Ferritins and bacterioferritin

Members of the ferritin family of proteins are distinguished by consisting of protein shells composed of 24 subunits that encompass a central cavity of 80 A diameter into which deposits of non-heme-iron can accumulate ([5] and references therein). X-ray structures suggest that the 24 subimits do not pack together to form the shell 

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Their subunits are folded in a central bundle of four a-helices, which assemble to form a roughly spherical protein shell surrounding a central cavity within which iron is stored (up to 4500 iron atoms per 24mer in ferritins and bacterioferritins, and around 500 in the smaller Dps protein 12mer). 

Probing Structure-Function Relations in Ferritin and Bacterioferritin... 

Probing Structure-Function Relations in Ferritin and Bacterioferritin P. M. Harrison, S. C. Andres. P. J. Artymiuk, G. C. Ford, J. R. Guest,... 

Some respiratory nitric oxide (NO) reductases, which contain a mixed dinuclear heme, nonheme iron site see Cytochrome Oxidase), and [2Fe-2S] ferredoxins see Iron-Sulfur Proteins), are covered in separate chapters of this encyclopedia. Ferritins and bacterioferritins, which contain a metastable nonheme diiron site are also covered elsewhere in this Encyclopedia see Iron Proteins for Storage Transport their Synthetic Analogs). Another chapter in this encyclopedia, Iron Models of Proteins with Dinuclear Active Sites, provides a synthetic perspective on the properties of nonheme, non-sulfur diiron sites in proteins. Recent reports of synthetic polypeptides that contain nonheme, non-sulfur diiron sites should also be noted. 

The mechanism of iron oxidation and core formation in Dps differs from that of ferritin and bacterioferritin in that the rate of minerahzation is faster than oxidation at the ferroxidase center in L. innocua ferritin and E. coli Dps core formation is 60% faster than the ferroxidation reaction. ... 

We thank the Wellcome Trust for providing financial support for our work on ferritin and bacterioferritin, and the Science and Engineering Research Council, who help support the Metallobiology Unit based at the University of East Anglia via its Molecular Recognition Initiative. 

PROBING STRUCTURE-FUNCTION RELATIONS IN FERRITIN AND BACTERIOFERRITIN... 

Other physical properties also show that the iron cores of native ferritins and bacterioferritins are different. Mossbauer spectra of ferritins measured as a function of temperature (Fig. 1) show quadrupole split doublets, with an isomer shift typical of Fe +, gradually being replaced as the temperature is lowered (between about 50 and 15 K) by a magnetic hyperfine spectrum (30, 31). The transition temperature, Tb, is lower than the ordering temperature, Tord (240 K) observed for bulk ferrihydrite (32), because of fluctuations in the direction of mag-... 

Toussaint, L., Cuypers, M. G., Bertrand, L., Hue, L., Romao, C. V., Saraiva, L. M., et al. (2009). Comparative Fe and Zn K-edge X-ray absorption spectroscopic study of the ferroxidase centres of human H-chain ferritin and bacterioferritin from desulfovibrio desulfuricans. Journal of Biological Inorganic Chemistry, 14, 35—49. 

Harrison, P. M., et al. Probing structure-function relations in ferritin and bacterioferritin. Adv. Inorg. Chem. 36 (1991), 449 87. 

EPR data also reveal a difference between the ferritin and bacterioferritin cores. At high temperatures the latter yield a broad signal with g 2 and at 4 K are EPR silent, while the former give signals at high temperatures at g 6 and g 2.2 that are lost at The origin of the... 

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