Ferritin bacterial

About a quarter of the total body iron is stored in macrophages and hepatocytes as a reserve, which can be readily mobilized for red blood cell formation (erythropoiesis). This storage iron is mostly in the form of ferritin, like bacterioferritin a 24-subunit protein in the form of a spherical protein shell enclosing a cavity within which up to 4500 atoms of iron can be stored, essentially as the mineral ferrihydrite. Despite the water insolubility of ferrihydrite, it is kept in a solution within the protein shell, such that one can easily prepare mammalian ferritin solutions that contain 1 M ferric iron (i.e. 56 mg/ml). Mammalian ferritins, unlike most bacterial and plant ferritins, have the particularity that they are heteropolymers, made up of two subunit types, H and L. Whereas H-subunits have a ferroxidase activity, catalysing the oxidation of two Fe2+ atoms to Fe3+, L-subunits appear to be involved in the nucleation of the mineral iron core once this has formed an initial critical mass, further iron oxidation and deposition in the biomineral takes place on the surface of the ferrihydrite crystallite itself (see a further discussion in Chapter 19). 

Ferrihydrites from ferritin also show a range of TbS, depending on the source organism (human > limpet > bacterial) (Webb St.Pierre, 1989) (see Fig. 17.3). The Tb of a 2-line ferrihydrite dropped from 50 to 25K when citrate was added at a level of ci-trate/Fe -0.08 (Zhao et al. 1994). Particle interactions in aggregates also affect the Mossbauer parameters. 

Fig. 17.3 Magnetic hyperfine field (left) and width of the outer lines of the sextets (right) obtained from Mossbauer spectra of ferritins, isolated from human spleen, limpet hemolymph and bacterial cells Pseudomonas aeruginosa) as a function of temperature (Webb St.Pierre, 1989 with permission).

Mann, S. Bannister, J.V. Williams, R.J.P. (1986 a) Structure and composition of ferritin cores isolated from human spleen, limpet (patella vulgata) hemolymph and bacterial (Pseudomonas aeruginosa) cells. J. Mol. Biol. 188 225-232... 

St. Pierre,T.G. Bell, S.H. Dickson, D.P.E. Mann, S. Webb, J. Moore, G.R. Williams, R.J.P. (1986) Mossbauer spectroscopic studies of the cores of human, limpet and bacterial ferritins. Biochim. Biophys. Acta 870 127-134... 

Ferritin, 36 449-451, 43 363, 399-400 amino acid sequences, 36 465-467 bacterial, see Bacfer biochemistry, 36 450-451 dimer and larger cluster formation, 36 479-481... 

I, 2, and 3 are correct. Haptoglobin removes hemoglobin, and transferrin mops up Fe3+ and even Fe. These can increase bacterial virulence if not rapidly sequestered. Ferritin is not associated with antibacterial action. 

Reconstitution experiments with apoferritins from animal and bacterial sources, whose native iron-loaded ferritins had crystalline and amorphous cores respectively, have been informative in showing that the core morphology is not determined by the protein shell. For example, Baaghil et al and Mann etalP were able to form crystalline cores in bacterioferritins, and Rohrer formed cores of iron-... 

Removal of Fe(lll) from storage in ferritin cores may require reduction to Fe(ll) again, possibly by ascorbic acid or glutathione. Some bacterial ferritins contain a bound cytochrome b which may assist in reduction. " 57a Released iron in the Fe " state can be incorporated into iron-containing proteins or into heme. The enzyme ferrochelatase " " catalyzes the transfer of free Fe + info protoporphyrin IX (Section 3) to form protoheme (Fig. 16-5). Iron in the Fe(II) state may also be oxidized to Fe + through action of the copper-containing ceruloplasmin (Section D) and be incorporated into heme by direct transfer from ferritin. ... 

Fig. 10. Fe Mdssbauer spectra recorded at 4.2 K for (A) human and (B) bacterial ferritin.

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