HOW THE PRESENCE OF 3 IRON-BINDING SITES AFFECTS THE IRON STORAGE FUNCTION OF THE FERRITIN (ECFTNA) OF ESCHERICHIA-COLI

The iron storage proteins, ferritins, are found in all organisms which use iron. Here iron storage processes in the Escherichia coli ferriti n (EcFtnA) are compared with those in human H-type ferritin (HuHF), Bo th proteins contain dinuclear iron centres that enable the rapid oxida tion of 2 Fe(II) by O-2. The presence of a third iron binding site in EcFtnA, although not essential for fast oxidation, causes the O-2/Fe r atio to increase from 2 to 3-4. In EcFtnA the rate of iron oxidation f alls markedly after the oxidation of 48 Fe(II) atoms/molecule probably because some of it remains at the oxidation site. However a compensat ory physiological advantage is conferred because this iron is more rea dily available to meet the cell's needs. (C) 1998 Federation of Europe an Biochemical Societies.