Ferritin three-dimensional

Figure 19.6 The three-dimensional structure of the Listeria innocua ferritin subunit (a) and the 12-mer (dodecameric) structure viewed down a three-fold symmetry axis. (From Lewin et al., 2005. Copyright with permission from The Royal Society of Chemistry, 2005.)...

Since the (Fen05(0H)6> unit is stable, it has been speculated(8b,17b) that it might also be present in the ferritin core. Since the majority of phosphate in ferritin is adventitious, surface bound and the metallic core can be reconstituted in the absence of phosphate groups with no change in the X-ray powder diffraction pattem(l), replacement of bridging phosphate by bridging carboxylate groups should not influence the three dimensional structure of the core. Calculations show that -409 Fell nnits could fill the apoferritin inner cavity. Further details can be found in reference 17. 

Fig. 5.25 Quasi-three-dimensional, point projection image of ferritin on tungsten at 30 K before applying a critical desorption field of ferritin. The image is a digital composite of seven images taken at different field strengths, thus at different depths of the covered methane layer. (Courtesy of J. A. Pantiz.)...

The three-dimensional structures of horse spleen apoferritin (85% L, 15% H subunit) (11), rat liver ferritin (66% L, 34% H subunit) (94),... 

The presentation in 1993 of the structure of the hydroxylase component of methane monooxygenase (MMOH) by Rosenzweig et al. (15) is the third published three-dimensional structure of a diiron-oxygen protein (Fig. 1). The previous two are from hemerythrin (Hr) (16,17) and protein R2 of E. coli ribonucleotide reductase (RNR-R2) (18, 19). Some other dinuclear iron proteins with known fi-oxo or p.-hydroxo bridges are purple acid phosphatases (PAP) [(e.g., uteroferrin (Uf)] (20, 21), ferritins (in early stages of nucleation) (22), rubrerythrin (Rr) (23-26), nigerythrin (26), and soluble stearoyl-acyl carrier protein A desaturase (A-AGP) (27, 28). 

The three-dimensional structure of the human H ferritin has been solved (i 78) and shows that the putative /t-oxo-bridged ferric dimer is located in the middle of and along the length of a four-helix bundle, similar to the situation in . coli RNR protein R2. In a bacterial ferritin, three iron sites per subunit have been found in an X-ray crystallographic study (22). Two of the iron ions make up the diferric site. The third ferric site remains an enigma as to its functional role, if any. Also here, it is interesting to compare protein R2 in RNR, where a third ferrous iron has been shown to participate in formation of the iron/free radical site (78, 84, 82). 

As with H-chain ferritins, the three-dimensional structure of BFR results in channels through the protein at the symmetry axes. However, while the hydrophilic threefold channels... 

Hempstead PD, Yewdall SJ, Femie AR, Lawson DM, Artymiuk PJ, Rice DW, Ford GC, Harrison PM. 1997. Comparison of the three-dimensional structures of recombinant human H and horse L ferritins at high resolution. J Mol Biol 268 424-448. 

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