Genetically engineered human ferritins over expressed in E. coli with various H/L chain ratios: A comparative Mossbauer study of their iron cores.

Ferritin is responsible for the storage and regulation of iron in living organisms. Mammalian ferritin consists of a spherical, hollow protein shell composed of 24 amino acid subunits of two forms: H and L. Iron is bio mineralized within the hollow protein as ferrihydrite. In our studies the electronic, magnetic and morphological properties of the ferrihydrite core are studied via Mossbauer (300<T<4.2K) and TEM measurements. Genetically engineered human ferritins overexpressed in E. coli, with controlled H/L ratio, are investigated. Herewith we present data on two samples: an H-rich ferritin with 21H- and 3L-chains and an L-rich ferritin with 2H- and 22L-chains. There is one ferroxidase center, which catalyzes the Fe2+→Fe3+ oxidation, per H-chain, while L-chains lack a ferroxidase center. The temperature profile of the Mossbauer spectra is analyzed in order to determine the blocking temperatures of the cores, which inform of their relative magnetic anisotropies and therefore their relative degree of crystallinity. This study aims to correlate the degree of crystallinity with the number of ferroxidase centers on the protein.