Identification and analysis of a Scophthalmus maximus ferritin that is regulated at transcription level by oxidative stress and bacterial infection.

Ferritins are conserved iron storage proteins that exist in most living organisms and play an essential role in iron homeostasis. In this study, we reported the identification and analysis a ferritin M subunit, SmFerM, from turbot Scophthalmus maximus. The full length cDNA of SmFerM contains a 5'-untranslated region (UTR) of 232 bp, an open reading frame (ORF) of 531 bp, and a 3'-UTR of 196 bp. The ORF encodes a putative protein of 176 amino acids, which shares extensive sequence identities with the M ferritins of several fish species. In silico analysis identified in SmFerM both the ferroxidase center of mammalian H ferritins and the iron nucleation site of mammalian L ferritins. Quantitative real time reverse transcriptase-PCR analysis indicated that SmFerM expression was highest in muscle and lowest in heart and responded positively to experimental challenges with bacterial pathogens and poly(I:C). Exposure of cultured turbot hepatocytes to treatment of stress inducers (iron, copper, and H(2)O(2)) significantly upregulated the expression of SmFerM in a dose dependent manner. Iron chelating analysis showed that recombinant SmFerM purified from Escherichia coli exhibited apparent iron binding activity. These results suggest that SmFerM is a functional M ferritin and is likely to play a role in iron sequestration and protection against oxidative stress and microbial infection.