phosphate does not affect the oxidation rate of the first 48 Fe(II) per ferritin aerobically added to apoferritin. But, it does increase the iron-oxidation rate of subsequent additions of 48 Fe(II) per ferritin by a factor of 6. Phosphate increases the oxidation rate of iron
crystal structures of Zn2+- and Cd2+-bound forms of HP-NAP, and Cd2+-bound and apo forms of HP-NAP are determined: The coordination patterns of Zn2+ and Cd2+ are different but both metal ions can bind to the ferroxidase center (FOC)
the first cadmium ion, Cd1 is coordinated in a trigonal-bipyramidal manner, in which the triangle is formed by the side chains of His25, Asp52, and a water molecule bridging two cadmium ions, and the corner of the pyramid is formed by the side chain of Glu56 and another water molecule. The second cadmium ion, Cd2 is coordinated in a distorted octahedral manner to the side chain of His37 and three water molecules, with two sites remaining unoccupied. Zinc ions are more likely to coordinate in a tetrahedral arrangement. Cadmium ions are also more likely to coordinate in both tetrahedral and octahedral arrangements, but also exhibit a versatile coordination geometry. Cadmium ions are found to be coordinated in a trigonal-bipyramidal manner
Fet31 and Fet34 contain a type 3 Cu2+ pair known as the binuclear Cu-cluster, recombinant soluble Fet34 contains a full complement of 4 Cu atoms per molecule
the active site within each subunit consists of two inequivalent fivecoordinate ferrous centers that are weakly antiferromagnetically coupled, consistent with a my-1,3 carboxylate bridge. The active site ligand set is unusual and likely includes a terminal water bound to each Fe(II) center. The Fe(II) ions bind to the active sites in a concerted manner, and cooperativity among the sites in each subunit is observed
wild-type, Km value 0.005 mM, mutant D283A, 0.019 mM, mutant E185A, 0.036 mM, mutant D409A, 0.019 mm, mutant E185A/D409A, 4 mM, respectively. The protein provides a binding site for Fe(II) that actually favors Fe(III), this coordination sphere places the bound Fe(II) in a state of entasis that can be relieved by loss of an electron. The EO of the bound Fe(II) is lowered relative to that of aqueous ferrous iron making electron transfer thermodynamically favorable. Carboxylates within this coordination sphere provide an electronic coupling pathway for the electron transfer via their H-bond network with type 1 Cu-histidine ligands thus making electron transfer kinetically efficient
HP-NAP is a dodecameric protein consisting of 17-kDa monomers, and has a spherical shell 9-10 nm in diameter with a hollow central core in which iron ions bind, HP-NAP can bind up to 500 atoms of iron per dodecamer in vitro, structure overview. Two ferroxidase centers are located in the interface of the dimer in Fe-loaded HP-NAP YS39. His25 and His37 of one subunit and Asp52 and Glu56 of the other subunit are chelated to iron ions
crystal structures of Zn2+- and Cd2+-bound forms of HP-NAP, and Cd2+-bound and apo forms of HP-NAP are determined: The coordination patterns of Zn2+ and Cd2+ are different but both metal ions can bind to the ferroxidase center (FOC)
the first zinc ion, Zn1 is coordinated in a tetrahedral manner to the side chains of His25, Asp52, Glu56, and a water molecule that bridges two zinc ions. The second zinc ion, Zn2 is coordinated in a distorted tetrahedral manner to the side chains of His37, Glu56, and two water molecules
DpsA-Te contains two Zn2+ bound at the ferroxidase center. The latter Zn2+ is displaced by incoming iron, such that Zn(II)-Fe(III) complexes are formed upon oxidation
structures and metal-binding properties of HP-NAP, crystal structure analysis of apoenzyme and enzymes bound to metals Fe2+, Zn2+, and Cd2+, detailed overview.The metal ions bind at the di-nuclear ferroxidase center (FOC) by different coordinating patterns. In comparison with the apo structure, metal loading causes a series of conformational changes in conserved residues among HP-NAP and Dps proteins (Trp26, Asp52, and Glu56) at the di-nuclear ferroxidase center. Trp26, in addition to His25, His37, Asp52, and Glu56, is well conserved among HP-NAPs and Dps proteins, and may play an important role in the conformational changes that occur upon binding of iron ions