Expression and structural and functional properties of human ferritin L-chain from Escherichia coli |
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Authors: | S Levi J Salfeld F Franceschinelli A Cozzi M H Dorner P Arosio |
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Institution: | Department of Biomedical Sciences and Technology, University of Milan, Ospedale San Raffaele, Milano, Italy. |
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Abstract: | The human ferritin L-chain cDNA was cloned into a vector for overproduction in Escherichia coli, under the regulation of a lambda promoter. The plasmid obtained contains the full L-chain coding region modified at the first two codons. It is able to direct the synthesis of the L-chain which can constitute up to 15% of the total soluble protein of bacterial extract. The L-chains assemble to form a ferritin homopolymer with electrophoretic mobility, molecular weight, thermal stability, spectroscopic, and immunological properties analogous to natural ferritin from human liver (95% L-chain). This recombinant L-ferritin is able to incorporate and retain iron in solution at physiological pH values. At variance with the H-ferritin, the L form does not uptake iron at acidic pH values and does not show detectable ferroxidase activity. It is concluded that ferritin L-chain lacks the ferroxidase site present in the H-chain and that the two chains may have specialized functions in intracellular iron metabolism. |
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