PMID:10769150
| Citation |
Yang, X, Le Brun, NE, Thomson, AJ, Moore, GR and Chasteen, ND (2000) The iron oxidation and hydrolysis chemistry of Escherichia coli bacterioferritin. Biochemistry 39:4915-23 |
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| Abstract |
Bacterioferritins are members of a class of spherical shell-like iron storage proteins that catalyze the oxidation and hydrolysis of iron at specific sites inside the protein shell, resulting in formation of a mineral core of hydrated ferric oxide within the protein cavity. Electrode oximetry/pH stat was used to study iron oxidation and hydrolysis chemistry in E. coli bacterioferritin. Consistent with previous UV-visible absorbance measurements, three distinct kinetic phases were detected, and the stoichiometric equations corresponding to each have been determined. The rapid phase 1 reaction corresponds to pairwise binding of 2 Fe(2+) ions at a dinuclear site, called the ferroxidase site, located within each of the 24 subunits, viz., 2Fe(2+) + P(Z) --> [Fe(2)-P](Z) + 4H(+), where P(Z) is the apoprotein of net charge Z and [Fe(2)-P](Z) represents a diferrous ferroxidase complex. The slower phase 2 reaction corresponds to the oxidation of this complex by molecular oxygen according to the net equation: [Fe(2)-P](Z) + (1)/(2)O(2) --> [Fe(2)O-P](Z) where [Fe(2)O-P](Z) represents an oxidized diferric ferroxidase complex, probably a mu-oxo-bridged species as suggested by UV-visible and EPR spectrometric titration data. The third phase corresponds to mineral core formation according to the net reaction: 4Fe(2+) + O(2) + 6H(2)O --> 4FeO(OH)((core)) + 8H(+). Iron oxidation is inhibited by the presence of Zn(2+) ions. The patterns of phase 2 and phase 3 inhibition are different, though inhibition of both phases is complete at 48 Zn(2+)per 24mer, i.e., 2 Zn(2+) per ferroxidase center. |
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| Keywords |
Amino Acid Substitution/genetics; Apoproteins/chemistry; Apoproteins/metabolism; Bacterial Proteins; Binding Sites; Catalase/metabolism; Ceruloplasmin/metabolism; Cytochrome b Group/antagonists & inhibitors; Cytochrome b Group/genetics; Cytochrome b Group/metabolism; Electron Spin Resonance Spectroscopy; Escherichia coli/chemistry; Ferric Compounds/metabolism; Ferritins/antagonists & inhibitors; Ferritins/genetics; Ferritins/metabolism; Ferrous Compounds/metabolism; Humans; Hydrogen Peroxide/metabolism; Hydrogen-Ion Concentration; Hydrolysis/drug effects; Iron/metabolism; Kinetics; Mutation/genetics; Oxidation-Reduction/drug effects; Oxygen/metabolism; Protons; Spectrophotometry; Titrimetry; Zinc/pharmacology |
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