Ferroxidase center apoferritin

Antitumor drugs cisplatin as, history, 37 175-179 platinum compounds future studies, 37 206-208 resistance to, 37 192-193 second-generation, 37 178 Antiviral agents, 36 37-38 AOR, see Aldehyde oxidoreductase Aphanothece sacrum, ferredoxins, amino acid sequence, 38 225-227 Apo-calcylin, 46 455 Apo-caldodulin, 46 449-450 Apoenzyme, 22 424 Apoferritin biosynthesis, 36 457 cystalline iron core, 36 423 Fe(III)distribution, 36 458-459 Fe(II) sequestration, 36 463-464 ferroxidase centers, 36 457-458 iron core reconstruction in shell, 36 457 mineralization, 36 25 Mdssbauer spectra, 36 459-460 optical absorbance spectra, 36 418-419 subunit conformation and quaternary structure, 36 470-471... 

Mineralization in apoferritin involves a prior oxidation of Fe(II) as it enters channels in the protein shell. The ferroxidase center seems to be composed of Glu (Gin) and His residues situated between four helices (P. M. Harrison, personal communication). There is scope for exploring the design of agents that could block the entry of iron into the core of the protein or hasten its passage out. It is possible that non-redox-active metal ions such as Ga(III), In(III), and Al(III) can act in this way. The nature of the Fe(II) complex in the cytoplasm, which acts as a donor to ferritin, is not clear yet, but perhaps it could be Fe(II) glutathione. 

The presence on apoferritin of ferroxidase centers is suggested by four observations (1) that tbe initial oxidation step when Fe(II) is added to apoferritin requires a specific oxidant, dioxygen (48Y, (2) that Fe(III) can be produced from Fe(II) in the presence of apoferritin—and intercepted by transferrin under conditions in wbicb hydrolysis is kept... 

A total of 16-22 Cu + ions have been shown to bind relatively tightly to the 24-meric horse spleen apoferritin and to have a small catalytic effect on the aerobic oxidative uptake of Fe + [32], This observation is particularly surprising given that Zn + has an inhibitory effect on the oxidative uptake of Fe + by horse spleen apoferritin [33, 34]. As noted above, Zn + inhibits the ferroxidase activity of E. coli bacterioferritin by binding to the binuclear center [20, 21] and thus it was of some interest to investigate the effect that Cu " has on the aerobic oxidative uptake of Fe + by , coli bacterioferritin. As described below, Cu + enhances the catalytic activity of bacterioferritin as far as Fe " " oxidation is concerned. 

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