Computational Study of Iron(II) and -(III) Complexes with a Simple Model Human H Ferritin Ferroxidase Center

Interaction of iron ions with a six-amino acid model of the ferroxidase center of human H chain ferritin has been examined in density functional theory calculations. The model, based on experimental studies of oxidation of Fe²⁺ at the center, consists of Glu27, Glu62, His65, Glu107, Gln141, and Ala144. Reasonable structures are obtained in a survey of types of iron complexes inferred to occur in the ferroxidase reaction. Structures of complexes of the model center with one and two Fe²⁺ ions, with diiron(III) bridged by peroxide and bridged by oxide−peroxide combinations, have been optimized. Calculations on diiron(III) complexes confirm that stable peroxide-bridged complexes can form and that the Fe−Fe distance in at least one is consistent with the experimental Fe−Fe distance observed in the blue peroxodiferric complex of ferritin.