Apoferritin mineralization

When pea seed apoferritin is reconstituted in vitro in the absence of phosphate, the reconstituted mineral core consists of crystalline ferrihydrite (Rohrer et ah,1990 Wade et ah, 1993 Waldo et ah, 1995). Conversely, horse spleen ferritin reconstituted in the presence of phosphate produces an amorphous core (Rohrer et ah,1990 St. Pierre et ah, 1996)... 

We now consider how the biomineralization chamber which is constituted by the interior of the apoferritin protein shell influences the growth of the core. Once sufficient core has been developed (>100 Fe atoms), Fe(II) oxidation and hydrolysis can proceed (Yang et ah, 1998) on the mineral surface of the growing core (equation 8) ... 

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... 

Ferricytochrome c, 32 49 NIR MCD spectrum, 36 233-234 Ferrihemoproteins, reduction rates, 36 430-431 Ferrihydrite, 36 422 chemical composition, 36 455 inside apoferritin cavity, 36 459 mineralization in iron storage proteins, 36 161-164... 

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. 

X-ray contrast variation has been best applied to the metalloprotein ferritin, which consists of a mineral iron core (electron density - 1000 e nm ) surrounded by a spherical protein shell (410 enm ) of 24 regularly-arranged subunits [149,158-160]. The protein shell was matched out in 53% sucrose (w/w) or 0.66 g sucrose/ml solution, leaving the observed scattering to be caused only by the iron core (Fig. 17). Control experiments were performed on apoferritin which lacks the iron core [149,160]. Thus the Rq for native ferritin is 3.7 nm, that of apoferritin is 5.6 nm and that of the iron core is 2.9 nm [158-160]. The outer and inner radii of the protein of ferritin were found to be 6.3 and 3.55 nm [160]. The radius of the iron core was found to be 3.66 nm and corresponded well to the scattering from a uniform sphere [149], rather than to other models based on a collection of spherical micellar domains that were proposed from electron microscopy studies (Fig. 17). 

MetaUoclusters play an important role in bacterial mineralization, and their investigation is the subject of a new branch of science called bioinoiganic soUd-state chemistry. This field studies the formation and structure of nanoscale materials in biological environments. A characteristic example is the formation of nanoparticles on the base of ferritin (Fig. 21). A nanoparticle of Fe3S4 is deposited in the inner part of the protein shell through chemical transformations under mild conditions. The process is simplified when a metal-free apoferritin is used for this propose. For... 

Zhao GH, Bou-Abdallah F, Arosio P, Levi S, Janus-Chandler C, Chasteen ND. 2003. Multiple pathways for mineral core formation in mammalian apoferritin the role of hydrogen peroxide. Biochemistry 42 3142-3150. 

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