council for BioIron, CHORI (Children’s Hospital Oakland Research Institute), 5700 Martin
Luther King, Jr. Way, Oakland, CA 94609, USA
Department of Nutritional Sciences and Molecular Toxicology, University of California-Berkeley,
Berkeley, CA 94720, USA
e-mail: etheil@chori.org
W.E.G. M€ uller (ed.), Molecular Biomineralization, Progress in Molecular
and Subcellular Biology 52, DOI 10.1007/978-3-642-21230-7_2,
# Springer-Verlag Berlin Heidelberg 2011
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